There is a single re-tracker dedicated to LRM mode ice waveforms. This re-tracker method is a heritage of the ice-2 re-tracker (also called ice_erf re-tracker) implemented in both ENVISAT and CryoSat-2 missions. It is a physical-based retracker.
This retracker is based in the Brown model, described by a triple convolution term (flat surface impulse response+height probability density function+radar point target response/PTR), and intended for ice caps studies. The basic idea behind the ice-2 retracker is to detect the waveform edge and then fitting an error function to the leading edge and an exponential decrease to the trailing edge.
The aim of the ice-2 retracker algorithm is to fit the measured waveform with a return power model, according to a Least Square Error (LSE) minimization.
The main outputs of this ice LRM retracker annotated in the Level-2 product are:
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corrected "ice" altimeter range
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corrected "ice" backscatter coefficient
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corrected "ice" leading edge backscatter coefficient (arithmetic average of the waveform samples in a window limited by the beginning of the leading edge and the end of the window used for the slope estimation)
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width of the leading edge
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slope of the first part of the trailing edge (potentially used to identify volume scattering in the signal for ice scenarios and misspointing angles over ocean surfaces)
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slope of the second part of the trailing edge
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PARAMETER
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Corrected Ice Backscatter Coefficient
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NETCDF NAME
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sig0_ice_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
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DESCRIPTION
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LRM mode: ice re-tracking.
The instrumental corrections already included are: AGC instrumental errors correction (agc_cor_[x1]_[x2]), internal calibration correction (sig0_cal_[x1]_[x2]). The ALT_PHY_BAC_01 algorithm computes the backscatter coefficient.
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UNITS
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10-2 dB
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DATA SET AVAILABILITY
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Reduced: None
Standard: 20 Hz Ku/C bands
Enhanced: 20 Hz Ku/C bands
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OPERATING MODE AVAILABILITY
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LRM
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DATA ORIGIN
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1 Hz Ku/C-bands: None
20 Hz Ku-band: ALT_PHY_BAC_01 algorithm
20 Hz C-band: ALT_PHY_BAC_01 algorithm
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ADDITIONAL INFORMATION
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None |
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PARAMETERS RELATED
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Corrected ice leading edge backscatter coefficient: sig0_leading_edge_ice_[x1]_[x2]
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PARAMETER DETAILED DESCRIPTION
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ESA's Global Land and Ocean Mission for GMES Operational Services
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Table 1. Ice backscatter coefficient
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PARAMETER
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Ice Width of the Leading Edge
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NETCDF NAME
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width_leading_edge_ice_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
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DESCRIPTION
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LRM mode : ice re-tracking using the ALT_RET_ICE_02 algorithm. The ALT_RET_ICE_02 algorithm is based on the ENVISAT RA-2 ice-2 re-tracker. The aim of the ice-2 re-tracker algorithm is to make the measured waveform coincide with a return power model, according to least square estimators.
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UNITS
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10-3 m
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DATA SET AVAILABILITY
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Reduced: none
Standard: 20 Hz Ku/C bands
Enhanced: 20 Hz Ku/C bands
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OPERATING MODE AVAILABILITY
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LRM
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DATA ORIGIN
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1 Hz Ku/C-bands: none
20 Hz Ku-band: ALT_RET_ICE_02 algorithm
20 Hz C-band: ALT_RET_ICE_02 algorithm
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ADDITIONAL INFORMATION
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None |
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PARAMETERS RELATED
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None
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PARAMETER DETAILED DESCRIPTION
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ESA's Global Land and Ocean Mission for GMES Operational Services
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Table 2. Width of the leading edge
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PARAMETER
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Ice Slope of the First and Second Part of the Trailing Edge
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NETCDF NAME
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slope_first_trailing_edge_ice_[x1]_[x2] slope_second_trailing_edge_ice_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
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DESCRIPTION
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LRM mode : Ice re-tracking using ALT_RET_ICE_02 algorithm.
The ALT_RET_ICE_02 algorithm is based on the ENVISAT RA-2 ice-2 re-tracker. The aim of the ice-2 re-tracker algorithm is to make the measured waveform coincide with a return power model, according to Least Square estimators.
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UNITS
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s-1
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DATA SET AVAILABILITY
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Reduced: None
Standard: 20 Hz Ku/C bands
Enhanced: 20 Hz Ku/C bands
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OPERATING MODE AVAILABILITY
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LRM
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DATA ORIGIN
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1 Hz Ku/C-bands: None
20 Hz Ku-band: ALT_RET_ICE_02 algorithm
20 Hz C-band: ALT_RET_ICE_02 algorithm
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ADDITIONAL INFORMATION
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None |
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PARAMETERS RELATED
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None
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PARAMETER DETAILED DESCRIPTION
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ESA's Global Land and Ocean Mission for GMES Operational Services
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Table 3. Slope of the leading edge
Ice re-tracking
