Detecting an mv = 16 GEO object in a 5 deg field of view must contend with 135,000 brighter stars and 393,000 slightly dimmer stars that share the same field of view. OPC has developed an interferometric tracker, which gives each object two unique AC signals, one for each axis proportional to its slew rate. Since star and GEO slew rates differ by about 15 deg/hour, this frequency difference allows separating out the star clutter from the true GEO objects using two simple Fourier transforms one for X data and one for Y data. Star signals are heavily suppressed by this Fourier transform process so that GEO objects can be reliably detected. In addition, the phase ramp of the AC signals allows the angular velocity of each GEO object to measured to about 1 meter/second. Such a precise velocity measurement highlights maneuvering GEO objects and also allows a maneuvering object to be tracked over time with much higher confidence to avoid loss of custody. The DoD and NASA have invested over $23M developing this new interferometric tracking capability, demonstrating it in a variety of military applications in the field and planned to fly in space next year (NASA).
