<title>Detecting small debris using a ground-based photon counting detector</title>

Abstract

We describe a sensitive technique for detecting small space debris that exploits a fast photon- counting imager. Microchannel plate detectors using crossed delay-line readout can achieve a resolution of 2048 X 2048 spatial pixels and a maximum count rate of about 106 photons per second. A baseline debris-tracking system might couple this detector to a 16-cm aperture telescope. The detector yields x, y, and time information for each detected photon. When visualized in (x,y,t) space, photons from a fast-moving orbital object appear on a straight line. They can be distinguished from diffuse background photons, randomly scattered in the space, and star photons, which fall on a line with sidereal velocity. By searching for this unique signature, we can detect and track small debris objects. At dawn and dusk, a spherical object of 1.3 cm diameter at 400 km will reflect sunlight for an apparent magnitude of V approximately equals 16. The baseline system would detect about 16 photons from this object as it crosses a 1 degree field of view in about 1 second. The line in (x,y,t) space will be significant in a diffuse background of approximately 106 photons. We discuss the data processing scheme and line detection algorithm. The advantages of this technique are that one can (1) detect cm-size debris objects with a small telescope, and (2) detect debris moving with any direction and velocity.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.