THE UNIVERSITY OF MICHIGAN COLLEGE OF ENGINEERING Department of Aerospace Engineering High Altitude Engineering Laboratory Technical Report A FOURIER TRANSFORM SPECTROMETER FOR THE MEASUREMENT OF ATMOSPHERIC THERMAL RADIATION L. W. C haney, L. T. Loh, M. T. Surh ORA Project 05863. under contract with: NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CONTRACT NO-. NASr - 54(03) WASHINGTON, D. C. administered through OFFICE OF RESEARCH ADMINISTRATION ANN ARBOR May 1967

ACKNOWLEDGEMENTS The work described in this report was successfully completed as a result of the dedicated help of the other members of the laboratory staff. Many thanks go to Fred Bartman who has directed the atmospheric radiation studies as well as being responsible for the balloon flights. The authors are particularly grateful to the following staff members who participated directly in the instrument development. Douglas Robinson carefully performed the many optical and electrical tests of the components as well as assembling and testing the completed instrument. Donald Bandkau designed many of the mechanical parts and prepared all the required drawings. Gunar Liepins designed the mirror drive magnetic circuit. Wan Lee wrote many of the computer programs and carried out the numerous computations. Thanks also go to the members of the Goddard Space Flight Center staff who under the direction of Dr. R. A. Hanel designed most of the electronic circuits for the IRIS instrument. Others who contributed to the success of the effort were the balloon flight crew and the Weather Bureau personnel at the National Center for Atmospheric Research Balloon Base in Palestine, Texas. The work described in this report has been supported by the National Aeronautics and Space Administration Contract NASr-54(03). ii

TABLE OF CONTENTS Page List of Figures iv I. Introduction 1 II. Radiation Data Obtained on 8 May 1966 Balloon Flight 3 III. Conclusion and Plans for Further Work 23 IV. Bibliography 25 Appendix I. Earth Radiation Measurements by Interferometer 28 From a High Altitude Balloon, (a paper presented to the Third Symposium on Remote Sensing of Environment, 14 October 1964, Ann Arbor, Michigan). Appendix II. An Infrared Interferometer Spectrometer (IRIS) for 48 Meteorological Studies (a paper presented to the 13th Infrared Information Symposium, 26 October 1965, Pasadena, California). Appendix III. The Measurement of the Earth's Thermal Radiation 66 by a Fourier Transform Spectrometer (a paper presented to the American Meteorological Society Conference on Physical Processes in the Lower Atmospheres, 20-22 March 1967, Ann Arbor, Michigan). Appendix IV. Fourier Transform Spectrometer Radiative Measure 100 ments and Temperature Inversion, L. W. Chaney, S. R. Drayson, and C. Young, (Applied Optics, February 1967). iii

LIST OF FIGURES Page 1. Scene photographs at 8:30 EST, 9:10 EST 19 and 10:06 EST. 2. Scene photographs at 11:09 EST, 12:34 EST 20 and 13:31 EST. 3. Scene photographs at 14:12 EST, 14:48 EST 21 and 15:11 EST. 4. Comparison of measured spectral radiance and 22 water vapor absorption. iv

A FOURIER TRANSFORM SPECTROMETER FOR THE MEASUREMENT OF ATMOSPHERIC THERMAL RADIATION I. Introduction The High Altitude Engineering Laboratory has been engaged for the past few years in developing Fourier transform spectroscopy' for meteorological measurements. The eventual application will be the measurement of the earth's thermal radiation from a satellite and the determination of the temperature structure of the atmosphere. This report is a tabulation of the measurements obtained on a balloon flight at 7 mb altitude May 8, 1966 from Palestine, Texas and a collection of four papers which document the instrument development. Nine sets of radiation data are presented covering the time from 8:30 EST to 15:11 EST at intervals of approximately 50 minutes. Each data set covers the spectral range from 500 cm to 2000 cm in 2 cm steps. The standard deviation of the measurements is approximately 0. 5 ergs sec cm sr. This uncertainty is exceeded in the range from 500 cm to 550 cm due to a drop in instrument sensitivity and in the region from 725 cm to 750 cm due to external vibration. The aerial photographs which follow the data tabulation correspond to each data set. The instrument field of view is outlined on each photograph from which an estimate of cloud cover can be made. h A bibliography at the end of the report lists many of the contributions to the development of Fourier spectroscopy. 1

The papers reproduced are as follows: (1) Earth Radiation Measurements by Interferometer from a High Altitude Balloon - presented to the Third S ymposium on Remote Sensing of Environment - October 14, 1964, Ann Arbor, Michigan. The paper describes measurements made June 26, 1963 from a high altitude balloon using a Block I-4 interferometer (5p to 15p) 50 cm. (2) An Infrared Interferometer Spectrometer (IRIS) for Meteorological Studies - presented to the 13th Infrared Information Symposium - October 26, 1965, Pasadena, California. A description is given of the interferometer which was developed in conjunction with Goddard Space Flight Center. The development of this instrument was a direct result of the successful measurements described in the first paper. (3) The Measurement of the Earth's Thermal Radiation by a Fourier Transform Spectrometer - presented to the American Meteorology Society Symposium on physical processes in the lower atmosphere March 21, 1967, Ann Arbor, Michigan. The installation of the IRIS instrument (described in the second paper) aboard a high altitude balloon is described. Some of the data obtained from the May 8, 1966 flight is presented. The errors both in wavelength and amplitude are discussed and finally a temperature inversion is presented. (4) Fourier Transform Spectrometer - Radiative Measurements and Temperature Inversion, by L. W. Chaney, S. R. Drayson, and C. Young - published in Applied Optics, February 1967. This paper presents the first data reduced from the May 8, 1966 balloon flight and compares the temperature profile measured by radiosonde with that obtained by an inversion of the Fourier transform spectrometer data. 2

A paper entitled, "The Determination of Meteorological Variables from Atmospheric Thermal Radiation Measurements, " by S. Roland Drayson and Charles Young which presents additional details on the inversion technique was presented to the American Meteorology Symposium March 21, 1965. A paper which expands on the technique is currently being prepared for publication. II. Radiation Data Obtained on May 8, 1966 Balloon Flight The data listed on the next fifteen pages was obtained on May 8, 1966 from a high altitude balloon flight over Palestine, Texas. The balloon float altitude was 110, 000 feet and the flight path followed is shown in Figure 6 of Appendix 3. The time at which the data was taken is listed across the top of each page and the wavenumber in inverse centimeters is listed in the left hand column. The radiation is given in ergs per second per square centimeter per steradian per inverse centimeter and has been written ergs/sec cm str. Following the data are three pages of photographs which correspond to the data. Although the photographs and the data are listed for the same time, this is not precisely correct. The data for each listed time was recorded over a period of 45 seconds and the photographs were taken once each minute, but not synchronized with the data recording. Hence, there can be up to one minute time displacement between the data recording and the photograph. 3

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 500 105.0 107.3 105.8 105.9 106.3 102.9 106.9 102.8 106.0 502 100.8 103.3 102.8 102.2 104.3 100.9 103.5 102.7 103.2 504 100.8 102.9 101.4 102.0 104.1 99.6 103.1 102.0 101.9 506 101.2 103.0 101.5 102.9 102.9 99.9 103.9 101.3 101.2 508 101.7 103.6 103.4 103.6 103.6 101.7 104.8 99.8 102.3 510 104.3 107.1 106.5 104.9 106.3 103.5 106.5 99.8 105.8 512 106.1 109.4 107.2 105.6 111.8 104.0 107.6 100.6 107.6 514 105.3 108.1 106.2 104.2 111.1 104.2 107.4 102.0 107.0 516 101.9 102.9 101.8 100.3 106.2 101.8 104.5 101.7 103.8 518 99.7 99.7 98.9 97.8 103.1 99.6 103.0 100.3 101.0 520 103.7 103.8 102.7 100.7 106.3 102.8 106.7 102.3 104.2 522 107.6 108.2 106.4 104.2 110. 10105.8 109.0 103.7 107.4 524 105.4 107.0 106.6 104.5 109.0 105.6 108.9 104.3 107.2 526 104.0 105.9 106.2 104.2 107.3 104.4 108.2 104.5 105.4 528 108.3 109.8 109.4 107.9 109.7 105.8 109.6 105.6 107.2 530 113.1 115.2 117.8 114.9 118.5 114.7 111.5 114.2 112.8 532 113.5 117.5 118.1 115.8 119.9 115.1 114.1 114.9 114.0 534 110.9 112.3 111.4 114.0 117.4 113.0 111.4 113.2 111.3 536 109.2 110.8 109.1 110.0 114.0 107.2 110.9 109.3 107.9 538 110.8 112.2 110.5 113.5 114.7 111.0 111.1 109.8 109.6 540 111.4 112.8 113.3 113.7 117.9 113.9 117.2 110.7 110.1 542 110.6 111.9 110.9 109.8 113.4 113.7 112.6 110.6 108.7 544 107. 3 109.3 109.1 108.3 109.7 108.8 110.8 107.6 107.3 546 103.9 105.9 105.5 105.5 107.1 106.9 108.5 105.7 105.5 548 104.1 107.1 105.9 106.0 108.2 107.0 108.6 106.5 106.4 550 107.4 110.9 108.5 109.2 111.4 109.1 110.2 107.8 108.7 552 108.9 113.2 114.6 113.0 117.3 114.2 111.8 114.3 111.0 554 110.2 114.1 113.7 113.2 114.6 114.4 111.0 114.4 110.4 556 112.3 115.3 115.0 114.5 118.2 114.9 113.4 114.6 109.9 558 114.0 119.8 120.2 120.8 121.1 119.9 118.3 119.8 113.9 560 114.9 120.1 121.3 121.5 121.6 120.8 119.2 119.9 114.9 562 114.4 114.8 118.0 114.9 119.2 118.5 116.8 115.0 114.4 564 111.7 112.0 111.9 110.2 114.6 114.1 110.8 110.6 109.9 566 108.7 109.0 108.6 108.5 110.7 109.8 109.9 107.7 109.5 568 105.5 105.0 105.4 105.7 107.6 107.4 107.6 106.5 106.2 570 107.0 106.8 106.8 107.3 109.2 108.8 107.9 107.9 106.5 572 109.7 110.3 109.3 109.8 111.2 110.9 110.0 111.5 108.8 574 109.2 109.9 108.8 110.0 111.9 110.5 110.2 109.6 109.4 576 106.5 107.7 107.7 107.7 110.0 108.4 108.9 108.6 108.3 578 104.8 107.0 107.5 105.9 109.1 107.6 108.2 107.9 107.5 580 103.4 106.2 106.1 104.8 108.4 106.9 107.2 107.4 106.2 582 103.0 105.7 104.7 104.9 108.1 106.3 106.2 107.4 105.6 584 104.5 106.6 105.8 106.0 108.4 107.0 106.1 108.0 105.8 586 104.8 8 1058 105.9 105.8 107.0 107.1 104.4 106.7 104.7 588 100.6 101.5 100.8 101.3 101.8 102.1 99.8 102.0 100.6 590 95.2 96.8 95.9 95.4 96.3 96.5 95.9 97.2 96.1 592 93.7 95.1 95.2 93.5 95.1 95.3 95.2 95.6 95.1 594 93.7 93.9 95.1 93.4 95.4 94.6 94.5 95.0 94.5 596 92.0 91.9 93.2 92.5 94.7 92.5 92.6 93.3 92.9 598 91.3 91.8 92.5 92.6 94.4 92.3 92.2 92.9 92.7

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 600 92.0 93.4 93.7 93.2 94.4 93.5 93.3 93.9 93.2 602 91.7 93.0 93.7 92.5 93.4 93.1 93.0 93.5 92.0 604 90.6 90.7 92.2 90.9 92.5 91.5 91.2 91.6 89.9 606 89.2 89.1 90.9 89.3 91.5 90.0 89.6 89.8 88.9 608 87.7 88.4 89.9 88.2 89.7 88.7 88.3 88.4 88.1 610 87.1 87.0 89.0 87.9 87.9 87.8 87.8 87.9 87.5 612 85.8 84.9 88.0 86.7 86.3 86.7 87.1 86.9 87.2 614 79.8 79.8 82.5 81.2 81.7 81.1 81.3 81.7 82.5 616 72.1 72.4 74.1 73.5 74.3 72.6 73.1 74.1 74.1 618 72.7 72.3 73.7 73.2 73.2 72.5 73.5 73.4 73.8 620 79.4 78.3 80.7 78.7 78.9 79.1 79.8 79.3 79.9 622 79.3 78.1 81.4 78.3 79.3 78.8 78.8 80.5 78.4 624 72.5 71.9 75.1 71.8 72.6 72.4 71.8 74.9 71.4 626 66.6 66.5 69.4 65.7 65.7 66.4 66.1 67.7 66.5 628 62.5 62.4 65.2 61.4 62.3 61.4 62.4 62.3 63.3 630 58.2 58.3 60.0 57.2 60.6 57.0 58.2 58.0 59.9 632 54.1 54.5 55.4 53.4 58.2 53.9 54.1 54.2 56.2 634 51.9 52.2 54.0 51.9 55.8 51.9 52.3 51.6 53.4 636 50.8 51.3 53.6 51.2 54.1 50.7 51.4 50.6 52.0 638 49.9 50.3 51.6 50.1 52.4 49.9 50.2 50.0 51.1 640 48.8 48.5 48.7 48.5 49.5 48.4 48.6 48.4 49.2 e^~~~ ~~~~n ~642 48.2 48.0 48.4 48.1 48.3 47.6 48.3 47.5 47.9 644 46.9 47.7 48.6 47.4 48.2 46.9 47.9 47.0 47.3 646 46.4 47.5 48.2 47.0 48.0 46.6 47.5 47.0 47.7 648 48.4 48.8 49.2 48.4 48.9 48.0 48.7 48.3 49.2 650 49.6 49.7 50.4 49.8 49.8 49.1 49.9 49.1 50.0 652 47.6 48.5 49.5 48.7 48.7 47.6 49.1 47.9 49.0 654 46.2 48.0 48.9 47.9 48.1 46.7 48.6 47.5 48.3 656 45.9 47.6 48.5 47.7 48.0 46.2 48.5 47.4 47.6 658 46.4 47.0 48.1 47.9 48.0 45.8 48.2 47.1 47.6 660 47.4 47.1 48.7 47.9 48.4 46.0 48.0 47.4 48.3 662 47.8 48.0 50.1 48.1 49.0 46.6 48.3 48.2 48.8 664 47.9 48.6 50.4 48.7 48.7 47.3 48.6 48.7 49.1 666 50.5 50.4 51.7 50.5 50.0 49.6 50.6 51.0 51.4 668 53.0 51.9 53.3 51.9 52.0 51.6 52.2 53.3 53.7 670 51.2 50.2 51.7 50.4 50.9 50.0 50.4 51.4 51.9 672 47.5 47.1 48.7 47.7 47.8 46.8 47.5 48.0 48.2 674 46.5 46.2 47.6 46.5 46.5 45.6 46.7 46.9 46.7 676 46.9 46.1 47.3 46.1 46.4 45.0 46.8 46.5 46.7 678 45.9 45.5 46.3 45.5 46.1 44.1 46.2 46.0 46.2 680 44.8 45.5 45.8 45.1 46.3 44.7 45.8 46.2 46.2 682 44.2 45.1 45.5 44.3 46.3 45.4 45.7 46.0 46.0 684 43.3 43.8 44.8 43.3 45.5 44.7 45.0 44.9 45.1 686 42.1 42.8 43.7 42.9 44.3 43.5 43.7 43.8 43.9 688 41.8 42.8 43.7 43.4 43.5 43.0 43.2 43.6 43.4 690 42.0 43.1 44.6 43.6 43.4 43.0 43.7 43.6 43.5 692 42.3 43.0 44.7 42.8 43.5 42.5 43.8 43.1 43.5 694 42.4 42.8 44.6 42.2 43.4 42.2 43.7 42.6 43.7 696 42.8 43.1 45.4 43.2 44.0 43.0 43.9 43.1 44.2 698 44.1 44.5 46.6 45.0 45.0 44.8 45.1 44.7 45.5

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 700 46.2 46.9 48.3 46.9 46.5 46.8 47.2 46.7 47.3 702 48.2 49.3 50.4 49.2 48.6 48.7 49.6 48.7 49.4 704 50.6 52.0 52.5 52.1 51.8 51.4 52.7 51.7 52.2 706 53.9 55.0 55.0 54.8 55.0 54.4 56.0 55.4 55.3 708 57.8 58.3 58.6 57.8 58.4 57.9 59.2 59.0 58.3 710 60.6 61.5 62.2 61.5 61.6 61.4 62.4 61.9 61.3 712 64.2 65.1 66.0 65.4 64.7 64.5 65.9 65.4 64.9 714 68.6 69.0 69.7 69.1 68.5 68.1 69.3 69.4 68.7 716 68.4 69.4 69.5 69.1 69.4 68.9 69.2 69.4 68.9 718 62.8 64.4 64.2 63.2 64.4 63.9 63.7 63.6 63.5 720 62.8 63.4 64.3 62.8 64.1 64.1 63.5 63.2 63.2 722 72.6 73.8 75.3 73.9 74.4 74.7 73.9 73.3 73.7 724 81.9 84.0 85.2 83.7 84.1 84.3 83.1 82.6 83.4 726 82.8 84.9 86.0 84.8 85.8 85.5 84.3 84.1 84.5 728 79.3 81.3 82.9 82.2 82.9 82.6 82.0 81.6 81.7 730 78.4 79.7 80.7 80.3 80.7 81.2 80.7 80.5 80.2 732 79.5 78.6 81.1 80.7 81.2 81.7 80.9 81.6 80.9 734 80.1 78.6 83.9 82.9 83.0 82.9 81.9 83.1 82.4 736 80.6 80.9 84.8 83.6 84.2 84.0 82.8 84.3 82.9 738 81.7 82.2 82.6 82.8 83.5 83.4 82.4 83.9 82.0 740 82.4 80.4 81.6 82.3 81.2 81.9 80.8 82.1 80.8 742 82.8 81.7 85.0 83.3 82.8 83.9 82.2 84.5 82.1 744 87.1 87.7 90.5 87.2 89.3 89.4 88.0 90.4 86.7 746 93.3 92.9 94.0 93.4 94.7 95.7 93.3 95.1 92.6 748 97.4 96.4 96.1 100.6 99.0 101.8 96.6 97.1 98.2 750 96.5 99.2 100.8 103.7 103.1 103.1 99.5 100.4 101.2 752 97.1 100.9 102.4 101.9 106.1 101.8 100.5 104.1 101.1 754 100.4 102.6 102.0 100.0 107.3 104.8 100.3 105.7 99.7 756 104.1 106.5 105.2 103.8 109.7 112.9 103.6 108.2 98.0 758 108.0 110.8 112.0 110.7 114.5 119.8 109.8 112.9 101.1 760 110.8 113.7 117.4 114.7 117.3 122.1 113.6 117.0 108.5 762 113.2 115.4 119.4 116.8 116.7 122.3 113.5 117.6 114.0 764 114.5 116.7 119.7 120.0 118.5 122.2 113.5 118.3 115.6 766 114.4 117.2 119.5 122.1 122.7 121.0 114.0 120.2 115.6 768 114.0 116.2 119.1 121.6 123.9 120.4 114.0 120.1 115.2 770 114.3 116.1 119.7 121.5 123.9 123.0 115.2 119.6 115.2 772 114.6 117.1 120.7 122.4 124.9 126.2 116.9 120.5 115.8 774 113.9 116.3 119.4 121.0 123.4 125.2 116.1 119.6 114.6 776 113.1 114.3 117.1 118.5 120.4 122.0 114.3 117.5 112.9 778 113.6 114.3 117.2 118.9 120.6 122.1 114.2 118.0 114.0 780 114.2 115.9 119.0 121.4 123.6 125.0 115.7 120.4 116.3 782 113.6 115.7 119.2 121.6 124.2 125.3 115.9 120.6 116.0 784 113.1 114.4 118.2 120.1 122.5 123.1 114.9 119.1 114.4 786 114.1 115.5 119.6 121.1 124.1 123.9 115.8 120.0 115.5 788 114.7 116.6 121.3 123.1 127.0 126.2 117.0 121.8 116.8 790 112.6 114.6 118.7 121.0 124.7 123.7 114.7 119.8 114.3 792 110.1 111.6 114.4 117.2 119.8 119.0 111.6 116.1 111.1 794 108.9 109.8 112.4 114.5 116.4 116.1 110.0 113.7 109.3 796 107.4 108.1 111.2 112.1 114.3 113.8 108.5 112.0 107.4 798 107.0 108.2 111.4 112.0 114.8 114.5 108.8 112.3 107.4

