More Details On:
Star Tracker Camera
The startracker
was a star-imaging sensor designed primarily for attitude determination, although
it was also used to collect scientific data. Clementine carried two startrackers
mounted to ensure that one would always have the Sun excluded from its field of view.
The startracker used silicon CCD technology with a 384 x 576 pixel array sensitive
between 0.4 and 1.1 micrometer. It had a wide field of view, 29 degrees x 43 degrees,
to make more stars available for attitude determination. Its instantaneous field
of view (IFOV) was 1.3 mrad. The Lawrence Livermore
National Laboratory (LLNL) startrackers used on Clementine
each weighed less than 290 g and, when compared to other startrackers, represented
a decrease in mass by a factor of 3 to 10, a factor of 2 decrease in power consumption,
and a factor of 2 to 5 lower cost. An image from a startracker was processed aboard
the spacecraft using a computer program, Stellar Compass, provided by LLNL. Stellar
Compass compared the angular relationships of stars in a startracker image to those
provided by a stored star catalog of 600 stars distributed over the celestial sphere.
Stellar Compass and the star catalog were resident in the R3081 RISC processor. Typically
attitude determination could be made within 100 ms using a single startracker image.
The LLNL startracker and Stellar Compass provided attitude determination of medium
accuracy, which is better than 150 microrad in pitch and yaw and 450 microrad in
roll.
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Mass |
290 grams |
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Size |
12 X 12 X 14 cm |
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Power |
4.5 W |
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Field of View |
29 X 43 degrees |
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Pixel Format |
384 X 576 |
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