MULTI-FREQUENCY, MULTI-POLARIZATION EXTERNAL CALIBRATION OF SIR-C/XSAR Final Report NASA/JPL GRANT JPL-958749 Submitted to: Jet Propulsion Laboratory ATTN: Dr. Anthony Freeman 4800 Oak Grove Drive Pasadena, CA 91109 Prepared by: Prof. Kamal Sarabandi (Pl) Department of Radiation Laboratory Electrical Engineering and Computer Science The University of Michigan Ann Arbor, MI 48109-2122 Tel: (313) 764-0500 Fax: (313) 747-2106 Project Management: K. Sarabandi, M.C. Dobson, L. Pierce, F.T. Ulaby RL-988 = RL-988

Contents 1 Introduction 3 2 Calibration Experiment 4 3 SUMMARY OF ACCOMPLISHMENTS 10 3.1 Calibration Algorithms For Point Targets............... 10 3.2 Mleasurement and Calibration of Differential Mueller Matrices 11 3.3 Characterization and Design of Precision Active Calibration Targets............................................... 11 3.4 Analysis. Design, and Construction of an Optimum Corner Reflector............................. 12 3.5 Calibration Algorithms for Polarimetric SAR Systems....... 13 3.6 (ross Calibration Experiment................... 13 3.7 Applications...........................13 4 Students Supported 14 5 Publications 14 6 Appendices A-H 15 2

MULTI-FREQUENCY, MULTI-POLARIZATION EXTERNAL CALIBRATION OF SIR-C/XSAR Abstract In t his final report a smnlmary of our activities with regard( to external calil)ration of the Shuttle Imaging Radar-C/XSAR (SIR-C/XSAIR) is providel. The U:niversity of Michigan was involved in tile developmlent of caliblration procedures and precision calibration devices to quantify the conlplex radar images with an accuracy of 0.5 dB in magnitude and 5 degrees in phase. Our researcl activities il the area of calibration of polarimetric SARs can b)e categorized into five areas: (1) development of calibratioll techniques for point targets, (2) development of polarimetric calibration techniques for distributed targets. (3) design of novel precision calibration targets, (4) development of polarimetric calibration techniques for SAR systems based on point and distributed targets, and (5) application of calibrated images for renlote sensing of vegetation and soil moisture. On April 9. and September 30, 1994 the SIR-C/XSAR instruments were launched twice, each time on an 11-day mission, aboard the NASA space shuttle Endeavor. During both missions several supersites received frequent overflights including the Raco supersite inl the upper peninsula of Michigan. The Raco supersite, centered on 46.392 N. Latitude and 84.885 WX. Longitllde, is located in Chippewa (ounty in the eastern part of Michigan's Upper Peninsula. The area under study and imaged in the SIR-('/X-SAR crossover region is approximately 20 kml E-W and 20 km N-S. This site was imaged twelve times between April 9 and April 19 and twelve time between Septenlher 30 and October 10. A team consisting of scientists and graduate students were involved in deployment of targets and collection of ancillary data. 1 Introduction In radar relmote sensing, calibration of polarimetric radar systenls is of great inlIortance because the success of any inversion algorithm or any radar classifier depends dlirectly on the accuracy of the measured data. To provide a cluantitative value for the measured backscatter and remove the distortion fronm different channels of tlle radar caused by the active components and the antenlna an external calibration must l)e performed. The external calibration of a radar system involves a comparison of the measured response of the unknown target with the measured response of one or more calibration targets of the known radar cross section. For this purpose appropriate calibration targets and convenient calibration algorithms are required. A metallic sphere is a desirable calibration target because it is one of the few geometries for which an analytical RCS exist and its backscatter cross section is independent of orientation angle. However, the drawback of a metallic sphere is its 3

relat ively smnall 1R('S. III calibIration of imagfes ac(1uiIed hOm S.;.-\ tl iiii )Oillt cali)brat iol tal'gcts. tlie RI( S of the calibration tIarget s ll1st e Il muc larger t hail tliose of t l( surrotldillOg ixe'ls ill tlhe inllage. I]lli s '(l r 'equirell('imeit eiures that tHle radar return front tlhe background is negligibl}le relative to tll( lieret u1I fromn the calibration target. In practice tlhe RC(S of calibration targets for imagilng radars can be measured using tlIe metallic sphere. The following characteristics are desirable for calibration targets of imaging radars: (1 ) large RCS. (2) wide RCS pattern (being insensitive to orientation angle). (3) easily dleployable (having small phlysical size), (4) stable R(S, and (5) insensitive RCS to its background (no interact ion with its surrounding). Accurate measurement of scattering matrices of calibration targets for SARs requires accurate calibration techniques for point targets. Once the calibration targets are designed and fully characterized, a calibration algorithm for the SAR image based on the point calibration targets is required. The accuracy of the overall calibration procedure must then be checked by comparing the calibrated image to the measurement of an independent calibrated instrum-ent such as a t ruck-mounted scatterometer system. Therefore a calibration procedure for distributed targets for nonimaging radars is also needed. In ain backscatter measurement of distributed targets the quantities of interest are the backscatter coefficients, which are the second moments of tlle scattered field per unit, area. (Calibration algorithms based on point targets for synthetic aperture radars must infer the calibration constant for backscattering coefficients from the RCS of the point targets. This process requires accurate knowledge of the SAR impulse function which is very difficult to characterize. To circumvent this problem calibration algorithms based on known distributed targets can be used. Such a calibration algorithm, however, provides the calibrated differential Mueller matrix of a region of the image as opposed to calibrated pixels. In what follows we briefly describe thle calibration experiments and then we summarize the techniques and devices developed during the course of this investigation. 2 Calibration Experiment In this section a brief description of our field activities during both SIR-C missions is given. Figure 1 shows the location of the Raco supersite where all of our calibration activities took place. The overall goal throughout the duration of the SIR-C(/X-SAR project has been the development of image calibration algorithms by determining extracting the effects of system distortion parameters from the SIR-C polarimetric radar images. The objectives andl methods used for assuring accurate calibration for both SIR-C' missions were as follows: 1. Design and development of appropriate point calibration targets. 4

2. ('haracterizatioln of I( 'S of p)oint targets. 3. l)eploy aIld llmonitor thle point targets in the calib)ration site. 4. l)evelopnenlt andl assessment of p)olarilletric calib)rat ion algorit linls usilg point I)Oint calil)ration targets. 5. I)evelol)ment of a procedure that would allow calibrationl of t lie ilmaging radars Ilsing distributed targets. 6. Deployment and measurement of backscatter for area exten(led targets with calibrated polarimetric scatterometer svstenl. 7. Absolute calibration of SIR-C/X-SAR imagery accuired at L('. and X bands 8. Accurate calibration over the geographical extent of the imaged scenes During the SIR-C flights point calibration targets were distributed ill open areas withil the area imaged by the sensors. Bothl passive and active targets were deployed. For the April mission six 1.07 m trihedrals and one C-band PA(RC were located at the Rifle Range near the Raco Airfield. Two 2.4 in trihedrals were located at the Raco Airfield. Four 2.4 m triliedrals, one L-band single anltenna polainrietric active radar calibrator (SAPAR C), one ('-band SAPAR('. and one C-band PARC( were located at Crvderman Field. See Figure 2 for the location of these fields. Details regarding target positioning, including gps derived coordinates, target type. and neasured elevation angles and azimuths, can be found in Table 1. The three target locations are depicted on the map SIR-C/XSAR Test Stands and Calibration Sites. Targets were repositioned algnd/or monitored for accurate positioning before each overflight using electronic levels and Brunton conpasses. Scatterometer measurements were made at L, ('C and X-bands in conjunction witll each SIR-C/X-SAR overpass. These measurements were made at C(rvderman field. 5

"a t " 0400000m E 06 5 08Ocoo0 EL ' '" -I. t: ' -T -l:!:'<e: AT 9:" SIR-C Supersite: Raco, Michigan Kilomootors ICC C 1J3 20C 300 40C 53 Ni is l)C * ' O.)?_)J Figure 1: Raco SIR-C/XSAR supersite. 6 L L

-6 5 6xfi 6 7 ~6 9 U0 CD 0 GGw0o60000 E. 6 7 4 6 80000rn E. 40435' 6 9 L;-.-e 1.6" Clarke 1866 (NAD 27) SIR-C Test Stands and Calibration Sites Raco, Michigan Supersite Kilometers 100 10 20 Miles 10 __0 1 I I I U Forest test stands LII calibration site LIII SIR-i ii u(llzed SwathI Figure 2: Location of test fields in Raco SIR-C/XSAR supersite.