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 800 109.4 110.3 113.7 115.3 117.9 118.7 111.1 115.2 110.0 802 111.1 112.0 115.4 117.6 120.1 121.0 112.2 117.5 111.6 804 111.1 112.7 116.0 117.9 121.0 121.2 112.3 118.4 112.2 806 111.5 113.7 117.2 118.8 122.1 122.6 112.8 119.2 113.4 808 112.3 114.6 118.1 120.2 122.8 124.1 113.7 119.8 114.1 810 112.8 115.3 118.7 121.3 123.7 125.1 114.8 120.6 114.4 812 112.5 115.0 118.9 121.7 123.9 124.6 114.7 120.5 114.2 814 111.8 114.2 118.2 121.5 123.3 123.4 113.2 120.0 113.4 816 112.3 114.9 118.3 122.0 124.4 124.5 113.5 121.3 114.0 818 113.3 115.8 119.6 123.0 126.8 127.3 115.6 123.2 115.9 820 113.2 116.0 120.0 122.8 127.6 127.9 116.4 123.2 116.1 822 112.4 115.5 119.8 121.9 126.9 127.2 115.8 122.0 115.1 824 111.4 114.5 118.5 121.0 125.3 125.8 115.0 120.6 113.9 826 110.9 113.5 116.6 120.4 123.9 123.5 113.9 119.4 112.7 828 111.3 113.4 116.6 121.0 124.5 123.2 113.7 119.8 113.0 830 111.5 114.3 118.0 121.9 125.8 125.2 114.2 121.4 114.6 832 111.1 114.8 118.4 122.1 125.7 126.5 114.5 122.3 115.1 834 110.9 114.4 117.4 121.7 125.2 126.0 114.4 121.6 114.2 836 110.8 113.7 116.6 120.9 125.2 125.2 113.9 120.6 113.7 838 109.9 112.5 115.9 119.3 123.7 123.7 112.7 119.2 112.7 840 108.9 111.6 115.4 118.3 122.1 122.3 112.2 118.0 111.8 842 108.6 111.5 115.6 118.7 122.4 122.1 112.4 118.1 112.5 844 108.4 111.5 115.8 118.9 122.8 122.4 112.5 118.6 112.8 846 108.0 111.2 115.2 118.4 122.0 121.9 111.9 118.0 111.5 848 107.1 110.1 113.8 117.0 120.2 119.7 110.4 116.2 109.9 850 105.6 108.5 111.5 114.7 117.3 116.7 108.3 113.8 108.1 852 104.3 106.7 109.7 112.9 114.4 114.6 106.9 111.5 106.2 854 104.6 106.9 110.0 113.4 114.8 115.4 107.1 111.6 106.5 856 106.1 108.8 112.3 115.7 118.0 118.7 108.6 114.2 108.5 858 106.9 109.8 113.9 117.3 120.2 120.9 110.3 116.5 109.9 860 106.4 109.5 114.0 117.5 120.4 120.7 110.6 117.1 110.2 862 105.5 108.9 113.5 116.9 120.0 119.9 109.5 116.4 110.0 864 105.1 108.3 112.4 116.0 119.0 119.2 108.0 115.1 109.4 866 104.9 107.9 111.5 115.3 118.6 118.8 107.9 114.7 109.0 868 104.7 107.7 111.4 114.8 119.0 118.3 108.5 115.2 108.7 870 104.8 107.2 110.9 113.8 118.0 117.2 107.9 114.7 107.8 872 105.1 106.7 110.7 113.5 117.1 117.4 107.6 114.2 107.0 874 105.3 107.0 111.3 114.2 117.7 118.7 108.1 114.6 107.4 876 104.6 107.1 110.8 114.0 117.8 118.1 107.4 113.9 107.7 878 103.7 106.3 109.7 113.1 117.2 116.2 106.2 112.7 107.1 880 103.3 105.7 109.3 112.6 116.5 115.3 105.7 112.4 106.2 882 103.2 105.2 108.8 112.1 115.5 115.8 105.8 112.6 105.4 884 102.5 104.4 108.1 111.3 114.1 115.9 105.6 112.3 105.1 886 101.5 103.7 107.6 110.4 112.8 114.6 104.5 111.2 105.5 888 101.2 103.7 107.7 110.2 112.6 113.6 103.8 110.7 105.7 890 101.8 104.0 108.6 110.9 113.6 114.1 104.3 111.5 105.5 892 102.6 104.2 108.9 111.9 114.4 114.7 104.4 112.1 105.4 894 103.0 104.2 108.3 112.4 114.8 115.4 104.4 112.0 105.6 896 102.6 104.0 108.2 112.1 115.4 116.7 105.2 112.0 105.9 898 101.7 104.0 108.5 111.6 116.0 117.2 105.4 112.2 105.8

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 900 100.8 103.9 108.1 111.7 115.9 116.8 104.5 111.5 104.5 902 100.6 103.4 107.6 111.8 115.8 116.7 104.2 110.5 103.5 904 100.5 102.8 107.2 110.5 115.3 115.6 104.3 110.2 103.5 906 99.7 101.9 105.7 108.4 113.6 112.9 103.4 109.7 102.3 908 98.3 101.1 104.0 106.8 111.3 110.8 102.2 108.3 100.0 910 97.8 101.0 103.9 106.7 110.6 111.2 102.2 107.4 100.1 912 98.7 101.2 104.5 107.4 111.9 112.4 102.6 107.8 102.2 914 99.3 101.2 104.6 108.4 112.7 112.5 102.6 108.6 103.2 916 99.0 101.2 104.8 108.6 112.1 112.2 102.7 108.8 102.8 918 98.4 100.9 104.1 107.3 110.9 111.6 102.3 108.0 101.8 920 97.8 100.2 102.9 106.1 110.5 110.9 101.4 106.9 100.8 922 97.2 99.3 102.1 105.7 109.8 109.6 100.8 105.8 99.9 924 97.0 98.9 102.3 105.7 109.6 109.0 100.9 105.4 100.2 926 97.3 99.0 102.5 105.4 109.6 109.9 100.9 105.9 101.0 928 97.2 99.2 102.4 104.8 109.1 111.0 100.7 106.0 101.0 930 96.5 99.1 102.5 104.7 108.8 111.1 100.7 106.1 100.6 932 95.9 98.9 102.2 105.0 108.8 110.5 100.3 106.2 100.6 934 96.1 98.6 102.0 105.5 109.4 110.4 100.3 106.3 100.9 936 95.9 98.0 101.6 105.6 109.2 110.1 100.5 105.9 100.4 938 95.1 97.1 101.4 105.5 108.7 109.6 100.3 105.6 99.7 940 94.4 96.7 100.9 104.3 107.9 108.5 99.6 105.0 98.8 942 94.3 96.3 100.6 103.2 107.9 108.2 99.5 104.8 98.4 944 93.7 95.9 99.8 101.9 106.5 107.6 98.7 103.5 97.8 946 92.8 95.0 98.3 100.3 104.5 106.4 97.3 101.6 96.8 948 92.3 94.1 97.2 99.2 103.6 105.5 96.3 100.8 96.1 950 92.6 94.3 97.4 99.9 104.4 105.6 96.0 101.4 96.2 952 92.1 94.2 97.3 100.6 104.4 105.3 95.6 101.3 95.6 954 91.1 93.6 96.8 100.4 103.6 104.7 95.4 100.8 95.0 956 91.1 93.4 97.2 100.5 103.5 105.1 95.8 101.3 95.7 958 91.6 93.6 97.6 100.3 103.9 105.6 96.5 102.1 96.3 960 91.3 93.3 97.1 99.8 103.7 105.2 96.5 102.0 95.9 962 91.2 92.5 97.1 99.6 103.7 104.7 95.9 101.7 95.4 964 90.9 92.0 96.4 99.1 103.0 104.2 95.0 100.9 94.8 966 90.3 91.8 95.3 98.5 102.1 103.5 94.4 100.1 93.8 968 89.9 91.4 95.8 98.2 101.7 103.1 94.3 99.8 93.4 970 89.1 90.7 95.6 96.9 100.8 102.1 93.4 98.4 92.9 972 88.1 90.1 93.7 95.3 99.5 101.0 92.1 96.7 92.1 974 87.3 89.3 92.8 94.7 98.5 100.4 91.1 96.1 91.4 976 86.7 88.6 92.7 94.5 97.9 99.8 90.7 96.0 90.7 978 86.8 88.7 92.2 94.7 98.5 100.1 91.2 96.6 90.9 980 86.9 88.7 92.2 94.5 98.8 100.7 91.5 96.9 91.5 982 86.2 88.4 92.9 94.0 98.4 100.4 91.3 96.2 91.3 984 85.1 87.5 93.0 93.5 97.8 99.5 90.5 95.2 90.6 986 84.4 86.9 92.4 93.2 97.4 99.1 89.5 94.5 90.2 988 83.9 86.0 91.2 92.5 96.4 98.4 88.7 93.4 89.1 990 82.9 85.1 89.7 91.5 95.2 97.1 88.1 92.4 87.8 992 81.6 84.1 88.1 90.4 93.8 95.4 87.0 90.9 86.9 994 80.3 82.9 86.7 88.8 92.5 93.7 85.6 89.1 85.9 996 78.7 81.2 84.8 86.6 90.4 91.9 84.2 87.7 84.1 998 76.8 79.2 82.3 84.1 87.4 89.4 81.9 86.1 81.4

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1000 75.0 77.3 79.9 81.7 84.6 86.6 79.3 84.0 79.0 1002 72.9 75.4 77.5 79.2 82.0 83.3 76.6 81.4 76.8 1004 70.6 73.0 74.6 76.3 79.4 80.0 73.9 78.5 74.2 1006 67.7 70.2 71.7 73.1 76.2 77.3 71.4 75.3 71.5 1008 64.5 67.3 69.0 70.1 72.7 74.5 68.7 71.9 68.9 1010 62.0 64.0 66.0 67.1 69.3 71.1 65.2 68.7 66.3 1012 59.2 60.8 62.7 64.1 66.1 67.6 61.9 66.3 63.7 1014 56.5 58.3 59.7 61.4 63.1 64.6 59.2 63.6 61.1 1016 53.7 55.9 57.3 58.4 60.6 62.0 57.1 60.5 57.8 1018 51.7 53.6 55.3 55.9 57.6 59.5 54.7 57.9 55.6 1020 50.6 51.7 53.6 53.8 55.3 56.7 53.2 56.0 54.0 1022 49.2 49.9 51.8 51.8 53.8 55.0 51.8 53.8 52.0 1024 47.7 48.6 50.2 50.5 53.0 53.7 50.4 52.1 50.2 1026 46.7 47.8 48.9 49.7 51.8 52.5 49.2 51.2 49.5 1028 46.4 47.1 48.6 48.8 50.5 51.1 48.4 50.2 49.0 1030 46.0 46.6 48.9 48.2 49.6 50.3 48.0 49.6 48.5 1032 44.9 45.9 48.0 47.6 48.6 49.7 47.1 49.1 47.5 1034 43.2 44.2 45.7 45.9 47.0 48.7 45.9 47.5 45.7 1036 41.2 41.8 43.4 43.2 44.9 46.8 44.2 45.0 43.4 1038 39.6 40.1 41.6 41.5 43.3 44.7 41.8 42.9 41.7 1040 42.5 42.8 44.1 44.6 46.1 46.9 43.5 45.7 44.3 1042 49.5 50.1 51.7 52.7 54.4 55.9 50.7 54.2 51.9 1044 52.0 53.3 55.6 56.9 59.1 60.8 54.4 58.7 55.7 1046 46.8 48.2 50.8 51.6 53.6 55.3 49.7 53.1 50.5 1048 40.4 41.2 43.2 43.7 44.8 45.9 42.7 44.9 43.1 1050 37.1 37.2 38.8 39.1 39.6 40.6 38.6 40.3 38.9 1052 35.7 35.6 37.6 37.2 38.0 38.8 36.8 38.6 37.2 1054 35.7 36.3 38.2 37.4 38.5 39.4 36.9 38.9 37.1 1056 37.1 37.9 39.4 39.4 40.6 41.5 38.6 40.8 38.6 1058 39.1 40.0 41.3 42.3 43.3 44.2 41.2 43.5 41.3 1060 42.7 43.5 45.0 46.2 47.0 48.3 44.6 47.4 45.2 1062 47.9 48.6 50.6 51.4 52.9 55.0 49.3 53.1 50.3 1064 53.5 54.4 57.0 57.6 59.6 61.4 55.5 59.3 56.0 1066 58.4 59.3 62.3 63.6 65.7 67.6 61.7 65.0 61.5 1068 62.7 63.9 66.9 68.8 71.0 73.5 66.7 70.3 66.8 1070 66.1 67.2 70.3 72.7 75.4 77.9 70.0 74.5 70.8 1072 67.2 68.4 71.2 73.6 76.3 78.8 70.5 75.4 71.6 1074 66.9 68.2 71.0 73.2 75.5 78.2 70.2 74.8 71.2 1076 67.0 68.1 71.2 73.4 76.1 78.9 70.6 75.1 71.5 1078 67.1 68.5 71.7 74.0 77.2 79.8 71.2 76.0 72.0 1080 66.8 68.5 71.9 74.3 77.5 79.9 71.3 76.4 72.2 1082 66.8 68.3 72.0 74.5 77.6 79.9 71.4 76.5 72.6 1084 67.0 68.4 71.8 74.2 77.5 79.8 71.5 76.3 72,7 1086 67.0 68.3 71.9 74.1 77.5 79.8 71.7 76.2 72.3 1088 66.6 67.5 71.5 73.9 77.0 79.2 71.5 75.7 71.6 1090 66.1 66.9 70.5 73.3 76.0 78. 1 70.9 74.6 70.9 1092 66.0 66.9 70.4 73.1 75.8 77.9 70.9 74.2 71.2 1094 66.1 67.3 71.4 73.9 76.5 78.5 71.3 74.7 72.2 1096 66.5 67.5 71.7 74.1 76.4 78.6 71.1 75.0 72.5 1098 65.9 66.7 70.4 72. 8 74.8 77.3 69.9 73.8 71.0

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1100 64.7 65.2 68.7 71.3 73.3 75.6 68.7 72.2 68.9 1102 64.3 64.7 68.0 71.0 73.2 75.2 68.3 71.8 68.3 1104 64.2 64.7 67.7 70.6 73.2 74.9 67.9 71.5 68.4 1106 63.5 64.0 67.5 69.5 72.6 73.9 67.2 70.9 67.7 1108 63.0 63.6 67.5 69.0 72.3 73.9 67.1 71.1 67.3 1110 62.9 63.7 67.3 69.4 72.6 74.3 67.5 71.7 67.7 1112 62.9 63.5 66.5 69.4 72.5 73.8 67.2 71.4 67.3 1114 63.0 63.8 66.4 69.6 72.7 74.1 66.9 71.3 67.0 1116 62.6 64.1 66.6 69.4 72.5 74.3 66.9 71.4 67.2 1118 61.1 62.9 65.7 67.7 70.6 72.3 65.8 69.6 66.0 1120 60.4 61.6 64.4 66.6 68.9 70.9 64.3 67.8 64.5 1122 60.8 61.5 63.8 66.9 69.0 71.4 64.1 67.7 64.4 1124 61.6 62.1 64.5 67.7 70.6 72.7 65.4 69.0 65.5 1126 61.4 62.2 65.2 68.3 71.4 73.3 66.4 69.6 65.7 1128 60.7 61.2 64.8 67.8 70.8 73.0 66.0 69.1 65.0 1130 60.3 61.2 63.8 67.1 69.9 72.3 64.7 68.5 64.7 1132 59.4 60.0 62.8 66.1 68.0 70.1 62.9 66.9 63.6 1134 57.3 58.1 60.9 63.7 64.5 66.0 60.3 63.8 60.5 1136 56.2 57.0 59.6 62.2 62.7 64.0 58.9 62.2 58.8 1138 57.1 57.9 60.4 63.5 64.4 66.3 60.2 63.6 60.4,~~~~~~i-i 1140 58.2 59.2 62.1 65.5 67.5 69.4 62.5 65.6 62.6 0 1142 58.1 59.4 62.8 66.1 68.8 70.1 63.2 66.0 63.1 1144 57.7 59.2 62.7 65.6 68.3 69.9 62.9 65.7 63.0 1146 57.2 58.3 62.2 64.1 67.1 69.1 61.8 64.7 62.2 1148 56.1 57.2 60.5 61.8 64.7 65.9 59.8 62.4 60.0 1150 55.4 56.3 59.0 60.4 62.6 63.0 58.5 60.8 58.5 1152 55.4 56.5 58.8 60.4 62.0 63.1 58.5 60.9 58.7 1154 55.7 57.1 59.8 61.6 63.3 65.5 59.7 62.3 60.1 1156 55.9 57.2 60.4 62.6 64.7 67.1 60.4 63.1 61.0 1158 55.9 57.1 60.2 62.6 64.7 66.5 59.9 62.9 60.8 1160 55.4 56.8 59.7 62.2 64.0 65.3 59.1 62.7 60.1 1162 54.3 55.7 58.6 60.9 62.8 64.0 58.2 61.9 58.6 1164 53.2 54.4 57.0 58.9 60.5 62.2 56.8 60.0 56.7 1166 53.2 54.3 56.7 58.5 59.6 61.7 56.3 59.3 56.3 1168 53.6 55.1 57.5 59.4 60.7 62.7 56.8 60.1 57.3 1170 53.1 54.4 57.0 59.1 60.7 62.5 56.6 59.6 57.3 1172 51.1 52.1 54.2 56.2 57.4 59.2 54.4 56.6 54.7 1174 49.5 50.6 51.9 53.8 54.5 56.2 52.2 54.3 51.9 1176 50.5 51.5 53.1 55.0 55.9 57.4 53.3 55.5 52.8 1178 52.4 53.2 55.7 57.5 58.8 60.2 55.8 57.8 55.6 1180 52.9 53.8 56.8 58.6 59.8 61.1 56.4 58.4 56.4 1182 52.2 53.3 56.3 58.1 59.2 60.5 55.7 57.7 55.4 1184 50.8 51.9 54.5 56.2 57.5 58.6 54.3 55.9 53.6 1186 49.5 50.5 52.7 54.1 55.2 56.2 52.6 53.8 51.7 1188 49.7 50.9 52.8 54.2 55.0 56.3 52.6 53.9 52.0 1190 51.0 52.0 54.2 56 560 56.7 58.7 53.8 55.9 54.1 1192 51.6 52.5 54.8 56.6 57.9 60.0 54.5 57.0 55.2 1194 51.4 52.1 54.4 56.2 57.8 59.5 54.2 56.6 54.6 1196 50.4 51.0 53.0 54.9 55.8 57.8 53.1 54.9 52.9 1198 49.5 50.0 52.0 54.0 54.0 56.6 52.4 53.6 51.9

