HSRRA: an advanced radar altimeter for Ocean and Cryosphere monitoring.
The monitoring of the cryosphere, i.e. mainly ice sheet and sea ice, is of primary importance for climate studies [1]. The required height accuracy is of the order of a few centimetres. Although laser altimeters provide high vertical and horizontal resolutions, the significant advantage of a radar a...
| Main Authors: | , |
|---|---|
| Other Authors: | , |
| Format: | Report |
| Language: | unknown |
| Published: |
EUROPEAN SPACE AGENCY
2000
|
| Subjects: | |
| Online Access: | http://discovery.ucl.ac.uk/75790/ |
| Summary: | The monitoring of the cryosphere, i.e. mainly ice sheet and sea ice, is of primary importance for climate studies [1]. The required height accuracy is of the order of a few centimetres. Although laser altimeters provide high vertical and horizontal resolutions, the significant advantage of a radar altimeter is its all weather capability, i.e. its relative insensitivity to clouds which are often encountered in polar regions and particularly close to the ice sheet margins.Current spaceborne radar altimeters are pulse-limited and therefore fail to deliver high accuracy surface height measurements over ice-sheet margins because of pulse spreading and slope induced errors [2]. Moreover, sudden changes in the topography often result in a loss of track. Higher resolution is also desirable in order to distinguish the sea-ice from the ocean surface.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 (UCL) for the European Space Agency (ESA). The concept is based on a Ku-band (13.6 GHz) nadir-looking radar which can be operated in the conventional mode over oceans. Over terrain lice or land) the "advanced" mode uses Doppler filtering for the enhancement of the along-track resolution. A second antenna mounted on the same satellite provides a second take of the scene which is used for surface height retrieval as it is usually done with SAR interferometry.An overview of the instrument concept including the processing is given in this paper. The instrument design is briefly described. Some simulation results of the performances over realistic surfaces are also presented and discussed.This altimeter concept (Doppler filtering and interferometry) has been proposed in the Cryosat mission in response to the Call for ESA Opportunity Missions. This mission has been recently approved for implementation. |
|---|