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Design of a day/night star camera system

This paper describes the design of a camera system capable of acquiring stars during both the day and night cycles of a high altitude balloon flight. The camera system will be filtered to operate in the R and I bands, and simulations have been run using MODTRAN atmospheric code to determine the worse case sky brightness at 35k. With a worse case daytime sky brightness of 2 X 10-5/sr/micrometers at 600nm, the sensitivity of the camera system will allow acquisition of at least 1-2 stars/degrees2 at star magnitude limits of 7.8-8.1. The system will have an F2.8, 64.3mm diameter lens and a 1340 X 1037 CCD digitized to 12 bits. The CCD is comprised of 6.8micrometers X 6.8micrometers pixels with a well depth of 45,000 electrons and quantum efficiency of 0.54 at 700nm. The camera's field-of-view will be 6.33 degrees2 and provide attitude knowledge to 8 arcsec or better. A test flight of the system is scheduled for fall 1999.