Scanning technique for Advanced Geosynchronous Studies Imager: conical scanning to compensate for image rotation

摘要

Abstract: The AGSI is a visible and IR instrument being proposed to satisfy both NOAA's operational weather and NASA's geostationary science requirements. It scans the full earth disk with a plane scan mirror in object space, mounted on a two-axis gimbal system. Image rotation is an intrinsic problem: scanning about one gimbal axis rotates the projection of the focal plane array (FPA) onto the earth's surface. The AGSI's needs for both higher angular resolution and higher radiometric resolution are satisfied by time delay and integration (TDI) in several FPA's. The electronic and opto-mechanical scan vectors must match to maintain image quality: the projection of the TDI axis of each FPA onto the earth's surface must always coincide with the scan direction and the scan rates must be equal. A new gimbal geometry, focal plane layout, and associated scanning techniques have been developed to scan the earth's surface in a series of conical arcs that satisfy these conditions. This technique has the additional advantages that the outer gimbal axis remains stationary during the data-taking portion of the scan pattern and that the magnitude of the angle of reflection remains relatively constant during a single scanning arc. !7