Radargrammetry of High Resolution Synthetic Aperture Radar Onboard

Radargrammetry of High Resolution Synthetic Aperture Radar Onboard KOMPSAT-5 Hoonyol Lee Department of Geophysics Kangwon National University Email: hoonyol@kangwon. ac. kr Homepage: http: //sar. kangwon. ac. kr

Contents Overview of KOMPSAT-5 COSI Radargrammetry of KOMPSAT-5 COSI ¡ Equator ¡ Mid Latitude ¡ Antarctica Conclusion

Overview of KOMPSAT-5 COSI X-band Altitude: 550 km Inclination: 97. 6 deg Dawn-dusk orbit 06: 00 am Mean Local Time of Ascending Node 15+1/28 revolutions per day Nodal Period: 95. 78 minutes 28 D 421 R (28 days revisit time after 421 revolutions) Ground speed: 6. 97 km/s Successive Orbit Distance: 2665 km (no image overlap between two successive orbits) Distance between adjacent pass: 95 km at equator

KOMPSAT-5 Orbit Elements Epoch: 2009 JUN 01 Mean Orbit Osculating Orbit 00: 00 UTC (J 2000) Semi-Major Axis (km) 6928. 11434 6937. 46791 Eccentricity 0. 001068966 0. 001201637 Inclination (deg) 97. 597531 97. 595674 R. A. of Ascending Node (deg) 339. 734883 339. 735375 Argument of Perigee (deg) 90. 0 67. 308762 Mean Anomaly (deg) 270. 0 292. 740966

Ascending Node Pass (Dawn) Orbit Number 2665 km © KARI Day Number

Descending Node Pass (Dusk) Orbit Number 95 km Day Number © KARI

Spot Mode Imaging Time of 1 Scene = 3 sec In-Cal and Fin-Cal Time = (0. 25+0. 25) sec Maximum Time btw. Target Change (20 -45 deg) = 2 sec Minimum Number of HR Images in 2 minutes = 22 © KARI

Stripmap Mode Imaging Time = 2 continuous minutes Maximum Time btw. Target Change (20 -45 deg) = 1. 5 sec © KARI

Scan. SAR Mode Imaging Time = 2 continuous minutes Maximum Time btw. Target Change (20 -45 deg) = 4 sec © KARI

Radargrammetry Stereographic mapping with two SAR images taken at different incidence angles All weather, day & night, high-resolution SAR Horizontal Resolution: ~ 8 x 8 pixels for cross-correlation Vertical Resolution ~ incidence angles and their difference Severe topographic distortion

Spaceborne Topographic Mappers Radargrammetry In. SAR (Single Pass) Photogrammetry Lidar EM Spectrum Microwave Optics All weather, Day & night ○ ○ × × Topographic conformality × × (○ : L, R Merge) 8 x 8 (○: L, R Merge) 3 x 3 ○ ○ 8 x 8 (Cross-Correlation) (Spectral Filtering) (Cross-Correlation) Relative Height Resolution 1~2 pixel meter ~ 1 pixel meter Past Systems Magellan SAR SRTM Numerous in repeat pass - Current Systems Radarsat-1 - Single pass: TERRA ASTER, SPOT-5 HRS, ALOS PRISM ICESAT GLAS Tan. DEM-X ? ? No system in operation Cloud Horizontal Resolution (Pixels) Future Systems Major Problem Radarsat-2, KOMPSAT-5 Topographic distortion 1

SSR vs. OSR Incidence angles ¡ ¡ Same-Side Radargrammetry (SSR) Opposite-Side Radargrammetry (OSR) Vertical Resolution: OSR is better than SSR Severe topographic distortion: SSR is better than OSR Same-Side Radargrammetry • Moderate sensitivity to height • Moderate distortion • Error in textureless area Opposite-Side Radargrammetry • High sensitivity to height • Severe distortion • Error in textureless area

SSR Geometry

OSR Geometry

Radargrammetry – An example Magellan SAR data of Lullin Impact Crater, Venus (Lee et al. 2003) Left-look, 44. 2 ° Left-look, 25. 1 ° Right-look, -24. 9 °

