Michael Hart, HartSCI LLC
Keywords: Adaptive optics, daytime imaging, laser guide stars, faint object characterization
Abstract:
Custody and characterization of satellites during the day is enormously challenged by the photon noise introduced by the bright daytime sky. In particular, daytime use of adaptive optics (AO) at large telescopes is generally infeasible because of noise or saturation of the wavefront sensor. That problem may be overcome through use of a sodium laser guide star observed through a magneto-optical filter to suppress the background, but the laser beacon is not sensitive to overall image motion. To estimate that, laser-guided AO systems generally rely on light from the object itself, collected through the full aperture of the telescope. Daylight sets a lower limit to the brightness of an object that may be tracked at rates sufficient to overcome the image jitter. Below that limit wavefront correction on the basis of the laser alone will yield an image that is approximately diffraction limited, but that moves randomly. I describe a new registration algorithm that recovers high-resolution long exposure images in this regime from a rapid series of short exposures with very low signal-to-noise ratio. The technique takes advantage of the fact that in the photon noise limit there is negligible penalty in taking short exposures, and that both past and future history are available to the registration algorithm. The algorithm is likely to find application in space situational awareness, where it is expected to enable access at high resolution to objects as faint as magnitude 12.
Date of Conference: September 11-14, 2018
Track: Adaptive Optics & Imaging