270 
Spaceborn camera instruments must be proofed under space condition in a special thermal vacuum chamber. The modular 
structure of the camera calibration facility allows to combine parts of the calibration facility (fig. 1) with the space simulation 
chamber. The camera system is mounted inside of the chamber and can be illumminated by the collimator through an optical 
window. With the help of the slit or pinhole motion stage the PSF of the camera can be measured inside the vacuum without 
moving of the camera in the chamber. First the change of the focal length can be determined which is caused by the 
difference of the refraction index between air and vacuum (fig. 10). 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
X2645, Di2645. Vk X-direction Y2645. M2645, Vk y-direction 
1.00 1.00 
0.80 0.80 
0.60 0.60 
0.40 0.40 
air Pair 
--vacuum 
0.20 0.20 
--vacuuimn N À. 
0.00 Looms] 0.00 d = 
0:0 5.0 10.0 15.0 20.0 25.9 30.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 
Steps [um] steps [um] 
M2645XLM2645XVk M2645YLM2645YVk 
1.00 1.00 
0.80 0.80 
  
  
0.60 0.60 
NI air-- 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
hir-* vacuum -vaquum 
0.40 NS 0.40 
0.20 
0.20 SS 
0.00 : p 
0.00 
0 20 40 60 80 100 
at 0 20 40 60 80 100 
mm- 1 
Fig. 10 Improvement of PSF/MTF from air to vacuum 
Second the influence of temperature at the image quality under space simulated condition can be proofed (fig.11). The 
known vacuum focal shift can be simulated with the collimator by a small deviation of the infinite adjusted state. Therefore 
the whole geometric calibration procedure of the spacborne camera take place in the laboratory with a small convergent 
adjusted collimator to simulate the vacuum condition. 
IAPRS, Vol. 30, Part 5W1, ISPRS Intercommission Workshop “From Pixels to Sequences”, Zurich, March 22-24 1995