IM and WS Mode Level 1 Product quality update

1
IM and WS Mode Level 1 Product quality update

• Introduction
• IM Mode Optimisation
• Updated IMS product quality (VV HH)
• Updated IMP product quality (VV HH)
• Updated IMM product quality (VV HH)
• Updated WSM product quality (VV HH)
• Conclusions

B. Rosich ESA/ESRIN
2
Introduction

• IM Mode products characterised and preliminary
  calibrated at the ECR (September) for VV
  polarisation.
• IM Mode optimisation peformed in October
  requires a revision of the product quality.
  Characterisation of HH polarisation also needed.
• Very prelimianry verification of WSM products at
  the ECR for VV polsarisation. An additional
  change in the mode requires revision of product
  quality. Characterisation of HH polarisation also
  needed.

3
IM Mode Optimisation

• IM mode optimisation at instrument level
• - Increase the Tx. Chirp BW to 16 MHz for all
  swaths (17-10-02)
• IM mode optimisation at processing level
• - Depends on product type

4
ASAR IMS Product charateristics

• Slant range, single look complex image.
• Single polarisation VV or HH. Multiple
  incidence angles (IS1 to IS7). Coverage from 100
  Km to 56 km
• Natural pixel spacing in range and azimuth.
  Azimuth resolution from 4 m to 5 m. Range
  resolution from 9 m to 18 m due to decreasing
  chirp bandwidth.
• Elevation antenna pattern correction not
  applied. Range spreading loss correction not
  applied.
• Hamming window with a0.75 applied in azimuth
  and range
• Processing algorithm Range Doppler. Phase
  preserving.

5
Change of processing settings products
characteristics for IMS products

• Range Processing Full BW processed for all
  beams. Constant slant range resolution from IS1
  to IS7.

• Change in quality requirements for IMS products.

6
IMS Absolute Calibration update

• Azimuth processing No changes.
• Gain settings No changes. Complete Tx. BW used
  before/after the BW change. No changes in the
  processor gain. Same K as for data acquired
  before the BW change.

7
IMS Product quality vs. time vs. PF-ASAR
version
8
IMS HH Ambiguities
Visible az. Ambigities for HH products -
Distributed target ambig. ratio -25.5 dB
(IS5), -24 (IS4) Point target ambiguity ratio
-26 dB
Ambiguity ratio requirement is 25 dB. Migth be
too high for HH products over low backscattering
areas.
9
Properties of IMP Products

• Ground range detected imagery
• Single polarisation (VV or HH)
• Elevation antenna pattern and range spreading
  loss corrections applied
• Size of up to 150Mbytes with 2 byte (16bit)
  amplitude pixel values
• Swath widths of 100 km (IS1) to 56 km (IS7) with
  azimuth extents of 100 km
• Azimuth resolution of 20.7m (4 looks of 320 Hz)
• Range resolution from 21m (IS2 far range) to 37m
  (IS1 near range) and 26m for IS3 to IS7
• 12.5m by 12.5m pixels

10
Change of processing settings product
characteristics for IMP products
Azimuth processing - No changes. Same number of
looks (4) and same look BW.

• Range Processing
• Range look BW same as before, i.e. same range
  resolution
• Number of range looks same as before (1).
  Increase in noise level expected for the higher
  inc. ang. beams.

• Gain settings
• Gain adjusted to compensate the fact that the
  full Tx. BW is only partially processed.
• Same K as for data acquired before the BW change.

11
IMP Range resolution
Measurements demonstrate that there is no change
in range resolution and values are well within
the requirements for VV HH
12
IMP Absolute Calibration
Measurements demonstrate that the same absolute
calibration factor applies for data acquired
before and after the BW change.
13
IMP Azimuth resolution, ISLR, PSLR

• Values are within the requirements
• High PSLR observed however in few cases

14
IMP Product quality vs. time vs. PF-ASAR
version
15
IMP HH Az. Ambiguities

• Clear Az. Ambiguities on HH products, over low
  backscattering areas.
• Amb.ratio
• -25.8 (IS5)
• -21.1 (IS4)

Processing only 2 looks in az. Amb.ratio
-28 dB (IS5)
16
IMM Product Characteristics

• Ground range projected detected products
• Nominal resolution lt 150 m . Pixel spacing 75 m
• 8 looks in azimuth, 4 looks in range. ENL gt 30
• Antenna pattern and range spreading loss
  correction applied
• Data output as unsigned 16 bit
• Systematic stripline processing products as long
  as the complete acquisition segment
• Innovative ground range projection to keep
  constant incidence angle at the center of the
  product (common to all stripline products)

17
Change of processing settings products
characteristics for IMM products
Azimuth processing - No changes. Same number of
looks (8) and same look BW.

