1.3.1 Radar Model

The radar model considered is electronically scanned  (ESCAN) in azimuth and mechanically scanned  (MSCAN) in elevation. This means that the radar can be aligned instantly in the azimuth direction, but time is required to move it in the elevation direction. The ESCAN axis is aligned with the direction of motion of the satellite. It is necessary for this to be the case, because the scan rate in the MSCAN axis is insufficient to keep the radar boresight aligned with a specific area on the ground while it is being imaged.
Further constraints are on the range of angles the radar can scan over. In the MSCAN direction, there is a minimum angle and a maximum angle  (both from the vertical) between which tasks can be viewed. In the ESCAN direction, there is an angle (also from the vertical), and only tasks that are within this angle (both ahead and behind the satellite) can be imaged. Understanding of this is aided by the following figures:

       

       
     
 

ESCAN direction

 
     
 

 
 

Direction of
satellite motion

 
 

 
       
Satellite    
  Figure 1-1 - Radar range in ESCAN direction  
e = Maximum scanning angle in ESCAN direction