Date post: | 24-Dec-2015 |
Category: |
Documents |
Upload: | ilene-freeman |
View: | 217 times |
Download: | 2 times |
Page 1ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
ASAR On-board Instrument
Instrument Stability and StatusInstrument AdjustmentsTracking Changes of Beam PatternsBeam Pattern MaintenanceRamon Torres
ENVISAT ProgrammeESA – ESTECNoordwijk, The Netherlands
Page 2ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Instrument Stability
Relies on the RF Subsystem internal control and the temperature compensation scheme implemented in the Antenna Sub-arrays (Before use of the Internal Calibration correction)
ASAR Instrument has proven to be very stable in short and long term Short term as demonstrated by the internal
calibration pulses viewed through time Long term as demonstrated by the use of the
Module Stepping calibration mode
Page 3ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Reminder: ASAR Antenna Major element in the ASAR end-to-end product quality
Active antenna with 320 individual subarrays T/R module: Transmit/Receive in H and V polarisation 5 panels 4 tiles 16 subarrays
Control and operations at tile level Temperature
compensation scheme based on individual sub-array on-ground characterisation
Radar mode timing Pattern definition at row
level 8 Stripmap beams 5 ScanSAR beams
Page 4ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Antenna Temperature
-10
-8
-6
-4
-2
0
2
4
6
8
10
6-Jul 16-Jul 26-Jul 5-Aug 15-Aug 25-Aug
-10
-8
-6
-4
-2
0
2
4
6
8
10
4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun 23-Jun 3-Jul 13-Jul
Initial temperatures were lower than predicted
Increased operations from May 3 achieved realistic temperature conditions:
0-6 for HR only
4-10 for full
Low temperatures corresponding to instrument switchoffs
Page 5ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Short Term Stability – Internal Calibration
Tx Main
Rx Main
RadiatingRow
T/R Module(1 of 32x10)
Signal BFN
Cal BFN
Tx Aux
Rx Aux Cal
Variations in Tx signal and Rx conditions during acquisition
Analysis of the internal calibration pulses P1 Tx P2 Rx P3 RF s/s
P2 P3
P1
Page 6ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Short term Stability
Instrument variations are taken into account by the ASAR internal calibration, nevertheless:
RF s/s conversion levels are extremely stable (P3 pulse July 21-August 9)
Variations of Tx and Rx characteristics due to temperature at antenna level are well handled by the temperature compensation scheme (P1 and P2 pulses for row 18, July 21-August 9)
Page 7ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Long Term Stability
Long-term (along the instrument lifetime): Sub-array T/R module failures, drifts and degradation
ASAR monitors T/R modules for failures or drifts for eventual correction
Use of Module Stepping Mode: Sampling all 320 T/R modules sequentially in
less than 1 s (Tx/Rx Gain/Phase) anywhere in the orbit
Comparison with reference measurement Statistical analysis of variations
Page 8ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Long Term Stability - Module Stepping Mode
Individual T/R Modules Tx and Rx H and V Gain and
Phase
Tx Main
Rx Main
Signal BFN
Cal BFN
Tx Aux
Rx Aux Cal
T/R Module
Radiating Row
Tx Rx
Page 9ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Module Stepping - Last Results - TxH
<> ± 1.5 dB<> ± 3.0 dB
<> ± 10.0 dB>< ± 10.0 dB
<> ± 5.65º<> ± 11.2º<> ± 22.5º>< ± 22.5º
Page 10ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Module Stepping - Last Results - RxH
<> ± 1.5 dB<> ± 3.0 dB
<> ± 10.0 dB>< ± 10.0 dB
<> ± 5.65º<> ± 11.2º<> ± 22.5º>< ± 22.5º
Page 11ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Module Stepping - Last Results - TxV
<> ± 1.5 dB<> ± 3.0 dB
<> ± 10.0 dB>< ± 10.0 dB
<> ± 5.65º<> ± 11.2º<> ± 22.5º>< ± 22.5º
Page 12ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Module Stepping - Last Results - RxV
