Abstract
This paper focuses on the idea of a multi-functional wide-field star tracker (WFST) and provides a description of the current state-of-the-art in this field. The idea comes from a proposal handed in to ESA at the beginning of 2011. Star trackers (STs) usually have more than one object-lens with a small Field-of-View. They provide very precise information about the attitude in space according to consecutive evaluation of star positions. Our idea of WFST will combine the functions of several instruments, e.g. ST, a horizon sensor, and an all-sky photometry camera. WFST will use a fish-eye lens. There is no comparable product on the present-day market. Nowadays, spacecraft have to carry several instruments for these applications. This increases the weight of the instrumentation and reduces the weight available for the payload.
Highlights
Attitude determination functions are basic functions in all space applications
Various attitude reference sources can be used for obtaining attitude information, e.g. Earth horizon sensors, which can be directed towards the Sun, Moon, or other planets and stars, Sun sensors, magnetometers, and star trackers (STs)
To decrease the mass and size of the current ST concept and to increase its functionality we proposed to design, develop, and verify the multi-functional wide-field star tracker
Summary
Attitude determination functions are basic functions in all space applications. Attitude information is used in Attitude and Orbit Control Systems to stabilize a spacecraft (S/C) in the required position and orientation. The coordinates were not related to inertial space, and the attitude information had to be provided indirectly by an external unit. This was due the insufficient power of the microcomputers. The first mode solves the lost-in-space function which does not have previous attitude information available, and the star pattern in the FoV has to be recognized. The other mode performs star tracking, which assumes that the current attitude is closely related to the previous attitude. This mode is easier for computation because it only tracks previously identified stars at known positions. They are: star light sensitivity, the detection threshold, the average number of stars in the FoV, and sky coverage
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