A star tracker insensitive to stray light generated by radiation sources close to the field of view
Authors: Romoli A., Gambicorti L., Simonetti F., Zuccaro Marchi A.
Autors Affiliation: CNR-INOA National Institute of Applied Optics,(Italy), Largo E. Fermi, 6, Firenze, 50125, Italy
Abstract: Aim of this work is to propose an innovative star tracker, practically insensitive to the radiation coming from the sun or from other strong planetary sources out of (but near) the Field of View. These sources need to be stopped in some way. The classical solution to reject the unwanted radiation is to place a shadow (or baffle) before the star tracker objective. The shadow size depends on the Field of View and on the minimum angle subtended by the source (i.e. the sun) with respect to the optical axis of the star tracker. The lower is this angle the larger is the shadow. Requests for star trackers able to work with the sun as close as possible to the Field of View are increasing, due to the need of maximum mission flexibility. The innovation of this proposed star tracker is conceived by using spatial filtering with a concept complementary to that of coronagraph for sun corona observation, allowing to drastically reduce the size of the shadow. It can also work close to antennas and other part of the platform, which, when illuminated by the sun, become secondary sources capable to blind the star tracker. This kind of accommodation offers three main advantages: no cumbersome shadows (baffle), maximum flexibility in terms of mission profile, less platform location constraints. This new star sensor concept, dated 2007, is now patent pending. Galileo Avionica (now Selex Galileo) is the owner of the patent.
KeyWords: Light; Patents and inventions; Stars; Stray light, Baffle; Classical solutions; Galileo avionica; Location constraints; Radiation source; Secondary sources; Spatial filterings; Star sensors, Star trackers