Skylab Multispectral Scanner (5-192)â€

Abstract

In this paper we describe the design and performance of a Multispectral Scanner. The optical system of Skylab Multispectral Scanner (S-192) consists of an image plane scanner (telescope), a spectrometer for separation of the radiation into 13 spectral bands, and a 13-element (Hg,Cd)Te detector array. The image plane scanner is a new system based on three interrelated main features: (1) a reflective adaptation of the Schmidt principle; (2) a conical line scan in which all field elements are brought to and corrected on axis; and (3) a scanning arrangement in which the aperture stop of the system, located in a relay unit, is imaged at the center of curvature of the spherical primary mirror. Replacing the physical stop used in the classical Schmidt configuration with a virtual one makes the system much more compact. As a consequence of the image plane scanning and the Schmidt symmetry, the system scans at a large radial angle (11-degree diameter) and at an extremely high rate (6000 rpm) with relatively small scanning mirrors and a large entrance pupil diameter (43 cm). The spectrometer divides the radiation into 13 spectral bands, 12 of which are located between 0.4 and 2.35 micrometers and the other, 10.2-12.5 micrometers. A dichroic beamsplitter separates the far IR band from the 12 lower wavelength bands, which are dispersed by prisms. Photographic reproductions of the actual flight recordings show 80-meter resolution at an altitude of 440 km.