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1200 49.9 50.6 52.7 54.8 55.0 57.5 53.1 54.5 53.0 1202 50.5 51.6 53.8 55.8 56.6 58.6 53.9 55.7 53.9 1204 50.6 51.3 53.4 55.3 56.4 58.5 53.9 55.4 53.6 1206 50.1 50.4 52.2 54.1 55.4 57.4 53.3 54.3 52.7 1208 48.6 48.8 50.5 52.2 53.7 55.2 51.7 52.3 50.8 1210 46.4 46.2 47.7 49.2 50.0 51.3 48.8 48.9 47.9 1212 45.2 44.9 46.2 47.5 47.5 48.7 46.7 46.9 46.6 1214 45.8 45.9 47.1 48.6 48.7 49.8 47.3 48.1 47.8 1216 46.1 46.5 47.6 49.2 49.8 50.7 48.0 49.1 48.2 1218 45.5 45.5 47.0 48.2 48.5 49.6 47.1 48.3 47.2 1220 45.0 44.8 46.7 47.5 47.6 48.7 46.4 47.8 46.6 1222 44.7 44.3 46.2 47.1 47.4 48.7 46.3 47.5 46.0 1224 43.9 43.6 45.1 45.9 46.1 47.6 45.5 46.2 44.7 1226 44.0 44.0 45.4 46.4 46.6 48.0 45.5 46.2 45.2 1228 45.2 45.3 47.0 48.4 49.1 50.5 46.7 48.0 47.2 1230 46.1 46.1 48.2 49.8 50.7 52.2 47.6 49.4 48.3 1232 46.0 46.1 48.4 50.1 50.7 52.4 48.1 49.7 48.5 1234 44.8 45.3 47.1 48.9 49.6 51.2 47.3 48.5 47.0 1236 43.4 43.7 45.0 46.7 47.5 49.0 45.2 46.4 44.6 1238 42.3 42.4 43.2 44.7 45.3 46.6 43.4 44.5 43.0.- 1240 41.2 41.0 41.8 43.0 43.5 44.6 42.2 42.8 41.8 1242 39.2 38.9 39.6 40.6 41.2 42.2 40.2 40.6 39.6 1244 37.4 37.3 37.9 38.8 39.2 40.3 38.4 39.2 38.1 1246 37.5 37.5 38.5 39.2 39.3 40.6 38.5 39.5 38.5 1248 38.4 38.3 39.6 40.4 40.4 41.6 39.6 40.5 39.4 1250 38.1 38.1 39.4 40.4 40.6 41.6 39.4 40.4 39.3 1252 36.7 36.6 37.9 38.8 38.8 39.8 37.8 38.7 37.6 1254 35.4 35.2 2 362 36.7 36.5 37.7 36.1 36.5 36.0 1256 34.1 33.7 34.3 34.7 34.6 36.0 34.6 34.6 34.5 1258 31.6 31.0 31.1 31.2 31.6 33.0 31.8 31.4 31.7 1260 28.0 28.3 28.6 28.3 29.0 29.3 29.0 29.2 28.5 1262 27.2 27.5 27.7 27.4 28.0 27.8 28.0 28.1 27.5 1264 27.2 27.2 27.8 27.4 27.8 27.5 27.7 27.7 27.5 1266 25.9 25.7 26.6 25.9 26.2 26.3 26.7 26.3 26.3 1268 23.8 23.8 24.6 23.9 24.0 24.6 25.3 24.6 24.6 1270 22.8 23.0 23.4 23.2 23.0 23.5 24.2 23.7 23.8 1272 23.7 24.0 24.3 24.5 24.0 24.4 24.5 24.9 24.5 1274 25.6 25.6 26.2 26.6 26.1 26.6 25.9 26.8 26.0 1276 27.0 26.9 27.6 27.9 27.5 28.2 27.2 27.7 27.4 1278 27.4 27.4 28.2 28.2 27.8 29.0 27.6 27.8 28.0 1280 27.1 27.1 28.0 27.6 27.5 28.3 27.3 27.7 27.6 1282 26.6 26.7 27.4 27.1 27.0 27.4 26.9 27.3 27.0 1284 26.6 26.7 27.3 27.1 27.0 27.4 27.0 27.3 27.4 1286 26.2 26.0 26.5 26.3 26.2 27.1 26.5 26.5 26.9 1288 24.9 24.6 25.0 24.9 24.9 25.7 25.1 24.9 25.2 1290 24.4 24.4 24.6 24.6 24.8 25.2 24.7 24.4 24.8 1292 24.3 24.3 25.0 24.7 24.9 25.3 24.5 24.8 24.9 1294 23.4 23.1 24.1 23.4 23.5 24.0 23.1 23.9 23.5 1296 22.2 21.7 22.5 21.8 21.8 22.1 21.6 22.5 21.9 1298 21.2 20.9 21.4 21.0 21.1 21.2 21.0 21.5 21.2

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1300 19.8 19.5 20.2 19.8 20.1 20.2 19.8 20.1 19.9 1302 17.8 17.3 17.9 17.6 17.7 17.6 17.6 17.9 17.6 1304 16.5 16.1 16.5 16.1 15.9 15.6 16.6 16.5 16.4 1306 17.9 17.9 18.2 17.5 17.3 17.2 18.5 18.2 18.3 1308 21.1 21.2 21.7 20.9 20.6 20.9 22.0 21.7 21.8 1310 22.7 22.5 23.5 22.7 22.3 23.0 23.8 23.7 23.5 1312 22.1 21.8 22.9 21.9 21.7 23.0 23.7 23.4 23.1 1314 21.5 21.3 22.0 21.1 21.0 22.7 23.2 23.0 22.7 1316 21. 21.1 21.8 21.0 21.0 22.6 23.0 22.9 22.8 1318 20.8 20.9 21.7 21.0 20.8 22.4 22.7 22.7 22.5 1320 21.6 21.6 22.4 21.7 21.4 22.6 22.9 23.3 22.8 1322 23.0 23.4 24.4 23.4 23.3 24.0 24.3 25.1 24.9 1324 25.4 25.0 26.7 26.0 26.4 26.7 26.2 26.8 26.2 1326 25.7 25.3 26.4 26.0 26.3 27.1 26.0 26.7 26.3 1328 25.3 25.1 25.7 25.6 25.7 26.7 25.3 26.3 25.4 1330 24.9 24.7 25.2 25.3 24.7 25.9 25.1 25.8 25.1 1332 23.9 23.8 24.0 23.4 23.5 24.9 24.3 24.6 24.3 1334 21.7 21.9 22.4 21.8 21.7 22.4 22.9 22.8 22.5 1336 19.5 19.3 20.1 19.6 19.6 20.2 21.0 21.1 20.7 1338 17.6 17.1 18.1 17.4 17.6 18.1 18.7 19.2 18.7 1,0~-'~* ~1340 17.1 16.9 17.8 16.9 17.2 17.6 17.9 18.5 18.1 N^~~~3~~~ ~~1342 18.5 18.5 19.2 18.7 18.7 19.1 19.3 19.8 19.4 1344 20.5 20.5 21.1 20.8 20.5 21.0 21.2 21.7 21.2 1346 20.8 21.0 21.5 21.2 20.9 21.2 21.4 22.1 21.3 1348 19.9 20.3 20.7 20.3 20.4 20.4 20.8 21.4 20.6 1350 19.9 19.8 20.2 19.9 20.1 20.2 20.7 21.2 20.7 1352 20.3 19.8 20.3 20.0 20.1 20.5 20.7 21.5 21.0 1354 19.8 19.4 20.1 19.6 19.7 20.2 20.3 21.3 20.7 1356 19.1 1 191 19.6 193 1919.3 20.0 20.3 20.9 20.4 1358 18.7 18.8 19.2 19.1 18.7 20,0 20.0 20.3 19.9 1360 17.4 17.6 18.1 18.0 17.5 19.2 18.6 19.0 18.5 1362 16.3 16.6 17.1 16.8 16.3 18.2 17.5 18.1 17.7 1364 16.8 17.0 17.5 17.1 16.8 18.5 18.1 18.6 18.6 1366 17.8 17.8 18.5 18.1 18.0 19.3 19.0 19.4 19.6 1368 17.8 17.7 18.3 18.3 18.1 19.4 19.0 19.6 19.3 1370 17.4 17.2 17.5 17.5 17.2 19.0 18.4 19.0 18.9 1372 16.4 16.4 16.7 16.3 16.2 17.8 17.3 17.9 18.1 1374 15.3 15.7 15.8 15.4 15.6 16.6 16.2 17.1 17.0 1376 15.6 16.0 16.2 15.9 16.1 17.0 16.8 17.7 17.4 1378 16.9 17.1 17.6 17.2 17.3 18.2 18.3 18.9 18.6 1380 17.6 17.9 18.7 17.9 18.0 18.9 19.3 20.6 19.3 1382 17.8 18.1 18.8 17.9 18.0 19.2 19.6 21.0 19.6 1384 17.1 17.5 17.9 17.2 17.2 18.5 18.9 20.2 19.1 1386 15.4 16.1 16.6 16.1 15.7 17.0 17.4 18.0 17.5 1388 14.3 15.4 15.9 15.4 15.0 16.5 16.6 17.2 16.4 1390 14.5 15.2 15.5 15.3 15.3 16.6 16.5 17.3 16.4 1392 14.2 14.5 14.8 15.2 15.1 15.9 16.0 16.9 15.9 1394 12.9 13.4 13.7 14.5 13.7 14.5 14.9 15.6 14.5 1396 11.8 12.7 13.1 13.7 13.0 13.5 14.3 14.8 13.8 1398 12.0 12.7 13.4 13.8 13.6 13.6 14.5 15.0 14.4

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1400 13.1 13.5 14.4 14.8 14.7 14.7 15.2 15.9 15.2 1402 13.8 14.2 15.3 15.4 15.4 15.5 15.7 16.5 15.7 1404 13.9 14.5 15.3 15.3 15.6 15..715.7 16.6 16.0 1406 14.2 14.8 15.1 15.2 15.5 16.2 16.0 17.1 16.5 1408 14.8 15.3 15.3 15.6 15.5 16.8 16.8 17.8 16.9 1410 14.8 15.1 15.3 15.5 15.1 16.7 16.9 17.4 16.7 1412 14.2 14.5 14.9 15.0 14.6 16.2 16.1 16.6 16.3 1414 13.3 13.8 14.2 14.5 14.0 15.3 14.9 15.8 15.6 1416 11.7 12.3 12.7 13.2 12.9 13.8 12.8 14.1 13.9 1418 10.4 10.9 11.0 11.6 11.5 12.1 10.9 12.5 12.3 1420 10.3 10.6 10.7 11.4 11.0 11.4 10.6 12.2 12.1 1422 10.7 11.2 11.2 11.9 11.2 12.0 11.4 12.7 12.7 1424 11.2 11.8 12.0 12.5 11.6 12.9 12.5 13.4 13.4 1426 11.7 12.0 12.4 12.8 11.9 12.9 13.2 13.8 13.6 1428 11.6 11.9 12.3 12.6 11.7 12.3 13.0 13.6 13.2 1430 10.9 11.4 11.8 11.8 11.3 11.9 12.2 13.0 12.5 1432 10.4 11.0 11.6 11.4 11.4 11.6 11.8 12.6 12.3 1434 10.1 10.6 11.1 11.2 11.2 11.0 11.3 12.1 11.8 1436 9.9 10.4 10.7 10.8 10.6 10.9 10.9 11.7 11.4 1438 10.1 11.0 11.0 11.3 10.9 11.7 11.6 12.3 11.9 l-~='~~ ~1440 10.9 12.2 12.1 12.7 12.3 13.1 12.8 13.5 13.1 CJ3 1442 11.4 12.4 12.6 13.3 13.0 13.8 13.2 13.9 13.7 1444 11.2 11.8 12.3 12.7 12.4 13.5 12.8 13.3 13.4 1446 10.3 11.0 11.4 11.6 11.3 12.4 11.7 12.1 12.1 1448 9.5 10.3 10.4 10.7 10.7 11.2 10.8 11.1 10.8 1450 9.1 9.6 9.4 10.2 10.2 10.7 10.5 10.5 10.4 1452 8.7 9.1 8.9 9.7 9.4 10.3 10.2 9.9 10.1 1454 7.5 8.3 8.2 8.8 8.2 9.2 8.8 8.8 8.9 1456 6.2 6.9 6.9 7.6 6.8 7.8 6.8 7.1 7.5 1458 6.2 6.4 6.8 7.2 6.6 7.6 6.4 6.9 7.0 1460 7.2 7.2 8.0 8.3 7.9 8.5 7.7 8.2 7.9 1462 7.7 7.8 8.9 9.2 8.9 9.2 8.8 8.9 8.7 1464 7.3 7.5 8.7 8.9 8.6 8.9 8.6 8.8 8.6 1466 7.2 7.6 8.4 8.7 8.5 8.8 8.3 9.1 8.8 1468 7.5 8.1 8.4 9.0 8.8 9.1 8.6 9.4 9.1 1470 7.0 7.6 7.9 8.3 8.0 8.7 8.1 8.5 8.2 1472 6.4 6.7 7.1 7.2 7.0 7.9 7.1 7.4 7.2 1474 6.2 6.3 6.8 6.9 6.7 7.5 6.8 6.9 6.8 1476 6.6 6.9 7.6 7.8 7.4 8.1 7.7 7.8 7.4 1478 7.4 8.1 8.7 8.5 8.6 9.0 8.9 9.1 9.0 1480 7.8 8.6 8.8 8.5 8.9 9.2 9.5 9.6 9.8 1482 7.7 8.6 8.5 8.5 8.5 8.9 9.3 9.2 9.4 1484 7.2 8.1 7.9 8.2 7.7 8.2 8.5 8.4 8.6 1486 6.1 6.9 7.1 7.3 6.6 7.1 7.6 7.5 7.6 1488 4.9 5.8 6.1 6.3 5.5 6.0 6.7 6.2 6.2 1490 4.9 5.8 6.0 6.3 5.7 5.9 6.3 5.7 5.8 1492 5.2 6.4 6.3 6.6 6.3 6.1 6.6 6.3 6.3 1494 4.8 6.3 6.3 6.5 6.2 5.8 6.7 6.6 6.4 1496 3.9 5.6 6.0 5.6 5.5 5.0 5.4 5.7 5.9 1498 3.9 5.2 6.1 5.2 5.3 4.8 4.7 4.7 5.5

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1500 4.4 5.5 6.0 5.6 5.6 5.0 5.3 4.6 5.5 1502 4.5 5.3 5.5 5.6 5.3 4.8 6.0 4.7 5.2 1504 4.0 4.5 4.7 4.9 4.6 4.0 5.2 4.3 4.6 1506 3.3 3.7 4.0 3.9 3.8 3.4 3.7 3.5 3.8 1508 3.3 3.7 4.3 3.4 3.8 3.8 3.3 3.2 3.5 1510 4.0 4.5 5.0 3.7 4.4 4.5 4.3 3.8 3.9 1512 4.4 5.0 5.1 4.0 4.2 4.3 5.3 4.1 4.4 1514 4.0 4.9 5.0 3.7 3.3 3.6 5.6 3.4 4.2 1516 3.2 4.3 4.6 3.4 2.5 2.7 5.4 2.7 3.2 1518 2.6 3.6 3.9 3.3 2.2 2.6 4.7 2.4 2.9 1520 2.6 3.3 3.0 3.4 2.2 2.9 3.6 1.9 3.0 1522 2.8 3.3 2.7 3.4 2.7 2.7 3.4 2.1 2.7 1524 2.8 3.5 3.1 3.5 2.9 2.5 3.9 2.8 3.0 1526 2.8 3.9 3.7 3.6 3.0 3.0 4.4 2.8 3.8 1528 3.1 4.3 3.9 3.6 3.3 4.0 4.6 2.8 4.4 1530 3.2 4.3 4.1 3.3 3.6 4.0 4.7 3.1 4.3 1532 3.2 3.9 3.8 2.8 3.5 3.0 4.2 3.1 3.8 1534 3.1 3.3 3.1 2.6 3.3 2.2 3.6 2.7 3.0 1536 2.8 2.9 2.4 2.4 3.4 2.0 3.2 2.4 2.6 1538 2.4 2.3 2.0 1.8 2.8 1.7 2.6 1.9 2.1 -- 1540 2.1 1.9 2.1 1.4 1.8 1.3 2.2 1.4 1.6 cF^~~~~~~P ~1542 2.1 2.3 2.6 1.9 2.1 1.5 2.8 1.6 2.1 1544 2.2 3.0 3.2 2.7 2.8 1.8 3.9 2.4 2.9 1546 2.7 3.6 4.1 3.5 3.6 2.6 4.9 3.4 3.6 1548 3.0 3.9 4.3 3.8 4.0 3.1 5.0 3.7 3.8 1550 2.9 3.8 3.8 3.6 4.0 3.1 4.6 3.2 3.5 1552 2.7 3.4 3.3 3.3 3.7 2.9 4.3 2.6 3.2 1554 2.5 3.0 2.7 2.8 3.3 2.6 3.8 2.0 2.9 1556 1.7 2.3 2.1 2.1 2.5 2.2 3.0 1.3 2.2 1558 1.2 1.9 2.1 1.8 2.1 1.8 2.7.8 1.5 1560 1.6 2.4 2.6 2.1 2.5 1.9 3.4 1.5 1.8 1562 2.6 3.3 3.3 2.8 3.4 2.5 4.4 2.8 3.0 1564 3.4 3.9 3.9 3.4 3.9 3.2 5.1 3.6 4.1 1566 3.5 4.1 4.0 3.6 3.8 3.6 5.0 3.6 4.5 1568 3.1 4.1 3.7 3.3 3.5 3.4 4.4 3.3 4.0 1570 2.9 4.1 3.7 3.1 3.7 3.5 4.1 3.3 3.6 1572 2.9 4.1 3.7 3.2 3.9 3.7 4.3 3.4 3.7 1574 2.7 3.7 3.3 3.4 3.6 3.5 4.5 3.2 3.6 1576 2.8 3.5 3.3 3.5 3.4 3.4 4.5 3.2 3.5 1578 3.6 4.1 3.8 3.9 4.0 4.0 5.0 4.0 4.3 1580 4.2 5.0 4.6 4.5 5.0 5.0 5.9 5.1 5.5 1582 4.4 5.4 5.2 4.9 5.5 5.9 6.5 5.7 6.0 1584 4.7 5.5 5.4 4.9 5.6 6.0 6.9 6.0 6.0 1586 5.1 5.7 5.8 4.9 5.9 5.8 7.3 6.3 6.2 1588 5.2 5.9 5.8 4.9 6.0 5.9 7.4 6.3 6.3 1590 4.9 5.7 5.5 4.8 5.7 6.0 7.1 6.0 6.3 1592 4.6 5.5 5.5 4.6 5.4 5.9 6.6 5.8 6.0 1594 4.5 5.1 5.6 4.7 5.3 5.6 6.4 5.7 5.7 1596 4.5 4.9 5.3 4.8 5.2 5.6 6.6 5.6 5.6 1598 4.5 5.0 5.1 4.9 5.1 5.8 6.7 5.7 5.4

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1600 4.5 5.1 5.3 4.9 5.3 6.0 6.6 5.8 5.5 1602 4.4 5.0 5.3 4.8 5.3 5.9 6.3 5.6 5.7 1604 4.2 4.7 5.3 4.6 5.1 5.6 6.1 5.1 5.6 1606 4.0 4.6 4.9 4.3 4.9 5.3 6.0 4.4 5.1 1608 3.9 4.6 4.3 3.8 4.8 5.0 5.7 4.1 4.6 1610 4.0 4.5 4.1 3.5 4.6 4.6 5.4 4.5 4.4 1612 3.8 4.4 4.2 3.4 4.3 4.6 5.5 4.7 4.4 1614 3.3 4.0 3.8 3.3 4.0 4.5 5.2 4.4 4.0 1616 3.0 3.5 3.4 3.0 3.7 3.8 4.2 4.0 3.6 1618 2.8 3.4 3.2 2.6 6 36 3.6 4.0 3.9 3.5 1620 2.6 3.5 3.4 2.8 3.7 4.0 4.8 3.7 3.8 1622 2.3 3.6 3.4 3.0 3.7 3.9 5.1 3.3 3.8 1624 2.6 3.7 3.7 2.9 3.6 3.5 4.6 3.5 3.8 1626 3.1 3.9 3.9 3.2 3.7 3.9 4.5 4.4 3.8 1628 3.2 4.0 3.7 3.4 3.9 4.6 4.8 4.8 3.8 1630 3.2 3.9 3.8 3.0 4.0 4.6 4.9 4.7 4.0 1632 3.1 3.8 4.0 2.8 4.2 4.4 4.5 4.3 4.1 1634 2.8 3.4 3.4 2.8 3.8 4.0 3.8 3.7 3.7 1636 2.3 2.7 2.6 2.4 3.1 3.4 3.3 3.3 3.0 1638 2.3 2.7 2.8 2.1 3.1 3.0 3.5 3.7 3.1,-a 1640 2.8 3.1 3.3 2.6 3.7 3.4 4.4 4.5 3.8 C. 1642 2.8 3.2 3.6 2.6 3.7 4.0 4.9 4.6 4.0 1644 2.5 2.9 3.4 1.9 3.1 4.1 4.4 4.2 3.8 1646 2.2 2.6 3.0 1.8 2.7 3.8 3.6 3.6 3.4 1648 2.1 2.4 2.9 2.1 2.7 3.6 3.1 3.2 3.1 1650 2.1 2.3 2.8 2.3 3.0 3.3 3.0 3.3 3.0 1652 2.1 2.0 2.5 2.6 3.0 3.2 3.0 3.6 2.9 1654 2.0 2.2 2.6 3.0 3.0 3.4 3.1 3.7 2.8 1656 2.3 2.9 3.2 3.4 3.4 4.0 3.6 4.2 3.1 1658 2.8 3.6 3.9 3.8 3.7 4.9 4.3 4.8 3.6 1660 2.9 3.6 4.1 3.7 3.6 5.1 4.7 4.6 3.9 1662 2.8 3.6 4.0 3.3 3.4 4.6 4.6 4.1 3.9 1664 3.0 3.6 4.0 3.2 3.7 4.5 4.7 4.1 4.0 1666 3.1 3.5 4.1 3.2 3.9 4.8 4.6 4.4 3.9 1668 2.7 3.1 3.9 3.0 3.7 4.5 3.9 4.0 3.4 1670 1.9 2.7 3.3 2.7 3.5 3.8 3.3 3.6 3.0 1672 1.7 2.7 2.9 2.4 3.5 3.7 3.5 3.8 3.0 1674 2.2 2.9 3.0 2.3 3.5 4.2 3.9 4.1 3.0 1676 2.4 2.9 3.5 2.6 3.7 4.7 4.2 4.3 3.3 1678 2.6 3.0 3.7 3.0 4.0 4.9 4.3 4.5 3.9 1680 2.6 3.1 3.4 2.9 3.9 4.7 4.0 4.4 4.0 1682 2.3 2.7 3.1 2.5 3.4 4.2 3.5 3.9 3.2 1684 1.9 2.4 2.9 2.0 3.2 3.8 3.4 3.7 2.6 1686 2.1 2.5 3.0 2.3 3.6 4.0 3.6 4.2 3.1 1688 2.6 2.9 3.4 3.0 3.7 4.4 3.9 4.5 3.5 1690 2.8 3.0 3.9 3.2 3.9 4.6 4.0 4.4 3.5 1692 2.6 3.0 3.9 3.2 4.2 5.6 4.0 4.3 3.5 1694 2.3 2.6 3.3 2.8 4.1 4.2 3.6 4.1 3.2 1696 1.9 2.3 2.9 2.3 3.5 3.6 2.7 3.4 2.7 1698 1.6 2.2 2.8 2.3 3.2 3.3 2.4 2.9 2.8

