Description: Optical Physics Company (OPC) proposes to develop a high accuracy version of its interferometric star tracker capable of meeting the milli-arcsecond-level pointing requirements. Such high accuracy tracker can be used for precision pointing of the large telescope, and can permit open-loop pointing of narrow-beam laser signals. The latter can enable deep-space lasercom missions without the technical and operational complexity of a ground based beacon. OPC has already built multiple versions of this star tracker for several applications for various DoD customers. Current technical maturity of the star tracker is TRL 5- which is expected to advance to TRL 6 during the proposed Phase I project due to space readiness and flight tests under parallel efforts. During the proposed Phase I effort, OPC will first develop requirements. This will be followed by design trades and formulation of a detailed design. Phase I will conclude with a Preliminary Design Review (PDR). During Phase II, the design will be advanced to the Critical Design Review (CDR) level and a prototype will be built and tested. Given that the existing baseline designs for OPC's visible and SWIR band interferometric star trackers are at TRL 5, OPC has a head start.

Benefits: This high accuracy tracker can be used for precision pointing of the large telescope. Its field of view is much wider than the fine guidance sensors (FGS) currently employed by HST and JWST. The JWST FGS, for example, has a field of view of only 0.04 x 0.04 degrees. With such a small field, fainter guide stars need to be used which then drives the sensor sensitivity and noise requirements. For the interferometric star tracker proposed, the angular sensitivity is defined by the angular period of the grating LSI, which can be independent of the field of view. This allows a wide field sensor to achieve similar level (milliarcsecond) of pointing performance, which then allows the use of brighter guide stars reduce the demand on sensor sensitivity. Another application is as reference sensor for laser beam pointing: A celestial reference based beam pointing eliminates the need for having a ground based beacon for return beam pointing which significantly reduces the operational complexity (power, pointing, regulatory compliance) and improves link performance (no round trip delay). OPC has also been funded recently for a study by JPL to investigate if its interferometric star tracker can be used for a spinning spacecraft. The study findings have shown the feasibility of adapting the interferometric tracker to provide accurate attitude information for a rapidly spinning spacecraft.

Application most relevant to this project is the use of star trackers for spacecraft. OPC is building a cubesat star tracker at this time to deliver to a DOD customer. The performance is power dependent - ranging from sub arcsecond to 2 arcsecond accuracy. The package is small - 250 cc in volume. Another visible band star tracker application was proposed to the Navy recently under the SBIR program. This proposal has been selected for award. The application involves space situational awareness, specifically to develop, build and deliver a version of the interferometric tracker capable of detecting and tracking dim objects. Another application is GPS denied navigation which has increasingly become a more acute need in the past few years. Customers are GPS denied navigation systems include virtually the whole armed forces. Our approach is primarily tailored to airborne platforms such as fighter aircraft, ground attack aircraft, next generation bomber, Tier II and Tier II UAVs, airborne early warning and control aircraft, ICBMs, and missiles including hypersonic missiles. OPC is currently funded under Navy RIF to build and flight test a stellar inertial navigation system prototype.