Implementation of TOPS mode on RADARSAT-2 in Support of the - - PowerPoint PPT Presentation

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Implementation of TOPS mode on RADARSAT-2 in Support of the - - PowerPoint PPT Presentation

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Program Monthly Review RADARSAT-2 TOPS Implementation of TOPS mode on RADARSAT-2 in Support of the Sentinel-1 mission G. Davidson, V. Mantle, B. Rabus, D. Williams MDA D. Geudtner ESA 1 MDA Proprietary RADARSAT-2 TOPS Background

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SLIDE 1

Program Monthly Review

MDA Proprietary

RADARSAT-2 TOPS

1

Implementation of TOPS mode on RADARSAT-2 in Support of the Sentinel-1 mission

  • G. Davidson, V. Mantle, B. Rabus, D. Williams

MDA

  • D. Geudtner

ESA

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SLIDE 2

RADARSAT-2 TOPS

MDA Proprietary

Background

  • Sentinel-1 Interferometric Wide Swath (IW) is main mode of
  • perations, using TOPS technique
  • Experimental RADARSAT-2 TOPS mode resembles as closely

as possible the performance of the Sentinel-1 IW mode

  • Processing of RADARSAT-2 TOPS data in the Sentinel-1 L1

(SLC) data product format

  • Provide Sentinel-1 like RADARSAT-2 TOPS SLC data to

Copernicus services and users prior to the Sentinel-1 launch

  • RADARSAT-2 operates at same C-band frequency
  • Phased array antenna supports multiple modes
  • Provide data as similar as possible to Sentinel-1
  • MDA develops the Sentinel-1 Instrument

Processing Facility (IPF) under ESA contract

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SLIDE 3

RADARSAT-2 TOPS

MDA Proprietary

TOPS Review

azimuth range

sub-swath 1 sub-swath 2 sub-swath 3 burst focused burst

Scan rate kq Targets swept by entire beam

  • illuminated by entire azimuth antenna pattern – no scalloping
  • illumination time reduced, and resolution reduced by a factor 𝛽 = 1 + π‘™πœ„π‘†

𝑀𝑕

  • Doppler sweep rate 𝑙𝑑 = 2𝑀𝑑

πœ‡ π‘™πœ„

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SLIDE 4

RADARSAT-2 TOPS

MDA Proprietary

RADARSAT-2 TOPS Beam Design

  • Based on existing RADARSAT-2 β€˜ScanSAR Narrow B’ mode
  • Mode comparison:
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SLIDE 5

RADARSAT-2 TOPS

MDA Proprietary

TOPS Implementation

  • TOPS: forward electronic scanning of antenna in azimuth
  • RADARSAT-2: antenna steering in coarse steps

– Beam switching time

  • In-orbit experiment found minimum

time to be about 15 ms

– Number of Timing Control patterns

  • Limits total number of azimuth steps

across all sub-swaths

  • Max azimuth pointing angle (burst
  • verlap) vs. step size
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SLIDE 6

RADARSAT-2 TOPS

MDA Proprietary

TOPS Implementation

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SLIDE 7

RADARSAT-2 TOPS

MDA Proprietary

Expected effect of coarse step size

  • Modulation of raw signal amplitude from point target

– Increased sidelobes in point target response (approx 0.7 dB degradation) – Slight variation in radiometry (approx 0.05 dB) Simulation results

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SLIDE 8

RADARSAT-2 TOPS

MDA Proprietary

Analysis of Expected RTOPS Coherence

  • Analyze spectral shifts due to

burst mis-synchronization and difference in antenna pointing

  • Statistical analysis of

RADARSAT-2 InSAR stacks

  • Probability distribution of

coherence due to burst synchronization, Doppler centroid difference, and baseline

Δ𝑔

π‘ˆ = π‘™π‘π‘ˆπ‘’π‘“π‘š

𝛽 βˆ’ 1 𝛽 Δ𝑔

𝑔 = Δ𝑔 𝑒𝑑

𝛽

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SLIDE 9

RADARSAT-2 TOPS

MDA Proprietary

Analysis of RADARSAT-2 InSAR stacks

  • Statistical characterization of baseline, burst mis-

synchronozation and Doppler centroid difference

50 Percentile (pairwise absolute difference) 90 Percentile (pairwise absolute difference) Burst Synchronization 16 milli-seconds 41 milli-seconds Doppler Centroid Variation 36 Hz 92 Hz Perpendicular Baseline 160 meters 435 meters

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SLIDE 10

RADARSAT-2 TOPS

MDA Proprietary

Analysis of RADARSAT-2 InSAR stacks

PDFs for the pairwise differences:

  • Baseline
  • Doppler centroid
  • Start time synchronisation

Create 3-D PDF for coherence: 𝛿(𝑐βŠ₯, π‘ˆ

π‘’π‘“π‘š, Δ𝑔 𝑒𝑑)

