A compact, lightweight, high accuracy star tracker is a key enabler for future NASA space missions, from precise pointing of the large space telescopes to autonomous navigation and formation flying. For high precision attitude determination system, one of the identified needs is to provide milli-arcsecond class pointing for large space telescopes. Optical Physics Company (OPC) has developed a novel interferometric star tracker than can provide milli-arcsecond class accuracy for future NASA space missions. The interferometric is similar to a standard star tracker, but with the addition of the interferometer subassembly in front of the imaging lens. This subassembly converts incoming starlight into a set of quadrature signals with sinusoidal dependence on the starlight incident angle. These quadrature signals are used to determine star position, rather than the centroiding used in standard start trackers which enables the high accuracy. OPC has designed and is presently manufacturing a compact (0.35U), lightweight (0.35 kg) and low power (<4W) interferometric star tracker for the Air Force.