Table 1: Calibration Targets Calibration Target Plan at Raco Supersite MET (dd/hh:mm:ss) 00/07:50:29 01/07:32:17 April 1994 Mission Orbit No. 6 22 Data-Take No. 6.1 22.2 Local magnetic declination is 6.1380 W Ascending/Descending D D North/South Looking (from Shuttle) S S All PARCs 1 1.0000 Look Angle (relative to SIR-C) 30.14 19.33 -1 -1.0000 Local Incidence Angle 31.387 20.132 SIR-C Azimuth Heading (True North) 127.461 128.428 Target Azimuth (True North) 127.86 127.86 Target Looking (N/S) N N Location Target Azimuth (Mag. North) 1 34 1 34 / Elevation Azimuth Elevation Azimuth Target Descendin Target Size Max. RCS Angles (From (from True Level Angles (From (from True Level Site Name g Latitude Longitude Type (cm) (dBm^2) horizontal) north) (degrees) horizontal) north) (degrees) RIFLERANGE T2-1 A/D 46.3337 -84.8593 Trihedral 107 30.5 128.9 1.7 30.7 127.9 0.8 T2-2 A/D 46.3360 -84.8575 Trihedral 107 29.2 128.9 1.1 15.6 155.9 16.6 T2-3 A/D 46.3453 -84.8497 Trihedral 107 29.6 127.9 5.8 7.5 152.9 15.7 T2-4 A/D 46.3452 -84.8512 Trihedral 107 27.2 124.9 1.4 29.6 129.9 0.4 T2-5 A/D 46.3481 -84.8487 Trihedral 107 30.0 128.9 1.3 30.5 128.9 1.0 T2-6 A/D 46.3506 -84.8500 Trihedral 107 31.2 127.9 -0.5 28.7 129.9 0.1 P4 A/D 46.3362 -84.8592 C-PARC #2 42.4 31.4 127.4 0.1 30.1 128.9 0.8 RACO T1-5 A/D 46.3468 -84.8058 Trihedral 240 30.3 128.9 0.6 29.8 128.9 0.2 AIRFIELD T1-6 A/D Trihedral 240 CRYDERMAN T1-1 A/D 46.4591 -84.9070 Trihedral 240 31.0 126.9 0.0 30.4 127.9 0.0 FIELD T1-2 A/D 46.4562 -84.9093 Trihedral 240 31.5 128.9 1.1 30.2 127.9 1.4 T1-3 A/D 46.4561 -84.9130 Trihedral 240 31.3 125.9 0.5 31.6 127.9 0.3 T1-4 A/D 46.4571 -84.9152 Trihedral 240 31.0 126.9 0.8 31.4 126.9 0.7 P1 A/D 46.4578 -84.9104 L-SAPARC 32.1 125.9 1.0 19.9 127.9 0.4 P2 A/D 46.4597 -84.9102 C-SAPARC??? 20.2 128.9 yes P3 A/D 46.4583 -84.9126 C-PARC #1 44.5??? 19.4 128.9 0.3 Date Day Time Saturday 9-Apr 14:55:29 Sunday 10-Apr 14:32:17

04/00:25:22 05/00:05:44 05/06:15:43 05/23:45:41 66 82 86 98 66.2 82.2 86.4 98.12 A A D A S S N S 21.65 29.53 23.77 35.512 22.65 30.849 24.531 36.801 51.853 52.341 131.101 52.911 232.86 232.86 311.86 232.86 N N S N 239 239 318 239 Elevation Azimuth Elevation Azimuth Elevation Azimuth Elevation Azimuth Angles (From (from True Level Angles (From (from True Level Angles (From (from True Level Angles (From (from True Level Site Target Name horizontal) north) (degrees) horizontal) north) (degrees) horizontal) north) (degrees) horizontal) north) (degrees) RIFLERANGE T2-1 30.6 53.9 0.1 30.2 236.9 0.1 30.9 310.9 0.2 9.9 232.4 0.4 T2-2 31.6 53.9 0.9 30.6 233.9 0.1 30.0 313.9 0.3 9.9 233.4 0.4 T2-3 29.6 54.9 0.5 28.5 234.9 0.2 29.9 315.9 0.4 9.9 232.4 0.1 T2-4 29.6 52.9 0.7 29.2 237.9 -0.3 30.5 311.9 0.2 9.3 233.9 0.0 T2-5 30.9 53.9 0.5 30.4 235.9 0.8 30.2 309.9 -0.2 10.1 233.9 0.1 T2-6 30.5 53.9 0.9 30.7 233.9 1.2 30.5 311.9 1.0 10.2 232.9 0.0 P4 20.7 52.9 0.1 30.8 232.9 0.1 24.5 311.9 0.0 36.8 232.9 0.0 RACO T1-5 30.5 231.9 0.4 30.1 311.9 0.1 9.8 232.8 0.2 AIRFIELD T1-6 1 30.0 233.9 0.7 30.3 312.9 0.1 11.0 233.1 0.2 CRYDEMAN T1-1 30.4 53.9 0.5 30.0 233.9 0.5 30.0 312.9 0.0 - FIELD T1-2 30.6 53.9 0.3 30.2 232.9 0.0 29.6 311.9 0.6 - T1-3 30.9 51.9 1.0 31.0 233.9 0.1 29.6 311.9 0.2 10.3 236.9 0.0 T1-4 31.1 52.9 -0.6 31.1 232.9 0.7 30.0 311.9 0.4 11.1 232.9 0.6 P1 21.6 51.9 0.5 30.9 232.9 0.8 24.9 312.9 0.1 35.1 239.9 2.0 P2 23.4 52.9 ok 30.7 235.9 ok 24.8 310.9 ok 36.5 236.9 ok P3 22.8 52.9 0.5 29.2 235.9 1.1 24.5 311.9 0.4 37.2 241.9 0.3 Wednesday 13-Apr 7:30:22 Thursday 14-Apr 7:10:44 Thursday 14-Apr 13:20:43 Friday 15-Apr 6:50:41

06/05:55:33 06/23:25:12 07/05:34:57 08/05:13:5 102 114 118 134 102.41 114.1 118.6 134.3 D A D D N S N N 30.701 40.09 35.903 39.787 31.747 41.799 37.268 41.306 131.674 53.567 131.959 132.328 311.86 232.86 311.86 311.86 S N S S 318 239 318 318 Elevation Angles Elevation Angles Elevation Angles Elevation Angles (From Azimuth (from (From Azimuth (from (From Azimuth (from (From Azimuth (fro Site Target Name horizontal) True north) Level (degrees) horizontal) True north) Level (degrees) horizontal) True north) Level (degrees) horizontal) True north RIFLE RANGE T2-1 29.6 312.9 0.5 11.0 232.9 0.0 - T2-2 29.9 313.4 0.5 10.6 231.9 0.0 - - - T2-3 29.8 311.4 0.4 10.8 232.9 0.2 - T2-4 - - - 10.9 233.9 0.2 9.7 311.9 0.4 10.4 309.9 T2-5 30.0 311.9 0.3 10.3 232.9 0.2 9.9 311.9 0.1 9.7 312.9 T2-6 - - 10.6 231.9 0.4 9.7 310.9 0.4 9.6 310.9 P4 31.7 311.9 0.0 41.8 232.9 0.0 37.3 311.9 0.0 41.0 313.9 RACO T1-5 29.3 313.4 0.4 9.3 234.7 0.3 - - - AIRFIELD T1-6 30.4 311.9 0.1 10.6 232.7 0.3 10.7 313.9 1.0 18.7 317.9 CRYDERMAN Ti-1- - - 12.2 223.9 2.9 11.0 311.9 0.4 10.5 311.9 FIELD T1-2 - -. I - - 9.4 314.9 2.3 10.8 318.9 T1-3 29.5 312.9 0.0 15.1 230.9 1.6 - - T1-4 30.0 313.9 0.4 9.9 232.9 1.0 P1 31.0 310.9 <2.0 41.7 232.9 2.0??? 42.0 312.9 P2 31.4 310.9 ok 40.9 227.9 ok 37.0 312.9 ok 42.1 312.9 P3 32.4 313.9 0.4 41.2 232.9 0.3 37.6 311.9 0.5 41.4 313.9 7 m,L Friday 15-Apr 13:00:33 Saturday 16-Apr 6:30:12 Saturday 16-Apr 12:39:57 Sunday 17-Apr 12:18:57