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1700 1.7 2.1 2.6 2.4 3.3 3.2 2.8 3.0 2.9 1702 1.8 2.0 2.7 2.5 3.6 3.3 3.1 3.5 2.8 1704 1.8 2.3 2.9 2.8 3.7 3.5 3.1 3.9 2.8 1706 2.1 2.6 3.1 2.8 3.7 3.8 3.4 4.1 3.1 1708 2.2 2.8 3.5 2.6 3.7 4.3 3.8 4.3 3.4 1710 2.3 2.9 3.9 3.0 4.9 5.5 4.1 4.7 3.5 1712 2.6 2.9 3.8 3.4 4.7 5.8 4.0 4.8 3.7 1714 2.6 2.6 3.3 3.2 3.6 5.9 3.7 4.5 3.5 1716 2.3 2.4 3.0 2.7 3.7 5.4 3.3 4.2 3.1 1718 2.3 2.7 3.2 2.8 5.1 4.9 3.5 4.3 3.2 1720 2.6 3.0 3.7 3.2 6.0 5.9 3.9 4.7 3.7 1722 2.5 3.2 4.1 3.4 6.1 6.4 4.5 5.8 4.1 1724 2.5 3.4 4.1 3.8 6.1 6.6 4.8 6.2 4.6 1726 2.6 3.5 3.8 4.0 5.2 6.6 5.6 5.9 4.7 1728 2.5 3.3 3.4 3.8 5.0 6.5 5.3 5.6 4.1 1730 2.5 3.0 3.4 3.4 4.7 6.2 5.0 5.4 4.4 1732 2.5 2.8 3.2 3.0 3.5 5.2 3.5 5.1 4.1 1734 2.3 2.4 3.0 2.7 3.4 3.5 2.9 4.1 4.0 1736 2.0 2.2 3.3 2.6 3.6 3.7 2.5 5.0 2.7 1738 1.9 2.2 3.7 2.8 3.4 5.6 2.9 4.9 2.5,..^~~~~~~ * 1740 1.9 2.4 3.5 3.0 4.3 4.4 3.2 3.9 2.6 0m 1742 2.0 2.5 3.5 2.8 4.3 5.6 3.2 3.9 2.8 1744 2.0 2.7 3.7 2.8 5.1 5.8 3.3 4.3 3.0 1746 1.9 2.6 3.4 2.7 4.1 5.7 3.3 4.2 3.1 1748 1.7 2.3 2.8 2.3 3.8 5.4 3.1 3.4 2.9 1750 1.9 2.3 2.5 2.4 3.5 5.3 3.3 3.1 2.8 1752 2.3 2.9 3.0 2.8 3.7 5.5 3.7 3.6 3.0 1754 2.5 3.2 3.4 2.8 4.5 4.8 4.7 3.9 3.3 1756 2.6 2.9 3.2 2.7 3.8 4.8 4.5 4.4 3.4 1758 2.7 2.9 3.0 2.7 3.6 5.0 3.1 4.6 3.4 1760 2.7 3.1 3.2 2.8 4.3 5.0 3.1 4.5 3.0 1762 2.5 3.1 3.4 3.0 4.8 4.8 3.4 3.9 3.0 1764 2.7 2.9 3.4 3.1 4.9 4.7 4.0 4.8 3.4 1766 2.8 3.2 3.0 2.9 4.5 4.6 2.9 4.9 3.4 1768 2.3 3.0 2.7 2.6 3.4 3.6 2.6 4.0 2.8 1770 1.9 2.7 2.5 2.3 3.0 3.2 2.3 3.4 2.3 1772 1.8 2.7 2.4 2.4 2.9 3.2 2.1 3.2 2.5 1774 2.1 2.6 2.6 2.7 3.1 3.7 2.4 3.4 3.0 1776 2.6 2.9 3.2 3.1 3.4 3.9 3.2 4.0 3.3 1778 2.7 2.9 3.5 3.3 3.3 4.2 3.7 3.9 3.3 1780 2.6 2.8 3.4 3.2 3.3 4.4 3.6 4.0 4.2 1782 2.6 3.1 3.2 3.0 4.1 4.5 3.5 3.6 3.3 1784 2.6 3.4 3.3 2.9 5.2 4.5 3.7 3.7 3.1 1786 2.7 3.4 3.4 3.2 4.7 5.0 4.4 3.5 3.3 1788 2.8 3.0 3.3 3.4 4.6 5.2 3.7 3.3 3.4 1790 2.4 2.5 2.5 3.2 3.2 4.6 2.9 3.1 3.0 1792 1.9 2.0 2.0 2.8 2.5 3.8 2.3 2.6 2.5 1794 1.9 2.2 2.4 3.0 2.6 2.7 2.5 2.4 3.4 1796 2.1 2.6 2.9 3.3 3.3 3.0 2.7 2.7 2.5 1798 2.1 2.7 2.8 3.1 3.5 3.9 3.6 2.8 2.4

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1800 2.0 2.6 2.7 3.1 3.3 4.1 3.4 2.5 2.7 1802 2.1 2.6 2.7 3.4 3.2 3.7 3.0 2.5 2.8 1804 2.5 2.9 2.9 3.5 3.3 3.7 3.2 2.8 2.9 1806 3.0 3.0 3.2 2 32 3.5 4.3 3.4 3.8 3.2 1808 3.1 3.2 4.1 3.0 3.4 4.0 3.5 2.8 3.2 1810 3.5 2.7 4.2 2.8 3.2 3.5 3.2 2.7 3.3 1812 2.9 3.2 4.3 3.2 2 3 3.4 3.3 3.7 3.7 1814 3.1 3.4 3.5 3.7 3.4 3.8 3.6 3.2 4.3 1816 3.1 3.7 3.5 3.8 3.3 4.0 3.6 3.0 3.8 1818 2.8 3.3 3.3 3.5 3.0 3.9 3.6 2.8 3.4 1820 2.7 2.7 3.2 3.1 2.6 4.0 3.4 2.7 3.2 1822 2.4 2.4 3.1 2.8 2.4 3.5 2.7 2.5 3.1 1824 2.1 2.4 2.9 2.9 2.4 3.2 2.3 2.3 2.9 1826 2.0 2.2 2.7 2.9 2.5 3.3 2.3 2.3 2.7 1828 1.9 2.0 2.7 2.6 2.3 3.3 2.6 2.4 2.4 1830 1.9 2.0 2.6 2.4 2.1 3.4 2.9 2.6 2.3 1832 2.1 2.3 2.6 2.3 3.0 2.8 2.8 3.3 2.4 1834 2.1 2.8 2.5 2.3 4.1 3.6 2.8 3.3 2.7 1836 1.8 2.3 2.2 2.2 4.2 4.0 3.0 2.8 2.5 1838 2.0 2.0 2.1 2.1 3.5 2.8 3.0 1.8 2.2 1840 2.0 1.7 2.1 2.0 3.1 3.0 2.5 1.8 2.4 ~ —,]~3 ~1842 1.6 1.4 1.9 1.6 2.8 3.1 2.0 1.6 2.1 1844 1.4 1.4 1.9 1.3 2.9 3.0 2.1 1.2 1.9 1846 1.6 2.1 2.3 1.4 3.3 2.0 2.5 1.3 1.9 1848 2.1 2.4 2.5 1.7 3.6 2.5 2.8 1.9 2.2 1850 2.6 2.4 2.7 2.2 4.5 2.9 3.1 2.3 2.7 1852 2.8 2.8 3.0 2.5 3.9 2.8 3.1 2.5 3.4 1854 2.7 2.6 3.2 2.2 3.2 2.5 3.0 2.5 3.4 1856 2.8 2.4 3.2 2.1 3.0 2.5 3.0 2.1 3.2 1858 2.7 2.6 3.2 2.8 3.4 2.6 3.1 1.9 3.1 1860 1.9 2.7 3.2 3.0 3.7 3.3 2.8 2.0 3.1 1862 1.8 2.7 3.1 2.5 4.1 3.3 2.6 2.0 2.8 1864 1.8 2.2 3.2 2.2 3.1 3.1 2.6 1.7 2.2 1866 1.5 1.7 3.1 1.5 2.5 3.4 2.3 1.5 1.5 1868 1.9 2.0 3.1.9 1.7 2.6 1.7 1.5 1.6 1870 1.9 2.1 3.2 1.1 2.2 2.9 2.2 1.4 2.1 1872 1.8 2.9 3.2 2.6 3.8 3.5 2.9 1.8 2.4 1874 2.1 3.2 3.4 2.6 4.7 4.2 3.0 2.8 2.6 1876 3.6 3.2 4.0 2.8 4.6 4.4 3.1 2.6 3.0 1878 3.6 3.2 3.9 3.1 4.5 4.1 3.4 2.9 3.2 1880 3.7 3.2 3.3 2.8 4.5 3.8 3.8 3.7 3.3 1882 2.3 3.0 3.2 2.7 4.5 4.0 3.5 3.6 3.2 1884 1.9 2.8 2.9 2.2 4.1 4.2 3.2 2.7 2.9 1886 1.8 2.8 2.8 2.3 4.1 3.9 3.3 2.8 2.7 1888 1.6 2.4 2.7 2.3 3.3 3.5 2.7 2.2 2.8 1890 1.6 2.3 3.2 2.1 3.5 3.5 2.4 2.0 2.8 1892 2.1 2.2 3.3 2.3 3.8 3.9 2.5 2.2 2.4 1894 2.1 2.5 3.6 3.7 4.4 4.0 3.0 2.4 2.8 1896 2.5 3.2 3.3 4.2 3.8 3.5 3.5 2.3 2.9 1898 2.6 3.4 3.2 3.8 3.8 3.2 3.7 2.5 3.8

SPECTRAL RADIANCE IN ERGS/SEC CM STR TIME — IN EASTERN STANDARD TIME — MAY 8, 1966 08 30 09 10 10 06 11 09 12 34 13 31 14 12 14 48 15 11 WAVE NO 1900 3.7 3.4 3.3 3.1 4.2 3.7 3.5 2.4 3.8 1902 3.3 3.2 2.8 2.8 4.2 4.2 2.9 3.3 3.3 1904 3.3 3.0 3.0 3.2 4.4 4.4 3.3 2.8 3.0 1906 3.1 2.9 2.8 3.2 4.4 4.5 3.7 2.3 2.8 1908 1.8 2.7 2.7 2.8 3.9 4.3 4.1 2.7 2.9 1910 1.6 2.4 2.7 3.0 3.7 4.0 3.8 3.8 3.0 1912 1.5 2.4 2.9 2.8 3.9 3.7 3.4 3.9 3.0 1914 1.6 2.5 2.6 2.8 3.5 3.9 3.3 3.8 3.0 1916 1.4 2.5 2.4 2.3 3.0 4.0 3.3 3.9 3.1 1918 1.3 2.3 2.5 1.9 3.0 3.3 2.9 3.9 3.0 1920 1.5 2.6 2.6 2.0 3.9 2 2.5 3.9 2.7 1922 3.1 3.0 2.9 2.0 4.3 3.9 2.7 4.0 2.9 1924 3.2 3.3 3.1 2.1 4.4 4.4 3.0 4.3 3.8 1926 4.0 3.7 3.4 3.0 4.4 4.4 3.7 4.4 3.9 1928 4.0 3.7 3.7 3.4 4.3 4.5 4.0 4.3 3.7 1930 3.8 3.6 3.9 3.4 4.3 4.7 4.1 4.3 3.7 1932 3.8 3.4 3.9 3.7 4.6 4.6 4.1 4.5 3.8 1934 4.1 3.2 3.2 4.0 4.8 4.6 4.1 4.5 3.8 1936 4.1 3.3 3.8 4.3 4.5 4.8 4.3 4.3 3.6 1938 3.7 3.4 3.8 4.1 4.1 4.6 4.3 4.0 3.5 I~~,_ -.'~~~ 1940 3.6 3.4 2.9 3.7 4.0 4.3 4.0 3.9 3.3 00 1942 3.7 3.1 3.0 3.7 4.1 4.3 3.7 4.0 3.1 1944 3.7 3.1 3.1 4.0 4.1 4.7 3.6 4.5 3.0 1946 3.8 3.3 2.9 4.1 4.2 4.9 3.9 5.0 3.0 1948 4.0 3.7 3.1 4.1 4.4 4.8 4.0 5.3 3.3 1950 4.2 3.9 3.6 4.3 4.4 5.0 4.0 5.5 3.7 1952 4.3 3.6 3.7 4.4 4.5 5.4 4.1 5.5 3.8 1954 4.2 3.5 3.5 4.2 4.8 5.4 4.3 5.3 4.1 1956 4.3 3.9 3.6 4.1 4.9 5.4 4.4 5.3 4.4 1958 4.5 4.1 3.6 4.1 4.5 5.3 4.3 5.5 4.6 1960 4.4 3.8 3.6 4.0 4.2 4.8 4.0 5.4 4.3 1962 4.2 3.5 3.9 3.9 4.3 4.7 4.0 5.4 4.1 1964 4.1 3.7 4.1 3.7 4.5 4.9 4.2 5.6 4.3 1966 3.8 3.7 4.0 3.8 4.5 4.8 4.0 5.2 4.5 1968 4.2 3.8 3.8 4.0 4.7 4.8 4.0 4.9 4.3 1970 4.5 3.9 3.8 4.4 4.9 5.3 4.5 5.2 4.4 1972 4.6 4.0 4.1 4.6 5.0 5.7 5.0 5.6 4.7 1974 4.9 4.1 4.5 4.8 5.1 5.8 4.9 5.6 4.9 1976 5.1 4.1 4.8 5.1 5.1 5.9 4.7 5.6 5.1 1978 5.1 3.8 4.6 5.1 4.8 6.2 4.8 5.7 5.3 1980 4.6 3.5 4.2 4.6 4.5 6.1 4.8 5.4 5.2 1982 4.5 3.3 4.4 4.6 4.5 5.9 4.7 5.2 5.0 1984 4.5 3.8 4.4 4.8 4.4 5.8 4.7 5.4 4.7 1986 4.2 3.6 4.0 4.4 4.2 5.8 4.7 5.5 4.5 1988 3.9 3.2 3.8 3.7 4.0 5.5 4.5 5.1 4.4 1990 3.9 3.2 3.4 3.3 3.9 5.2 4.4 4.9 4.3 1992 4.0 3.3 3.3 4.1 4.0 5.1 4.3 5.0 4.3 1994 4.2 3.4 3.8 4.5 3.9 5.4 4.4 5.4 4.3 1996 4.3 3.5 4.2 4.3 3.9 5.5 4.7 5.4 4.1 1998 4.3 3.6 4.1 4.1 4.1 5.4 4.7 5.2 4.1

08:30 E.S.T. 09:10 E.S.T. I0:0 6 E.S.T. The nine scene photographs reproduced here and on the following two pages correspond to the data given on the preceding fifteen pages. The photographs were taken with a Maurer 220 camera from a float altitude of 110, 000 feet. The black circle shown in the center of each photograph outlines the 80 interferometer field of view. The camera developed a light leak during the later portion of the flight and four of the later photographs are streaked along one side. Figure 1. - SCENE PHOTOGRAPHS 19

11:09 E.S.T. 12:34 E.S.T. 13:31 E.S.T. \ 20

14:12 E.S.T 14:48 E.S.T.: I h'. 4fi 15:11 E.S.T. Figure 3. - SCENE PHOTOGRAPHS 21

0 -20 30 30]J\ l/ /Ill | nWATER VAPOR ABSORPTIONo | V / \ WATER IN pr. cm.= 0.0102 F 40~1 \, \; P. IN mm Hg. = 810 o - \} i \ \" \ REF. BURCH3 et ol - AFCRL-62-698 P. 307 m 50 -60 z 60- /\6 DATA RECORDED AT 9:10 E.S.T. | /\l\ 07. = RADIANCE AT 288-K.- GROUND TEMP. ' 70- / I 100%7= RADIANCE AT 218-K.-TROPOPAUSE s-PROBABLE RADIATION WITHOUT METHANE OR NITROUS OXIDE 90 100 -I i i~ 1200 1250 1300 1350 1400 WAVENUMBER, CM'FIG. 4. COMPARISON OF WATER VAPOR ABSORPTION AND MEASURED SPECTRAL RADIANCE TO DEMONSTRATE ABSORPTION DUE TO METHANE AND NITROUS OXIDE.

III. Conclusion and Plans for Further Work The data presented in this report meets the accuracy requirements -1 -1 -1 originally specified (0. 5 ergs sec cm sr ) in order to make reasonable temperature inversions. Furthermore, the results obtained justify the effort expended to develop Fourier transform spectroscopy for this application and represent a demonstration of the power of the technique. The specified minimum noise is based on the use of seven independent frequencies in the CO2 band to compute the temperature profile. If more frequencies are used, the allowable noise could be increased or the number of spectral scans required decreased. An advantage of the interferometer is that more frequency measurements are available and an investigation of this point is now being madeo Although measurement of the spectrum of the 15,u band was a primary purpose of the development, additional data in other spectral bands is available and may prove valuable in the future. There is the possibility of using the 9o 6A data to determine the ozone profile. A water vapor profile can be calculated, even though the data in the 6. 3p region is accurate to only about 20%o. In fact, the data has been used by Smith to infer the water vapor structure. Also the data in the "window" region can be used to determine the ground temperature under a cloudless condition or make an estimate of the cloud height for the case of complete cloud cover. Whenever the cloud cover is partial any analysis is difficult. In the case of the data presented here, the photographs were not synchronized with the data which was collected from three scans over a period of 45 seconds. Hence, when clouds appear near the edges of the field of view there can be considerable error in estimating the percentage of cloud cover, There is, however, a definite correspondence between the "window" measurements 23

and the cloud cover. By observing the radiance measured at 900 cm the steady increase in radiance during the morning can be observed as well as the effect of clouds at 14:12 EST and 15:11 EST. The following assumptions were made relative to the data at 14:12 EST, (1) the cloud cover is 33%, (2) the radiance in the clear area is the same as that at 13:31 EST, and (3) the lapse rate is -20C/1000 feet. Under these conditions the calculated cloud height is 14, 000 feet. Considering the crudeness of the estimates, the 2 agreement with Colorado State University aircraft flight observation of 16, 000 feet maximum is quite good. The absorption band at 1304 cm is thought to be due primarily to the CH41306 cm line with some contribution from the NO2 1285 cm line. The conclusion was reached by comparing the flight spectra in this region with laboratory water vapor spectra and noting the variation in structure (fig. 4). The present plans for further development of the instrument call for an increase in resolution to 3 cm1 and an extension of the wavelength span to 200 cm to include the rotational bands of water vapor. If these goals are realized, the determination of a water vapor profile by radiation measurements will be more readily accomplished. REFERENCES I. Smiths W. Lo, "An Iterative Method for Deducing Tropospheric Temperature and Moisture Profiles from Satellite Radiation Measurements, " to be published in Applied Optics. 2. Marlatt, W. E., private communication. 3. Burch, D. E., Gryvnak, D., Singleton, E. B., France, W. L., and Williams, D., "Infrared Absorption by Carbon Dioxide, Water Vapor, and Minor Atmospheric Constituents", Ohio State University Contract AF 19 (604)-2633-AFCRL-62-698 July 1962. 24

