Abstract's details
Combining Fully Focused and Swath Processing for Glacier applications
CoAuthors
Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)
Session: Instrument Processing: Measurement and Retracking
Presentation type: Type Forum only
Contribution: PDF file
Abstract:
High PRF altimeters transmit pulses at a high pulse repetition frequency thus making the received echoes suitable for coherent processing on-ground.
Conventional delay-Doppler processing (DDP, commonly called SAR or High Resolution) coherently integrates echoes in a burst-by-burst basis to provide single look waveforms referred to a specific ground location, which after being correctly aligned (compensating for the slant-range migration, among others) can be incoherently averaged, increasing the performance in terms of the speckle reduction and the along-track resolution compared with the traditional Low Resolution Mode and in turns in terms of geophysical retrieval.
The Fully Focused delay-Doppler processing (FF-DDP, also known as Fully Focused SAR) moves one step ahead and intends to coherently integrate the echoes over a time longer than a burst to get an even higher along-track resolution with an improved speckle reduction with respect to (unfocused) DDP.
The Open Burst (or interleaved) transmission mode to be implemented in Sentinel 6 and the Copernicus polaR Ice and Snow Topography Altimeter (CRISTAL) missions makes more suitable the exploitation of the FF-SAR thanks to the uniform along-track sampling of the scene. However, in the conventional Closed Burst mode (like in CryoSat-2), replicas induced by the non-uniform sampling of the Doppler spectrum will be mixed with the main echo and, in most cases, won't be able to be filtered out.
Swath mode processing has been used to monitor elevation of areas with complex topography such as over ice sheet margins, ice caps and mountain glaciers, improving upon the resolution of conventional radar altimetry. Swath mode relies on an accurate angle of arrival of the measured echo, this is obtained from the SAR Interferometric mode of CryoSat-2 and CRISTAL and post-processing strategies resolving the ambiguous nature of the phase measurement.
The CRISTAL Mission will include Open Burst and Interferometric capabilities. It will be the first altimeter to be able to combine both methodologies to increase both the along and across-track resolutions improving the current performances of CryoSat-2 over small glaciers that can't be observed properly.
In this poster, we present the benefits that the combination of these methods will bring into the glacier monitoring by comparing results obtained after processing CRISTAL simulated data with the classical DDP retrievals, DDP+Swath retrievals and FF+Swath.
Conventional delay-Doppler processing (DDP, commonly called SAR or High Resolution) coherently integrates echoes in a burst-by-burst basis to provide single look waveforms referred to a specific ground location, which after being correctly aligned (compensating for the slant-range migration, among others) can be incoherently averaged, increasing the performance in terms of the speckle reduction and the along-track resolution compared with the traditional Low Resolution Mode and in turns in terms of geophysical retrieval.
The Fully Focused delay-Doppler processing (FF-DDP, also known as Fully Focused SAR) moves one step ahead and intends to coherently integrate the echoes over a time longer than a burst to get an even higher along-track resolution with an improved speckle reduction with respect to (unfocused) DDP.
The Open Burst (or interleaved) transmission mode to be implemented in Sentinel 6 and the Copernicus polaR Ice and Snow Topography Altimeter (CRISTAL) missions makes more suitable the exploitation of the FF-SAR thanks to the uniform along-track sampling of the scene. However, in the conventional Closed Burst mode (like in CryoSat-2), replicas induced by the non-uniform sampling of the Doppler spectrum will be mixed with the main echo and, in most cases, won't be able to be filtered out.
Swath mode processing has been used to monitor elevation of areas with complex topography such as over ice sheet margins, ice caps and mountain glaciers, improving upon the resolution of conventional radar altimetry. Swath mode relies on an accurate angle of arrival of the measured echo, this is obtained from the SAR Interferometric mode of CryoSat-2 and CRISTAL and post-processing strategies resolving the ambiguous nature of the phase measurement.
The CRISTAL Mission will include Open Burst and Interferometric capabilities. It will be the first altimeter to be able to combine both methodologies to increase both the along and across-track resolutions improving the current performances of CryoSat-2 over small glaciers that can't be observed properly.
In this poster, we present the benefits that the combination of these methods will bring into the glacier monitoring by comparing results obtained after processing CRISTAL simulated data with the classical DDP retrievals, DDP+Swath retrievals and FF+Swath.