09/04:52:22 09/22:20:59 150 162 150.2 162.3 D A N S 42.55 47.325 44.308 49.67 132.785 54.17 311.86 232.86 S N 318 239 Elevation Angles Elevation Angles (From Azimuth (from (From Azimuth (from Site Target Name horizontal) True north) Level (degrees) horizontal) True north) Level (degrees) RIFE RANGE T2-1 10.6 52.9 0.1 T2-2 10.4 52.9 0.0 T2-3 10.6 52.9 0.1 T2-4 10.1 311.9 -0.3 T2-5 9.6 312.4 -0.1 T2-6 9.6 311.9 -0.6 P4 43.8 311.9 0.5 RACO T1-5 10.0 59-6.14 0.0 10.0 52.9 0.0 AIRFIELD T1-6 10.0 311.9 0.0 CRYDERMAN T1-1 10.4 310.9 0.4 FIELD T1-2 10.4 318.9 1.5 T1-3 11.4 51.9 0.4 T1-4 10.8 51.9 1.2 P1 44.9 312.9 0.3 P2 44.2 313.9? P3 43.8 312.9 0.6 Monday 18-Apr 11:57:22 Tuesday 19-Apr 5:25:59

In tilhe October miission 21 calibrat'ion targets were' )osit ioned(. Six 1.07 il trihedrals. one L-l)and SAPARC. one ('-band SA-PA\('. and four 2.1 In1 trihedrals were located at tlie tRifle R1ange near thle Raco Airfield. Two (I)andl1 PAR( S were located at tlle Raco Airfield. Four 2.4 nl triliedrals were located at C'ryvlerian Field. In addition, three distril)uted targets areas were established at the Rifle Ranlge. Details regarding point target positioning. including GPS derived coordinates, target type, and measured elevation angles and azimuths, can be found in Table 2 (October SIR-C/X-SAR Calibration Point Targets). Point targets were repositioned and/or monitored for accurate positioning before each overflight using electronic levels and Brunton compasses. During the 11-day mission, polarimetric scatterometers were used to collect data at L, C. and X-bands in conjunction with each SIRC/X-SAR overpass. This data is used to define the average Mueller matrix of distributed targets. Three distributed targets, or surfaces, were defined and located at the rifle range. These were approximately 100 m X 100 m. Each plot (SI to S3) had a distinctive surface roughnless with RMIS roughness ranging from 2 to 6 cm. (Tables 8 and 9). The locations of the distributed targets are documented on the map SIR-C/X-SAR October 1994 Rifle Range Distributed and Point Target Locations. The details of experimentations and results are reported in [1] and [2] which are also given in Appendix A. 8

9 2 SIR-C[X-SAR Octot Rifle Range Distrit Point Target Locati Jf 9A Zp 7924 z.I - A F,.f, I-, ' -1.a 1-1 -1 DULUTH_ 4 I 4 1 9 I -i ber 199 )uted and ' ions N 181 0 wrr....L 906 ~ '. 7S.A (N 'I1.2;. (102, TI3 '' 2 I, 1000 0 1000 2000 3000 4 ~.5 0 Figure 3: SIR-C/XSAR October 1994 Rifle Range distributed and point target Ue x locations. 9

I csble 2I table6.formatted Table 6: October SIR-C/X-SAR Calibration Point Targets_______________________________ MET (dd) __ _ _ ___ _- __ 1 ___ Otbr19Msin ___ MET (hh:mm:ss) _____ __50 _ __ _ 7:31:51 __October 1994 Mission ___ Orbit No. _ _ 22 Launch scheduled for 7:16 am on September30 _______ Data-Take No. _ _ __ _ 22.2 _Local magnetic declination is 6.138~ W Ascending/Descending.___ D __ D ___North/South Looking (from Shuttle) S. [ S All PARCs: 1 _Look Angle (relative to SIR-C) | - 30.689 20.382 -1 -1 _ Local Incidence Angle I.... 31.846. 1 21.106 _ _ SIR-C Azimuth Heading (True North) 127.508. 128.131 Target Azimuth (True North)___ _ ____.. 127.862 127.862 Target Looking (N/S)...N.... N Location Target Azimuth (Mag. North) 1 34 134 Elevation Angles Elevation Angles Ascending/ Max. RCS (From Azimuth (from Temp (~C) or (From Azimuth (fron Site Target Name Descending Latitude Longitude Target Type Size (cm) (dBmA2) horizontal) true north Level (degrees) Atten. (dB) horizontal) true north) Rifle Range __ P1i A/D 46.3481 -84.8487 L-SAPARC __ 30.0 __ 134.0 __ 0.0 16~ 21.1 134.0 P2 A/D 46.3369 -84.8519 C-SAPARC 30.0 134.0 0.0 16~ 21.2 134.0 T1-7 A/D 46.3360 -84.8575 Trihedral 240 29.9 134.0 0.2 29.8 134.0 T1-8 A/D 46.3453 -84.8497 Trihedral 240 30.2 135.0 0. 1 29.9 134.0 T1-9 A/D 46.3368 -84.8595 Trihedral 240 29.6 134.0 0.2 30.0 135.0 T1-10 A/D 46.3506 -84.8500 Trihedral 240 30.3 135.0 0.3 30.1 135.0 T2-1 A/D 46.3337 -84.8593 Trihedral 107 29.9 135.0 0.3 29.8 134 0 T2-2 A/D 46.3452 -84.8512 Trihedral 107 29.8 134,0 0.0 29.9 134.0 T2-3 A/D 46.3422 -84.8461 Trihedral 107 30.0 135.0 0.1 30.0 135.0 T2-4 A/D 46.3406 -84.8457 Trihedral 107 29.7 135.0 0.2 29.8 135.0 T2-5 A/D 46.3393 -84.8519 Trihedral 107 29.8 134.0 0.0 30.0 134.0 T2-6 A/D 46.3365 -84.8503 Trihedral 107 29.9 134.0 0.2 29.9 134.0 Raco Airfield P3 A/D 46.3568 -84.8048 C-PARC #1 44.5 31.8 134.0 0.4 21.1 134.0 P4 A/D 46.3508 -84.8196 C-PARC #2 42.4 31.8 134.0 0.5 21.2 134.0 Cryderman T1-1 A/D 46.4591 -84.9070 Trihedral 240 _ 30.0 136.0 0.6 30.0? 136.07 T1-2 A/D 46.4562 -84.9093 Trihedral 240 30.5 133.5 0.4 30.5? 133.5? T1-3 A/D 46.4561 -84.9130 Trihedral 240 29.9 134.0 0.4 29.9? 134.0? T1-4 A/D 46.4571 -84.9152 Trihedral 240 30.2 134.5 0.1 30.2? 134.57 ______ __ __ Local Day_.....__..-.Friday I Saturday _____Local Date______ ___ __ __ ___ __ 30-SeP i; 1-Oct Local Time __ _ 15:06:29 ], 14:47:51 n Page 1

