antenna elevation pattern estimation from rain forest data
DESCRIPTION
Antenna Elevation Pattern Estimation from Rain Forest Data. M. Zink ENVISAT Programme ESA-ESTEC. Content. Estimation Approach Fine-Tuning of VV patterns at ScanSAR sub-swath boundaries HH Beam Patterns VH Beam Patterns HV Beam Patterns Comparison with pre-launch patterns. - PowerPoint PPT PresentationTRANSCRIPT
Page 1ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Antenna Elevation Pattern Estimation
from Rain Forest Data
M. ZinkENVISAT Programme
ESA-ESTEC
Page 2ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Content
Estimation Approach Fine-Tuning of VV patterns at ScanSAR sub-
swath boundaries HH Beam Patterns VH Beam Patterns HV Beam Patterns Comparison with pre-launch patterns
Page 3ENVISAT Cal/Val Workshop – ESRIN – 9/13 December
2002
Estimation Approach Based on IMP, WSM, (APM)
products
Range power profile calculated applying simple threshold masking
Imaging geometry reconstructed from annotation parameters
Re-apply AP corrected in the processor
tan(inc) correction
Combined estimate from all available IM+WS products
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2002
WS/VV Range Power Profiles at ECR
1474
1610
1975
2111
Approx. 0.5 deg around the beam merging region not used in estimation
Over-compensation at beam edges, especially SS1
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2002
new old
Refined VV Patterns (SS1, IS3-IS6)
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2002
WS Profiles after Pattern Refinement
1474
1610
1975
2111
Consistent slopes where the beams overlap
Absolute levels agree with cal factor from transponders and expected RF o
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2002
Sample Images HH
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2002
Elevation Beam Patterns - HH
Standard deviation of estimates <0.1dB
Even one homogeneous data set provides useful estimate
Maximum deviation from pre-launch patterns 0.5dB
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2002
Range Power Profiles – IM/HH
VV
HH
Gain correction via internal cal to be confirmed
IS1 profiles higher as for VV pol
Assumption on flat gamma profile at low incidence angles not valid?
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2002
Range Power Profiles – WS/HH
Consistent slopes where the beams overlap
Processing gains as for VV pol – different levels in SS4/SS5
Absolute levels too high by 3dB because of problems in reading XCH file
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2002
Sample Images AP/VH
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Elevation Beam Patterns - VH
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2002
Range Power Profiles – AP VV/VH
Reasonable flat co-pol profiles using patterns derived from IM/WS
Problems with cal pulses in some beams
Mixture of PDS data and products from instable standalone version
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2002
Sample Images AP/HV
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2002
Elevation Beam Patterns - HV
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2002
Range Power Profiles – AP HH/HV
Consistent processing based on reference energy levels for normalisation
No data for IS3&IS6
Cross-pol ~6dB below co-pol
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2002
Range Power Profiles – AP
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2002
Difference Pre-Launch – RF Patterns / VV
Residual receiver gain droop would cause consistent near-to-far range trend
No trend visible
Confirmation of gain droop compensation
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2002
Difference Pre-Launch – RF Patterns
IS1
IS4
IS7 Accuracy of pre-launch measurement does not
match highly accurate RF estimates
Limited control/knowledge of module gain/phase settings during pre-launch characterisation
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2002
Conclusions Elevation patterns for all beams – except
HV IS3&IS6 ScanSAR beams fine-tuned at beam
boundaries Absolute levels to be confirmed (internal cal
corrections not fully reliable) Cross-pol 6dB lower than co-pol No residual gain droop effects Difference to pre-launch patterns due to
limitations in the on-ground characterisation
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2002
ASAR External Characterisation
M. Zink & H. JacksonENVISAT Programme
ESA-ESTEC
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2002
Tx Main
Rx Main
RadiatingRow
Signal BFN
Cal BFN
Tx Aux
Rx Aux Cal
P1
Ground Receiver
External Characterization Mode Cal Pulse P1 (cw) recorded onboard and by coherent ground
receiver
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2002
Signal received by transponder
Phase from single column transmission is used to correct row stepping sequence
External Characterization Results (1)
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2002
Phase and amplitude difference between onboard recording and receiver measurements
Linear phase term due to off-boresight position of transponder
Residual linear phase due roll mispointing (offset between mechanical and electrical boresight)
Measured values [deg]: V: 0.070, 0.057, 0.066H: 0.015, 0.011
External Characterization Results (2)
Good agreement with boresight from synthesized IS0 beam
VV
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2002
Consistent results for H pol from two measurements
External Characterization Results (3)
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Comparison ExChar Factors in V and H higher amplitude variations across the 32 rows in H
than VPhase shows similar spread
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Verification of ASAR ISP DatationBoresight TransponderDate 2002/10/24 2002/11/28Orbit 3404 3905Tpr 4 4Tpr Inc 60.83 60.83
Prog. boresight time (Hrs,Mins) 21:19 21:19Prog. boresight time (S) 30.000000 26.000000 aSoftware trigger offset -3.000000 -3.000000 bTrigger delay 0.001002 0.001002 cTrig to stt, 22nd RS seq (S) 3.182797 3.765409 dAbs Rx time, stt 22nd RS seq (S) 30.183799 26.766411 e=a+b+c+d
Prop delay (Berthyl's SW) 0.002976 0.002975 fAbs Tx time, stt 22nd RS Seq (S) 30.180823 26.763436 g=e-f
onboard time 1st SP 30.180450 26.763055
Time, stp 1st col to stt 22nd seq -0.000373 -0.000381
Requirement: 200 s
RA-2 datation accuracy very similar: between
-300 and –400 s
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2002
Conclusions Consistent measurements in both polarisations
Roll misalignment confirmed by pattern synthesis based on actual Module Stepping mode measurements
EC factors close to 1.0 and therefore small impact on elevation gain reconstruction
EC factors are different for H and V – different HW
ASAR datation error currently around 380s
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2002
External Characterization Mode (2)• Single column transmission followed by row stepping
sequence and single column transmission