The Envisat Burst Mode Echoes– a new look from satellite radar altimetry
Philippa A. Berry(1) , James D. Garlick(1) , Catherine Rogers(2) , and Jerome Benveniste(3)
De Montfort University,
Leicester LE1 9BH,
(2) SciSys, Methuen Park, Wiltshire SN14 0GB, United Kingdom
(3) ESA ESRIN, via Galileo Galilei, Frascati, Italy
Over the past two decades, the series of radar altimeter missions flown has gathered a huge amount of useful data over the earth’s land surfaces.
Enhancements to the instruments for acquisition of non-ocean data have greatly increased the capability of altimeters to make useful measurements over rough terrain, and advances in retracking the complex echoes returned from land surfaces has allowed height measurements to be made even over mountainous topography. However, the onboard averaging applied to the individual echoes prior to telemetering these data to ground has severely restricted the measurement of high frequency changes in the underlying surface, even when only a part of the returned signal is retracked to improve the spatial resolution.
The ability of the Envisat RA-2 to store and transmit the individual echoes has given a first glimpse into the full potential of satellite radar altimetry over land. This paper presents results from retracking these unique echoes. The unexpectedly low noise in these data allows the echoes to be utilised with minimal averaging, whilst the ability of the RA-2 to maintain lock even over mountainous terrain by dynamically adapting the range window is generating a huge database of burst echoes over all terrain types. This allows, for the first time, a full investigation into the information which is gathered by a radar altimeter over land, and illustrates the huge potential of these instruments to measure and monitor land surface processes.