Integrate 3-D PDF to get probability of coherence exceeding a certain value 50% chance of exceeding 0.84 90% chance of exceeding 0.66

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SLIDE 11

RADARSAT-2 TOPS

MDA Proprietary

Processing

  • Pre-processing with RADARSAT-2 processor

– Ingest – Range compression – Formatting

  • Doppler centroid estimation
  • Sentinel-1 Instrument Processing Facility (IPF)

– Inputs range compressed data and formatted annotation – upsampling – RCMC and SRC – Azimuth compression – Resampling – Formatting in Sentinel-1 L-1b (SLC) product format

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SLIDE 12

RADARSAT-2 TOPS

MDA Proprietary

Acquisition of various Scene Types

12

  • Sea-ice (Lancaster Sound, Canadian Arctic)
  • CSA Transponder sites, Montreal and Ottawa

(calibration)

  • Ocean Currents (Gulf stream, Agulhas current)
  • Gibraltar (ship detection)
  • Richmond, BC, Canada
  • Amazon, Brasil (calibration)
  • Pacific Doldrums (NESZ estimation
  • Markermeer, Netherlands (NESZ estimation)
  • Uyuni Salt Flats, Bolivia, (InSAR pair)
  • Petermann Glacier (Greenland) (InSAR pair)
  • Lambert Glacier (Antarctica) (InSAR pair)
  • Mt. Etna Volcano (Italy) (InSAR pair)
  • Mexico-City (Mexico) (InSAR stack)
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SLIDE 13

RADARSAT-2 TOPS

MDA Proprietary

Richmond Acquisition

Slant range images

  • verlap
  • verlap
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SLIDE 14

RADARSAT-2 TOPS

MDA Proprietary

Richmond Acquisition

GRD product

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SLIDE 15

RADARSAT-2 TOPS

MDA Proprietary

Image Quality Results

  • Point target analysis – target of
  • pportunity in Richmond scene

– Azimuth response shape agrees with simulation

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SLIDE 16

RADARSAT-2 TOPS

MDA Proprietary

Image Quality Results

  • Point target analysis – CSA Transponders in Montreal scene

– Expected values in range are from Hamming (0.75) window – Expected values in azimuth are from simulation of effect of coarse step

Expected

  • St. Hubert

Ottawa Range Resolution [m] 5.0 5.06 5.09 Range ISLR [dB]

  • 16.1
  • 15.62
  • 15.37

Range PSLR [dB]

  • 21.3
  • 21.19
  • 20.44

Azimuth Resolution [m] 29.4 / 29.2 / 29.0 29.08 29.50 Azimuth ISLR [dB]

  • 15.39
  • 15.37
  • 15.51

Azimuth PSLR [dB]

  • 20.66
  • 21.62
  • 20.67
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SLIDE 17

RADARSAT-2 TOPS

MDA Proprietary

Image Quality Results

  • Radiometry over Amazon

– Apply gain factors so that g0 over Amazon is approx. -6.5 dB – g0 profile for three sub-swaths vs. incidence angle

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SLIDE 18

RADARSAT-2 TOPS

MDA Proprietary

Image Quality Results

  • Azimuth profile over a burst

– Verify removal of residual scalloping using model of antenna element pattern

sub-swath 1 sub-swath 2 sub-swath 3

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SLIDE 19

RADARSAT-2 TOPS

MDA Proprietary

Image Quality Results

  • Noise Equivalent Sigma 0 (NESZ)

– Estimate using HV data over Doldrums – Three sub-swaths vs. incidence angle, compared to expectation

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SLIDE 20

RADARSAT-2 TOPS

MDA Proprietary

Doppler Grid

  • 96 Doppler estimates vs. range
  • ver all 3 sub-swaths

– 32 overlapping range segments per burst

  • 5 estimates in azimuth per burst

– Deramp in azimuth to remove antenna scanning effect – Overlapping azimuth segments for Doppler estimates – Correct for small error in Doppler sweep rate

  • Deviation from mean Doppler

centroid estimate derived from attitude information Gulf Stream Scene

Superimposed on ocean current map (CLS using ASAR 2008)

Agulhas Scene

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SLIDE 21

RADARSAT-2 TOPS

MDA Proprietary

Interferometry

Uyuni : Sub-swath 1, Burst 1

coherence phase phase superimposed on amplitude

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SLIDE 22

RADARSAT-2 TOPS

MDA Proprietary

Conclusion

  • Experimental TOPS mode successfully implemented on

RADARSAT-2

– Effect of coarse step size is not severe

  • Statistical analysis of the timing and antenna pointing of

existing InSAR stacks shows good probability of coherence

  • Image quality results in line with performance expectations
  • Demonstration of Doppler grid over ocean currents
  • Good coherence observed in interferograms