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CAPABILITIES OF ERS-1 RADAR ALTIMETER MISSION FOR SCIENCE AND APPLICATIONS 
by 
Guido PACI 
European Space Agency 
Directorate of Affplicaiton Programmes 
Earth Observation Programme. Department 
Remote Sbnsing Programme Division 
18 avenue Edouard Belin 
31055 TOULOUSE cedex, France 
The altimeter was originally proposed as a tool for a better determination 
of the geoid (1960's). 
With GEOS-3 wave height and surface wind measurements were confirmed and/or 
discovered. 
With SEASAT the quantity of greatest importance to physical oceanography i.e. 
the difference between the local mean sea level and the marine geoid started 
to receive some attention. 
Today the radar altimeter is considered an extremely powerful tool for applic- 
ations and science, and various satellite missions are currently planned which 
consider an altimeter. 
Among these ERS-1 will provide operational data before the end of the decade. 
The paper presents a review of the measurements possible on the pulse 
returned from the ocean, ice or land, the geophysical parameters to which they 
are linked, and the different user products which can be extracted based on 
models, 
The main application objective of the ERS-1 altimeter mission is to use oper- 
ationally the unique capability of the altimeter to provide global monitoring 
of ocean waveheight and surface wind. 
As the latitudinal coverage extends from + 82 to - 82 degrees, additional 
important applications are sea-ice boundary location and continental ice sheet 
topography. 
In terms of scientific applications, ESA is currently studying the operational 
impact of accurately repeat the sub-satellite tracks to the level of 1 km 
or better. This will permit geoid independent techniques to be used for the 
detection and measurements of the oceanographic signal to the 10 cm level. 
Because of the limitations in the knowledge of the satellite orbit these 
techniques will be practically limited to arc lengths of the order of 2000 km. 
The major contribution of ERS-1 to physical oceanography will therefore be the 
determination of the eddy field. This capability could be further enhanced 
by the simultaneous measurement of the water vapour content below the 
satellite. 
The possible contribution of ERS-1 to the determination of the global ocean 
circulation in case that a precise orbit determination experiment is eventually 
selected following the ESA Announcement of Opportunity, is discussed. 
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