Time Trend Evaluations of Absolute Accuracies for PRISM and AVNIR-2

Transcription

1 The 3 rd ALOS Joint PI Symposium, Kona, Hawaii, US Nov. 9-13, 2009 Time Trend Evaluations of Absolute Accuracies for PRISM and AVNIR-2 Takeo Tadono*, Masanobu Shimada*, Hiroshi Murakami*, Junichi Takaku**, Akira Mukaida**, and Sachi Kawamoto** * Earth Observation Research Center (EORC), Japan Aerospace Exploration Agency (JAXA) tadono.takeo@jaxa.jp ** Remote Sensing Technology Center of Japan (RESTEC) Bird s eye view of Keauhou, Hawaii, US using PRISM DSM with ortho-rectified pan-sharpened image by PRISM and AVNIR-2

2 Outline Introduction Satellite and operation status Data acquisition status in the world Geometric Calibration AVNIR-2: Time trend of absolute geometric accuracy PRISM: Time trend of absolute geometric accuracy Circular Error 90% (CE90) Radiometric Calibration AVNIR-2: Absolute radiometric accuracy updated Field-of-view (FOV) calibration PRISM: Stripe noises reduction Absolute radiometric accuracy updated ALOS Follow-On Mission: ALOS-2, ALOS-3 Conclusions Pan-sharpened image of TKSC using PRISM (Mar. 27, 2006) and AVNIR-2 (Mar. 25)

3 ALOS Daichi Advanced Land Observing Satellite (ALOS) (Advanced Land Observing Satellite) Jan. 24, 2006: Launch by H-IIA #8 from TNSC Nov. 9, 2009: 3.8 year (1,385 days) after launch Star Tracker PALSAR 8.9m Data Relay Antenna (DRC) [Data rate: 240Mbps] GPS Antenna Mission objectives: - Cartography (1:25,000 scale), - Regional environment observation, - Disaster monitoring, and - Resources surveying. 2.9m PRISM AVNIR-2 Solar Array Paddle 22m Velocity Nadir PRISM : Panchromatic Remote-sensing Instrument for Stereo Mapping AVNIR-2: Advanced Visible and Near Infrared Radiometer type 2 PALSAR: Phased Array type L-band Synthetic Aperture Radar

4 ALOS Basic Observation Scenario PRISM (Descending) One global coverage annually (OB1 Triplet; OB2 selected areas) 2 cycles (2 x 46 days) required for each region (+/-1.2deg. pointing angle) Timing based on cloud statistics, seasonality and sun elevation AVNIR-2 (Descending) One global coverage annually (0deg. pointing) One observation within 2 cycles Timing based on cloud statistics, seasonality and sun elevation PALSAR (Ascending / Descending) Asc.: 2-3 global coverage annually (Summer FBD34deg.; Winter FBS34) Global InSAR coverage every 2 yrs Pol-InSAR campaigns every 2 yrs Desc.: One global ScanSAR coverage annually Intensive ScanSAR sites PRISM (green: OB1, yellow: OB2) AVNIR-2 > Since Cycle 28: Prioritize no acquisition areas and cloud-covered areas for optical * Observation Scenario can be find on web PALSAR Asc. (FBD34.3) PALSAR Desc. (ScanSAR) Basic Observation Scenario (Cycle28: Jun 12 - Jul 27, 2009)

5 Acquisition Status in the world May 16, 2006 Apr. 26, 2009 PRISM 35km (OB1) (Cloud cover: 0-2% / scene) PRISM 70km (OB2) (Cloud cover: 0-2% / scene) More than 5 AVNIR-2 (Cloud cover: 0-2% / scene) Image coverage map of PRISM and AVNIR-2 based on the basic observation scenario Spatial coverage: PRISM OB1 55% with 0-2% cloud cover in scene OB1 69% with 0-20% cloud cover in scene AVNIR-2 70% (0-2%); 83% (0-20%)

6 Geo Cal AVNIR-2 Geometric Correction Accuracy Released on October 22, 2008 Time trend of geometric accuracies of AVNIR-2 0deg. compared between before and after alignment parameters updated (Oct. 22, 2008). Geometric errors in Y direction of AVNIR-2 had a linear relationship between observation dates before updating alignment parameters (*). Normally, AVNIR-2 is operating as 0 deg. pointing angle Satellite orbit inclination change (yaw maneuver) has been done on June and July 2008 AVNIR-2 alignment parameters has been updated on October 22, 2008 Errors in X direction (x) are caused by quantization of the pointing angle setting

