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éATITUDE (3) 
Figure 1: Look-angle profiles during the three initial 
imaging cycles of Magellan. 
  
This results in a need to cope with very large data sets if one 
wants to process Magellan data efficiently. At the Mission’s 
Image Processing Laboratory, a disk farm with 190 GB is kept 
on-line. 
Figure 2 presents a set of radar images from each of the 3 
cycles. 
3. PROCESSING STRATEGIES 
The genesis of Magellan's stereo coverage as an “after 
thought", combines with the non-existence of funds to develop 
and process stereo data in a systematic manner, to obstruct the 
796 
well-thought-out definition of a stereo processing strategy. 
However, the basic elements of a process are obvious. 
Processing must be automated to be feasible at all, given the 
monumental data quantities. 
3.1 Ephemeris Adjustment 
The spacecraft state and attitude vector must be known to 
within a pixel or better than 75 m. This is not a trivial 
accomplishment for orbits around a distant planet; it is, 
however, feasible. To accomplish this goal, individual groups 
of orbits are adjusted with the simultaneous use of Earth-based 
Doppler observations, star-observations, use of "tie-points" 
(i.e. landmarks in overlapping images) and a rigorous sensor 
model. At the time of this writing, it was not clear whether tie-