Intelligent Star Tracker

We describe our Intelligent Star Tracker System. The Intelligent Star Tracker System incorporates an adaptive optic catadioptric telescope in a silicon carbide housing. Leveraging off of our active optic technologies, the novel active pixel position sensors (APPS) enable wide dynamic range and allows simultaneous imagery of faint and bright stars in a single image. Moreover, the APPS, in conjunction with the adaptive optics technologies, offer unprecedented accuracy in altitude and navigation applications. ATTITUDE DETERMINATION The most obvious application for the Intelligent Star Tracker is star tracking for spacecraft attitude determination. To assess the true star density in the Intelligent Star Tracker FOV we will use our Space Technologies Applied Research Laboratory (AFRL StarLab) to produce accurate star patterns. AFRL has already set this up for adaptive optics purposes. The AFRL StarLab also provides a convenient method to accurately test the Intelligent Star Tracker with accurate star densities. CATADIOPTRIC TELESOPE As shown in figure 1, our novel Intelligent Star Tracker incorporates a totally new optical design which consists of a high high-resolution adaptive optic telescope folded into a single low cost, Silicon Carbide structure. There are several catadioptic telescopes that could be used in a star tracker. Figure 1 illustrates the Intelligent Star Tracker using a MatsutovBouwers configuration. Other catadiopptic telecopes include Schmidt-cassegrain, and Baker-Schmidt. In each of these catadiptric _____________________________________ *Dept. Electrical Engineering, New Mexico State University, Las CrucesNM 88003 telescopes uses a full-aperture refracting element to provide the aberration correction needed to get good imagery over a wide field. SILICON CARBIDE TELESCOPE The dramatic difference in weight between conventional and SiC optical systems has led to SiC material being applied to a number of optical applications associated with next generation remote sensing concepts. SiC material have a number of bulk property advantages, very high specific stiffness and outstanding thermal stability, which makes it particularly well suited for the Intelligent Star Tracker system. The superior thermal stability in conjunction with the outstanding specific stiffness, make SiC ideally suited for star trackers. SiC provides excellent light-weighting capabilities (approximately 80% of beryllium.), and is 50% the hardness of diamond. Historically, there are two problems associated with CVD SiC materials: (1) the CVD process very expensive with furnacing runs costing on the order of $100k each and (2) CVD SiC cannot be produce in very lightweight geometries. A state of the art CVD SiC mirror can be expected to have a density on the order of 30-50 Kg/m2. Hence, any complex geometries that are required, or any lightFigure 1. Intelligent Star Tracker. Optic Axis MEMs Micro-Mirrors Star