7 Geo Cal PRISM Alignment Parameter (AP) ALOS AOCS system and coordination PRISM CCD coordinate for Nadir For Forward view For Backward view Pointing det. parameter Pointing alignment parameter STT STT STT attitude reference frame Attitude determination parameter ECI(J2000) coordinate STT coordinate - Precise Orbit Determination from TAC - Precise Attitude Determination (PAD) - Pointing Alignment Parameter (AP) Evaluation of variation during recurrent, seasonal change, and temporal change. > It is better to use high latitude and night time GCPs EOC Pointing AP is basically updating every two months i.e. time gap is occurred between observed date and processed date. Two months time gap! Ex) #16 AP Release: Sep. 25, 2008 Evaluation: Mar. 18 Sep. 17, 2008 > Go / No go PPDS - Standard product - Evaluation - GCP - Evaluation - Sensor alignment estimation EORC - GCP - Evaluation - Sensor parameters = We recommend the data order will be better to submit two months after observation date.

8 Geo Cal PRISM Geometric Correction Accuracy Averaged error in X (m) Averaged error in Y (m) /01/07 06/01/07 08/01/07 10/01/07 12/01/07 01/31/08 04/01/08 06/01/08 08/01/08 10/01/08 04/01/07 06/01/07 08/01/07 10/01/07 12/01/07 01/31/08 04/01/08 06/01/08 08/01/08 10/01/ Observation date Observation date Averaged geometric errors of nadir looking radiometer of PRISM L1B2 (left: X (pixel) direction, and right: Y (line) direction). STDV of error in X (m) STDV of error in Y (m) /01/07 06/01/07 08/01/07 10/01/07 12/01/07 01/31/08 04/01/08 06/01/08 08/01/08 10/01/08 04/01/07 06/01/07 08/01/07 10/01/07 12/01/07 01/31/08 04/01/08 06/01/08 08/01/08 10/01/08 Observation date Observation date Standard deviations of geometric errors of nadir looking radiometer of PRISM L1B2 (left: X, and right: Y). Time trends of geometric correction accuracy of PRISM/N since April 2007 Averaged error: Absolute geometric correction (i.e. system correction) accuracy Each colored plot: different pointing alignment parameters (APs) to use image processing

9 Geo Cal PRISM Circular Error 90% (CE90) a) Nadir (5,499CPs, CE90=11.8m) b) Forward (1,771CPs, CE90=12.4m) c) Backward (4,839CPs, CE90=13.4m) Geometric errors distribution and circular error 90 (CE90) of PRISM. Histogram of geometric distance errors of PRISM (left: nadir, middle: forward, right: backward). Geometric accuracy evaluation of PRISM acquired from Jun. 22, 2007 to Jun. 4, 2009 Worldwide ground control points (GCPs) were used as check points Geometric accuracy (RMS): Nadir 7.8m, Forward 7.8m, and Backward 8.7m

10 Radio Cal TOA Reflectance Function Scheme The scheme is a cross calibration using the similar geometric condition; solar zenith (θ 0 ), and relative azimuth (ϕ) angles which depend on local time and inclination angle of the orbit (ALOS Terra Aqua (N-S line symmetry) ENVISAT). We use top-of-atmosphere (TOA) reflectance function of satellite zenith angle (θ) at target points using MODIS observations for the reference. Merits: we can get many samples, not only nadir, and don t need in-situ data MODIS scanning in 16 days N +θ -θ θ 0 Geometric condition of AVNIR-2 and PRISM (Nadir) are similar to geometries in 16 days MODIS observations. E ALOS pointing θ AVNIR2 ϕ W geometric condition S Orbit Repeat Cycle ALOS and EOS observations ALOS AVNIR-2 Terra MODIS Aqua MODIS Sun- Sun- Sun- Synchronous Synchronous Synchronous Descending Descending Ascending 10:30 10:30 13:30 46 days Sub Cycle: 2 days Repeat Cycle: 16 days Sub Cycle: 2 days Altitude km 705 km Inclination deg 98.2 deg Satellite 44~+44 deg zenith (pointing) 65~+65 deg (scanning) FOV (swath) 70 km 2330 km IFOV 10 m 250~1000 m AVNIR-2 and MODIS channels AVNIR2 MODIS 1 (463nm) 3 (466nm) 2 (560nm) 4 (554nm) 3 (652nm) 1 (646nm) 4 (821nm) 2 (856nm) -

11 Radio Cal AVNIR-2 Cross-Cal with MODIS X axis: Terra/ MODIS AVNIR2 Band 1 AVNIR2 Band 2 AVNIR2 Band 3 AVNIR2 Band 4 X axis: Aqua/ MODIS - Number AVNIR2/MODIS AV2 Band Terra Aqua Difference caused by Antarctic data Bands 1~3 agree Terra/Aqua MODIS within 3.2% Band 4 agree Terra/Aqua MODIS within 7.3%. The half of error can be explained by water vapor absorption Many samples can be obtained!

