Clementine Star Tracker Cameras

Description

The Clementine spacecraft was equipped with two star tracker cameras. Each camera consisted of a knife-edge baffle vane and a lens mounted to the CCD camera housing. Both cameras were located at one end of the spacecraft, near the main thruster. The main purpose of the star tracker cameras were to image the background stars in order to provide attitude determination for the spacecraft. This was done by comparing stellar images to an onboard star catalog to establish absolute angular references for navigation. However, images of the Earth and moon for scientific purposes could also be obtained.

The cameras had a wide field of view (28 by 43 degrees), entrance pupils 14 mm in diameter, bandpass filters of 0.4 to 1.1 micrometers, and focal lengths of 17.5 mm. In each camera, a concentric optics design with a fiber optic field flattener coupled the image surface to a Thompson CCD focal plane array of 384 x 576 pixels, each pixel being 23 x 23 micrometers in size. Only broadband operation was available, and the line-transfer electronic shuttering limited imaging to dim targets such as the lunar surface illuminated by earthshine.