MATHEMATICAL MODELING OF THE ATTITUDE TRACKER 
B.Gokhman and F. C. Billingsley 
Jet Propulsion Laboratory, 
California Institute of Technology 
Pasadena, California 91109, USA. 
Comission III. 
l. Introduction 
Future sensors of the linear array type will return lines of data 
which are independent in the sense that there is no data tie 
between them. It is essential for mapping and stereo work that 
the data lines used for analysis be in precisely the correct 
geometrical position. If the sensed image lines are not in the 
correct positions, interpolation or other compensation must be 
used before analysis. Position determination depends on the exact 
knowledge of the platform attidude. While the spacecraft control 
parameters will be marginally adequate, the problem is exacer- 
bated with an aircraft platform due to the ubiquitous platform 
instability. The use of ground control points will be necessary 
for precise tie to the ground, but would be cumbersome for conti- 
nued use for the altitude tracking, and in any event, surveyed 
ground contro] points will not be available for many areas. What 
is needed is a system, capable of analyzing the platform motion 
from the collected image information, which can be used to verify 
the platform stability and to provide the data for geometric 
correction. This may be used to further improve the expected good 
performance of the platform or to compensate for any degraded 
performance. 
2. System design 
The design concept of the attitude tracker system was proposed by 
F.C. Billingsley (Billingsley,1982)., Consider a 3 X 3 array of 
small (relative to the length of the imaging line array) square 
imaging devices placed in the focal plane of the camera (Figure 
1). 
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Figure 1. System geometry.