Systematic Product Analysis Christopher Buck ENVISAT Programme ESA ESTEC

Systematic Product Analysis Christopher Buck ENVISAT Programme ESA/ESTEC ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 1

Purpose § ASAR generates typically ~100 products per day § Each contains vital information on the health of the instrument, level settings, processing problems etc § Systematic product analysis is required to monitor the instrument and product status, providing inputs to the instrument and processor operation and flagging any problems in a timely fashion ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 2

Product Types Ingested for Analysis § § § Module Stepping Mode: ASA_MS__0* Image Mode Medium Resolution ASA_IMM_1* Wave Spectra ASA_WVS_1* Wave Image ASA_WVI_1* Global Monitoring ASA_GM 1_1* Alternating Polarization Medium Resolution ASA_APM_1* ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 3

Module Stepping Mode Analysis § § § § Source packet chirps read in Compressed with ideal chirp Gain and phase of each module determined Transmit and Receive Horizontal and Vertical Polarization Time stamped Entered into Database ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 4

Module Stepping Mode Database A 1 -E 4 1 -16 H or V ASA_MS__0*. N 1 320 ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 5

Module Stepping Mode Analysis § Provides: § Instant health check of all modules tx/rx, H/V, Gain/Phase § History of tx/rx, Gain/Phase for each module and each polarization § Phase and amplitude errors as input into antenna pattern analysis ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 6

Module Stepping Mode Health Check < 1 LSB error > 2 LSB error > 3 LSB error ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 7

Antenna Gain Test Results Pattern and Gain Calibration Transponder External Characterisation Internal Calibration Module Stepping Embedded Row Test Results Beam Antenna Gain Beam Coefficients Antenna B/F Near-field data Rain Forest Doppler Spectrum Beam Radiation Pattern Antenna B/F Test Results ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 8

Module Stepping Mode History § Long-term comparison against pre-launch reference data set shows trends in module behaviour ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 9

Antenna Stability - Tx = 0. 25 d. B ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 10

Antenna Stability - Rx = 0. 4 d. B ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 11

Internal Calibration • • • ASAR is equipped with an automatic temperature compensation scheme to compensate for phase/gain drifts at T/R module level Direct monitoring of any residual gain drifts for later correction Continuous measurements even during data acquisition Tx Aux P 2 Tx Main P 1 T/R Module (1 of 32 x 10) P 3 Radiating Row P 1 A Signal BFN Rx Main Rx Aux Cal BFN Cal Use of special calibration signals (cal pulses) and additional hardware (cal network) • ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 12

Image Product Analysis § Product header parameters systematically extracted from ASAR products and entered into database for subsequent analysis § Parameters extracted are: § Internal calibration pulses (P 1, P 1 a, P 2 and P 3) for each of the 32 rows § Product quality parameters (3 d. B IRF width, sidelobe level, ISLR, peak location, chirp power and scaling factor) § Doppler ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 13

Image Product Database 32 ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 14

Interface § Implemented in IDL § Backed by My. SQL Database dummy ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 15

Product Analysis § Confirmation of correct functioning of internal calibration § Generation of INS files with computed default calibration pulse values § Provides overview of main quality parameters § Confirmation of correct pointing and correct Doppler estimation ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 16

Calibration Pulse Analysis - Wave ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 17

Calibration Pulse Analysis Wave P 2 Spurious results, if ignored, can lead to problems in processed imagery ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 18

Calibration Pulses - APM ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 19

Doppler Analysis § In white, 27000 Doppler estimates from Wave Mode Data § In red, the predicted Doppler calculated from orbit parameters ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 20

Doppler Estimation ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 21

Doppler Bias Subtracting the predicted Doppler from that estimated from the image data shows a bias of – 54 Hz ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 22

Doppler Analysis – Effect of Relief Doppler prediction based on WGS 84 hence high altitude of Greenland results in an offset ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 23

Internal Calibration Wide Swath, SS 5, HH Occasional spurious results Fall outside threshold limits and are replaced by the nominal values in the processor ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 24

Calibration Pulse Phase Unwrapping White: PF-ASAR Red: In-house code § PF-ASAR currently has a problem when unwrapping the phase of the calibration pulse § This introduces noise in the elevation gain factor calculation § In-house code unwraps correctly and will soon be implemented in PFASAR ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 25

Corrupted Wave Pulses § Normal wave pulses have blocks of 108 samples of constant amplitude § Occasional corrupted wave pulses display irregular amplitude 1 st ten source packets plotted ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 26

Corrupted Wave Pulses 2 § Corrupted pulses change the elevation gain § Problem is not restricted to the northern hemisphere § Not deterministic meaning that if it were dependent on the timing then it would always appear in the same SWST segment ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 27

Corrupted Cal Pulses in Wide Swath § P 2 calibration pulse in wide swath mode is corrupted for sub-swaths 4 and 5 SS 1 SS 2 SS 3 SS 4 ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 SS 5 Page 28

Gain Droop Compensation § P 2 gain droop compensation is incorrect when the calibration sequence changes (cal order 0 or 1) in Wide Swath mode § Lower curve is from PF-ASAR with droop compensation using pre-launch characterization data § Upper curve is inhouse code and no compensation ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 29

Conclusions § Systematic product analysis proving to be extremely useful for: § § Troubleshooting Health checking Consistency checking Updating processor parameters § So far over 2500 products ingested § § 949 IMM 1346 WVS 213 WSM 57 APM ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 30

Conclusions 2 § Antenna in great shape, very good stability § 0. 25 d. B tx, 0. 4 d. B rx § Doppler tracking error ~50 Hz consistent with 10 -15 mdegrees of mispointing § Problem with noisy calibration pulse gains identified due to phase unwrapping - solution ready § Problem with P 2 gain droop compensation identified – solution at hand ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 31

Conclusions 3 § Ongoing problems requiring further analysis: § Occasional corrupted Wave pulses § Corrupted cal pulses in Wide Swath Mode § Further problems with the internal calibration are just starting to be addressed in AP and GM modes ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Page 32