High spatial resolution radar altimeter for ocean and ice-sheet monitoring

The monitoring of the ice-sheet height over Antarctica and Greenland is of primary importance for climate studies. The required height accuracy is of the order of a few centimetres. Current spaceborne altimeters are pulse-limited and therefore fail to deliver high accuracy surface height measurements over land and ice because of pulse spreading and slope induced errors. Moreover, sudden changes in the topography often result in a loss of track. Several techniques have been investigated during the past ten years in order to improve the spatial resolution of radar altimeters and therefore the accuracy of elevation estimates over terrains. Most of these techniques result in a significant increase in cost and complexity compared to a conventional altimeter. This paper presents the results of a recent feasibility study for a spaceborne high-spatial resolution radar altimeter (HSRRA) performed by Alcatel and the University College of London for the European Spatial Agency (ESA). This paper gives an overview of the concept and of the processing scheme. The theoretical altimeter waveforms derived for a flat tilted surface are also presented and discussed.