Page 1ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 ASAR On-board Instrument Instrument Stability and Status Instrument Adjustments Tracking

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


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


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


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


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


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)


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


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


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


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


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


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


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)


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


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


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


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


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


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


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


Azimuth (degrees)

Directivity (dB

)


-5 -4 -3 -2 -1 0 1 2-40

-35

-30

-25

-20

-15

-10

-5


Azimuth (degrees)

Directivity (dB

)


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


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


2002

Antenna Elevation Pattern Maintenance

Antenna IMBFTest Results

ReferenceModuleStepping


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


Offset/K0

New Coefficients

Rain Forest

(TSS Failures)

Rain Forest

Far sidelobes

MS Analysis

Far sidelobes


2002

Antenna Azimuth Pattern Maintenance


ReferenceModuleStepping


Synthesised Patterns



ModuleStepping

ModuleStepping

ModuleStepping

ModuleStepping

Offset/K0Correction

TRM DriftsTRM Drifts

TRM Failures


Offset/K0

Transponder


Transponder

(TSS Failures)

MS Analysis

Offset/K0

MS Analysis

Offset/K0

MS Analysis

New Coefficients

Documents

Page 1ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 ASAR On-board Instrument Instrument Stability and Status Instrument Adjustments Tracking