IV: BIBLIOGRAPHY Bell, E. E (1966), Infrared Physics 6, 57. Billings, B. (Feb. 1963), Research in Infrared Interferometry and Optical Masers, Baird Atomic, Inc., Final Report AF 19(604) 2264. Bosomworth, D. R. and Gush, H. P. (1965), Cam. J Phys. 43, 729. Bouchariene, P. and P. Connes, J. Phys. Radium 24, 134 (1963). Chamberlain, J. E., J. E. Gibbs and H. A. Gebbie, Nature 198, 874 (1963). Chaney, L. W., Drayson, S. R., and C. Young (Feb. 1967), Applied Optics 6. Connes, P. (1956), Rev. Optique 35, 37. Connes, J. (1961), Rev. Optique 40, 45, 116, 171, 231, an English translation is available as a Navy publication, NAVWEPS report no. 8099, NOTSTP 3157, published by the U. S. Naval Ordnance Test Station, China Lake, California. Connes, J. and P. (1966), J. Opt. Soc. Am. 56, 896. Connes, J. and H. P. Gush, J. Phys. Radium 20, 915 (1959). Connes, J. and V. Nozal, J Phys. Radium 22, 359 (1961). Cooley, J. W. and J. W. Tukey (1965), Math Computations 19, 296. Dowling, J. J. Opt. Soc. Am. 54, 663 (1964). Dowling, J. M. (1966), J. Opt. Soc. Am., Annual Meeting, FC 1. Fellgett, P. B. (1958), Thesis, University of Cambridge, 1951: J. Phys. Radium 19, 187. Filler, A., J. Opt. Soc. Am. 54, 762 (1964). Fizeau, H., Ann. Chim. Phys. (3) 66, 429 (1862). Forman, M. L., W. H. Steel and G. A. Vanasse, (1966), J. Opt. Soc. Am. 56, 59. Forman, M. L., W. H. Steel and G. A. Vanasse, Non-linear Phase Connections of Interferograms Obtained in Fourier Spectroscopy, AFCRL-65-518. 25

Gebbie, H. A., G. A. Vanasse, and J. Strong, (1956), J. Opt. Soc. Am. 46, 377. Gebbie, H. A., Phys. Rev. 107, 1194 (1957). Gebbie, H. A., K. J. Habell and S. P. Maddleton (1962), Proc. of the Conf. on Opt. Inst. and Tech., Chapman and Hill, Ltd., London 1963. Genzel, L. and R. Weber, (1958), Z. Angew. Phys. 10, 127 (1958): 10, 195. Gibbs, J. E. and H. A. Gebbie (1965), Infrared Physics 5, 187. Greschushnikov, B. N., G. I. Distler, I. P. Petrov, Soviet Physics Crystallography 8, 367 (1963). Gush, H. P. and H. L. Buijs, (1964), Cam. S. Phys. 42, 1037. Hanel, R. A. and L. W. Chaney, (July 1964 and March 1965), The Infrared Interferometer Spectrometer Experiment (IRIS), Goddard Space Flight Center Reports X-650-64-204 and X-650-65-75. Hilliard, R. L. and G. G. Shepherd (1966), 56, 362. Jacquinot, P. (1958), J. Phys. Radium 19, 223: Reports on Progress in Physics 23, 267, (1960). Jacquinot, P. and C. Dufour, J. Recherches du C.N.R.S. 6, 91(1948). Kiselev, B. A. and P. F. Parshin, Optics and Spectroscopy 12, 169 (1962). Loewenstein, E. V. (1966), Applied Optics 5, 845. Mellon Institute Symposium on Far Infrared Transpose Spectroscopy (1965), Pittsburg, 10-11 June 1965, reported in Applied Optics 4, 1374, (1965). Mertz, L. (1959), I C.O., Stockholm, Hetrodyne Interference Spectroscopy. Mertz, L. (1965), Transformations in Optics, John Wiley & Sons, New York. Mertz, L., Infrared Spectra of Astronomical Bodies, Proceedings of the Twelfth International Astrophysical Symposium, Liege, June 1963, p. 120. Michelson, A. A., Phil. Mag. (5) 31, 256 (1891). Parshin, P. F., Optics and Spectroscopy 14, 207 (1963). Parshin, P F., Optics and Spectroscopy 14, 156 (1963). Parshin, P. F. Optics and Spectroscopy 16, 275 (1964). 26

Pritchard, J. L., H. Sakai, W. H. Steel and G. A. Vanasse, (1966), Mobius Band Interferometer and Its Application to Fourier Spectroscopy, Collogue Sur les Methods de Spectroscopie Instrumentale, Bellevue France. Renk, K. F. and L. Genzel, Applied Optics 1, 643 (1962). Richards, P. L. (1964), J. Opt. Soc. Am. 54, 1454. Rubens, H. and R. W. Wood, Phil. Mag. 21, 249 (1911). Strong, J. and G. A. Vanasse (1959), J. Opt. Soc. Am. 49, 844. Strong, J. and G. A. Vanasse, J. Opt. Soc. Am. 50, 113 (1962). Stuart, S. R. Huppi, A. T. Stair, and G. A. Vanasse, I. C. O. Tokyo, 1964. Surh, M. T. (1966), Applied Optics 5, 880. Vanasse, G. A., J. Opt. Soc. Am. 52, 472 (1962). Wheeler, R. E. and J. C. Hill (1966), J. Opt. Soc. Am. 56, 657. Williams, T., J. Opt. Soc. Am. 50, 1159 (1960). Willson, R. C., the Theory, Design and Development of an Interferometer Spectrometer, University of Colorado Science Report No. 1, Yoshinaga, H. Applied Optics 3, 805 (1964). 27

Institute of Science and Technology The University of Michigan Appendix I EARTH RADIATION MEASUREMENTS BY INTERFEROMETER FROM A HIGH ALTITUDE BALLOON (a paper presented at the 3rd Symposium on Remote Sensing of Environment, 14 October, 1964, Ann Arbor, Michigan) ABSTRACT The earth's thermal radiation was measured with an infrared interferometer (5gi to 15i1), 50 cm-1. The platform used was a high altitude balloon which maintained a float altitude of 112,000 feet for eleven hours. The data obtained are discussed. 1. INTRODUCTION The High Altitude Engineering Laboratory of The University of Michigan has conducted a series of tests in support of the Meteorological Satellite Program. As a part of this program, an interference spectrometer was flown on a high altitude balloon. The results of this test are the subject of this paper. The current satellite radiation instruments are radiometers having various spectral characteristics. The need for higher resolution radiation data is becoming more apparent. This is particularly true if we are to measure temperature as a function of altitude from a remote position in space. Success in this effort will require the measurement of small differences in radiation in adjacent spectral channels. The interference spectrometer offers an attractive possibility for performing this function. The advantages of this instrument over a diffraction grating instrument have been discussed elsewhere. 1,2,3 The instrument which was flown in the evaluation test was a Block Associates 1-4 Interferometer. The instrument as it was purchased was not designed for a balloon flight. Hence, several modifications were required, but the basic instrument remained unchanged. The modifications and laboratory calibrations have been discussed in a separate report.4 2. INSTRUMENT SPECIFICATIONS The instrument as it was modified for flight had a theoretical resolution of 50 cm. The -1 useful spectral response covered the region from 600 to 1600 cm. This just nicely included the 15n CO2, 9.6 03, and the 6.3i H20 bands. The instrument field of view was a circular 150 which covered an area five miles in diameter on the ground. The data reduction scheme selected required the measurement of the amplitude of coefficients of the Fourier Series. This was accomplished with a loop tape recorder, wave 28

Institute of Science and Technology The University of Michigan analyzer, and x-y plotter, The instrument was then calibrated as though it were a 31 channel radiometer. The scanning time for one complete spectrum was 0.5 seconds. However, in* the data reduction process a total of 34 spectra were integrated for a total of 17 seconds. The instrumentation package (Figure 1) as flown measured 7 1/2 in. X 10 in. x 15 in. and weighed 34 pounds including the calibrating blackbody and a 24 hour battery supply. A copper shield can (not shown) covered the entire package during flight. 3. INSTRUMENT INSTALLATION The instrument inside its copper shield can was mounted in the gondola which is shown ready for launching (Figure 2). The instrument was completely self-contained, but external lines to the telemetry were required. In addition, a command signal from the gondola master timer actuated the calibration blackbody. The blackbody was mounted on a track and moved in front of the interferometer for 50 seconds every 15 minutes. The instrument looked down at a zenith angle of 30. This was done so that the interferom - eter data could be compared with the Tiros 5-channel radiometer. The radiometer had to be mounted at a 30 angle in order for the space side of the instrument to look past the balloon. 4. CALIBRATIONS Extensive calibrations of the instrument were carried out in the laboratory prior to the flight. Several tests were made by using the instrument to observe the atmosphere from the earth side. The procedure in calibrating the instrument was to hold the bolometer at a fixed temperature while varying the target temperature over the calibrating range. The bolometer would then be changed to another fixed value and a similar calibration performed. In this way, a table was composed from which it was possible to interpolate to find the measured temperature. The complete data reduction scheme and the method of presenting the data have been described previously. The in-flight calibrations were checked post-flight by adjusting the interferometer temperature and the blackbody temperature to those measured during the flight, and recording the instrument output. The correspondence between the in-flight and the post-flight calibrations is shown in Figure 3. The discrepancy through the specified spectral range is less than 30 C and the average variation is less than 10C. 5. MEASUREMENT CONDITIONS The meteorological conditions which existed on the day of the flight were ideal. The balloon was launched from Sioux Falls, South Dakota on 26 June 1963 at 457 CST and terminated south 29

Institute of Science and Technology The University of Michigan of Wall, South Dakota at 1815 CST. Until 1130 CST, the balloon flew over completely cloudless skies at a height of 112,000 ft. The sky gradually became cloudy and at 1350 CST the balloon flew over very high storm clouds and emerged on the western side of the storm two hours later. Scattered clouds were again observed until cut-down. To summarize: 1) observations were made through clear sky as the earth heated, 2) broken clouds were observed on both sides of the storm, and 3) storm clouds were observed directly. 6. DATA A complete set of reduced data is given in the data table (Figure 4). The data is given in equivalent blackbody temperatures in degrees centigrade as a function of both wavelength and time. Equivalent blackbody temperatures rather than spectral radiance is used since this is the manner in which the instrument was calibrated. The data have been reduced for fiveminute intervals during the first half of the ascent and at ten minute intervals during the last half. While at float altitude, a reduction was made once each hour except for three selected periods when a reduction once each minute for four minutes was made. The temperatures are reduced for 31 discrete wavelengths. In essence, the instrument might be considered a 31 channel radiometer. Some of the data have been plotted for fixed time as a function of wavelength, and some at fixed wavelength as a function of time. The Tiros and Nimbus radiometers flown on the same balloon were compared as follows. The equivalent blackbody temperatures were converted to spectral radiance and multiplied by the appropriate filter function. The resulting function was integrated to obtain radiance. The equivalent blackbody temperature was then obtained from the radiometer calibration curve. The temperature comparison chart (Figure 8) compares the temperatures obtained by this method, the temperatures measured by the Tiros radiometer, temperatures measured by the 10.3,i interferometer channel, and the actual surface temperatures measured by W. E. Marlatt from Colorado State University.5 7. DISCUSSION The temperature comparison chart (Figure 8) indicates excellent agreement between the Tiros radiometer measurements and the adjusted interferometer measurements. The average variation is less than one degree and the maximum is three degrees centigrade. This com30

Institute of Science and Technology The University of Michigan parison was a great aid in establishing confidence in the interferometer. The comparison between the Nimbus filter function and the 10.3j interferometer channel shows that both read closer to ground temperatures than the Tiros. The 10.3: channel is slightly closer to ground temperatures. The Nimbus temperatures are 3.5 C below the average ground temperatures measured by Marlatt. It should be noted that the measured ground temperatures varied by ~2.50C from point to point in the field. Spectra of the clear sky (Figure 9) are plotted for the maximum measured difference in surface temperatures. The points to be noted are: 1) increase in CO2 absorption, 2) increase in water vapor absorption, 3) deterioration of the edges of the window, and 4) constant ozone absorption. These changes can be accounted for by the upward movement of the tropopause and the increase in water vapor. The spectra of clear sky and that of a high cloud area are compared (Figure 10). The most interesting point to note is that in the case of the high cloud, the coldest temperatures appear in the window and that the former absorption bands now appear as emission spectra. Since these temperatures are very low, there is an average scatter of about ~3 C at 10.3jA and ~50C at 6.3A. A pair of spectra for opposite sides of the storm cloud are given in Figure 11. In this case the window temperatures are identical. It should be noted that the latter spectrum indicates a colder tropopause and warmer water vapor temperatures. This should be expected after passing over a frontal storm. Temperature variations as a function of time have been plotted. The best window at 10.3/ (Figure 12) appears at the top of the graph. You will note that except for relatively minor fluctuations there is a steady rise in temperature due to the earth's heating. The drop in temperature at 1300 and 1400 CST is due to scattered clouds in the field of view. The sudden drop in temperature at 1500 and 1600 CST is due to the passage over a large high storm cloud. The ozone at 9.6/1 exhibits a different character. The first few data points on ascent follow the "window." This is followed by a slight drop as the balloon reaches the tropopause and then a sudden drop around 52,000 ft. The drop continues somewhat past the tropopause and a minimum was recorded at 82,000 ft followed by a slight rise to float altitude. A relatively constant temperature near -2 C was recorded during the clear sky portion of the flight. The effect of clouds is clearly seen in this channel. The C02 at 14.5/i exhibits a very smooth rapid drop in temperature at 50,000 ft followed by a rise as the balloon moved from 70,000 to 112,000 ft. Throughout the day there is a steady 31

Institute of Science and Technology The University of Michigan decline in temperature indicating a slow rise in the height of the tropopause. The high clouds have very little effect on this channel. Referring to Figure 13, the 8.5i "window" exhibits the same tendencies as the 10.3j except that the temperatures are lower indicating a poorer "window." The 7.6/ channel is in the wings of the water vapor bands and clearly shows the dip in temperature as the balloon passed through the tropopause and a steady decline in temperature caused by the gradual increase in water vapor. Again the effect of high clouds is clearly seen. The 6.4/ water vapor channel follows much the same pattern as the CO2. The minimum temperature occurs at the tropopause followed by a rise and another drop after reaching float altitude. This could possibly be explained by trapped moisture in the gondola which disappeared after being at float altitude for a short time. The random error in this data is -7 2 -1 approximately ~2 x 10 watts/cm /cm. This represents a temperature fluctuation of 0.5 C in the warm "window" to 20 C for the coldest water vapor readings. 8. CONCLUSIONS This instrument has two inherent shortcomings: poor resolution, and systematic errors due to unstable wavelength calibration and secondary spectra. The data gathered indicate that the interferometer is a fruitful technique for studying the earth's atmosphere. The conclusions to be drawn from this data are: 1) The 14.5w channel is essentially unaffected by high clouds and is reasonably indicative of the tropopause temperature. 2) The best window is located as close to the ozone absorption band at 9.6/i as possible 3) More information can be obtained regarding water vapor by a channel located in the wings of the water vapor band than at 6.4/i. A new instrument which we hope to test in the next year is now being developed. 32

Institute of Science and Technology The University of Michigan REFERENCES 1. Felgett, P. B., Ohio State Symposium on Molecular Spectrometry, 1952. 2. Gebbie, H. S., J. Phys. Radium, 19, 230, 1959. 3. Connes, J., Reu d' Opt., 40, 45, 101, 151, 213, 1961. 4. Chaney, L. W. and Loh, L. T., An Infrared Interference Spectrometer-its Evaluation Test and Calibration, NASA Contractor Report CR-61, June 1964. 5. Marlatt, W. E., Investigations of the Temperatures and Spectral Emissivity Characteristics of Cloud Tops and of the Earth's Surface, 1st Semi-annual Progress Report under Contract NaSu-147 between the NASA and Colorado State University, Technical Paper No. 51, Dept. of Atmospheric Science, Colorado State University, Fort Collins, Colorado, February 1964. ACKNOWLEDGMENTS The author wishes to thank F. L. Bartman and many other members of the High Altitude Engineering Laboratory of The University of Michigan for their assistance in carrying out the instrument modification and calibration, the balloon flight operation, and data processing. Others who made the work possible are personnel of Raven Industries for balloon flight operations, and the United States Weather Bureau personnel at Sioux Falls for weather forecasting assistance. The work described in this paper has been supported by the National Aeronautics and Space Administration under contract NaSr-54(03). 33

Institute of Science and Technology The University of Michigan BLACK BODY HOUSING INTERFEROMETER FIGURE 1 34

Institute of Science and Technology The University of Michigan f _ / '1 " ' __,,\ % *n FIGURE 2 E / '/ Ri

I S05t INTERFEROMETER BALLOON FLIGHT P g6~" 26 June 1963 - Calibration e l C 0I 0 0 OXofx b c - o9 7:00 CST /NFL/GHT CAL/BRAT/ON ~~~~~~~~~~~~~~~I.-^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I I i I I i I I I I I 0I I __. 00 a cWc) 8:00 CST INFL/GHT CALIBRATION x ^ X —~~x 7. o:00 CST POSTFLuGHT-SIMULATED I ~ I I, 600 800 1000 1200 1400 1600 1800 2000 WAVE NO. (CM-') ' FIGURE 3 0 (Q

23 -4" C INTERFER0OETER DATA (/3 { Equivalent Black Body Temperatures, 'C CD wave No. (cm'1), 620 655 690 723 760 795 830 865 900 935 970 1005 1040 1075 1110 ~ CT WaveleDth (p): 16.1; 15.3 14.5 13.8 13.2 12.6 12.1 11.6 11.1 10.7 10.3 10.0 9.65 9.52 9.05 0,00,l00 19 19 16 14 15 11 10.5 12 12 14 15 13.5 0 5:04:55 5.3 11.5 11.7 15.7 16.7 14 15.5 14.5 13.5 13 13 15 13 13.5 15.5 - 5:09:55 3.7 -.03 2.5 7.0 12.0 12.3 13 14 12.3 11.8 13.2 14.3 15.7 12.2 12 A 5:14:54 - 6.3 - 7. - 7.5 1.3 11 12 13.5 13.3 13.3 13.3 12.7 14.2 12.7 11.8 12.5 5:19:54 -11.0 -20.7 -21.7 - 5.7 9.8 12.7 14.5 15.7 13.5 13.5 15.5 14.5 13.5 12 15.7 0 0 5:24:54 -21.3 -33.3 -35 -14.7 8.0 13.5 14 12.7 12 11 12.7 13.5 11.5 11.7 12 ( 5:29:54 -29 -49.3 -41.5 -17.7 7.5 14 13.5 13.5 11.7 11.5 12.7 1.35 8.7 9.8 12.5 5:3:54 -54.5 -55.2 -58.8 -20.7 6.7 11.5 13.6 13.6 13.8 15.5 14 12 8.7 10.5 12 5:39-55 -33 -63.2 -61.5 -27 7.0 11.5 13.0 13.4 13 13 13 12.7 8.0 9.5 12.0 5:44:54 -34.5 -61.5 -67.2 -21.7 7.5 1~ 14.5 13.8 13.8 14.3 13.6 13.5 7.5 9.0 15.8:49:54 -32.8 -64 -62 -27.5 7.2 15.5 15 16 15.2 14.3 14.8 15.0 6.3 10. ID.7 5:54154 -33.5 -61.3 -67.2 -27.7 7.0 14.3 15.2 16.2 14.5 15.3 19.3 lk.5 2.8 7.3 15 3:59:54 -36.2 -55 -58.3 -29.5 7.3 15.5 16.5 15.7 16 16 16.5 15.7 - 2.0 4.0 16.2 6:09:54 -38.3 -55.5 -62.3 -32.3 6.7 16 17 15.8 16.5 16.7 17 14.5 - 6.2 0.0 16.3 6:19:54 -35 -55 -57 -30.2 6.3 16.5 17.5 16.0 17 17 17 14.8 - 7.7 - 1.0 16.3 6:29:54 -31 -45.7 -50.2 -26.2 6.8 17.5 18.5 19 18.3 19 20.5 17.5 - 4.5 0.02 17 Co 6:39:54 -33 -44 -48.2 -26.5 6.0 16.8 18.8 19 18.2 20 18.5 17 - 4.0 0.0o5 7.7 6i49:54 -32.5 -42.5 -46 -26 6.8 17 18 19.2 20 20.7 19.5 17 - 2.0 0.03 18 8:00:00 -37 -50 -55 -35 5 21 22 24 24 24.5 24 23 - 3 -1 22 8:36:00 -3? -47 -54 -34.3 5.0 23 25.3 26 26.5 26.3 26 25 - 1.0 3 26 81 37:00 -30 -46 -54 -34.3 4.0 23 25.3 27.5 27.5 27.5 27.0 25.5 - 0.5 3 26 8:38100 -35 -47 -55 -34.3 0.5 23 26.5 26.5 26.5 27.5 27.5 25 0.0 3 26 8:41100 -35 -44 -49 -33 }.? 22 25.3 25.5 25.5 26.8 26. 24.5 - 0.5 2 25 9:00:00 -49 -46 -53 -31 7 19 25 25 25 26 25 22 -} 1 22 10:00:00 -41 -49.7 -57.5 -34 8.o 21 26.3 26 26.8 26.5 28.1 2e.1 - e.2 8.3 27 10:01:O0 -29.7 -49.2 -56 -31.2 9. 21 23.3 23. 25.2 24 25.8 25.5 -.5 9.0 28.3 10:02:00 -31.8 -49 -?5.5 -30.8 9.5 22.3 28.2 27.2 28.8 29.2 31. 26.7 1.4 1.5 29.1 10102:30 -38.2 -51.2 -58.8 -36.6 8.2 21.4 27.5 27.4 29.5 28.2 30.4 26 -.2 7.5 28.6:3 11 00:00 -40 -36 -58 -33 8 20 27 26 28 29 30 26 -2 7 28 ~D 12:00:00 -50 -56 -58 -33 9 22 27 27 51 52 34 29 -1 13 34 13:00:00 -56 -60 -60 -32 8 15 20 20 5 24 26 18 -1i 8 26 = 13:59:15 -58 -60 -65 -37 -6 2 6 6 11 7 14 6 -20 -3 14 14100:00 -56 -60 -60 -33 2 8 14 11 15 17 17 11 -14 5 21 a IOOlOO -56 -52 -6 9 -69 - -69 -74 -72 -74 -74 -69 -69 -69 -69 -?8 - 15:58:20 -74.5 -64 -77.4 -64.2 -68.4 -70.3 -75.2 -75 -89.6 -87.2 -81 -71 -73.5 -76.2 -69.5 -' 16:00:20 -64.5 -62 -73.5 -61 -61.6 -67.5 -71.2 -64.8 -82 -84.4 -76 -70.2 -69.2 -75.8 -64.3 ' 16:01:20 -77.5 -65.5 -76.2 -62.7 -67.2 -67.5 -75.7 -76.4 -91.9 -90.5 -81.4 -71.4 -70 -78.8 -68.3 0 17:00:00 -55 -70 -60 -13 20 21 26.5 27 27 27 30 10 -9 23 30 - FIGURE 4a n Ce 0