table6.formatted ________ ______ _ ___ _______ MET (dd) 4 4. ___________ ___MET (hh:mm:ss)_ 0:25:32 ___ _____ ____ October 1994 Mission ___ ______ Orbit No. ____..... _. 66 ___ __________ __ __Launch scheduled for 7:16 am on September 30 Data-Take No._........66.2 L________________________ocal magnetic declination is 6.138~ W A_____Ascending/Descending __________ A _ _______ __ _North/South Looking (from Shuttle) ____... S. ______ ___ ___ _ All PARCs: ____ 1 1 Look Angle (relative to SIR-C) _ _ ___ 21.263 _____________ _____________-1..- - Local Incidence Angle ________ — ____-_ 22.009 ____..___.___.___ _________ _____ _________ ____ _____ SIR-C Azimuth Heading (True Nortah... 5...5 1887 _____ ____ ____ ____ _____ Target Azimuth (True North). 232.862 _____ Target_ Looking N/S..___ -..-.... N ___________ ________ Location Target Azimuth (Mag. North) 239 Elevation Angles Temp (~C) or Ascending/ Max. RCS (From Azimuth (from Temp (~C) or Level (degrees) Atten. (dB) Site Target Name Descending Latitude Longitude Target Type Size (cm) (dBm^2) horizontal) true north) Level (degrees) Atten. (dB) 0.0 ____Rifle Range _ P1 A/D 46.3481 -84.8487 L-SAPARC.._ 22.2. 59.5 0.1 5 0.0 3 dB pad P2 A/D 46.3369 -84.8519 C-SAPARC _______....21.9.. 59.0 _ yes 5e 0.2 T1-7 A/D 46.3360 -84.8575 Trihedral 240.__. 180~ off 0.1 ___ _______ T1-8 A/D 46.3453 -84.8497 Trihedral 240 _ __ - 180 off 0.1 T1____ I-9 A/D 46.3368 -84.8595 Trihedral 240. - 180 off 0.3 __T-10__ ___ T A/D 46.3506 -84.8500 Trihedral 240 - 180~ off 0.1 __ T2-1 A/D 46.3337 -84.8593 Trihedral 107 - 180~ off 0.1 _ T2-2 A/D 46.3452 -84.8512 Trihedral 107 - 180~ off 0.1 _____ __ T2-3 A/D 46.3422 -84.8461 Trihedral 107. - 180~ off 0.0 ______ _____T2-4 A/D 46.3406 -84.8457 Trihedral 107 __ - 180 off 0.2 ________ ______ T2-5 A/D 46.3393 -84.8519 Trihedral_ 107 - 180~ off 0.2 _______________T2-6 A/D 46.3365 -84.8503 Trihedral 107 - 180~ off___-_____________ 0.2 ____Raco Airfield P3 A/D 46.3568 -84.8048 C-PARC #1 44.5 22.0 2390 08 0.6 ______ P4 A/D 46.3508 -84.8196 C-PARC #2 42.4 22.0 240.0 0.5 ____..... 0.6? ____ _CrYderman Ti-1 A/D 46.4591 -84.9070 Trihedral 240. - 180~ off 0.4? ___ _________ T1-2 A/D 46.4562 -84.9093 Trihedral 240 _ _.. -. 180~ off - drizzle 0.4? __ _______ T1-3 A/D 46.4561 -84.9130 Trihedral 240 _ - 180~ off 0.1? ______ T1-4 A/D 46.4571 -84.9152 Trihedral 240 - 180~ off ______________ ____~__ ___~________ ____ _ _____~ ________ _Tuesday _..._. _._._..._.__._._.......... 4-Oct _ ___ _______ ______ ______~ _7:41:32 r -i Page 2

table6.formatted 5 fMET (dd) 1 5 ____ ______ 5_ ________________ __.{.-t _____ ____________ __ ___V _ __ __ MET __ _ _,_ ~ _,5 _____0:06:02 ___ ________ ________ ______ MET (hh:mm:ss)__ 6:15:59 82 October 1994 Mission ____ _____ ___ Orbit No. I 86 82.2 ___ __ ___ _____Launch scheduled for 7:16 am on September 30 __ __ Data-Take No. 86.4 A L___ ___ ______ ocal magnetic declination is 6.138 W __ AscendingDescending -.___ ' D _S ______ _ North/South Lookin_.from Shuttle) N 29.916 ____ _ Ail PARCs: 1 1_____ Look Angle (relative to SIR-C-) I _ _ 24.432 31.022 1- ________ -1 -1 Local Incidence Ange_ _.__ 1 25.367 52.304..................______SIR-C Azimuth Heading (True North) 131.411 232.862 _ - _____ _____ __Target Azimuth (True North) 311.862 N, I Target Looking (.N/S) S 239 Location Target Azimuth (Mag. North) 318 Elevation Angles Elevation Angles (From Azimuth (from Temp (~C) or Ascending/ Max. RCS (From Azimuth (fro horizontal) true north) Level (degrees) Atten. (dB) Site Target Name Descending Latitude Longitude Target Type Size (cm) (dBmA2) horizontal) true north 31.0 59.0 0.1 1~ Rifle Range P1 A/D 46.3481 -84.8487 L-SAPARC 25.4 318.0 31.2 59.0 yes.e 4~, 3 dB pad.. P2 A/D 46.3369 -84.8519 C-SAPARC 25.4 3180 30.0 59.0 0.1 T1-7 A/D 46.3360 -84.8575 Trihedral 240..... 29.6 59.0 0.1 __ Tl__ T1-8 A/D 46.3453 -84.8497 Trihedral 240 29.6 59.5 0.4 _________________ T1-9 A/D 46.3368 -84.8595 __ Trihedral 240 30.3 60.0 0.3_____ _ T1-10 A/D _ 46.3506 -84.8500 Trihedral 240 - 30.2 59.5 0.1 _______ T2-1 A/D 46.3337 -84.8593. Trihedral 107 30.3 59.0 0.3 ____ ___ T2-2 _ A/D.46.3452 -84.8512 Trihedral 107 - 30.4 59.0 0.6 ____ T2-3 A/D 46.3422.-84.8461 Trihedral.. 107 29.8 57.0 0.2 _____ __ T2-4 A/D 46.3406 -84.8457 __Tnhedral _107p 29.6 59.0 0.2 _____ ___ __ T2-5 A/D 46.3393 -84.8519 Trihedral 107 29.8 59.0 0.1 _________ T2-6 A/D 46.3365 -84.8503 Trihedral 107 - 31.0 239.0 0.0 Raco Airfield ___ P3 A/D 46.3568 -84.8048 C-PARC #1 __ _ 44.5 25.4 318.0 31.0 243.0 0.4 P______ 4 A/D 46.3508 -84.8196 C-PARC 2 42.4 25.4 318.0 29.9 59.0 0.1 Cryderman T1-i A/D 46.4591 -84.9070 Tnrihedral 240 9.9 59.0 30.3 59.0 0.0 ______ _____ T1-2 A/D 46.4562 -84.9093 Trihedral 240 10.3 59.0 29.9 318.0 0.1 T1-3 A/D 46.4561 -84.9130 Trihedral 240 299 3180 30.1 319.0 0.1 T1-4 A/D 46.4571 -84.9152 Trihedral 240 30.1 319.0 ____Wednesday_______________ __ __ __ Local Day.... i Wednesday _5-Oct _______________Local Date 5-Oct 7:22:02____ ____________ _ Local Time..... 13:31:59 I Page 3

table6.formatted _ _ _ _ _ __ _ _ _ _23:45:44 __MET (hhmm ss 98______October 1994 Mission OrbitNo. _______ _____98.1 _______Launch scheduled for 7:16 am on Septemberr 30 _ __ Data-Take No. _____________ _A ____ ___ ______Local ma netic declination is 6.1 3811 W Ascending/Descending _____36.666 ~All PARCs: ___ 1 Look Angle (relative to StROC) _ _ _ _ _ _ _ _ _ _ _ _38.082 _ _ _ _ __ L _ _ _ _ _ _ _ _ _ _ — 1 1 _ _Local Incidence Angle __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 53.149 _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __StR-C Azimuth Heading (True North) _ _ _ _ _ _ __ _ _ _ _232.862 _ _ _ _ _ _ __ _ _ _ _ Target Azimuth (True North) __N ______ _Target Looking (N/S) _ _ _ _ _ _ __ _ _ _ _ _239 __ _ _ _ _ _ _ _ _ _ _ _Location Target Azimuth I ag. North) I_ _ _ _ _ _ Elevation Angles Temp (IC) or (From Azimuth (from Temp (IC) or Ascending/ Max RCS Level (degrees) Atten. (dB) horizontal) true north) Level (degrees) Allen. (dB) Site Target Name Descending Latitude Longitude Target Type Size (cm) (dBMA2) 0.1 12- 38.1 59.0 0.1 ______Rifle Range Pi__ A/D ___46.3481 -84.8487 L-SAPAFRC aes 141, 3 dB pad 38.1 59.0 - s_-_____ _____ P2 A/D 46.3369 _-84.8519 C-SAIPARC _ _ _ _ _ _ _ _ _ _ _ _ - - - __ _ _ _ _ _Ti-7 A/D 46.3360 _ -84.8575 Trihedral 240 ______ _____ 10.1 59.0 0.2 ____________ T1-8 A/D__ 46.3453 — 84.8497 Trihedral- 240 __- - - _ __ T1-9 A/D 46.3368 -84.8595 Trihedral 240 __ ____ 10.0 _ 59.0 _ 0.3 Ti-1b A/D 46.3506 -84.8500 Trihedral 240 _______10.1 58.5 0.1 ______ T2-1 A/D 46.3337 -84.8593 Trihedral 1 07 ____9.8 59.0 0.3 __T2-2 A/D 46.3452 -84.8512 Trihedral 107 - - - T2-3 AID 46.3422 -84.8461 Trihedral 1 07 9.2 59.0 0.4 T2-4 A/D 46.3406 -84..8457 Trihedral 1 07 ____ — __ - __ T2-5 A/D 46.3393 -84.8519 Trihedral 1 07 - - - T2-6 A/D 46.3365 -84.8503 Trihedral 1 07 0.5 38.0 239.0 0.7 Raco Airfield _ P3 _ A/D 46.3568 -84.8048 C-PARC #1 44.5 0.4 38.1 239.0 0.6 P4 A/D 46.3508 -84.8196 C-PARC #2 42.4 0.1 ______ 9.9 59.0 __ 0.1 Cryderman TI-i A/D 46.4591 -84.9070 Trihedral 240 0.1 _______ 10.6? 59.0 0.1 _____________ T1-2 __ A/D 46.4562 -84.9093 Trihedral 240 0.1 ______ 29.5? 318.0 0.1 _____ T1-3 _ A/D _46.4561 -84.9130 Trihedral 240 0.1 33.3? 322.0? 1.4? T1-4 A/D 46.4571 -84.9152 Trihedral 240 _____ Thursday _ __ __ _- -.Local Day __________________________6-O ct _________________ ______ _____L o-call-D ate, __ _ _ _ __ _ _ 7:01:44 __ __ ___Local Time -i Page 4

