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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
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Image number 
—Ak2 
Figure 8. The relationship between the distortion coefficient k 2 
and the number of images 
As can be seen from figures 5,6,7,8 with the incensement of 
number of images, there are an overall improvement trend in 
the calibration accuracy of the camera parameters, but the 
tendency isn't consistent. The reason is that the distribution of 
all participated images will affect the calibration result during 
the calibration process. Generally, when the number of 
participated images increases, the probability of the calibration 
with high accuracy becomes larger, but if the distribution of the 
control points in the later joined image is bad, the whole 
calibration accuracy will drop. 
4.3 Calibration Experiment based on selected multi images 
Based on the analysis above, the more the number of images 
doesn’t mean the higher the calibration accuracy, which 
depends on the distribution of each participated image. Based 
on the distribution of each star image, the fifth, the eighth, and 
the tenth images are selected as the first set images, and the 
calibration result based on these three images is noted by C3. In 
the same way, the fifth, the seventh, the eighth and the tenth 
images are selected as the second set images, and the 
calibration result is denoted by C4. The first, the fifth, the 
seventh, the eighth and the tenth images are selected as the third 
set images, and the result is denoted by C5. Lastly, the 
calibration result using the all ten images is noted by CIO. All 
the calibration results are shown in Figure 9. 
Figure 9. The comparison based on selected combine images 
and all images 
It is seen that the calibration accuracy based on the selected 
images are better than based on all ten images, which indicates 
that the calibration result based on all images isn’t necessarily 
highest. Meanwhile, it verifies that selecting image in view of 
the distribution of participated image is very important step to 
improve the on-orbit calibration accuracy of the stellar camera. 
5. CONCLUSION 
During the attitude determination by star sensor, the change of 
the stellar camera parameters might cause the decline of the 
attitude accuracy, the on-orbit calibration method based on 
space resection is employed. Selecting image for this approach 
is proposed in this paper. 
From experiment, two conclusions are drawn. For the on-orbit 
calibration based on space resection, the distribution of star 
image points has strong effect on the calibration accuracy, and a 
good selection of images can significantly improve the 
calibration accuracy. 
Therefore, automatically selecting the star images considering 
its distribution is essential for this approach, which has the 
practical meaning for improving the calibration accuracy and 
accelerates the on-calibration period. 
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