Ultra-Miniaturized Star Tracker for Small Satellite Attitude Control

Creare and Embry-Riddle Aeronautical University (ERAU) propose to complete the design, development, and testing of an ultra compact star tracker specifically intended for small satellites such as the CubeSat platform. Our design is based on proprietary "folded optics" technology previously developed by ERAU for use in military and commercial optical applications that require a compact footprint and high performance. Furthermore, the design utilizes recent advances in high pixel count CMOS imaging sensor technology. The folded optics design is superior to conventional refractive optics in miniature star trackers because (1) the compact footprint is achieved without sacrificing accuracy; (2) the light-gathering aperture is much greater, leading to better sensitivity; (3) the aperture geometry makes the shielding baffles smaller; and (4) the imaging sensor can be shielded efficiently from cosmic radiation. During the Phase I project, we demonstrated a pointing accuracy of the order of 1 arc second testing a brassboard model of our design. We furthermore completed the design, performed analysis to determine the optimal design parameters, and confirmed the brassboard sensitivity and resolution. In Phase II, we will fabricate the optimized design, test the prototype in the laboratory and in the field, and deliver the prototype to NASA so that NASA can fly the prototype on a NASA high-altitude balloon mission.

Many NASA science missions are exploring the use of pico- and nano-satellites as alternatives to expensive, large satellites. In order to enable their mission profiles, these satellites need high accuracy attitude determination sensors. Our star tracker will enable highly precise attitude determination (i.e., 1 arc second or better) in a package that is significantly smaller, has much lower mass, and uses less power than any alternative star trackers on the market with comparable accuracy. As the market for and uses of small and nano satellites increases, the demand for our star tracker will increase to enable missions that are not possible with today's technology. Furthermore, the compact star tracker will enable high accuracy attitude determination on sounding rockets and high-altitude balloon missions, which will be useful for a variety of science payloads.

Both the military and commercial ventures are looking to small satellites to provide a cost effective space mission platform. However, the majority of missions still require high attitude accuracy. There is therefore a need for compact high-accuracy star tracker technology. Furthermore, the military is looking at star trackers for high-altitude unmanned aerial vehicle (UAV) attitude determination. These will typically need to provide arc-second accuracy in a small form factor with low power demands, which makes our proposed miniaturized star tracker ideally suited. Furthermore, our reflective optics can readily be adapted to act as a powerful telescope for imaging applications in both the visible band and in the near and far infrared spectrum. This opens up applications in reconnaissance, surveillance, and search and rescue operation.

This is a mature technology (TRL 7) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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