table6.formatted _ _ _ _ _ _ _... _ _ _.. _ _. _.._.. _ —___ _-__6_ _______ ______,._______7__ ___________ __ __ I_ _.. _ METd) 6 7 4MET (dd) _________ 5:55:31 ________________ ______ 23:25:02 _____.... MET (hh:mm:ss 1___ober _02 114 __ __M___ 1994 Mission _. Orbit No ________ __102.41 _ _ ____ __ ______ 114.1 __ _ _ __....Launch scheduled for 7:16 am on September 30 Data-Take No. ____________D _A....._________._______.A. Local magnetic declination is 6.138~ W Ascending/Des _________ N ____ __________ S ___________ ___ _______North/South L( ________ 32.5 -— _____41.976 ______ _______ __ All PARC: __ 1 _ 1 Look Angle (rel _________ 33.818 _ 43.656 ______ ____ ________ ___ -1._ -1 Local Incidence 131.876 _ 53.667 ____ __ L. __..... __ _. SIR-C Azimuth 311.862 ____ 232.862 ____ _ ___ _.. Target Azimuth.S.. -__ N _______ __ ____________ Target Looking 31 _______ 239 Location Target Azimuth Elevation Angles Elevation Angles (From Azimuth (from Temp (~C) or (From Azimuth (from Ascending/ horizontal) true north) Level (degrees) Atten. (dB) horizontal) true north) Level (degrees) Site Target Name Descending Latitude Longitude Target Typ 33.3 318.0 0.0 15~ 43.7 59.0 0.1.111_ Rifle Range _ _ P1 A/D 46.3481 -84.8487 L-SAPARC 32.2 310.0 yes 20~ 43.7 59.0 ___ yes __ 13~ ___ P2. A/D. 46.3369 -84.8519 C-SAPARC 29.9 318.0 0.3 - - ___ ___T1-7 A/D 46.3360 -84.8575 Trihedral - - - 10.0 59.0 0.1 T1-8 A/D 46.3453 -84.8497 Trihedral 29.9 317.0 0.1 - - - T1-9 A/D 46.3368 -84.8595 Trihedral - - - __ 10.3 58.5 0.1 T I-10 A/D 46.3506 -84.8500 Trihedral - -____ _______ 10.0 58.5 __ 0.1 T2-1 A/D 46.3337 -84.8593 Trihedral - - -9.7 59.0 0.0 T___ 2-2 A/D 46.3452 -84.8512 Trihedral 29.6 318.0 0.1.. - - _....-.. ______ _ T2-3 A/D 46.3422 -84.8461 Trihedral - - 9.7 59.0 0.2_ _ T2-4 _A/D 46.3406 -84.8457 Trihedral 30.0 318.0 0.4 _____- - - _T2-5 A/D 46.3393 -84.8519 Trihedral 30.1 318.0 0.2 - -- ____ __T2-6 A/D 46.3365 -84.8503 Trihedral 33.8 318.0 0.4 43.7 239.0 0.2 __ Raco Airfield P3 A/D 46.3568 -84.8048 C-PARC #1 33.8 318.0 0.4 ______ 43.8 239.0 0.2 _____ _ P4 A/D 46.3508 -84.8196 C-PARC #2 9.9 59.0 0.1 9.9 59.0 0.1..Cryderman Ti-1 --- _ A/D 46.4591 -84.9070 Trihedral 10.6? 59.0 0.1 ______ 10.6 59.0 0.1 T __ -2 A/D 46.4562 -84.9093 Trihedral 29.5? 318.0 0.1 _________ ___ 29.5? 318.0 0.1 T1-3 A/D 46.4561 -84.9130 Trihedral 33.3? 322.0? 1.4? 33.3? 322.0 1.4? T1-4 A/D 46.4571 -84.9152 Trihedral Thursday __....______. Friday __....... Local Day ____ 6-Oct_______7-Oct_____ Local Date ____1___ 13:11:31 6:41:02 Local Time s) CE )0 lat H I ](,( Page 5

table6.formatted 7 8......... _________________________________ 1 14 __ __________________ 5_3_46 __ _ _ _________ 5:13:40 __ ___ ___ 118 134______ _ October 1994 Mission 118. 1 34.3 ----- 118.6 _..134.3.___ - _... _ Launch scheduled for 7:16 am on September 30 _ding _D ______ Local magnetic declination is 6.138~ W ___(fro __Shuttl ___ ___________________________D________ ________..__,;ing (from Shuttle) N N '- - -— ___ _.. ve to SIR-C) ____ _39.559 39.594 All PARCs: 1 gle 41.211 41.247 -__-_. ------— __ _-. -... I -1 ading (True North) 132.43 __ _ 132.427 __ rue Norh) 311.862 311.862 True North)__ _____ ]____ 1.6__________ _ _._ _ 3 18 2 _ _ __ _~~ /S) S __ _ ___ _.................... I - ag. North) 318 ____.___ ____ 318___________ Elevation Angles Elevation Angles Max. RCS (From Azimuth (from Temp (~C) or (From Azimuth (from Temp (IC) or Ascending/ Size (cm) (dBm^2) horizontal) true north) Level (degrees) Atten. (dB) horizontal) true north) Level (degrees) Atten. (dB) Site Target Name Descending Latitude 41.2 (31.5 41.2 (42.7 AirSAR) 318.0 0.0 18~ (20~ AirSAR) AirSAR) 318.0. 0.0.. 2-5 Rifle Range _ P1 A/D 46.3481 41.2 (31.5 316.5 (318 3dB pad (22~, 2 41.2 (42.7 15~ SIR-C (15~, 3 AirSAR) AirSAR) yes dB pad AirSAR) AirSAR) 318.0 0.0 dBpad AirSAR) _ _..P2 A/D 46.3369 240 10.1 318.0 0.1 10.0 318.0 0.0..___ _. T1-7 _ A/D 46.3360 240 __________ - - - 10.1 318.0 _ 0.1 __ T1-8 A/D 46.3453 240 10.0 318.0 0.1 ___ __.9 _ 317.5 0.0 T1-9 A/D 46.3368 240 ___ - - - 9.9 _ 318.0 0.6 Ti-10 A/D 46.3506 107 - - 6 ____ __~ 9.6 318.0 0.0 T2-1 A/D 46.3337 107 _ ___- ___'9.5 318.0 0.2 T2-2 A/D 463452 107 10.0 318.0 0.0 ___ __ 9.9 318.0 0.0 T2-3 A/D 46.3422 107 -.._ 9.9 318.0 0.1 T2-4 A/D 46.3406 107 9.9 318.0 0.0 ___ 9.9 318.0 0.2 T2-5 A/D 46.3393 107 _______ 10.0 318.0 0.1 9.8 318.0 0.0 T2-6 A/D 46.3365 44.5 41.2 318.0 0.5 41.2 318.0 0.1 _ ____ Raco Airfield P3 A/D 46.3568 42.4 41.2 318.0 1.2 41.2 318.0 0.7 P4 A/D 46.3508 240 9.9 59.0 0.1 10.3 318.0 0.1 __ Cryderman Ti-1 A/D 46.4591 240 10.6 59.0 0.1 10.0 318.0 0.1 T1-2 A/D 46.4562 240 29.5 318.0 0.1 10.0 318.0 0.1 T1-3 A/D 46.4561 240 ____33.3 322.0 1.4 10.0 318.0 0.2 ____________T1-4 A/D 46.4571 Friday Saturday... Local Da 4. 4 7-Oct1 3 8 0 4 3._ R8-Oct Local Date _________ 12:50:46 12:29:40 _____ Local Tim. ____ _________ -___________AirSAR Data __________ ____________________________________________Da 1 - 1 oC Page 6

