Systematic Product Analysis

1
Systematic Product Analysis

• Christopher Buck
• ENVISAT Programme
• ESA/ESTEC

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

3
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

5
Module Stepping Mode Database
A1-E4
H or V
1-16
ASA_MS__0.N1
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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

7
Module Stepping Mode Health Check
lt 1 LSB error gt 1 LSB error gt 2 LSB error gt 3 LSB
error
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Pattern and Gain Calibration
Antenna Gain Test Results
Transponder
Beam Antenna Gain
External Characterisation
Embedded Row Test Results
Internal Calibration
Beam Coefficients
Module Stepping
Antenna B/F Near-field data
Beam Radiation Pattern
Rain Forest
Doppler Spectrum
Antenna B/F Test Results
9
Module Stepping Mode History

• Long-term comparison against pre-launch reference
  data set shows trends in module behaviour

10
Antenna Stability - Tx
? 0.25dB
11
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

T/R Module (1 of 32x10)
Radiating Row
Signal BFN
Tx Main
Rx Main

• Use of special calibration signals (cal pulses)
  and additional hardware (cal network)

13
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
?
?
32
15
Interface

• Implemented in IDL
• Backed by MySQL Database

dummy
dummy
dummy
dummy
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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
Wide Swath, SS5, HH
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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

White PF-ASAR Red In-house code
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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