Download - Systematic Product Analysis
ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002Page 1
Systematic Product Analysis
Christopher BuckENVISAT Programme
ESA/ESTEC
ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002Page 2
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
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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_GM1_1* Alternating Polarization Medium Resolution
ASA_APM_1*
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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
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Module Stepping Mode Database
TestInstanceInstIdTimeStampPolarizationFilename
ResultResultIdTileModuleTxGainTxPhaseRxGainRxPhaseInstId320
H or V
ASA_MS__0*.N1
A1-E4
1-16
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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
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Module Stepping Mode Health Check
< 1 LSB error< 1 LSB error> 1 LSB error> 1 LSB error> 2 LSB error> 2 LSB error> 3 LSB error> 3 LSB error
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ExternalCharacterisation
Antenna B/FTest Results
Antenna GainTest Results
Beam Antenna
Gain
Beam Radiation Pattern
ModuleStepping
Antenna B/FNear-field data
Transponder
InternalCalibration
Rain Forest
Pattern and Gain Calibration
Embedded RowTest Results
Beam Coefficients
Doppler Spectrum
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Module Stepping Mode History Long-term comparison against pre-launch
reference data set shows trends in module behaviour
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Antenna Stability - Tx
= 0.25dB
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Antenna Stability - Rx
= 0.4dB
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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 Main
Rx Main
RadiatingRow
T/R Module(1 of 32x10)
Signal BFN
P2
P1A
P3
P1
Cal BFN
Tx Aux
Rx Aux Cal
P1P1
• Use of special calibration signals (cal pulses) and additional hardware (cal network)
ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
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Image Product Analysis Product header parameters
systematically extracted from ASAR products and entered into database for subsequent analysis
Parameters extracted are: Internal calibration pulses (P1, P1a, P2 and
P3) for each of the 32 rows Product quality parameters (3dB IRF width,
sidelobe level, ISLR, peak location, chirp power and scaling factor)
Doppler
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Image Product Database
CalCalIDZeroDopplerTimeuSecsANXBeamPolarization3dBwidthSidelobeISLRPkCorrelationChirpPowerScaleFactorFileID
DopDopIDZeroDopplerTimeANXBeamPolarizationDopplerConfidenceBadFlagLatitudeLongitudeFileID
FileFileIDFilenameProduct
32
PulsePulseIDRowNumberMaxP1MaxP2MaxP3AveP1AveP1aAveP2AveP3PhaseP1PhaseP1aPhaseP2PhaseP3CalID
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Interface Implemente
d in IDL Backed by
MySQL Database
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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
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Calibration Pulse Analysis - Wave
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Calibration Pulse Analysis Wave P2
Spurious results, if ignored, can lead to problems in processed imagery
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Calibration Pulses - APM
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Doppler Analysis
In white, 27000 Doppler estimates from Wave Mode Data
In red, the predicted Doppler calculated from orbit parameters
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Doppler Estimation
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Doppler Bias
Subtracting the predicted Doppler from that estimated from the image data shows a bias of –54Hz
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Doppler Analysis – Effect of Relief
Doppler prediction based on WGS84 hence high altitude of Greenland results in an offset
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Internal Calibration
Occasional spurious results
Fall outside threshold limits
and are replaced by the nominal values in the processor
Wide Swath, SS5, HH
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White: PF-ASAR
Red: In-house code
Calibration Pulse Phase Unwrapping
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 PF-ASAR
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Corrupted Wave Pulses Normal wave
pulses have blocks of 108 samples of constant amplitude
Occasional corrupted wave pulses display irregular amplitude
1st ten source packets plotted
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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
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Corrupted Cal Pulses in Wide Swath
P2 calibration pulse in wide swath mode is corrupted for sub-swaths 4 and 5
SS1 SS2 SS3 SS4 SS5
ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
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Gain Droop Compensation
P2 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 in-house code and no compensation
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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
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Conclusions 2 Antenna in great shape, very good stability
0.25dB tx, 0.4dB rx
Doppler tracking error ~50Hz consistent with 10-15 mdegrees of mispointing
Problem with noisy calibration pulse gains identified due to phase unwrapping - solution ready
Problem with P2 gain droop compensation identified – solution at hand
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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