Exploitation of the ENVISAT radar altimeter individual echoes and S-band data for ocean, coastal zone, land and ice/sea ice altimetry (RAIES).
Radar altimeter individual echoes and s-band (R.A.I.E.S), is a project for ESA ESRIN led by the National Oceanography Centre, Southampton, in collaboration with the EAPRS lab and SciSys (Space & Defence) Ltd.
The Envisat RA-2 altimeter has a unique capability that allows the transmission of small segments of data without averaging to be returned to the ground; this is in contrast to previous altimeters that have averaged a significant number of individual echoes.
The aims of this project are to examine and exploit the additional information content available in the Envisat burst echo mode data. These burst echoes have allowed a far finer investigation of the complex and intricate nature of the response of the Earth's land surface to Ku-band altimetry than has been possible with other data.
This work has led to a clear requirement for future altimeter to have a far higher sampling rate alongtrack globally.
This image shows a sequence of EnviSat RA-2 echoes over the Congo basin. Echoes are plotted vertically and stacked horizontally to show the rapidly changing surface response. As usual over inland water, complex combinations of quasi-specular and diffuse components are evident. To illustrate the enhancement offered by the burst echoes, the short section delineated by blue vertical lines shows one second of echoes for which a burst is available.
This shows the corresponding one second of 18Hz data. Several components are evident.
This figure shows the actual burst sequence. Here, far greater detail is seen of the changing surface response. Over surfaces such as inland water and sea-ice, where multiple bright targets may contribute to the echo, the enhanced along track resolution of 1800Hz data permits far more detail to be gathered from the underlying surface.
