94 
6. 
95 
6. Models must be designed and verified, based on the 
measurements suggested under point 5. 
This set of measurements is by no means easily collected. 
Therefore a major part of mission planning, coordination, 
reorganisation will have to deal with the collection and the 
handling of these data sets. At best, a centralised database 
will have to be built. The database will accept data from: 
- The mission specific SAR system 
- The selected sensors (both airborne and spaceborne) used for 
data collection and model development before and during the 
mission 
- The ground and sea truth campaigns organised before and 
during the mission 
- The on board instruments used for spacecraft and sensor 
monitoring 
- The calibration sites and targets 
The database will have to be organised well in advance and 
will have to set standards for data collection and formatting 
throughout the mission preparation and operation. 
The database must allow temporal and geophysical 
referencing of the data sets, and will have to include the most 
recent model for creating the calibration information. 
Examples of such databases do not exist. Their use in the 
global calibration of a sensor has been proposed. Their structure 
should resemble those proposed as "geographical information 
systems" [18] and "geocoded databases" [19]. The classifications 
for these databases are described in the references above, and 
Figure 8 shows two typical structures. Depending on the specific 
calibration application, some other classifications will have to 
be considered: target types, coverage type, J, categories, etc. 
SUMMARY 
Problems related to the acquisition, validation, simulation 
and calibration of remote-sensing data have been considered, with 
particular reference to synthetic aperture radars. Work in these 
areas is continuing at the Earthnet Programme Office in Italy as 
part of the build-up to the ERS-1 mission.