12 Radio Cal AVNIR-2 FOV Calibration RGB Image 2007/ 11/13 Radiance (or DN) Unrealistic inter-channel difference Released on May 9, 2008 L1B radiance = Real data + FOV noise + small-scale noise (e.g., o/e, cal table error..) Real data + FOV anomaly Real TOA radiance Pixel (FOV; ~70km) Pixel (FOV; ~70km) 1. FOV noise Corrected by cross-calibration with MODIS (using a directional function of MODIS TOA reflectance) Temporal change is described using the internal lamp of AVNIR-2 2. Gain-mode difference Gain-modes 2 and 3 are corrected using the lamp data 3. Small-scale noise (<~0.5DN) Corrected by small scale average of smooth & bright area (polar snow fields) Line average plot of Band 3 on 2007/11/13 L1A L1B Corr. tables Pixels

13 Radio Cal AVNIR-2 FOV Calibration Antarctic 2007/11/19 Band 3,2,1 RGB image old new Band-1~4 line plot Differences between old and new are +/- 2%

14 Radio Cal PRISM Stripe Noise Reduction Odd-Even pixel and inter-ccd unit difference were large sometimes in PRISM images We assume PRISM sensor itself is stable and the error is caused by insufficient frequency of the darkcurrent downlink (optical black i.e. offset error) We estimate the dark current statistically using each scenes 1. Inter-CCD unit difference (offset) is corrected by overlap samples (32 pixels) after the default radiometric correction The correction coefficients are tuned to keep mean radiance of all CCD unit 2. Odd-Even pixel difference (offset) is corrected by statistics of the Even minus neighboring two Odd samples in each CCD 3. Above statistics are processed in each one of five line-blocks, and correction offsets are linearly interpolated by the line number Irregular and high-contrast samples are excluded in the statistics Block 1 Block 2 Block 3 Released on October 19, 2007 Block 4 Block 5 CCD 1 CCD overlap A) Odd N-1 PRISM image B) Even N CCD 2 CCD 3 C) Odd N+1 Dif = B (A + C)/2 CCD 4 Statistics in each segment

15 Radio Cal PRISM Stripe Noise Reduction ALPSM Forward Before After

16 Radio Cal PRISM Cross-Cal with AVNIR-2 Comparison of TOA radiances between simulated PRISM by AVNIR-2 (x axis) and actual PRISM (y axis). Example of images observed simultaneously with PRISM nadir (left) and AVNIR-2 over Arizaro Salt Lake, Argentina on May 2, Response functions comparison Absolute radiometric calibration of PRISM is achieved by cross-cal with simultaneously acquired AVNIR-2 The nadir image can observe under same geometry and same atmospheric condition at the same time Comparison is done by top-of-atmosphere (TOA) radiances calculated from simulated PRISM reflectance by AVNIR-2 and actual PRISM radiance The radiances agree well with 3.6% (RMSE)

