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

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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

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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)

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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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dummydummy

dummydummy

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

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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

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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