• Range Processing
• Range look BW same as before, i.e. same range
  resolution
• Number of range looks 10 (5 before). ENL
  increase expected.
• Look overlap different for different beams.
  Different ENL expected.

18
IMM ENL

• Measurements not available yet for all swaths.
• No changes expected for IS1 and IS2.
• For the beams with very small look overlap,
  values up to 80 looks are achieved
• Initial requirement for IMM ENL was 30 looks.
• Only negative impact is throughput

Change in quality requirements needed.
19
IMM Spatial Resolution

• Range Azimuth Resolution match expected
  theoretical values for all beams
• Theoretical values ranging from 107 m (far range
  IS1) to 160 m (near range IS1)

20
IMM Absolute calibration
No changes in processing gain. Changes in product
level expected between data acquired before/after
the BW change.
Change of K between products with original Tx.
Chirp BW and products with new full TX. Chirp BW.
21
IMM Product quality vs. time vs. PF-ASAR
version
22
IMM HH Az. Ambiguities

• Visible Az. Ambiguities for HH products
• Distributed target ambig. ratio -20 dB

• IMM reprocessing using 4 rather than 8 looks in
  azimuth
• Amb. Ratio - 24.5 dB

23
WSM Product characteristics

• Ground range projected detected products
• Nominal resolution lt 150 m
• Swath width 406 Km
• Pixel spacing 75 m
• ENL gt 12 for all the different subswaths
• Antenna pattern and range spreading loss
  correction applied
• Data output as unsigned 16 bit
• Systematic stripline processing products as long
  as the complete acquisition segment

24
WSM Initial product quality

• Initial instrument settings (till 13-08-02)
• Tx.Chirp BW    
• Mode timeline (pulses per burst)
• SS1-SS5 50, 80, 67, 87, 74
• Initial processing/product settings (version lt
  3.01)
• Rg. Look BW
• Number of range looks 3

• Result
• - Range resolution 150 m and Azimimuth
  resolution 90 m
• - ENL below the requirements (12) -gt from 8 for
  SS1 to 6 for SS5

25
First WSM optimisation (I)

• First mode optimisation at instrument level
  (13-08-02)
• IncreaseTx.Chirp BW

26
First WSM optimisation (II)

• Result
• Range resolution 120 m
• Azimimuth resolution 90 m -gt High
  undersampling not-square resolution
• ENL higher than initial spec (12)

• Inter-burst ambiguities (-21 dB) detected in
  high contrast scenes (already present before the
  BW change)

27
Second WSM optimisation

• Second WS mode optimisation at instrument level
  (30-10-02)
• Change of mode timeline (expect SS1)
• SS1-SS5 50, 65, 55, 71, 60
• New processing settings
• None. Only AUX data updated

• Result
• Removal of inter-burst ambiguities
• Increase of Az. Res.

WSM 2703
28
WSM Final products resolution

• Nominal products are still undersampled 1.2 in
  range, 1.4 in azimuth.
• Resolution is almost square. Could be adjusted
  to be more similar in both directions.
• IRF measurements performed on oversampled
  products of 40x40 m.

29
WSM Absolute calibration update
K (VV) from rain forest 69.08 dB
30
WSM Noise Equivalent s0

• Noise level for SS1 expected to be higher than
  for the other swaths.
• Measured values for final settings
• SS1 -22 dB
• SS2-SS5 -24,-25 dB
• The difference in noise level between SS1 and SS2
  is clearly visible in the images.

SS1
SS2
31
Conclusions

• IM mode BW increase has resulted in an improved
  IMS and IMM product quality and will increase the
  IM InSAR performance. Products quality shall be
  now stable.
• The BW increase shall be almost transparent for
  IMP products. Quality could be improved with
  multi-look in range.
• WSM optimizations provide very good product
  quality. Products should be now stable.
• Quality results for HH polarisation are
  equivalent to those for VV polarisation.