78 
25.2. 
79 
b. The processing systems, normally incapable of accepting the 
data stream at the real speed require: 
- playback of recorded data at reduced speed 
- bit error rate between recording and playback of at 
least 1076. 3 
Ce The archiving medium and system must offer a guarantee of 
data preservation in the long term (up to 10 years) with a 
bit error rate between input and output to the archive of 
at least 1076, Depending on the duration of the mission, 
the archiving system must tackle problems of: 
data volume 
retrieval time 
- data quality (monitoring and logging) 
— catalogue and data access 
Recording During Acquisition 
Data rate in input varies between 118 Mbit/sec (SEASAT), 
100 Mbit/sec (ERS-1), 46 Mbit/sec (SIR-B). The other radar 
missions foreseen in the next 10 years (e.g. Radarsat) fall 
within this range. 
Landsat thematic mapper data rate is 85 Mbit/sec. 
Landsat-3 return beam vidicon camera was 45 Mbit/sec. 
High density digital recorders (HDDR) have been the 
solution to remote sensing data acquisition since the start of 
the Landsat missions. 
For the high bit rate instruments, the trend is to use 28 
track recorders with error correction, or 42 track recorders 
(Table 1). The different densitites to be used in recording 
account for the choice of one or the other solution. Table 2 
shows the different relationship between recording speed and 
playback speed.