table6.formatted ________ MET (dd) ________ _________ ___ 9 I.__.. _.. ____ MET hh:mm:ss)_________ ___ 4:51:57___ 4:30:20 _____ Orbit No. ___ _____ 150_________ 166 - Data-Take No._____ _ _______150.2 _____._______ __ 166.1 Ascending/Descending ___ _ D D__ __ __North/South Looking (from Shuttle) N..._ N_ Look Angle (relative to SIR-C)_ _____________ 39.596 ___.__ ___ 39.-596 ____Local Incidence Anle ______________41.248.... _____._ _41.248. ____ ___ SIR-C Azimuth Heading (True North) 132.424 132424 _______ Target Azimuth (True North) ____________.____ 311.862 ' -____ 311.862 -o Target Looking (N/S) S -.._______.S tion_______ Target Azimuth (Mag. North) 318 318 _____________ Elevation Angles Elevation Angles Max. RCS (From Azimuth (from Temp (~C) or (From Azimuth (from Temp (~C) or Longitude Target Type Size (cm) (dBm^2) horizontal) true north) Level (degrees) Atten. (dB) horizontal) true north) Level (degrees) Atten. (dB) 5~. 3 dB pad -84.8487 L-SAPARC__ _________ 41.2 318.0 0.0 4.5~ 41.2 318.0 0.0 XMIT -84.8519 C-SAPARC 41.2 318.0 0.1 5~ 41.2 318.0 0.0 5, 3 dB pad RCV -84.8575 Trihedral 240 12.4 321.5 0.3 ____ __ 10.3 318.0 0.1 -84.8497 Trihedral. 240 9.9 317.5 0.0 __ 9.9 318.0 0.0 -84.8595 Trihedral 240 9.9 317.5 0.1 10.1 317.5 0.0 -84.8500 Trihedral 240 10.2 316.0( 0.1 10.6 318.0 0.2 -84.8593 Trihedral 107 10.0 318.0 0.1 10.0 318.5 0.1 -84.8512 Trihedral 107 10.0 317.5 0.1 9.9 3175 0.1 -84.8461 Trihedral 107 10.0 318.0 0.0 10.0 318.0 0.1 -84.8457 Trihedral 107 9.9 318.0 0.2 10.0 318.0 0.1 -84.8519 Trihedral 107 9.9 318.0 0.2 9.9 318.0 0.0 -84.8503 Trihedral 107 9.8 318.0 0.1 9.9 318.0 0.0 ____... -84.8048 C-PARC #1.. 44.5 41.2 318.0 0.4 41... _12. 318.0 0.5 -84.8196 C-PARC #2 42.4 41.2 318.0 0.9 41.2 318.0 0.3 _____ -84.9070 Trihedral 240 10.0 318.0 0.2 10.1 318.0 0.1 -84.9093 Trihedral 240 10.1 318.0 0.1 __ 10.2 318.0 0.1 -84.9130 Trihedral 240 ____ 10.0 318.0 0.1 9.9 318.0 0.1 -84.9152 Trihedral 240 10.0 318.0 0.1 10.1 318.0 0.0 __ _ - _ _ Sunday....Monday 9-Oct t__ 10-Oct _ __________ ___12:07:57 __ 11:46:20 _________________________________AirSAR Data______________ ________________________________ Page 7

3 SUMMARY OF ACCOMPLISHMENTS:\s Ienl(tiolle(d. accurate calilbratioIn of l)olarinictrii( iimaging radars iinvolves InIaiiy st()eps. T(owards l his goal. w\e lhave focused our act iviti's ill f)our areas: (1) developInellt of calibration algorithms f'or the purl)ose of characterizing the scattering matrices of the SAR calibration targets. (2) design and claracterization of precisionl calibration targets, (3) developmnent of a calibration technicue for measurenent of differential Mueller matrices of distributed targets which is required for cross calibration and calibration methods based on known distributed targets. and (4) developnient of calibration algorithms for imaging radars. A summary of the work accomplished in each area is given next. 3.1 Calibration Algorithms For Point Targets Three distinct algorithms have been developed for the measurement of scattering matrices of point targets. Our objective in the development of these algorithms was to characterize the scattering matrices of SAR calibration targets with a high degree of accuracy by comparing them against a precision metallic sphere. The choice of the calibration algorithm depends on the particular system and the accuracy-versus-complexity criterion. For example, in the calibration technique which will be referred to as IACT (isolated antenna calibration technique) only a metallic sphere and any other target with relatively high cross-polarized component are required to determine the radar distortion parameters [4]. The scattering matrix of the depolarizing target need not be known. This technique is very convenient, however it is only applicable to radar systems with low cross-talk. Refer to Appendix B for a detailed explanation of the procedure. Another calibration technique that, is not based on any a priori knowledge of the system was also developed [4]. In this technique the transmit and receive distortion matrices of the radar system are characterized using three in(lelpendent targets with known scattering matrices. Although this method is very general, its drawback is the errors caused by orienting the calibration targets with respect to the antenna system coordinate frame (see Appendix B). Using the prol)erty of reciprocal passive antennas, a convenient calibration technique was later developed that determines the distortion parameters of' a radar system-n using only a, metallic sphere [5]. This technique will be referred to as ST(CT (single target calibration technique). Using this calibration technique the scattering matrix elements of a target can be measured with an accuracy of 0.5 dB in magnitude and ~5 degrees in phase. The calibration procedure is described in Appendix B. 10

3.2 Measurement and Calibration of Differential Mueller Matrices I he oxverall accllracy of a calib)ration l)roced(lre for ilmaging rad(ars call be assessedl if an iIlnle(e>llcndeI acclurate Imeasureclent of an area withliII t11' ilmlage were available. \Vithl this pulrpose in mind. \we developed aIl algoritlhm for backscatter measurement of uniform (listributed targets using a scatteromleter systen. A major difficulty in the lMueller matrix measurement of distri)buted targets is thle lack of known distributed tIargets. andl therefore the calil)ration coefficient must be inferred frolm point calibiration targets. Tills process is rather complex. particularly when the radar distortions vary over tlhe illuminated area. This is the case when a scatteromleter is used for tile measurement. Amplitude al(n phase variation of tlhe radiation pattern of the scatterometer antenna causes variation in the distortion parameters of the radar over its illuminating area. In this case the distortion parameters must be (letermined over the entire main beam of the radar system using point calibration targets in order to find the calibration coefficient for distributed targets [6]. I;sing this procedure, the differential Mueller matrix of an area can be deterllined. which in turn can be used to calibrate a polarimetriic SAR. In such a calibration technique, it can be shown that the impulse response of the SAR (ambiguity function) need nol be determined. The detailed procedure and explerimental results of the Mueller matrix measurement is given in Al)pendix C. 3.3 Characterization and Design of Precision Active Calibration Targets lThere are significant differences between point calibration targets used for convelntional ra(dars and imaging radars. These differences are the direct result of the target deployment configuration. For imaging radars, the calibration targets are placed on the ground (in the presence of the distributed target ), whereas in the case of conventional radars the calibration targets are p)laced in free space. The success of an external calibration procedure relies on the knowledge of the scattering matrix of the calibration targets. II order to reduce the effect, of background (direct contribution) on the RCS of a calibration target for imaging radars, it is required that the RCS of the target be much larger than that of the surrounding background. (Calibration targets, in general, can be categorized into two major groups: (1) passive calibrators and (2) active calibrators [7]. Passive calibrators are nmore stable aind reliable than their active counterparts, however, their large physical dimensions is their major drawback. Trihedral corner reflectors are the most widely used targets for imaging radars because of their high RCS andI wide IC(S pattiern. In recent years, polarimetric active radar calibra 11

