Hiroyuki KAWANO^*, Haruhiko SHIMOJI, Shoji YOSHIKAWA, Katsumasa MIYATAKE, Kazumori HAMA¹, and Shuji NAKAMURA¹

Mitsubishi Electric Corp., Advanced Technology R&D Center, Amagasaki, Hyogo 661-8661, Japan
¹Institute for Unmanned Space Experiment Free Flyer (USEF), Tokyo 101-0052, Japan

(Received October 1, 2007; Accepted January 8, 2008)

We developed a technique for measuring the intensity distribution of a point image in sub-pixel resolution even after assembly of a lens and an image sensor, which is especially suitable for defocus adjustment of a star sensor used to determine the attitude of a spacecraft. The star sensor optical system is usually aligned in a defocused position to calculate the luminance centroid of a star image in sub-pixel resolution. In the measurement technique, the point image is carefully scanned around a certain pixel on the image sensor, and the intensity change of the pixel is recorded during the scanning. We applied this technique to the alignment of our star sensor's optical system, and we were able to suppress the spot size in a range between 1.2 and 2.2 pixels at 1/e² diameter at a certain defocus position, making it appropriate for luminance centroid calculation.

Key words: star sensor, defocus, ground test

^*E-mail address: Kawano.Hiroyuki@ap.MitsubishiElectric.co.jp