.4. C (D o O1 f% IWI'ERFEROME~ER DATA (Concluded) (D Wave__ No. (am-x): 1145 1180!215 1250 1285 1~20 1~9 139Q 1425 14~9 1499 1~0 1~56'~ 1600 1635 CST Wavelength ( M ): 8.7~ 8.49 8.24 8.01 7.8:L7.58 7.3?_ 7.2 7.0~ 6.86 6? 6.5~ 6.4 6 26 ~3 ~ 6.12_ O. 5:00:00 13.5 15 13.5 14 16 19 19 15.5 21 19 17.5 5,04:55 14.8 15 15 i~.2 14 2 15 5 13 11 12 L~ 15 14.5 15 5 12.9 15.8 -~ ~ (~ 5,09,55 15 13 3 15 10.5 12 10.7 6.8 5 0 2 5 4 5 5.7 9 6 - 2.5 D.O. c~ ~5,14:~ 14 13.5 L~.9 10.5 8.5 7.2 4.9 1.5 - 2.5 0.O - 6.0 1.0 - 4.2 -Ll.~ - 8.5 5:19:5~ 14.7 14 5 14 12 6 6 5 - 5.2 - 5 ~- - 7 -15 2 -14.2 - 9 5 -22 5 -25 5 O_. ' -18.2 O 5,24,54 15 15 12 lO 2.5 - 1.5 - 5. -8.8 -lO -18.D -28.5 -32 -38.8 -26.2 -29 5:29:~4 15.5 15 12.5 ll.7 8.2 - 5.2 - 5.5 -10.5 - 9.0 -19 -54.5 -22.5 -40.3 -20 '~ -49. 5t~,~ 15.5 1~.5 I5 10. - 1.0 - 5..5 -0.8 - 7.7 -14 -21 -31.5 -42.7 -47 -55. -26.8 5:591~ 13.6 13.9 12.6 9.0 - 2.5 - 6.3 - 2.7 - 9.6 -15.9 -22 -31.5 -49.2 -52.2 -29.5 -3~ —5 5,~J~,~ 14.0 14.5 13.7 11.8 - 5.0 - 6 - 2.4 - 9.0 -ll -17.7 -51.8 -58.7 -~6.0 -51.5 -25.5 5,49,~ 14.5 15.5 14.5 12.5 - 1.8 - 6.5 - 1.4 - 5.5 -10 -15.5 -55.5 -41 -7Q-~ -12 -2~.~ 5:~:~ 14.~ 1~.5 14 1.2.5 - 1.5 - 6.5 - 1.0 - 6.3 -15.7 -15.5 -25 -45 -57 -28 -~kq.2 5,~,~ 15 15.5 15 12.5 0.05 - 4.7 - 0.7 - 3.7 -12.5 -18.5 -52.8 -38.5 -4~.7 -17.5 -19.5 6,09,~ 14.~ 14.5 15.5 9.0 1.0 - 6.7 0.05 - 62) -12.5 -19.2 -55' -~.3 -48.5 -24.2 -21.8 ~ 6,19:~ 16.5 1~.7 16 15.5 4.0 - 5.5 1.2 - 5.5 - 7.0 -ll.5 -25 -33.7 -43.2 -24.2 -15.5 6:29,~ 19.5 17.7 16.8 14.5 15.5 - 2.7 4.0 - 1.~ - 9.0 -12 -27.5 -~ -59.5 -25 -20 O0 6,~),~ 16.8 17 19.3 14.8 9.0 - 5.0 2.~ - 5.9 -14.5 -10 2 -28.5 -27 -47.3 -24.5 -15 03 6,49,~ 17.5 17.5 17.7 16 8.0 - 2.0 2.7 - 1.3 -10.5 -12.5 -24.5 -51.5 -42.5 -47 -46.9 8,00,00 22 20 22 16 4 -10 - 5 - 7 -14 -14 -55 -55 -75! -35 -20 8,~6,00 25 2).5 23.5 19 1.0 -n. - 4 -12 -18 -20 -~ -5~ -65 -45 -25 8:57:0o ~6 2~.5 23.5 19 1.0 -12 - 4 -12 -17 -19 -~ -55 -70 -~0 -25 8,38,00 25 25.5 23.5 19 2.0 -L~ - 5 -15 -15 -20 -Sk -55 -75 -55 -25 8:41,00 25 25.5 22.3 19 1.0 -10 - 4 -10 -15 -17 -~0 -40 -75 -35 -19 9:00:00 22 21 21 ~7 2 -12 - 5 -14 -16 -25 -52 -50 -66 -35 -25 10:OO=00 26 2~.4 2~.4 18 - 0.07 -15.7 ll.5 -25.5 -27 -26.5 -49 -55.5 -70.7 -50 -53 10:01:00 2~.6 24.7 24.7 19.4 - 9.5 - 9.7 -16.5 -25.6 -20.8 -40.6 -~4.6 -65.7 -17.2 -~.2 10:02:00 26.2 25.6 24.6 19.7 - 2.2 - 7.7 - 6.7 -18.3 -25.8 -~0.5 -41.6 -41 -64 -~9.8 ~ — ~ 10,02, ~0 25.6 25.5 24.2 19.4 - 5.9 -14.5 -13 -24.8 -32 -41.5 -52.5 -52.5 -73.2 -49.D -~8 mr' 11,00,0O 28 26 25 18 - 5 -15 -1~ -21 -28 -53 -60 -60 -7~! -~8 -~0 ~ 12:00:00 52 29 26 17 - 4 -22 -15 -21 -21 ~55 -45 -70 -75! -75 -~8 15:0O:0o 2~ 25 20 10 -12 -22 -15 -28 -55 -~6 -56 -95! -75! -~ -70 ~5,59, ~5 8 9 6 - 2 -28 -51 -28 -~6 -6o -68 -95 -95 -75 -75 -75 ~' ~,o0:oo 16 17 14 2 -19 -26 -2~ -40 -4~ -69 -75 t -75 -75 -3~ -7~ ~ 15,00:00 -65 -65 -65 -65 -65 -55 -60 -65 -52 -60 -50 -40 -40 -~O -40 15:58:20 -77 -81.5 -71 -73 -86.5 -l% -65.6 -68.8 -59 -71 -47.6 -78.5 -73.2 -66 -81 -~' 16:00:20 -70.2 -80.8 -75.5 -68.5 -77.0 -68.5 -57.7 -67.7 -52.8 -65.2 -48. -5~.5 -61.7 -~6.4 '~ -91.8 16:01:20 -76.~ -85.6 -82.5 -74 -86.5 -74.8 -7~.5 -70.6 -57 -70.~ -50 -6~.~ -69.8 -65.~ -~1.8 O 19,00:00 27 26 24 7 -10 - 9 '- 4 - 9 -15 -25 -)5 -40 -90 -55 -1"~ '" t% FIGURE 4b:t.:[

Institute of Science and Technology The University of Michigan FIGURE 5 39

Institute of Science and Technology T h e University of Michigan. 3 ~'~,..,~ '.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-iliiii~i.~~1-:- l i I':~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~': II./~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:....... _~~~~~~~ - -lw FIGURE 6 40