tors (IPAR(s) ave blee\ i tused(1 e xtensixvelv aii e arle plainn'ecl to (.be empl'!oy(ed for ext'ern'al calilb)ratio) of tole SIR-( /XSAR IlliiOl. In a(i(lit iOll to hligh ('S ali wide i('S patt'eral. e.PARC\( are desirab)le fo tile'il r'lat i'vel small p)}Iysical size. II.Jullle 1)990)). tlie scatt('erI'Ig mIatlrices of.JI')1. - amidC ('-band )PARC{(s w('ere ' easure(l and t lie results were Ireported [S]. I lie ieasur111i'Cts weref conllucte(l over a wide range of incidence angles in azimuthl. elevationl. 45. aId( 13.5 Iplaies. It was found that tlhe RCtS patterns of thle L-baInd )PAl('s whose antennas \were in close proxiniity, were unsymnlletric arnd the p)liase lpatterIs exlil)iited rapid fluctuations. Tlhese un(lesiral)e chIaracteristics prompted design of a novel single antenna PAR(' (see Append(ix D). T'he new PAR(' can pIrovide a very higli RCS while having a relatively small physical size. W\e are currently in the process of manufact turing two L-}baid and( twvo ('-lband single antennia PARCs (SAPAR('). Tlhe features adIld )(e'formlnace characteristics of a ('-b)and SAPA(RC was reporte(d [9]. 3.4 Analysis, Design, and Construction of an Optimum Corner Reflector P'AR('s are excellcnt calibration targets in regard to large RC'S a(nd wide RCS pattern Irequireinents. However, the scattering matrix of a PAR( is singular and can only provide tlhree equations for the unknown distortion parameters of a radar insteadl of four [10]. Besides, in order to check the validity of a calilration algorithm, independent known targets are required. Trihedral corner reflectors are suitable for this lIurpose. Large ordinary trihedrals are not very reliable forI calibration. The frame of these trihedrals are not sturdy enough and causes geometrical deformations. Obviously construction of a sturdy trilledra.l with sucih large dimensions renders them practically undep)loyable. The other problem is the coherent interaction of the trihedral with the ground. The reflected wave from the surface in front of thle trihedral scatters off of the lower panel edge and returns to the radar. Also rays from the scatterers on the groiund may enter the trihedral cavity and reflect back towar(ls t}1'e ra(dar. Basically, the image of these scatterers in the trihedral are visible. T'is interactioin occurs with tlie upper portion of the side panels. IThe significance of this interaction depends on the tilt angle of the lower )panel. since the low\er panel can shadow some of the scatterers in front of the trihedral (RS analysis of trihledral corner reflectors shows that only a portion of thle trihedral is contributing to the RCS. A new class of corner reflectors thlat does not suffer from tl-e aforementioned problems were designed and constructed. These corner reflectors are suitable for calibration of imaging ]radar systems [11] (also see Appendix E). 12

3.5 Calibration Algorithms for Polarimetric SAR Systems \VCWe ave (levelol)ed( t \vo ap)lro(aches for cali)rat ion of Ipolariinlet ic s(iit lielt tic ap)ert ure radars. The first app)roaclh is based on )point calibration targets [12]. IIn this nlethod the p)olarimetric ambiguity flllnction of the SARl is estimated froml a trilledral in tlie inlage aidl using a model simlilar to tile oIne used in S ('CT. the calibration constant and distortion paramneters of tile SAR can be obtained. Accuracy of this calibration directly depends on the knowledge of thie scattering matrix of the trihedral calibration target. Tlhe detailed p)rocedure and actual implementation of this technlique is given in Appendix F. In the second aIpproach a uniform distributed target is used as a calibration target [13]. The differential Mueller matrix of this target can be characterized using the scatterometer systems, and the radar distortion parameters and the calibration constant can be obtained directly from this algorithm. The outcome of this calibration algorithn is the calibrated differential Mueller matrices of the uniform regions in the image. The advantages offered here are a.s follows: (1) point targets are not needed and tile calibration is not influenced by the interaction of the targets with their backgroullds, (2) estimation of polarimetric ambiguity function is not required, (3) since the differential Mueller matrix is calculated from many independent neasurements the effect of noise and measurement errors are minimized. In Appendix F this procedure is explained in detail. 3.6 Cross Calibration Experiment In June 1991 a cross calibration experiment using JPL AirSAR and the University of Michigan scatterometer system was conducted to assess the accuracy of SAR calibration using point targets. The results of this experiment is reported in Appendix G. Four different uniform distributed targets, three rough surfaces with different, roughness and a hay field, were measured with both the scatteromteres and the JPL SAR at three different incidence angles. After processing thle data, significant discrepancies between the two measurements were observed. Two factors are believed to be resp)onsible for these discrepancies, both related to the trihedrals used in the experiment. One is the effect of coherent and incoherent interaction of thle ground with the trihedrals. These factors affect the scattering matrix of the trihedrals used in the calibration. The second factor is the possible geometrical deformation of the trihedrals. 3.7 Applications In the p)ast two years we have examined the applications of calibrated polarimetric SARs in radar remote sensing of vegetation. First high fidelity scattering models for short vegetation was developed [13,14] and then inver 13

SioIn algorit hllms wver' developed andll physical )araiil eter of' \ege at ion were I(etrie\ve( fromI cali )brate(l l)olarimletric SAlRs [1 1.15]. Appendix II includes copies of t lhese Ipapers. 4 Students Supported Throughout the course of this investigation the effort of the following Ph.D. and MI.S. students were supported fully or partially by this )roject. Ph.D. Students 1. Nlichael \Vhitt 2. Yisok Oh 3. Tsenchieh Chiu 4. Jimr Stiles 5. Roger DeRoo M.S. Students 1. MI. Ali Tassoudji 2. JamIes Ahne 3. A. Zambetti 5 Publications Journal Plublications: 1. Sarabandi, K., F.T. ITlaby, and M.A. Tassoudji, "Calibration of polarimetric radar systems with good polarization isolation", IEEE Trans. Geosci. Remote Sensing, vol. 28, no. 1, Jan. 1990. 2. Whitt, M.\W., and F.T. Ulaby, "A polarimetric radar calibration technique with insensitivity to target orientation," Radio Sci, vol. 25, no. 6., pp. 1137-1143, 1990. 3. \Vhitt. M.W., F.T. IUlaby, P. Polatin, V.V. Liepa, "A general polarimetric radar calibration technique: Theory and experiment," IEEE Trans. Antennas Propagat., vol. 39, no. 1, Jan. 1991. 14

-1. Sarabadl(i. K.. aInd F.TI. 1 lal '..- A co(I'eC ielt techlIli(ll(e fl.r )olari lleitric ('alibrationI of radar svste'ms". IEEE Trans. Geosci. Remote Sensing. vol. 28. lno. 6. Nov. 1990. 5. SaraJbaindi. K.. \ l.. andl F.T. Ilab)v. "Mleasurelelle t anld calibratiol of differential NMueller Ilatrix of distributed targets." IEEE Trans. Antennas Propagat., vol. 40. no. 12. pp.1524-1532. Dec. 1992. 6. Sarabandi. K., Y. Oil, and F.T. Ulaby. " Application andcl performance characterization of polarimetric active radar calibrator". IEEE Trans. Antennas Propagat.. vol. 40, no. 10, Oct. 1992. 7. Sarabandi. K.. L.E. Pierce, and F.T. TUlaby, "Calilration of a polarimetric imaging SAR", IEEE Trans. Geosci. Remote Sensing., vol. 30. no. 3, May 1992. 8. Sarabandi. K., "Calibration of a polarimetric synthetic aperture radar using a known distributed target"' IEEE Trans. Geosci. Remote Sensing., vol. 32, no. 3, 575-582, May 1994. 9. Sarabandi. K., L. Pierce, M.C. Dobson, F.T. ITlaby. J. Stiles, T.C. Chiu, R. De Roo, R. Hartikka, A. Zambetti, and A. Freeman, "Polarimetric calibration of SIR-C' using point and distributed targets," IEEE Trans. Antennas Propagat., vol. 33, no. 4, pp. 858-866, July 1995. 10. Freenlan, A., MI. Alves, B. Chapman, J. Cruz,, Y. Kim, S. Shaffer, J. Sun, E. Turner, and K. Sarabandi, "SIR-C Calibration Results," IEEE Trans. Geosci. Remote Sensing.. vol. 33, no. 4, pp. 848-857, July 1995. 11. Sarabandi, K., and T.C(. Chiu," An optimum corner reflector for calibratioll of imaging radars," IEEE Trans. Antennas Propagat., vol. 44, no. 10, Oct. 1996. 12. Chiu, T.C., and K. Sarabandi. "Electromagnetic Scattering from Short Branching \egetation," IEEE Trans. Geosci. Remote Sensing., submitted for publication (.Jan. 98). 13. (Chiu, T.C., and K. Sarabandi, "Electromagnetic scattering interaction between a dielectric cylinder and a slightly rough surface," IEEE Trans. Antennas Propagat., submitted for publication (June 1997). 14. Svendsen, M.T., K. Sarabandi, and H. Skriver, "Retrieval of vegetation parameters from SAR data using a coherent scattering model for grassland," IEEE Trans. Geosci. Remote Sensing., submitted for publication (April 99). C('onference Papers: 15