<> ± 1.5 dB<> ± 3.0 dB
<> ± 10.0 dB>< ± 10.0 dB
<> ± 5.65º<> ± 11.2º<> ± 22.5º>< ± 22.5º
Page 13ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Long-term Stability
Tx H Rx H Tx V Rx V
Gain 0.25 dB
0.40 dB
0.30 dB
0.49 dB
Phase 2.9º 3.4º 3.2º 3.4º
Analysis on the T/R modules from Sep/02 to Nov/24
Close to the LSB step both for gain and phase
Tx / Rx difference from Rx gain droop not compensated in calibration modes: 0.22 dB (Rx gain
droop) 0.25 dB (gain control)
Page 14ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Instrument Adjustments Early corrections:
On board beam coefficients for ScanSAR modes
Up and down converter levels
Sub-array gain and phase offsets
Timing parameters Wave Mode exit timing
Control Software patches from operational failures Historical Swath
parameters N-2 echo-shift Wave mode telemetry Alternate Polarisation
mode annotation Global Monitoring mode
exit Parameter optimisation from calibration activities: Receiver gain adjustments Image and WideSwath
bandwidths WideSwath timeline
Page 15ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Adjustments: Early Corrections
ScanSAR beam coefficients wrongly burnt in the on-board EPROMs upload of new
Up and down converter levels too low for Module Stepping mode upload of new
Gain and phase offsets to correct on-ground deviations and post-launch drifts upload
Timing parameters not compatible with orbit data upload of new
Wave Mode exit timing not compatible with complete vignette termination MPS control
Page 16ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Adjustments: Parameter Optimisation Receiver Gain for all modes and beams in order to
maximise the dynamic range Image Mode Bandwidth increased to maximum 16MHz
for all beams WideSwath Bandwidth increased:
WideSwath Timeline modified by reducing the number of pulses per burst to improve azimuth ambiguities:
SS1 SS2 SS3 SS4 SS5
7.15 5.33 4.39 3.01 2.82
14.75 12.86 10.48 9.54 8.78
SS1 SS2 SS3 SS4 SS5
50 80 67 87 74
50 65 55 71 60
Page 17ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
On-board Software Patches
Historical Swath Parameters Switchdowns Uploaded 02-Aug-2002. Anomaly solved!
N-2 Echo Shift Large shifts in images Uploaded 05-Sep-2002. Anomaly solved!
Wave Mode telemetry handling between vignettes Switchdown Uploaded 17-Oct-2002. Anomaly solved!
Alternate Polarisation Annotation of the SWST changes Shift between polarisations Uploaded 11-Nov-2002. Anomaly solved!
Global Monitoring exit Switchdown Uploaded completed 9 December at 18:56:16. GM
operating correctly from 9 December at 19:02:30
Page 18ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Tracking Beam Pattern Changes
Estimation based on Module Stepping results and the radiation model of each sub-array based on On-ground characterised
embedded row pattern for elevation
Uniform distribution for azimuth Generation of antenna radiation
patterns: full elevation and azimuth
pattern for ambiguity analysis swath elevation pattern for
tracking changes swath azimuth pattern for
Doppler estimation and descalloping
A single MS generates the full set of antenna patterns (Tx/Rx and Hpol/Vpol)
-60 -40 -20 0 20 40 60-60
-50
-40
-30
-20
-10
0ASAR Antenna. IS3 beam at 5.331 GHz
Elevation (degrees)
Directivity (
dB
)
Tx H polTx V polRx H polRx V pol
-16 -14 -12 -10 -8 -6 -4-35
-30
-25
-20
-15
-10
-5ASAR Antenna. IS1 two-way pattern at 5.331 GHz
Elevation (degrees)
Dire
ctiv
ity (
dB)
IS1HIS1V
-0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25-28
-26
-24
-22
-20
-18
-16
-14
-12
-10
-8ASAR Antenna. IS1 two-way pattern at -9.6º and 5.331 GHz
Azimuth (degrees)
Dire
ctiv
ity (
dB)
IS1HIS1V
-12 -10 -8 -6 -4 -2 0-30
-28
-26
-24
-22
-20
-18
-16
-14
-12
-10ASAR Antenna. IS2 two-way pattern at 5.331 GHz
Elevation (degrees)
Dire
ctiv
ity (
dB)
IS2HIS2V