Institute of Science and Technology The University of Michigan FIGURE 7.iGL:...... FIGURE 7 41

~~~~~~30~~ __ F~~~~~~~~~o x' x~~~~~~~ el 40 I I CD 20- 006 0~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 I 000o _ woITEFROETR103 ^/ 20 g A~A NORMALIZED BY TIROS FILTER FUNCTION ^ /^\~~~~2 - 0 - 10-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~( W Q IC Y PARTLY HIGH co NRCLEAR I SKY N S E CLON \CUMULUS I n ~~~~~~~~CLOUDYCOD -20 Ct S3TEMPERATURE COMPARISON (M -30 -N~~~~~~~I z ~ -40 5Q a-aoo INTERFEROMTER /IO. 3 CY Am~A NORMALIZED BY TIROS FILTER FUNCTION w -60- omo TIROS CHANNEL i0 x m NORMALIZED BY NIMBUS FILTER FUNCTION ___ SURFACE TEMPERATURE MEASURED BY -80- W.EMARLATT COLORADO STATE UNIV C C 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 TIME, CST Figure 8 A (0 Q

Institute of Science and Technology The University of Michigan 0 0oW _0^^ ^^0 (D XQ o 0 I/- ^ -0 o C-.. z w ~z > -J I 0 I (Y-) ^^ ^w 0 _ X x~o X 0 00 X 0 I USO 0 -0 0 0 0 0 0 0 0 0 0 0 0 0 MO VYJ- GOI I I I I3 (30) cIbN3L i A006 >3OV]B 1N31V103 43

Institute of Science and Technology The University of Michigan 10 0 0 o 0x b(0I~ x x oI/'~ 0 x r0 CQ - o x -- T z C ^ 0 0 - I J x 0 o 00 )1 - / o-4 0) o 0 0_o x 0 b x z _X o~? xj x — o 0- ^0 0 PO ^~- ed r 'ux3 D (0 0 0LO~~~~~~~~~~I I I I I I (o9) 'dVY31 A008 4DV-18 IN31VAIn03 44

3 V* WAVELENGTH (^) 1615141312 11 10 9 8 7 6 30 C- vcrwDnlio Ogro, ~20 1I -0xo~ I 0 1\ I C I~I U - A1 2 0 w f xmx 0 I \ * ^ OQ o om \ m -20 - ~-0 x.^" V -30- o0 r C~~~~~~~~~~~~~~~~~~~~~1 H ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~~~~~~~~C x~~~~~~~~~~~~~ ~z~~~~ -400 - 1 o w ~ -50 \ w -60 -0 0 -80~~~~~~~~~~~~~~~~~ -70 - 0-0 //.OO CST -80 -x~x 1700OCST C c - 1I III IIIII 600 800 1Q00 1200 1400 1600 WAVE NO. (CM-') FIGUREI 1 A

0 SI WN'DO 3~~~~~~~~~~~~~~~~~~~~~0~~~~~~~0 (a 30 0 F- 20- pe..00 0 %osom m 0 -0 0 o 14.5u C 2 A^t WINDOW -J C -10 \ - " -I os ~ z -40 1 _ w c~~0Q~LJ0o o0 0 0 2 ~-50 OI f - 2 -60 o oo 0 -70 -80 CLEAR SKY LZ PARTLY CLOUDY - ASCEN CLOUDS 5:00 7:00 9:00 11:00 13:00 15:00 17:00 TIME (CST) FIGURE 12 3 -

3 CD 0 (') 3 \ I, C 100 X^ T '\ A\ / Sm -401 \ o lr I 64# HI L (70 -30 -80 GH ' ~~ ^ CLEAR SK.,^I Y -PARTLYCLoUDYntlEMtJTJ^^~^]\ -^ -- ASC.ENTI Cows 1 C (0 -90 FIGURE 13 z~~~~~~ OV ICOUD C.::3~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ w -7~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 o~

APPENDIX II AN INFRARED INTERFEROMETER SPECTROMETER (IRIS) FOR METEOROLOGICAL STUDIES (a paper presented to 13th Infrared Information Symposium October 26, 1965, Pasadena, California) ABSTRACT: The instrument discussed is the breadboard of a satellite interferometer spectrometer (5 - 20u ), 5 cm resolution. This instrument will be used to measure the earth's thermal radiation from a balloon floating at more than 100, 000 feet. INTRODUCTION: The development of improved meteorological satellite instrumentation is of continuing interest to Goddard Space Flight Center. As a result of this interest, they have supported the University of Michigan, High Altitude Engineering Laboratory in the development of interferometry for radiation measurements. Our first measurements were made from a high altitude balloon in June 1963. The instrument used for these measurements was a Block I-4, which has been modified and calibrated for balloon flight. The spectral range was from 5u to 15AL with a resolution of 50 cm. This represented a significant increase in spectral information compared to present meteorological radiometers. The data from this flight were extremely encouraging and served to indicate that an interferometer has good possibilities as a meteorological 48

3 4 instrument. As a result of this work and the work of Kaplan (1959), Wark (1961) and Drayson (1963) on CO2 emission, we became interested in the possibilities of designing an interferometer for relatively high resolution measurements in the 15, band. The purpose of these measurements would be the determination of the vertical temperature structure of the atmosphere. The individual lines in the P and R branches of the 15, CO2 band have a line -1 separation of about 1. 6 cm. To identify individual lines a resolution of about 0. 1 cm would be required. This is not presently possible in a satellite borne instrument. The next best choice is to resolve the band contour as well as possible, Kaplan and Wark have shown that 5 cm1 is sufficient for this purpose. As a consequence, 5 cm became a design goal for a new interferometer. While we were in the process of considering the design of a 5 cm ' interferometer, we made a joint proposal with Goddard Space Flight Center to fly an interferometer on a Mars mission. This instrument would have had a broad spectral range 5M - 33p and a relatively low resolution. However, we later decided that one instrument could be designed having both the resolution required and a wide spectral range that would include both the rotational bands of water vapor and the vibrational bands at 6. 3p. DESCRIPTION: The project was initiated as a joint effort of the University of Michigan and Goddard Space Flight Center. The objectives and a complete desciption of the proposed instrument are completely described in GSFC report #X650-65-75. A brief resume of the instrument specifications is as follows: Spectral range: 2000 - 500 cm (5-20i ) Spectral resolution: 5 cm over entire range (Rayleigh Criteria) 49

Travel of drive mirror: 0. 2 cm. Diameter of effective aperture: 3. 6 cm. Detector: Thermistor Bolometer in conical light pipe Detector time constant: 1.2 mil-sec. Duration of interferogram: 10. 5 sec. Electrical frequencies at detector: 20-80 cps. Sampling: every second fringe of 5852 A monochromatic source Sampling rate: 312 words per second Output: Serial Bi-phase words Words per interferogram: 3472 Bits per word: 12 Field of view: 1.57 x 10-2 ster (appr. 8~) Peak signal/noise: 1500 -8 2 -1 Minimum detectable signal: 8 x 108 watts/cm sr cm Mirror drive velocity: + 1% Reference temperature: 250~K The general features of the optical design can be best explained by referring to the optical head layout (Fig. 1). Spectral range: The long wavelength end of the range is set by the cutoff of the KBr used in the beam splitter, window and lens. The short wavelength end is set by the germanium beam splitting surface. Moving mirror: The mirror is attached to a scan platform which is driven by a coil in a closed magnetic field. The scan distance is 0. 2 cm which sets the resolution at 5 cm. The magnetic circuit is specially designed to eliminate stray flux. 50

Field of view: The field of view is 80. The 3. 6 cm diameter Michelson mirror forms the front stop and the 3. 5 mm cone opening forms the back stop. Detector optics: The optics consist of an F-l KBr lens and a gold coated conical light pipe. In theory this combination should produce an ideal F-0. 5 system. The detector is a thermistor balometer having a flake 3.8 mm square. This is masked by the gold cone to a circle 3. 5 mm diameter. Monochromatic: The neon lamp source is mounted in the position shown. The energy is reflected on to the beam splitter through a right angle prism and the energy is focused on a silicon photodiode. Electronics: The electronic system will be explained with the aid of the block diagram (Fig. 2). The IR signals are first amplified in a 40 db preamplifier before passing to the band pass filter. The switched attenuator automatically changes the gain 20 db when the signal level exceeds + 3.2 volts. When the attenuator is switched this information is stored as the third bit in the A-D converter. The signal to be digitized appears at the A-D converter input. The digitizing encode pulses are derived from the monochromatic signal and hence one pulse occurs after the mirror moves exactly 1. 1704,A The monochromatic signal is amplified in a pre-amplifier, passed through the filter and formed into pulses by the trigger circuit. The sequence and timing circuit serves the following functions: provides an input to the mirror drive amplifier for the duration of the drive, furnished encode pulses to the A-D converter, provides pulses to operate the commutator. The project was planned to be carried out in several stages: scientific breadboard, engineering breadboard, prototype, and flight model. At this 51

time we have demonstrated the scientific breadboard in the laboratory, and have now completed the packaging of this breadboard for a balloon flight. Figure 3 is a photograph of the optical head of the balloon flight instrument and Figure 4 shows the electronics package. Spectra obtained with this instrument are shown in Figures 5 and 6. SPECIFICATION MODIFICATIONS: This instrument deviates in several ways from the original specification. Resolution: The achieved resolution is approximately 8 cm. This is almost twice the planned resolution, but we believe that 5 cm resolution can be achieved with more careful adjustment of the zero retardation and the elimination of variation in the mirror drive velocity. Signal/noise: The peak signal to noise is approximately 1000. The specification is 1500 and this should be achievable with a more carefully designed detector optic. Mirror velocity: The specification calls for a mirror velocity of + 1o. The actual variation is + 5% in one unit and + 10% in another unit. This can be greatly improved by using a much longer feedback coil. A better solution would be to use the monochromatic light frequency in a feedback circuits This was attempted in the original design, but had to be abandoned due to insufficient time to develop the circuitry. Reference temperature: The planned reference was 250 K which is approximately equal to the average earth temperature. This would be best in a satellite instrument since there would be no net exchange of energy between the instrument and the target. We were, however, beset with many practical 52

problems in trying to achieve this reference temperature. The main problem is that the interferometer is extremely temperature sensitive. In this design, gradients in excess of 10 C produce significant changes in sensitivity. In fact, temperature stability on the order of 0. 10 C is required for accurate measurements. The reference temperature was changed to 2730K to take advantage of the thermal stability of the melting ice temperature. This technique works very well and a hollow aluminum base plate was designed for this purpose. The plate holds 1725 cc of water which after freezing will hold the instrument at 10 C for 20 hours. The temperature stability of a given point is better than 0.1 IC. ENGINEERING PROBLEMS: In the course of any development such as this, engineering problems arise which must be solved or disposed of in some way. The areas to be discussed are as follows: 1) Mirror drive, 2) Beam splitter, 3) Fixed mirror, 4) Detector optics, 5) Neon reference channel, 6) Electronics, 7) Thermal control. Mirror drive: (see Figure 1) Initially, the design of the mirror drive was considered to be the most difficult part of the development. The rotation of the moving mirror relative to the fixed mirror should be held to + 2 arc seconds throughout the 2 mm travel. This specification has been achieved in the breadboard, but at a sacrifice in versatility. It was our original concept that the instrument should operate in any position. The present design is restricted to a single plane due to gravitational effects on the drive system. The final design configuration is a most elementary parallelogram. The drive coil is mounted in the center of the scanning platform. The motivation behind this particular design was to provide a closed magnetic 53

circuit in order to reduce stray magnetic fields, but this has an additional advantage. By driving the scanning platform near its center of mass, the angular rotation is appreciably reduced (by a factor of approximately 3). Beam splitter: At the outset of the project the design and construction of a satisfactory beam splitter was considered a major problem. This has not been satisfactorily solved and is the major problem to be dealt with in the development of interferometry in this spectral region. The basic problem is that there is no satisfactory material available for a substrate. We investigated various materials and of these, only KBr and IRTRAN-4 offered reasonable possibilities. The initial effort was concentrated on IRTRAN-4 because KBr was considered too fragile and too easily contaminated to be useful. IRTRAN-4 has the basic advantage that it is impervious to water and has good dimensional stability. The disadvantages are that it is nonhomogeneous and scatters an appreciable proportion of the incident radiation. Also, the high index of refraction results in large reflective losses. The large unwanted reflections made it very difficult to make the original visual alignments. These disadvantages made it extremely difficult for us to use IRTRAN-4 and we tlurned all of our attention to KBr. It was demonstrated that KBr cut in the 111 plane and suitably mounted would withstand the satellite vibration specification. The positive result from this test allowed us to go ahead with the development of KBr beam splitters. However, a successful beam splitter mounting has not yet been developed, In order to demonstrate the scientific breadboard, the substrate was glued at three points near the edge using rubber cement. This is the only mounting that 54

we have been able to use which does not distort the substrate. New mounting techniques are currently under development. Fixed mirror: No difficulties were expected with the fixed mirror, but five separate models were made in an attempt to obtain a satisfactory design. The present design uses a pair of differential screws for adjustment and a spring pivot for the third point. The differential screws are driven through slotted couplings in order to eliminate unwanted torques. The basic problem is that screws, no matter how well made, are too crude for such a close adjustment. We hope to develop a better adjustment in the future by using either magneto-strictive or piezo-electric devices. Detector optics: The detector is a standard design and had the predicted detectivity. However, the complete optic was low in sensitivity by approximately 30%, This was due to the optical design which did not properly account for all the off axis rays. The F-1 KBr lens has been satisfactory; but for any future design, completely reflective optics would be more satisfactory. Monochromatic reference: The neon 5852 A~ line was originally picked because of its good visibility. Good visibility greatly simplifies the initial line-up of the optics. However, a signal to noise ratio in excess of 10 is required for accurate digitizing. This requirement is only marginally satisfied at the end of the sweep. Further investigation has revealed that another neon line at 7032 A is stronger and the silicon detector is more sensitive to this line. The available signal is more than doubled but we decided not to change because our data reduction scheme had already been keyed to the 5852 A~ line. 55

Electronics: (see Figure 2) All of the electronics met the original specifications. However, the analog filters are the source of electrical phase shift which is non-linear with frequency. The effect of the phase shifting is to make the interferogram asymmetric which complicates the data reduction process. It is no longer sufficient to take the cosine transform, but it is now necessary to take the power spectrum and from the sign of the sine and cosine terms determine if the radiation is positive or negative. Thermal control: The development of an adequate thermal control was a major unanticipated project. In addition to developing a vacuum-tight hollow aluminum mounting plate for cooling the interferometer, a means of providing a dry nitrogen atmosphere had to be designed. A shroud completely surrounds the instrument and liquid nitrogen is boiled into the instrument. The gas leaks out across the windows to keep them moisture free. One liter of nitrogen will be sufficient for a 10-hour balloon flight. DATA REDUCTION: The data reduction or data processing from an interferom-:ter is rather elaborate compared to other instruments. For each interferogram reduced to spectra, 41, 664 bits must be processed. This can also be an advantage in that it is easy to do additional processing of the data since it is already on the computer. The output of the instrument is serial Bi-phase words 12 bits long. Each word consists of 8 bits from the A-D converter, a gain bit to indicate the position of the automatic attenuator, a parity bit, and two synch bits. This information is recorded on a tape recorder at 60 ips and reproduced at 7 1/2 ips. A CDC-160 A computer is programmed to translate this information 56

into IBM compatible format. The IBM compatible tape is used with an appropriate programto apodize the interferogram, compute the transform, apply phase corrections, apply calibration factors, and compute spectral radiance. The spectra presented (Figure 6) represents the results obtained thus far. In this case, the interferogram was apodized and the transform computed without applying any calibration factors. The data indicate that the wavelength calibration is very good. This should be expected since the wavelength calibration is determined by the 5852 A~ neon line. The actual resolution can only be estimated from this data. The reduction in resolution by apodizing can easily be seen by comparing Figure 5 and Figure 6. Now that a working instrument is available, a very complete calibration and evaluation must be performed before measurements can be made. It is also necessary to determine the best apodizing function and the instrument profile. Once the instrument has been properly calibrated, it will be flown on a high altitude balloon to further evaluate the instrument performance. SUMMARY: The continuing central problem with the interferometer is the obtaining of an adequate beam splitter. Temperature sensitivity is also a difficult problem and a possible solution is to servo control the fixed mirror so that it lines up with the moving mirror. It is our intention to continue to work on these problems until an adequate instrument for meteorological studies is produced. 57

LIST OF FIGURES Page FIGURE NO. TITLE I. Optical Head Layout 60 2. Electronics Block Diagram 61 3. Balloon Flight Optics 62 4. Balloon Flight Electronics 63 5. Polystyrene Absorption Spectra Unapodized 64 6, Polystyrene Absorption Spectra Triangular Apodization 65 58

REFERENCES 1. Chaney, L. W., and Loh, L. T., 1963, An Infrared Interference Spectrometer-Its Evaluation, Test, and Calibration, The University of Michigan ORA Report 05863-3-T. 2. Chaney, L. W., 1964, Earth Radiation Measurements by Interferometer From a High Altitude Balloon. Proceedings of the Third Symposium on Remote Sensing of the Environment, Ann Arbor, Michigan. 3. Kaplan, L. D., 1959, Inference of Atmospheric Structure From Remote Radiation Measurements. J. Opt. Soc. Amer., 49, pp. 1004 -1007. 4. Wark, D. Q., 1961, On Indirect Soundings of the Stratosphere From Satellites, J. Geophys. Res., 66, p. 77. 5. Drayson, S. R., 1963, Errors in Atmospheric Temperature Structure Solutions From Remote Radiometric Measurements. Univ. of Mich. Tech. Report. 6. Hanel, R. A., and Chaney, L. W., 1965, The Infrared Interferometer Spectrometer Experiment (IRIS) Vol. II, Meteorological Mission, Goddard Space Flight Center Report X-650-65-75. 59

8" FIELD OR VIEW NEON SOURCE MOVING MIRROR COMPENSATING PLATE RIGID MOUNT \ DRIVE COIL n / BEAM SPLITTER \ \CLOSED MAGNETIC MRO CIRCUIT SILICON PHOTO DIODE W/}////V^////////M \^^ rPD ^ ^_/_ ~~~GOLD CONE \^ \ ^V^^l^ ii ^^^^ ~~~~~~THERM ISTOR PARALLEL \ Kb^^ II ^^1^^ BOLOMETER SPRINGS \ SCAN PLATFORM pIL pi SCREWS FIXED MIRROR OPTICAL HEAD LAYOUT Figure 1

10 BIT- 3RD POS. F )BAND PASS SWITCHED C TO D PAR lFM ~ FILTER i30D.B IFM FILTER 30 D. B. O 8 BITS + TOSERIAL OPTICAL 20-8.0 CPS ATTENUATOR PARITY CONV. CUBii M 2 SYNCN HOUSEKEEPING = + I-0) L TINPUTS-16 CHAN.-P E PRE AMPS 7072 A TO TCOUNTS T BAND PASS SCHMITT SEQUENC 682 CP FILTER TRIGGER aI 400-800 CPS I POLARITY SWITCH START E 6944 COUNTS ^a CL PULSE <b I ^^ ^^^ ~~7072 ENCODE PULSES MIRROR I > I VELOCITY FEEDBACK BI-PHASE OUTPUT 0 ^ TO TELEMETRY OR + TAPE RECORDER POWER SUPPLY 24 VOLTS @ 0.3 AMPS BALLOON INTERFEROMETER ELECTRONICS BLOCK DIAGRAM Figure 2

Cl)::-:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~',-:!?iiiii,:i. —:~_::i::I!:- ~:~~~~~~ ~ ~ ~ ~C m!i~ ~ ~~i::-'.i::: co ~~~~~~~9 ~~~~~~~~~~~~c~...... C.............. C.. 62

Jigur 4 iics Figure 4 - Balloon Flight Electronics

1oo SCIENTIFIC BREADBOARD DATA JULY 8, 1965 90 - POL YSTYRENE -.003 BLACKBODY= 60~C DETECTOR= 27~C 0o- UNAPODIZED ABSORPTION SPECTRA IAI 70 260 30 -20 -10 0 v 600 700 600 900 1000 11O 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 WAVE NO. CM Figure 5

,00- SCIENTIFIC BREADBOARD DATA JULY 8, 1965 POLYSTYRENE=.003.90- ^ \ BLACKBODY= 600C DETECTOR= 27 C TRIANGULAR APODIZATION ~70O ~60O C) 1c h 40 30 20 I0 0 I 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1600 1900 2000 2100 2200 2300 2400 2500 WAVE NO. CM Figure 6

Appendix III THE MEASUREMENT OF THE EARTH'S TERMAL RADIATION BY A FOURIER TRANSFORM SPECTROMETER (presented to American Meteorological Society Symposium March 21, 1967, Ann Arbor, Michigan) 1. Intrioduction The High Altitude Engineering Laboratory under the sponsorship of Goddard Space Flight Center began an investigation of Fourier transform spectroscopy in the spring of 1961. During the course of the original literature survey it was discovered that Block Associates was manufacturing an infrared interferometer. The Block instrument covered the spectral range from 15u to 5u with a resolution of 40 cm. The instrument was purchased, modified and calibrated for a high altitude balloon flight and flown from Sioux Falls, South Dakota, June 26, 1963. Following the successful flight, a study was made to determine the feasibility of designing a higher resolution instrument. The primary objective in building the instrument was to carry out the temper2 ature inversion experiment proposed by Kaplan. The experiment required measurements in the 15u CO2 band with a radiation accuracy of 0. 5% and a resolution of 5 cm. 66

The study was in its early stages when the laboratory was approached by Dr. R, A, Hanel of Goddard Space Flight Center to make a joint proposal to fly an interferometer on the Mars 1966 mission. The original proposal3 to fly such an instrument was made in February 1964 and the basic design was accepted for the mission in May 1964. The Mars 66 mission was subsequently cancelled but G. S. F. C, continued to support the instrument development for the Nimbus satellite program. The objective of the development was to produce an instrument the output of which could be used to make a temperature inversion. The instrument development was completed for use in the laboratory by October 1965. The instrument is basically a Michelson interferometer whose design features and operation have previously been described. The purpose of this report is to describe the balloon flight preparations, the data reduction and the data analysis.. 2. Balloon Flight Environmental Problems and Testing. The principal problems associated with flying the instrument on a high altitude balloon arise as a result of the enviroment. The environmental conditions which influence the instrument operation are as follows: 1. Pressure - 1000 mb to 7 mb 2, Temperature - +25~C to -650C 3. Humidity - to 100% 4. Vibration - induced from other equipment. 67

In addition to making provisions to overcome the adverse environmental conditions, calibration of the instrument had to be provided. 2.1 Pressure The principle problem associated with the decrease in pressure is the corresponding decrease in the spark breakdown voltage. Except for the detector, all the voltage breakdown points were eliminated. Unfortunately we were unable to seal the detector and had to operate with an open flake. This created two problems: one, the "swish" noise created by air passing over the flake made the instrument "noisy" in the standard atmosphere; and two, the spark breakdown point was approached rather closely at "float" altitude. For example, if the pressure dropped below 3 mm a detector burn out could be expected, but at a pressure of 4, 5 mm there was no problem. We actually had several detector failures before we realized that one of the atmospheric test chambers would momentarily reduce the pressure below 3 mm. 2. 2 Temperature and Humidity In order to measure radiance it is necessary to know the reference temperature quite accurately. Also the optical alignment of the interferometer is disturbed by any change in temperature differentials across the cube. The temperature control problem was solved in the following way (Fig. 1)' The optical base plate is a vacuum tight container in which 1500 cc of water has been sealed. The water is frozen by circulating cold alcohol through an aluminum coil attached to the base. After the water has been completely frozen the alcohol is removed and cold nitrogen gas is circulated through the coils. The instrument is insulated 68

with two inches of urethane foam completely surrounding the package. The temperature of the instrument under these conditions will remain constant at or near 0 C for a period of 15 hours. The detector, due to self heating, will assume a temperature of 0. 8 C. The nitrogen in addition to cooling the base plate serves two other purposes. First, the liquid nitrogen is forced up to the input of the cold black body. The nitrogen boils, passes through the black body and lowers the temperature to 240 K. The gas is then fed into the base plate cooling coil from which it emerges at 2730K. From here it is fed directly into the optics and leaks out through the exit door. The purpose in the latter case is to maintain a purge of the optical head. The purge is necessary because both the beam splitter and the lens are made of potassium bromide which is very hygroscopic. Any "fogging" of these pieces will attenuate the monochromatic digitizing signal with disastrous results. Whenever the instrument is outside of the laboratory, it is necessary to maintain a nitrogen purge of the optics. The multiple use of the liquid nitrogen created conflicting requirements. In the final package the cooling of the black body placed the greatest demand on the system. The final specifications were as follows: Liquid Nitrogen Storage Capacity = 3 liters liquid Flow Rate = 2.8 liters gas per minute Flow Duration = 11. 4 hours 69

The usual procedure was to freeze the sealed water, fill the liquid nitrogen flask, connect the nitrogen purge and turn the heat on the warm black body. When the black bodies reached their operating temperature a final adjustment of the fixed mirror was made while observing the output of the monochromatic detector. The instrument then operated in the flight mode. The flight mode signifies that the programmer is in operation, the drive mirror is triggered every 15 seconds, and the view mirror is rotated in front of the black bodies and the earth viewing port. A polythylene bag was taped on the under side of the gondola over the view window and purged with dry nitrogen. This kept moisture off of the instrument during the checkouts and permitted the opening of the view window. In the actual flight the view window opened after reaching the float altitude. The electronic system was arranged so that the digitized output, the monochromatic signal, and the infrared interferogram could be checked and monitored at the gondola. The monochromatic signal was used to monitor the final alignment of the fixed mirror. The infrared signal was used to check the operation of the view mirror. By observing the form of the interferogram (Fig. 4), it is possible to determine the position of the view mirror. An observation of the digital output on an oscilloscope was sufficient to determine the data encode rate and the output bit rate. However, to determine that the encoding was correct and that the gain switching was operative a more elaborate check was required. 70

