The Advanced Along-Track Scanning Radiometer (AATSR) Mission Status and Early Results

Transcription

1 The Advanced Along-Track Scanning Radiometer (AATSR) Mission Status and Early Results M. C. Edwards (University of Leicester, UK) D. Llewellyn-Jones (University of Leicester, UK) D. L. Smith (Rutherford Appleton Laboratory, UK) H. Tait (VEGA Group, UK) Page 1

2 Presentation Overview! Introduction to AATSR Mission Background Principles of Operation Products! Status of Commissioning! Instrument Performance! Algorithm Verification and Geophysical Validation! Early AATSR Images! Summary and Conclusions Page 2

3 Advanced Along Track Scanning Radiometer Mission Background! Funded primarily by the UK Department for Environment, Food and Rural Affairs (DEFRA) to support programme of climate research and prediction! Designed to measure sea surface temperature at the levels of precision and accuracy required for climate research (better than 0.3 K ± 1 sigma limit)! Third in a series: ATSR, ATSR-2 and AATSR! 15+ year record of accurate SST measurements on a global scale! Data for a wide range of other applications (land, oceans, cryosphere and atmosphere) Page 3

4 AATSR Principles of Operation! 7 spectral channels 3 IR (3.7 m, 11 m, 12 m) 4 Vis/NIR (0.55 m, 0.67 m, 0.87 m, 1.6 m)! 500 km swath! 1 km IFOV at nadir! On board calibration 2 on-board black bodies for IR calibration VISCAL unit for visible channel calibration! Stirling Cycle Coolers, cooling low noise detectors to 80K! Dual view Page 4

5 Name Level 0 GBTR Gridded BT/Reflectance Browse GST Gridded Surface Temp. AST Averaged Surface Temp. Meteo Product ID ATS_NR 0P ATS_TOA_1P ATS_AST_BP ATS_NR 2P ATS_AR 2P ATS_MET_2P AATSR Products Description Instrument source packets Full resolution top-of-atmosphere BT/reflectance for all channels and both views (1 km resolution) 3 band colour composite browse image (4x4 km sampling of GBTR) Full resolution SST, land and cloud parameters Spatially averaged SST, land and cloud parameters, over 50km and half degree cells SST and averaged BT for all clear sea pixels, 10 arc min cells, for Meteo users Page 5

6 Current Status of Commissioning Activities! Almost all SODAP commanding completed Instrument switch-on Instrument checkout First cooldown and instrument optimisation, including: Scan mechanism checkout Black Body tests Pixel map alignment verification Visible gain and IR gain-offset loop optimisation! Cooler Checkout to be re-run mid-july! No major on-board instrument anomalies! Instrument now running nominally! Analysis of data acquired ongoing Page 6

7 Instrument Performance to Date (1) Blackbody Calibration Subsystem Both Black Bodies are performing well +XBB -XBB Reading Difference Reading Difference Baseplate average PRT PRT PRT PRT PRT PRT6* Page 7

8 Instrument Performance to Date (2) Visible Calibration System Good signal, expected duration Further characterisation over time is ongoing Page 8

9 Instrument Performance to Date (3a) Cooler/Focal Plane Assembly Cool down to 80K achieved within 5 hours Page 9

10 Instrument Performance to Date (3b) Cooler/Focal Plane Assembly Following cool down, temperature of FPA remains stable (± 0.3K) Page 10

11 Instrument Performance to Date (4) Scan Mirror Scan mechanism is running in as expected Levels of jitter observed so far are lower than the equivalent on ATSR-2 Temperature and power consumption of SMU are as expected Scan rate = 150 msec/scan Pixel Map Alignment All segments of the pixel map have clear views of their targets with the default pixel map. No major modifications required. Page 11

12 Instrument Performance to Date (5)! Radiometric Performance Analysis of signal to noise etc. not complete NEDT below 50 mk on IR channels Dark noise on visible channels below digitisation levels Frequency analysis on BB signal shows no significant pickup below 3 Hz from the cooler or other mechanisms. Results are comparable to ATSR-2 levels Page 12

13 Algorithm Verification! Samples from these data are currently being examined as part of an Algorithm Verification exercise. Objectives are: Check product format Check product content against algorithms applied Review/optimise auxiliary data used in processing Page 13

14 AATSR Validation Programme! Comprehensive validation programme during the commissioning phase and throughout the mission! Objectives: To determine whether the AATSR instrument is returning an acceptable global skin SST To make an assessment of the quality and accuracy of AATSR data products! SST validation: 3 categories Global buoy comparison Measurements with autonomous instruments Precision measurements! Validation of vis/nir channels Vicarious over land and cloud Ground measurements Page 14

15 Validation Status! Validation activities have begun 2 cruises in Australian waters: 24 May to 2 June, 5 to 14 June SCIPIO cruise in the Indian Ocean: 1 June to 11 July Autonomous instruments operating Page 15

16 AATSR Images Page 16

17 ATSR-2 vs. AATSR Page 17

18 Summary and Conclusions! AATSR Instrument functioning nominally! Science data are being acquired! Provisional assessment suggests radiometric performance comparable to ATSR-2 at this stage! Comprehensive validation programme in place! Indications are that instrument and (A)ATSR mission objectives will be met Page 18