1I. '. v..Sve'Idse(. all(d 1\. Sarablall(li. "R{'trieval of v(gettat i()ll )Iaratllet'ers ro(l S.-\ (ata tsilng a coherent scatterilig o11(del for grasslalnd." Proc. 2nd Int. Workshop on Retrieval of Bio- and Geo-physical Parameters from SAR data for Land Appl., Noordwijk. Netherlalnds. 21-'23 Oct.. 1998. (invited) 2. T. (]lill and K. Sarabandi. "Electromagnetic scattering interaction between leaves and thin branches," Proc. IEEE Trans. Geosci. Remote Sensing Symp.. Seattle. 1998.:3. rT. Chliu and K. Sarabandi. "A coherent second-order scattering model for short vegetation," Proc. IEEE Trans. Geosci. Remote Sensing Symp.. Seattle. 1998. 4. Y. Kobayashi, K. Sarabandi, L. Pierce. M.C. Dobson. '"Extracting Tree Heights using JPL TOPSAR DEM data," Proc. IEEE Trans. Geosci. Remote Sensing Symp., Seattle, 5. Chii, T.C., and K. Sarabandi, "Electromagnetic scattering interaction between a dielectric cylinder and a slightly rough surface." Proc. IEEE Trans. Geosci. Remote Sensing Symp., Singapore, 1997. 6. Sarabandi, K.. and T.C. Chiu, "Optimum corner reflectors design," Proc. IEEE National Radar Conference, Ann Arbor, Michigan. May 1996. 7. Saralbandi, K.. L. Pierce, M.C. Dobson, T.C. Chiu, F.T. Ulaby, and J. Stiles. "Polarimetric calibration of SIR-C using point and distributed targets." Proc. IEEE Trans. Geosci. Remote Sensing Symp.. Firenze, Italy, July 1995. 8. Sarabandi, K., and T.C. Chiu, "Optimum corner reflectors for calibrationl of Imaging radars," Proc. IEEE Trans. Geosci. Remote Sensing Symp., Firenze, Italy, July 1995. 9. Sarabandi. K., and Y. Oh, "Effect of antenna footprint, on the statistics of radar backscattering,"Proc. IEEE Trans. Geosci. Remote Sensing Symp., Firenze, Italy, July 1995. 10. Sarabandi, K.. and A. Nashashibi, "A novel bistatic scattering matrix measurement technique using a monostatic radar," Presented at AP/URSI symposium, Seattle, June 1994. 11. Freeman, A., A. Azeem, D. Haub, and K. Sarabalndi, "Development of SIR-( ground calibration equipment," Presented at SAR Calibration Workshop, Noordwijk. The Nether Lands, Sept. 1993. 16

12. SarabandiI. 1\.. J. Alhne. I. I laby. and A. 1FreeiI1anI. "SiIngle-a Ilntenna polarimet ric actlive i adar calibirators for t1he SIRl-(' Missioin." 1r('ese{lt(e(l at SAR (Cali)bratio \\WOrkshlop. Xoor(lwijk. The NetIher Lands. S(ept. 1 99):3. 13. Sarabandi. I., 1.T. ['labv. M.C. Dobson. "AIRSAR and POLARS('AT cross-calibration using point and distributed targets." Ipresented at ICGARSS'93. Tokyo, 1993. 14. Ahne. J. J.. IK. Sarabandi. anlld FT.. labl. I1) esign and imijleInent at iol of single antenna polarimetric active radar calibrators," Proc. IEEE Trans. Antennas Propagat. Symp., Ann Arbor, 1)993. 15. Dobson. M.('.. K. Sarabandi, L. Pierce, and F.T. Ulaby. "External calibration of ERS-1 SAR," presented at IGARSS'92, Houston, May 1992. 16. Sarabandi. L.E. Pierce, Y. Oh. M.C. Dobson. A. Freeman, and P. Dubois. "Cross calibration experiment using JPL AIRSAR and truckmounted polarimetric scatterometers." presented at IGARSS'92, Houston, May 1992. 17. Sarabandi, K., L.E. Pierce, and F.T. Ulaby. "Calibration of a polarimetric imaging SAR", JPL Airborne Geosci. Workshop. Pasadena. May 1991. 18. Sarabandi, K., Y. Oh, and F.T. ITlaby, "Application and performance characterization of polarimetric active radar calibrator", JPL Airborne Geosci. Workshop, Pasadena, May 1991. 19. Sarabandi, K., and F.T. IUlaby, "A convenient technique for polarimetric calibration of radar systems", Proc. IEEE Trans. Geosci. Remote Sensing Symp., Maryland, May 1990. 20. Sarabandi, K.. F.T. Ulaby, M.W. Whitt, and P. Polatin, "Comparison of several 1)olarimetric radar calibration techniques", Proc. International Union of Radio Science, Hyannis, May 1990. 21. Liepa, V.V.\. K. Sarabandi, and M.A. Tassoudji. " A pulsed network analyzer based scatterometer", Proc. of IEEE Geosci. Remote Sens. Symp., V\ancouver, July 1989. 22. Sarabandi, K., and F.T. Ulaby,"Calibration of polarimetric radar systems". Proc. of IEEE Geosci. Remote Sens. Symp., Vancouver, July 1989. 1998. 17

References [1] Sarabandli. K.. L. Pieirce. I.('. l)ol)son. 1F.1. labl)..J. St iles. T.('. Chin. I. )(e oo. R. I lairtikka. A. Zambetti. al(1t A. IFrecmana. "lolariiet,;ric calil)ratioll of SIH-(' using point and distributed targets." IEEE Trans. Antennas Propagat.. vol.:33. no. 4. Ip. 858-866. July 1!995. [2] Freeman. A.. N1. Alves. B. Chapman. J. Cruz,. Y. Kimi. S. Shaffer, J. Sun. E. Turner. and K. Sarabandi, "SIR-C Calibration Results." IEEE Trans. Geosci. Remote Sensing.. vol. 33. no. 4, pp. 848-857. July 1995. [3] Sarabandi, K.. F.T. Ulaby, and M.A. Tassoudji, "Calibration of polarimetric radar systems with good polarization isolation". IEEE Trans. Geosci. Remote Sensing. vol. 28, no. 1. Jan. 1990. [4] \Whitt. M.\W.. F.T. Ulaby, P. Polatin, V.V. Liepa, "A general polarinetric radar calibration technique: Theory and experiment," IEEE Trans. Antennas Propagat., vol. 39, no. 1, Jan. 1991. [5] Sarabandi, K.. and F.T. Ulaby, A convenient technique for polarimetric calibration of radar systems", IEEE Trans. Geosci. Remote Sensing. vol. 28, no. 6. Nov. 1990. [6] Sarabandi, I., Y. Oh, and F.T. UTlaby, "Measurement and calibration of differential Mueller matrix of distributed targets," IEEE Trans. Antennas Propagat., vol. 40, no. 12, pp.1524-1532, Dec. 1992. [7] Brunfeldt, D.R., and F.T. Ulaby, "Active calibrators for radar calibration," IEEE Trans. Geosci. Remote Sensing, vol:22, no 2, 1984. [8] Sarabandi. K., and Y. Oh, "RCS measurement of polarimetric active radar calibrators.". Radiation Laboratory Report No. 027165-1-T, The lTniversitv of Michigan, June 1990. [9] Ahne. J.J, K. Sarabandi, F.T. Ulaby, "Design and implementation of a (-'-band single antenna polarimetric active radar calibrator," Radiation Laboratory Report No. 027587-1-T, The University of Michigan. August 1993. [10] Sarabandi, K.. Y. Oh, and F.T. Ulaby, " Application and performance characterization of polarimetric active radar calibrator", IEEE Trans. Antennas Propagat.. vol. 40, no. 10, Oct. 1992. [11] Sarabandi, K., and T.C. Chiu," An optimum corner reflector for calilration of imaging radars," IEEE Trans. Antennas Propagat., vol. 44, no. 10. Oct. 1996. 18

[12I Sarabaindi. I.. L.E.. '. ad. Clal). "(alibration of a plolarinietric i maging SAI{". IEEE Trans. Geosci. Remote Sensing.. vol. 30.,o.:3. Mayv 1992. [13] SarabaIndi, lK.. "Calibration of a polarimetric syintletic aperture radar, using a knownl distributed target" IEEE Trans. Geosci. Remote Sensing.. vol. 32. no. 3. 575-582. Mlay 1994. 19

APPENDIX A RESULTS OF SIR-C/XSAR EXPERIMENTS 20