Abstract
We present a micro star tracker with curved vanes that offers a short length of the baffle and a sharp cutoff of stray light. The curved vanes are derived mathematically by ray-tracing in such a way that all the stray light from outside of the desired field of view (FOV) is reflected out. The proposed curved vane design allows a smaller number of vanes to completely cut off stray light, leading to a shorter length in baffle design. Furthermore, the capability of a sharp cutoff of stray light eases the sensitivity requirement of image sensors. For the experiment, we fabricated three micro star tracker baffles with curved vanes for 22° FOV, which are required to handle a maximum star magnitude of 5.35 for 100% sky coverage. The sizes of the baffles fabricated are ${16}\;{\rm mm}\;\Phi \times {16.5}\;{\rm mm}$ L with double curved vanes, ${24}\;{\rm mm}\;\Phi \times {12.1}\;{\rm mm}$ L with a single curved vane, and ${27}\;{\rm mm}\;\Phi \times {14.4}\;{\rm mm}$ L with double curved vanes. In comparison, the straight vane baffle designed for 22° FOV requires seven vanes with 18 mm length but results only in mild stray light attenuation with the cutoff at 32°. The proposed star tracker utilizes a 5-megapixel image sensor, ${16}\;{\rm mm} \times {16}\;{\rm mm} \times {39}\;{\rm mm}$ in size and weighing 9.2 g with an accuracy of 1.288 arcsecond, a 20.6% improvement over when no baffle is used.
© 2020 Optical Society of America
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