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OFF-LINE PROCESSING OF ERS-1 SYNTHETIC APERTURE RADAR DATA 
WITH HIGH PRECISION AND HIGH THROUGHPUT 
J. Gredel, W. Markwitz, W. Noack, G. Schreier 
Deutsche Forschungs- und Versuchsanstalt 
für Luft- und Raumfahrt 
DFVLR 
8031 Oberpfaffenhofen 
Federal Republic of Germany 
1. Introduction 
The first European remote sensing satellite ERS-1 will be launched by the European Space Agency (ESA) in 
1989. The expected lifetime is two to three years. The spacecraft sensors will primarily support ocean inves- 
tigations and to a limited extent also land applications. Prime sensor is the Active Microwave Instrumentation 
(AMI) operating in C-Band either as Synthetic Aperture Radar (SAR) or as Wave-Scatterometer and simul- 
taneously as Wind-Scatterometer. 
In its SAR mode the AMI will cover a 100 km wide swath with a 23? incidence angle at mid swath. The 
satellite orbit will be sun-synchronous, with a nominal altitude of 777 km. The ground repeat pattern will be 
3-days during the initial stages, but will be changed up to twice a year to give variable repeat pattern up to 
30 days. 
ERS-1 will perform 5256 orbital revolutions per year. Assuming an average of 8 minutes SAR acquisition time 
per orbit - corresponding to 32 scenes (100 km x 100 km) - a total of 168,000 scenes per year will be acquired. 
The raw data will be transmitted in real time with 105 Mbps via an X-Band link to a world wide network of 
acquisition stations where all data will be recorded on High Density Digital Tapes (HDDT). A significant 
amount of this data volume will be received with European ground stations. 
In Europe there will be two distinct types of processing for ERS-1 SAR data, Fast Delivery Processing and 
Precision Processing. 
Fast Delivery Processing will be carried out at the ground stations and up to three Fast Delivery products per 
pass will be delivered to end users via satellite within three hours after data acquisition. 
Precision Processing will be carried out in delayed time and products will not be generated until several days 
or weeks after data acquisition. However, a wide range of products will be generated by several Processing 
and Archiving Facilities (PAF) in a joint effort coordinated by ESA. 
The German Remote Sensing Data Center (Deutsches Fernerkundungsdatenzentrum DFD) will develop and 
operate one of these facilities. DFD has been implemented by DFVLR to promote and support the utilization 
of remote sensing data in the Federal Republic of Germany (FRG) The related activities include the acquisition, 
processing and evaluation of such data for scientific, public and commercial users. 
Since many years DFD is involved in processing of SAR data including data from the SEASAT L-Band SAR, 
the Canadian airborne X/C/L-Band SAR and the Shuttle Imaging Radar SIR-B. For SEASAT several hundred 
scenes acquired over Europe were processed under ESA contract with a processor that was developed by the 
Canadian firm MDA [Bennett, 1981] under a joint contract from the Canadian Center for Remote Sensing and 
DFVLR. 
Based on this experience the German Remote Sensing Data Center is presently performing a phase-B study 
regarding the development of a SAR processor for ERS-1. The conceptual design of this processing facility 
is briefly outlined in the following chapters. 
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