Waveform Analysis of Envisat RA-2 data

1
Waveform Analysis of Envisat RA-2 data

• We have pre-processed 9 days of data from
  Envisat and piped them through the expert system.
• Summary
• Data over land are in ocean mode only. This
  limits the scope of our analysis and degrades
  data quality
• S band and Ku band waveform shapes are generally
  as expected and appear valid. S band waveforms
  show more difference from Ku than C band, as
  expected, but topographic component is largely
  still dominant
• Global statistics have been calculated for each
  15 degree square, relative performances are shown
  on next page (left side) as percentages of valid
  waveforms. Comparison 55-100 ranges forced on
  each dataset are shown on right side for
  intercomparison. Cycle 62 of ERS-2 has been used
  for comparison.

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Envisat and ERS-2 statistics
Envisat valid waveforms (freescale)
Envisat valid waveforms forced 55-100
ERS-2 Cycle 62 valid waveforms (freescale)
ERS-2 valid waveforms forced 55-100
3
Conclusions

• Global statistics show an anomalously poor
  performance of Envisat RA-2 over the Amazon and
  Congo river basins. (More detail has been
  presented in the report). Most rejected waveforms
  are due to no leading edge being present in the
  data.
• Generally over land in ocean mode, RA-2
  performance appears similar to Topex Ku band.
  Significant loss of data is evident. Mode
  switching must occur over land if potential of
  Envisat RA-2 is to be realised.
• Performance over rivers is anomalously and
  seriously degraded compared to ERS-1/2 ice and
  ocean modes, Topex Ku and Topex C band data.
  This is a serious problem. More data are required
  to make a comprehensive analysis and assess
  other river networks.
• We require at least one full cycle of data with
  returns in all three modes to assess performance
  as required by our Cal/Val terms of reference.