SSR vs. OSR Same-Side Radargrammetry • Moderate sensitivity to height • Moderate distortion • Error in textureless area Opposite-Side Radargrammetry • High sensitivity to height • Severe distortion • Error in textureless area Anaglyph DEM

KOMPSAT-5 COSI Imaging Modes s Pas t n ce a Adj m k 95 Nadir 0 km 185 km nes sce Altitude 550 km 18 20 ° 5 k m No 30 mina 5 k l m Co 49 verag 0 k m e , 22 m k ), 5 m 1 t( km 0 Spo 8 00 x 8 x km km 30 0 , ) 0 1 (3 m m), p 0 a 2 ( pm SAR Stri n a Sc 45 ° Ext 18 ende 5 k d m 55 ° Nominal 490 km 675 km Extended

Number of Pass for a Ground Target Condition for Complete Coverage of SSR: N=C/A>2 N: number of pass, C: Image Coverage width, A: Adjacent pass distance(=95 km at equator) Incidence Angles Ground Coverage from Nadir Image Coverage width Number of Pass Nominal 20°~45° 185~490 km 305 km 3. 2 Extended 45°~55° 490 ~ 675 km 185 km 2. 0 Total 20°~55° 185 ~ 675 km 490 km 5. 2

Uniqueness of K-5 COSI for SSR Repeat Cycle / Revolutions ERS-1/2 RADARSAT-1 Terra. SAR-X 35 days 500 rev. 24 days 343 rev. 11 days 167 rev. COSMO-Sky. Med KOMPSAT-5 COSI 16 days 237 rev. 28 days 421 rev. Image Coverage (C) Adjacent Pass Distance (at equator) (A) Number of pass (N>2 for SSR) 100 km 80 km 1. 25 500 km 116 km 4. 3 Strip, Scan: 295 km Spot: 480 km 240 km 1. 2 for Strip and Scan, Similar to COSI (? ) 170 km 1. 8 - 2. 9 (? ) 305 - 490 km 95 km 3. 2 -5. 2 2 for Spot

Uniqueness of COSI for SSR Radarsat-1 has been unique for SSR Limited SSR availability of Terra. SAR-X and COSMO-Sky. Med unless significant satellite maneuvering SSR will be valuable before the widespread of single-pass interferometers (e. g. , Tan. DEM-X). KOMPSAT-5 COSI is dedicated to SSR.

Radargrammetry At Equator

z (up) K 5 Orbit Geometry for Radargrammetry Right Look At Equator Left Look -2 -1 n =0 1 2 3 4 Satellite Pass θi Earth Surface (Equatorial plane) θl H = 550 Km x Xg =95 km at equator R = 6378 Km δ Earth Center East R: Earth radius H: Altitude of satellite Xg: Ground distance of adjacent pass n: Pass number from nadir x: Image location from nadir to east |x|<Xg/2 θi: Incidence angle Nominal: 20° < θi < 45 ° Extended: 45 ° < θi < 55 ° θl : Look angle Rg: Ground range Nominal: 185 km < Rg < 490 km Extended: 590 km < Rg < 675 km Rs: Ground range

Incidence angle as a function of x (position from Nadir)

Radargrammetric Geometry (x = -47. 5 km) z (up) Left Look -2 -1 Right Look n=0 1 Nominal Mode 2 3 Extended Mode 4 Xa=95 km Altitude H = 550 Km x = -47. 5 km -47. 5 0 +47. 5 x (east) 5 6 7 8

Radargrammetric Geometry (x = 0 km) z (up) Left Look -2 -1 Right Look n=0 1 Nominal Mode 2 3 4 Xa=95 km Altitude H = 550 Km x=0 km -47. 5 0 +47. 5 x (east) Extended Mode 5 6 7 8

z (up) Left Look -2 -1 Radargrammetric Geometry (x = +47. 5 km) Right Look n=0 1 2 3 4 Xa=95 km Altitude H = 550 Km x=+47. 5 km -47. 5 0 +47. 5 Extended Mode Nominal Mode x (east) 5 6 7 8

Height Sensitivity of Parallax

Height Sensitivity of Parallax 5 -3 and 3 -2 pairs are recommended with height sensitivity of 0. 6 -0. 9