-0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25-35
-30
-25
-20
-15
-10ASAR Antenna. IS2 two-way pattern at -6.1º and 5.331 GHz
Azimuth (degrees)
Dire
ctiv
ity (
dB)
IS2HIS2V
-0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25-25
-20
-15
-10
-5
0ASAR Antenna. IS7 two-way pattern at 12º and 5.331 GHz
Azimuth (degrees)
Dire
ctiv
ity (
dB)
IS7HIS7V
6 8 10 12 14 16 18-70
-60
-50
-40
-30
-20
-10
0ASAR Antenna. IS7 two-way pattern at 5.331 GHz
Elevation (degrees)
Dire
ctiv
ity (
dB)
IS7HIS7V
Page 19ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Synthesis of Elevation Patterns IS1 Pattern:
Elevation VV Measured Pre-
launch Estimated
Rainforest Simulated from MS
Elevation HH Measured Pre-
launch Estimated
Rainforest Simulated from MS
Conclusion: MS agrees with RF
within ± 0.2 dB Same order as pre-
launch patterns
Page 20ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Synthesis of Azimuth Patterns
-6 -5 -4 -3 -2 -1 0 1 2 3-40
-35
-30
-25
-20
-15
-10
-5
0ASAR Antenna. Transponder fly-over azimuth pattern
Azimuth (degrees)
Directivity (dB
)
IS3 data from transponder #1Data simulated from MS
-5 -4 -3 -2 -1 0 1 2 3-40
-35
-30
-25
-20
-15
-10
-5
0ASAR Antenna. Transponder fly-over azimuth pattern
Azimuth (degrees)
Directivity (dB
)
IS3 data from transponder #3Data simulated from MS
-5 -4 -3 -2 -1 0 1 2-40
-35
-30
-25
-20
-15
-10
-5
0ASAR Antenna. Transponder fly-over azimuth pattern
Azimuth (degrees)
Directivity (dB
)
IS3 data from transponder #2Data simulated from MS
June 2002 image mode IS3 over Edam, Zwolle and Swifterband Very good correlation between
simulated data and transponder flyovers
Better than 2 db at the level of –20db (0.02db)
IS1 synthesised from MS Mispointing agrees with
doppler
-0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25-25
-20
-15
-10
-5
0ASAR Antenna. IS1 two-way azimuth pattern at -9.6º and 5.331 GHz
Azimuth (degrees)
Directivity (
dB
)
IS1HH from MSIS1VV from MSIS1HH from IMBFIS1VV from IMBF
Page 21ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Pattern Estimation: Conclusions
Rainforest estimation: Estimation approach based on combinations of pattern estimates
in different modes (IM&WS) with a standard deviation of ~0.1dB Long process as it requires several acquisitions per beam and
polarisation Synthesis from Module Stepping results:
Very good tool to track variations of the antenna radiation patterns From a 1-second acquisition full set of radiation patterns can be
generated as frequently as needed (no orbit constraint) Elevation patterns can be simulated with an error of 0.2dB due to
limited quality of ground characterisation data Embedded row patterns measured with only 14 tiles and insufficient
control of T/R modules Azimuth patterns and pointing can be simulated better than
0.02dB and 0.01
Page 22ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Antenna Elevation Pattern Maintenance
Antenna IMBFTest Results
ReferenceModuleStepping
Antenna IMBFTest Results
Rainforest Patterns
Rainforest Patterns
Rainforest Patterns
ModuleStepping
ModuleStepping
ModuleStepping
ModuleStepping
Offset/K0Correction
TRM DriftsTRM Drifts
TRM Failures
MS Analysis
Offset/K0
TRM DriftsTRM Failures
Offset/K0
MS Analysis
Rain Forest
TRM DriftsTRM Failures
Offset/K0
New Coefficients
Rain Forest
(TSS Failures)
Rain Forest
Far sidelobes
MS Analysis
Far sidelobes
Page 23ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Antenna Azimuth Pattern Maintenance
Antenna IMBFTest Results
ReferenceModuleStepping
Antenna IMBFTest Results
Synthesised Patterns
Synthesised Patterns
Synthesised Patterns
ModuleStepping
ModuleStepping
ModuleStepping
ModuleStepping
Offset/K0Correction
TRM DriftsTRM Drifts
TRM Failures
TRM DriftsTRM Failures
Offset/K0
Transponder
TRM DriftsTRM Failures
Transponder
(TSS Failures)
MS Analysis
Offset/K0
MS Analysis
Offset/K0
MS Analysis
New Coefficients