2. 3 Vibration Interfering vibrations were produced by other equipment on the gondola. The aerial cameras' film advance mechanism created a large impulse. The basic programmer was a matrix of Ledex switches that periodically produced a series of pulses. Finally, another radiation instrument produced a steady vibration. When the instrument was originally placed on the gondola with all the equipment in operation, the mirror drive vibrated so badly that it was impossible to make any measurements. Several steps were taken to correct the situation. The entire programmer was shock mounted. The aerial cameras were shock mounted and the interferometer itself was placed on vibration isolators. The instrument as it was flown on the gondola is shown in Fig. 2. The gondola ready for flight, hanging on the launching truck, is shown in Fig. 3. 2. 4 Calibration and Altitude Chamber Tests Prior to the balloon flight the instrument was tested several times in altitude chambers to simulate the balloon flight environment. A series of five tests were carried out in the Bendix Systems environmental chamber in Ann Arbor and three tests were performed in a Chrysler Corporation chamber in Warren, Michigan. The first tests were required to perfect the liquid nitrogen cooling-purge system and the later tests checked the spark breakdown conditions. The last test was used for making calibrations. These tests were very valuable in that they uncovered instrumental difficulties which were corrected before the balloon flight. The corrected problems were: 71

(1) formation of moisture on some of the integrated circuit boards (2) motor arcing noise due to the reduced atmospheric pressure (3) faulty microswitch action due to the cold temperature. During the final test the instrument was held at the simulated float altitude for calibration. The basic procedure was to use an external target which was first cooled to -100 C by means of liquid nitrogen. The target temperature was monitored at four places by means of platinum resistance thermometers. The thermometer voltages were measured with a Dymec data logging system. The temperature of the black body corresponding to a given interferogram was established to within 0, 1 C. A study of the data showed that the Fourier transform of the interferogram and the actual radiance were linearly related such that / (v ) = c+k(3 '(v)) where 3 '(v) is the Fourier transform of the recorded interferogram. The instrument was calibrated at every two wave numbers from 500 to 2000 cm, 3, Field Preparations After the series of tests and calibrations were completed in the Chrysler chamber the instrument was transported to Palestine, Texas, the site of the National Atmospheric Research Center balloon facility. Several complete checkouts of all the gondola equipment were carried out in order to determine that all the equipment was working properly. Because of the uncertainty of the weather it was necessary to hold extensive count downs prior to each intended launch. The instrument was prepared for launching four times prior to the actual launching. Therefore, by the day of the actual launching the procedure was almost routine, 72

After checking the instrument output at the gondola, the telemetry system was turned on and the same outputs were checked at the mobile telemetry station ( Fig. 5). The data was recorded for at least 15 minutes to fill one magnetic tape. As a final check the tape was played back at (72 ips), 1/8 of the record speed, and recorded on a galvanometer recorder operating at 64 ips. This combination allowed the visual recording of the individual bits. Using the bit information available, the peak of interferograms were plotted as analog signals. If a plotted curve was a reasonable representation of an interferogram and made a smooth transition across all gain change values, the instrument was assumed to be in proper adjustment. 4. The Flight On the day of the flight the same procedure was followed as described for the check out with the following additions. A secondary 1- liter liquid nitrogen container was placed on top of the gondola to keep the primary 3 liter bottle filled during the flight preparations. The flight preparations started at midnight for a 6 am launch. About 15 minutes prior to launch, when the gondola was hanging from the launch truck, the secondary 1 -liter bottle and the plastic bag over the view window were removed. The gondola program was set so that the command to open the view window occurred just as the balloon reached the float altitude. The balloon was launched at 0653 EST and impacted at 1711 EST. Data was recorded throughout the entire flight at the rate of three tapes per hour. 73

As the balloon rose, the background noise decreased just as it had done during the altitude chamber tests. There were bursts of noise throughout the flight and a large amount of noise was generated as the view door opened. Furthermore, noise was generated as the view mirror scanned to a new position. Later analysis determined that most of the noise was due to arcing brushes in several D. C. motors. In addition to the two motors used in the interferometer, several were employed by the other equipment. Fortunately the motors were not in continuous operation and there were periods of relative quiet. The flight path of the balloon is shown in Fig. 6 and it can be seen that for most of the early part of the flight the balloon circled the Palestine area and later drifted in a southwesterly direction. The impact point was 63 miles from the launch site. The interferometer functioned properly throughout the flight and interferograms were recorded until shortly before impact. However, the monitor channels failed at 1528 EST and the aerial cameras ceased to take photographs just prior to this time. These failures were the result of a problem with the programmer and it was realized prior to impact that the view door would also fail to close. This information was relayed to the ground crew who were at the impact site as the gondola came down and closed the door almost immediately. This was extremely fortunate since nitrogen was still being exhausted, although the liquid nitrogen container was empty. Post flight checks of the instrument have indicated that the sensitivity remained unchanged from the time of the flight, 74

5, Post Flight Data Reduction Immediately after the flight a few interferograms were converted from digital to analog form by hand to see that good data had been recorded. Once this fact was established the equipment was packed and returned to Ann Arbor. 5. 1 Formatting The data recorded in the field was in the form of serial bits recorded on an analog tape (Fig. 7). It was necessary to translate this presentation into a parallel 6 x 6 format understandable to the 7090 IBM computer. We were extremely fortunate in being able to use the Meteorology Department's computer facility which was ideal for the job. Their equipment consists of an analog computer which we used for shaping the signals, a CDC-160A digital computer, digital tape recorders, and a Cal-Comp plotter. The computer was programmed to decode each 8-bit word plus gain bit and store the result as a new 12-bit word in the memory. Each interferogram consists of 3472 words. When the correct number of words have been stored the contents of the memory is automatically plotted in analog form. By examining the plot any irregularities such as noise, gain change, or housekeeping commutator errors can be detected. If the interferogram is satisfactory, it is stored on magnetic tape and the computer can accept another interferogram. The playback and formatting was done at 1/8 the speed of the original recording. This allowed 80 seconds to store the interferogram and 40 seconds for plotting and examining the results. As long as everything was satisfactory the decoding proceeded automatically. 75

5.2 Computer Calculations There was a great deal more data available than could possibly be processed and since there were intermittent noise bursts throughout the flight, the analog plots from the CDC-160A were carefully examined and samples from each tape were selected for processing on the IBM 7090 computer. The sequence of interferograms selected from each tape was as follows: one cold black body, one warm black body, three successive scenes, followed by one cold black body and one warm black body. The selected information from each tape was presented on a single sheet as three separate plots. The first interferograms to be reduced to spectra occurred immediately before and immediately after the window opened, The characteristic 14i absorption line due to the polyethylene window was observed in the before spectrum (Fig. 8) and was absent in the following spectrum (Fig. 9), These spectra have a rather strange appearance because they are relative spectra. The measured radiation is both negative and positive with respect to the detector reference of 0. 80C. We encountered a slight problem in originally reducing the data because of the need to know the polarity of the radiation, Referring again to Fig. 4 it can be seen that both the cold and the warm black bodies have well, defined peaks which define the zero retardation point whereas the scene zero retardation point falls on a signal minimum, If the calculation is started away from zero retardation by one sample, the phase error will be from 22~ to 900~ We originally used the maximum peak as the starting point which produced phase errors from 1540 to 5600. 76

The originally calculated spectra were used to identify many spectral lines. In fact, almost all the lines appearing in the spectra could be identified. This was the first positive indication that the instrument performed as expected and was a source of great encouragement. 5. 3 Calibrations The instrument had been calibrated before the flight in the vacuum chamber and the first procedure was to apply these calibrations to the in-flight black body data. The result was quite a disappointment, The cold black body appeared to be colder than it should have been and the error became larger at the shorter wavelengths. The conclusion was reached that the altitude chamber was severly contaminated by water vapor. This proved to be the case and calibrations were applied to the data using the in-flight calibrations. A linear relation between the radiance and the relative amplitude had to be assumed since there were only two calibrating temperatures. The measurement results were compared in the region. between -1 -1 600 cm and 750 cm with theoretical calculations of the spectral radiance (Fig. 10). The theoretical radiance was calculated by Young and Drayson using the average temperature profile obtained from radiosondes flown on the same day as the flight from several surrounding weather stations. The comparison is extremely good and was a source of encouragement to all concerned with the project, 77

6, Data Analysis Three successive scans were averaged for each tape and the results are tabulated in the appendix. Two plots were made of the data from each tape. One plot extended from 500 cm to 900 cm. The other plot extended from 500 to 2000 cm. The scene data is the average of three scans, but the black bodies are single scans taken just before and just after the scene. Two examples of the plots are given in Figs. 11 and 12. These two plots represent the maximum difference in cloud cover during the flight. The corresponding photographs are shown in Figs. 13 and 14. 6, 1 Noise Study The excellent comparison between the measured and the theoretical radiance was extremely gratifying, but in order to establish the accuracy of the measurements a noise analysis of the data was made. The first step in the noise study was to fit a fourth order curve to a single scan black body spectrum (Fig. 15) and calculate the standard deviation (Fig. 16) of the data from this curve. The standard deviations -i are averaged over 20 cm intervals. Therefore, the values obtained are equivalent to a four scan average computed over a 5 cm 1 interval. The black body standard deviation plot shows that the noise is a sensitive function of wavelength, A false line appeared in the flight data -1 at 740 cm and is very apparent in the standard deviation plot. It is also apparent that the signal to noise ratio decreases from 600 cm to 500 cm due to signal attenuation through the potassium bromide. Except for the two areas noted, the average noise is less than 0. 5 ergs sec cm sr which was the original goal for the instrument, 78

Another technique for evaluating the noise is to calculate the signal in the non-signal area of the spectrum and assume that anything measured is noise. The electronic filter attenuates the signal sharply beyond 2500 cm and the fold over point is at 4272 cm (Fig. 17). Hence, in the region between these two limits the only signal should be noise. The standard deviation of the signal in this area was calculated for several interferograms and all were found to be less than 0. 5 ergs sec cm sr When the instrument was originally proposed, a noise study indicated that a signal to noise ratio of 2000:1 in the interferogram would re-1 -1 -1 suit in spectral noise of less than 0. 5 ergs sec cm sr. The measured signal to noise ratio of the instrument for a single scan is 1000:1 or 2000:1 for a four scan average which is in agreement with the original calculations. 6, 2 Wavelength Calibration The wavelength accuracy of the instrument was checked by comparing the percent transmission measurements made using the interferometer with those made using a Perkin-Elmer 13U spectrometer (Fig. 18). The agreement is excellent, and the deviations in percent transmission can be attributed to the difference in source temperature. It is always desirable to know the instrument scanning function, but thus far we have not had the equipment required to make the measurement. A laser would be an excellent tool for this purpose or a high resolution monochromator. 79

7. Conclusion The final results (Figs. 11 and 12) are measurements which met the proposed accuracy requirements of the temperature inversion experiment. The data has been used by Drayson and Young4' 5 to perform the temperature inversion. An example of their results is reproduced here (Fig. 19). There is, of course, a great deal more information available in the data, and we hope to make use of this in studying the distribution of ozone and water vapor. 80

LIST OF FIGURES Page 1. Gondola Interferometer installation - outline. 83 2. Gondola installation - photograph. 84 3, Gondola on launching truck. 84 4. Interferogram comparison. 85 5. Telemetry station block diagram. 86 6. Gondola flight path. 87 7, Digital data format, 88 8. Relative spectrum through polystyrene window. 89 9. Relative spectrum at 8:30 EST and line identification. 90 10, Comparison of calculated and measured radiance. 91 11, Spectral data at 11:09 EST. 92 12, Spectral data at 15:11 EST. 93 13. Photograph of scene at 11:09 EST. 94 14, Photograph of scene at 15:11 EST, 95 15. Black body spectrum, 96 16. Standard deviation of black body data, 97 17. Spectral data through the fold over region. 97 18. Wavelength calibration. 98 19. Temperature inversion typical. 99 81

LIST OF REFERENCES 1. Chaney, L. W. and L. T. Loh, An Infrared Interference Spectrometer - Its Evaluation Test and Calibration, NASA Contractor Report CR-61, June 1964. 2. Kaplan, L. D., J. Opt. Soc. Am 49, 1004, 1959. 3. Hanel, R. A. and L. W. Chaney, The Infrared Interferometer Spectrometer Experiment (IRIS), Goddard Space Flight Center Report X-650-64-204 and X-650-65-75, July 1964 and March 1965. 4. Drayson, S. R. and C. Young, The Determination of Meteorological Variables from Atmospheric Thermal Radiation Measurements, Am. Met. Symposium, March 21, 1967. 5. Chaney, L. W., S.. R. Drayson, and C. Young, Appl. Opt. 6, 347, 1967. 82

COLD BLACK BODY LIQ. N, URATHANE SHOCK MOUNTS. RADIINSULATION BLACK BODY ^^Nt GAS// _________^. ^BASE PLATE GONDOLA BD DOOR I i Figure 1 - Gondola Interferometer installation oune

l,~~~~~~~~~o: Figure 2. - Gondola installation Fligure 3S. - Gondola on launching truck 84

Balloon Flight Interferometer 8:30 EST, May 8, 1966 Palestine, Texas +, z I BLACK BODY 286.20 K. z ZERO RETARDATION 00 ac j I ^BLACK PODY 240.9' K. z zI~ t yl^ | EARTH RADIATION I-nA OPTICAL PATH DISPLACEMENT + nA Figure 4 - Interferogram Comparison

BRUSH IRIG TIME AMPEX MARK 1 TELEMETRY CODE FR-1300 GEN. RECORDER 0-~?'^it a??? TEKTRONICS 502A SCOPE DIGITAL________ MONOCHROMATIC-_______ ________INFRARED____________ MICROPHONE 00oo CEC 5-124 GALVA NO METER RECORDER TO AMPEX ON PLAYBACK Figure 5. - Telemetry station block diagram

SY SYNC. SYNCGAIN - ~ IA-D-D LANK- BLANKBLANK (BIT FUNCTION) N lox I 2 4 8 16 32 1 64 1128 (BIT VALUE) g I I I 0 0 0 4 0 0 0 64 0 0 0 co co 1040 rSEC. 2930 pSEC. J Figure 7 - Digital data format

C') 0 A W co9 > - 7p ABSORP 0 80 000 1200 1400 160000 WAVENUMBER, cm-' Figure 8 - Relative spectrum through polystyrene window CtT I4 ABSORPTION BAND 7l ABSORPTION BAND.J 3 ) Q: z 600 800 1000 1200 1400 1600 1800 2000 WAVENUMBER, cm-' Figure 8 - Relative spectrum through polystyrene window

U).w 0:: t1 I ~1041 a. 4< \ ~ yW/V 1594 740Q 1306 1458 H CO2c4 0 I00 800 1000 1200 1400 1600 -719 667 649J -678 600 800 1000 1200 1400 1600 1800 2000 WAVENUMBER, cm-i Figure 9 - Relative spectrum at 8:30 EST and live identification

120 10.0 E &o U 0\ k 6.0 w 4.0 - 0 -I co C-) w C) 20 HIGH ALTITUDE ENGINEERING LABORATORY UNIVERSITY OF MICHIGAN 500 540 580 620 660 700 740 780 820 860 900 WAVENUMBER, cm-' Fig. 2. Theoretical radiances calculated using transmissivities of Drayson 8 Young4 (600-750 cm-'), and an average radiosonde temperature profile for Eastern Texas on May 8, 1966 ( ----). Balloon flight Fourier Transform Spectrometer radiance measurements May 8, 1966-07:30 CST Palestine, Texas. A three scan average (500-900 cm-I) (-). Figure 10 - Comparison of calculated and measured radiance

14.0 SPECTRAL RADIANCE MEASUREMENT IRIS INTERFEROMETER —PALESTINE, TEXAS (o12.0- A ^~V~ THREE SCENE AVERAGE - CLEAR E F 11:09 EST, MAY 8, 1966 10.0 o w 0 z 6.0 -4.0 -oL BBLACK BODY TEMP. 2S6 K. n- 2-40.IPK. 2.0 -500 750 1000 1250 1500 1750 2000 WAVENUMBER, cm-' Figure 11 - Spectral data at 11:09 EST

14.0^~~~~~~ - ~~SPECTRAL RADIANCE MEASUREMENT IRIS INTERFEROMETER- PALESTINE, TEXAS THREE SCENE AVERAGE-ESTIMATED i2_ 0 -^^/^~~~~~~ CLOUD COVER 25%, 15:11 EST, MAY 8, 1966 Io. 0 - E 3: 8.0 =LI w 0 z 6.0 -< CD _ 4.0- ~ Lt V ^BLACK BODY TEMP. 28&6* K. O^~~~~~~~ BLACK BODY TEMP. 2B0.9 K. 26K 8j 2. - ^- ^ ^^ U) 500 750 1000 1250 1500 1750 2000 WAVENUMBER. cm-' Figure 12 - $pectral data at 15:11 EST

Figure 13 - Photograph of scene at 11:09 EST 94

DiA Figure 14 - Photograph of scene at 15:11 EST 95

14.0 -E 12.0 - CE 10.0 z 8.0 -~CDa~~ J^~~ ^^^I~ ^HIGH ALTITUDE ENGINEERING LABORATORY ^ 4.0- ^ UNIVERSITY OF MICHIGAN w acn 2. ~~ Fi0ur b sc 500 750 1000 1250 15001702 0 WAVENUMBER. cm-' Comparison of Fourier transform spectrometer single scan radiance measurement of 286.21 K calibration black body and theoretical radiance of 286.20 K black body. Figure 15 - Black body spectrum

141 ";.Standard Deviation, 20 cm" Interval - 1' Flight Black Body 286.6 K. 1.0- \ 1108 EST. May 8. 1966 Palestine. Texas U, 0.8 \> OS\ u, 0.6 \f (9 — w 0.4 0.2 500 750 1000 1250 1500 1750 2000 WAVENUMBER. cm' Figure 16 - Standard Deviation of black body data v,^~~~~~ - 3~M,~ ~Relative Amplitude of Complete Spectrum Z) Reference Temperature 0.8' C. CO^~~~~~~~~ "~ YI~~~~~~~~~.I I ~Scene 11-09 E ST, M ay 8. 1966 Palestine. Texas IJI 43~~~~~~~~~~~~~~~~~U Q_ ~ \ Ld>^~~~~~~~~~ FW^OLDn OVER OR REFLECTION POINT. <( ' \ 3000 cm-11 4272 cm-' L NON-SIGNAL AREA * NOISE ONLY z 01000 2000 3000 4000 5000 6000 WAVENUMBER, cm-' Figure 17 - Spectral data through the fold over region

100 z 90 0 cn 80 C' 70 z60 ' 50 J,\ i. V i i iii..40 -I I: _ I z a,al W 30 - O~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I Ia: w 20 co a. 00~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~: 10 aa a a, ' 500 750 10-00 1250 1500 1750 2000 WAVENUMBER, cm-, Polystyrene percent transmission measurements. Perkin-Elmer model 13U at approx. 2 cm-' resolution and with Nernst glower ( ----). I.R.I.S. scientific breadboard with approx. 5 cm-' resolution and a blackbody source at 3330 K. (-) Figure 18 - Wavelength Calibration

5 ( --— ) AVERAGE RADIOSONDE (- / / ) INVERSION SOLUTION I00 -co " -^^^^^ ~ HIGH ALTITUDE ENGINEERING LABORATORY UNIVERSITY OF MICHIGAN I000 200 210 220 230 240 250 260 270 280 290 300 310 TEMPERATURE, (OK) Comparison of tempera ure profile by radiosonde measurements in Eastern Texas on May 8,1966 aond temperoture profile obtained by the inversion of Fourier Tronsform Spectrometer dat a. Figure 19 - Temperature inversion typical

APPENDIX IV FOURIER TRANSFORM SPECTROMETER RADIATIVE MEASUREMENTS AND TEMPERATURE INVERSION L. W. Chaney, S. R. Drayson, and C. Young (a paper published in Applied Optics, February 1967) As part of a program to develop improved meteorological satellite instrumentation, a Fourier transform spectrometer for radiation measurements has been developed in cooperation with Goddard Space Flight Center (Hanel and Chaney, 1964 and 1965). The purpose of the instrument is to measure the earth's thermal radiation in the spectral band from 500 to 2000 cm1 with a resolution of 5 cm and a radiance error not exceeding 0. 5o. The final version of the instrument is planned for a Nimbus satellite to be launched late in 1967. The breadboard version was flown on a high altitude balloon from Palestine, Texas, on May 8, 1966. The balloon was launched at 0553 CST and rose to a stable float altitude of 7 mb or 110, 000 feet, which was reached at 0736 CST. The sky was perfectly clear at the time of launch and throughout most of the day. Scattered clouds appeared during the latter part of the afternoon. The balloon gradually drifted southwest and impacted 63 miles from the launch site near Easterly, Texas, at 1611 CST. The dry bulb air temperature at the time of launch was approximately 19 C and increased to 29~C by 1400 CST. The data from the initial portions of the balloon flight have been reduced to radiation measurements and are reported here. 100

The complete radiance spectrum is plotted in Figure 1. These are, to our knowledge, the highest resolution thermal radiation measurements in the 5 to 20- spectral region which have been made from a high altitude balloon. Starting from 500 cm the following features of the spectrum can be observed: 500 - 600 cm rotation water vapor 600 - 750 cm 1 CO2 800 - 950 cm. thermal window 950 - 1050 cm ^ ozone 1100 - 1250 cm thermal window plus wings of water vapor 1300 - 2000 cm I water vapor An absorption band is noted at 1306 cm which has tentatively been identified as CH4. In addition to developing the instrumentation for making the measurements, an extensive theoretical study of the carbon dioxide molecule to determine the transmissivity of the atmosphere in the 600-750 cm spectral region was carried out. By using the calculated CO2 transmissivities and a temperature profile obtained by radiosonde data on the day of the flight, a calculated radiance curve extending from 600 to 750 cm was obtained. The effects of water vapor and ozone were neglected in the theoretical calculations. The measured and calculated radiances are compared in Figure 2. The measured values are the average of three spectrometer scans of 10 seconds each, taken 15 seconds apart at 0730 CST just as the balloon reached float altitude. The agreement shown demonstrates the capability of the Fourier transform spectrometer to make the required radiance measurements as well as the reliability of the theoretical calculations. 101

The first application of the data has been to invert to an atmospheric temperature profile. The inversion method employed was to calculate the deviations from an initial guessed profile expressing the solution as a matrix equation (cf. Kaplan, 1961). The instabilities in the matrix inversion were suppressed using a truncated eigenvector expansion (Mateer, 1965). The results of a temperature inversion using the measured radiation and a monthly average profile as an initial guess is shown in Figure 3. The inversion profile is compared with a measured profile obtained from the average of the radiosondes flown in eastern Texas on the day of the flight. The agreement through the tropopause is very good, and the deviation above the tropopause is probably due to the higher radiance measured from 670 cm 1to 720 cm1 combined with the smaller radiance at the peak of the Q-branch. Although the results are still tentative, the agreement between theory and measurement is very encouraging. In fact, our confidence in the reliability of the data is based on the excellent agreement. Thus far, the examination of the errors in the data have been confined to observing the deviations of measured black body spectra from the calculated radiation using Plank's equation and the measured black body temperature. A comparison for the two black bodies incorporated in the instrument was made. In each case the measured spectra represented the average of three 10-second scans. The least square error was calculated for each black body data set, and -7 -2 -1 -1 through most of the spectral range it is less than 0. 3 x 107 watt cm sr /cm 1 There is one bad spot in the data at 740 cm1 which can be atrributed to external vibration arising from some auxiliary instrumentation. The systematic error 102

is probably due to inaccuracies in measuring the temperatures of the black bodies. The total error is less than 1 x 10 watt cm sr /cm. The results obtained thus far indicate that the breadboard instrument matches the theoretical instrument performance within a factor of 2. It is planned to continue development of both the instrument and the techniques for obtaining temperature profiles as well as the investigation of the ozone band. This research was supported under contracts with the Laboratory for Atmospheric and Biological Sciences, NASA Goddard Space Flight Center and the National Environmental Satellite Center, ESSA. REFERENCES lo Hanel, R, Ao, and L. Chaney, The Infrared Interferometer Spectrometer Experiment (IRIS), Goddard Space Flight Center Reports X-650 -64-204 and X-650-65-75, July 1964 and March 1965. 2o Kaplan, L. D., Jo Quant. Spectrosc. Radiat. Transfer 1, 89-98, 1961. 3, Mateer, C. L., J. Atmos. Sci. 22, 370-381, 1965. 4. Drayson, S. R. and Co Young, Intensities of the Carbon Dioxide Bands in the 12 to 18-Micron Spectral Region, paper presented at Symposium on Molecular Structure and Spectroscopy, The Ohio State University, September 1966. LIST OF FIGURES Page 1o Balloon flight Fourier transform spectrometer radiance measurements. 104 2. Comparison of theoretical and calculated radiances. 105 3o Comparison of temperature profile measurements by radiosonde and in- 106 version solution. 103

14.0 a -0 12 tHO 2O S WINDOW 3 E 12.0- X L _ I I n\V I | HIGH ALTITUDE ENGINEERING LABORATORY hlEv^ A^\'~~~R c m UNIVERSITY OF MICHIGAN "10.0 07:30 CST Palestine, Texas. Altitude 33.5 KM. A four scan average. 4CH _ METHANE 6.0 -Iw 2.0 -01 500 750 1000 1250 1500 1750 2000 WAVENUMBER, cm-, Fig.l. Bolloon flight Fourier Transform Spectrometer radionce measurements May 8, 1966 07:30 CST Palestine, Texas. Altitude 33.5 KM. A four scan average.

12.0 10.0 E 8.0 - 6.0 w 0 O M. S) 20 _ HIGH ALTITUDE ENGINEERING LABORATORY UNIVERSITY OF MICHIGAN 500 540 580 620 660 700 740 780 820 860 900 WAVE NUMBER, cm-' Theoretical radiances calculated using transmissivities of Drayson 8 Young3 (600-750 cm-'), and an average radiosonde temperature profile for Eastern Texas on May 8, 1966 ( ----). Balloon flight Fourier Transform Spectrometer radiance measurements May 8, 1966-07:30 CST Palestine, Texas. A three scan averaqe (500-900 cm-r) (-).

5 ( ----) AVERAGE RADIOSONDE E / -(~-) INVERSION SOLUTION ' -7I 10 L / E / ~ ir 100 I 00 HIGH ALTITUDE ENGINEERING LABORATORY -t^'^>^^^ UNIVERSITY OF MICHIGAN 200 210 220 230 240 250 260 270 280 290 300 310 TEM PE RATURE, ( K ) Fig. 3 Comparison of temperature profile by radiosonde measurements in Eastern Texas on May 8,1966 and temperature profile obtained by the inversion of Fourier Transform Spectrometer data.

UNIVERSITY OF MICHIGAN 3 9015 02651 5067