|Student Name:||Issac Thornton, 1Lt|
|Thesis:||Development of Adaptive Tilt Tracker That Utilizes Quadrant-Cell Detector to Track Extended Objects|
|Location:||Bldg 640/Rm 317|
|Date & Time:||02/27/2014 at 1230|
|Abstract:|| Atmospheric turbulence causes tilt distortion that requires telescopes to track and remove image jitter effects. This research develops an adaptive tilt tracking system to detect and compensate for centroid gain volatility while tracking extended objects. The adaptive tracker counteracts deviations in tilt measurement and correction, due to unintended centroid gain changes. Non-adaptive trackers experience suboptimal bandwidths and possible instabilities. This research conducts a rigorous QUAD-Cell characterization that shows the QUAD-Cell is inherently unreliable while measuring tilt distortion of resolvable LEO objects that have asymmetrical characteristics. This work develops an innovative methodology that rotates the LEO object’s image to create a suitable intensity distribution for the QUAD-cell. Along with image rotation, an adaptive gain term yields significant improvements in QUAD-cell measurement performance, up to 91% for the simulated tilt processes. The developed tilt tracker model dithers the fast steering mirror to detect non-optimal centroid gains. For a SNR of five, results show the adaptive tracker counteracts centroid-gain deviations to attenuate the aperture’s one-axis, one-sigma G-tilt angle deviation up to 97.76%; average maximum long exposure Strehl ratio is about 0.67, a 116% improvement over the non-adaptive tracker.