Days of SSR Orbits 2 nd Pass 1 st Pass 2 3 4 5 6 7 28 1 2 3 4 5 27 28 1 2 3 4 26 27 28 1 2 3 25 26 27 28 1 2 24 25 26 27 28 1 23 24 25 26 27 28

Radargrammetry at Mid-Latitude (Daejeon, Korea)

KOMPSAT-5 Orbits near Daejeon, Korea Elevation angle: 0 -90 degree

Elevation Angles 5 orbits have 20°- 45°of incidence angles for nominal imaging mode (descending orbits only)

Height sensitivity of parallax at Daejeon, Korea θ₂(n) θ₁(n) 22. 92° (4) 29. 05° (5) 34. 46° (6) 39. 14° (7) 43. 16° (8) 22. 92° 29. 05° 34. 46° 39. 14° 43. 16° (4) (5) (6) (7) (8) 0. 00 -0. 56 -0. 91 -1. 14 -1. 30 0. 56 0. 00 -0. 34 -0. 57 -0. 73 0. 91 0. 34 0. 00 -0. 23 -0. 39 1. 14 0. 57 0. 23 0. 00 -0. 16 1. 30 0. 73 0. 39 0. 16 0. 00 Height Sensitivity : 0. 5 – 0. 8 Radargrammetry Pair : 5 -4, 7 -5, 8 -5

Orbits near Sejong Station, Antarctica

Elevation Angles at Sejong Station 12 orbits have 20°- 45°of incidence angles for nominal imaging mode (descending orbits only)

Height sensitivity of parallax at Sejong Station, Antarctica θ₂(n) θ₁(n) 19. 97° (6) 23. 17° (7) 26. 08° (8) 29. 03° (9) 31. 79° (10) 34. 36° (11) 36. 69° (12) 38. 91° (13) 40. 93° (14) 42. 83° (15) 44. 58° (16) 19. 97° 23. 17° 26. 08° 29. 03° 31. 79° 34. 36° 36. 69° 38. 91° 40. 93° 42. 83° 44. 58° (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) 0. 00 -0. 42 -0. 71 -0. 95 -1. 14 -1. 29 -1. 41 -1. 51 -1. 60 -1. 67 -1. 74 0. 42 0. 00 -0. 29 -0. 53 -0. 72 -0. 87 -0. 99 -1. 10 -1. 18 -1. 26 -1. 32 0. 71 0. 29 0. 00 -0. 24 -0. 43 -0. 58 -0. 70 -0. 89 -0. 96 -1. 03 0. 95 0. 53 0. 24 0. 00 -0. 19 -0. 34 -0. 46 -0. 56 -0. 65 -0. 72 -0. 79 1. 14 0. 72 0. 43 0. 19 0. 00 -0. 15 -0. 27 -0. 37 -0. 46 -0. 53 -0. 60 1. 29 0. 87 0. 58 0. 34 0. 15 0. 00 -0. 12 -0. 22 -0. 31 -0. 38 -0. 45 1. 41 0. 99 0. 70 0. 46 0. 27 0. 12 0. 00 -0. 19 -0. 26 -0. 33 1. 51 1. 10 0. 80 0. 56 0. 37 0. 22 0. 10 0. 00 -0. 09 -0. 16 -0. 22 1. 60 1. 18 0. 89 0. 65 0. 46 0. 31 0. 19 0. 00 -0. 07 -0. 14 1. 67 1. 26 0. 96 0. 72 0. 53 0. 38 0. 26 0. 16 0. 07 0. 00 -0. 06 1. 74 1. 32 1. 03 0. 79 0. 60 0. 45 0. 33 0. 22 0. 14 0. 06 0. 00

Conclusions The orbit and imaging modes of KOMPSAT-5 COSI is dedicated to radargrammetry. Orbit pairs for Radargrammetry (Height sensitivity of 0. 6 -0. 9, Descending only) ¡ Equator: two pairs ¡ Mid-Latitude: Three pairs ¡ Height resolution: Ten Pairs Wider selection of pairs are theoretically provided. Combination of ASC/DES, and L/R-looking will provide more opportunity. Note that all calculations are true at equator. Further analysis is necessary for global configuration. Terra. SAR-X and COSMO-Sky. Med data may provide tests of high-resolution examples, but not so versatile as KOMPSAT-5 COSI.