17 Standard Product PRISM 1B2 AVNIR-2 1B2 Calibration Results of PRISM/AVNIR-2 Previous results as of Sep. 29, 2007 Geometry Absolute Accuracy (RMS): using 1,390 GCPs Pixel (X) Line (Y) Distance Nadir 6.5m 7.3m 9.8m Forward 8.0m 14.7m 16.7m Backward 7.4m 16.6m 18.1m Relative Accuracy (1σ) 3 radiometers 1.9m 2.3m 3.0m Geometry (-41.5 to deg. pointing) Pixel (X) Line (Y) Distance Absolute Accuracy (RMS) 106m 19m 108m Relative Accuracy (1σ) 4m 4m 6m Results as of July 1, 2009 (Public*) Geometry (Jun. 22, 2007-Jun. 4, 2009) Absolute Accuracy (RMS) Pixel (X) Line (Y) Distance Nadir 5.6m 5.3m 7.8m using 5,499 GCPs, 586 scenes Forward 4.9m 6.1m 7.8m using 1,771 GCPs, 225 scenes Backward 5.0m 7.1m 8.7m using 4,839 GCPs, 525 scenes Relative Accuracy (1σ) 3 radiometers 1.4m 1.8m 2.4m CE90 Nadir 11.8m, Forward 12.4m, Backward 13.4m Radiometry Absolute accuracy: similar to that of AVNIR-2 Geometry (all period) * Latest ALOS calibration result can be find at in English Absolute Accuracy (RMS) Pixel (X) Line (Y) Distance 0 deg. pointing 71.1m 7.5m 71.9m +/-41.5 deg. 60.9m 96.6m 114.2m Relative Accuracy (1σ) 3.4m 7.7m 8.5m using 1,035 GCPs, 54 scenes Radiometry (all period) Absolute accuracy Band 1-3: 3.2%, Band4: 7.3%

18 Concept of ALOS Follow-On Mission ALOS F/O Mission: ALOS-2 (SAR) and ALOS-3 (Optical) National land monitoring and managements Resources managements Disaster monitoring ALOS-2 is planed to be launch in , and ALOS-3 is hoped in (TBD) Current System Concept (under investigation) Monitoring disaster area affected by earthquake, volcano, flood, etc. Observing the disaster affected area within 3 hr (6 hr in night) A satellite constellation of two optical sensor satellites and two SAR satellites ALOS-2: 3m resolution (3x1m in spotlight mode) with 50km swath (SAR) ALOS-3: Panchromatic - 0.8m resolution in 50km swath; multi - 5m in 90km swath; and hyper-spectral 30m in 30km swath (TBD) ALOS series will be continued ALOS-2: SAR Satellite ALOS-2 will be introduced at 15:00- on Wednesday. August, 2009-: Project Team was established -December 2009: Preliminary Design Phase -October 2010: Critical Design Phase ALOS-3: Optical Sensor Satellite

19 ALOS-3 Specification (TBD) Sun-Synchronous Sub-Recurrent Orbit Altitude: Approx. 620 km LST: 13:30 in descending orbit Design Life Launch Satellite Target Rocket Mass Solar Paddle 5 years JFY H-2A Approx. 2 ton Two-wings type panel ALOS-3: Optical Sensor Satellite 11 bits quantization JPEG 2000 onboard compression Stereo function (two telescopes?) Body pointing function (+/-60 deg.) Mission Data Transmission Mission Sensor Major Observation Mode Mission Objectives Panchromatic Multi spectral Hyper spectral Direct / via. Data Relay Satellite Optical instruments Resolution: 0.8 m, Width: 50 km Resolution: 3.2 m, Width: 90 km Resolution: 30 m, Width: 30 km Cartography, volcano monitoring, surface change detection Sea ice, river, forest and agriculture monitoring etc.

20 ALOS-3 Image Simulation ALOS PRISM (2.5 m GSD) Jan. 19, 2009 ALOS-3 Pan simulation (0.8 m GSD) Using airborne optical sensor (ADS40) acquired on Dec. 21, (Pasco co., Ltd.) ALOS ALOS 3 Quantization 8bit 11bit Data compression JPEG JPEG2000

21 ALOS-3 Pointing Simulation Time Pointing Spring Summer Winter 20 deg. 60 deg. * GSD, quantization, S/N, MTF, data compression, and atmospheric effect were considered.

22 Conclusions I introduced updated Cal/Val results of PRISM and AVNIR-2, in particular, 1) satellite condition, operation and data acquisition status, 2) the time trends of geometric accuracy of AVNIR-2 and PRISM (NDR: 7.8m), 3) radiometric calibration updated for AVNIR-2 (B1-3: 3.2%) and PRISM, 4) stripe noises reduction of PRISM as relative radiometric calibration, and 5) ALOS F/O Mission introduced. ALOS and instruments are working very well, and data are available for all users. Cal/Val is also continuously carrying out to keep accuracies and qualities of products as operational Cal/Val. More detail of ALOS Cal/Val will be published in IEEE TGARS ALOS special issue, Vol. 47, No. 12, Dec (in press). For more information of ALOS, JAXA/EORC : New images, data acquisition plan and technical documents For data search and order, ALOS User Interface Gateway (AUIG) All archived data can be searched with Guest account RESTEC : Commercial data distributor