Optical Design of RIS (Retrorefector In-Space) for the ADEOS Satellite

Abstract

This paper describes optical design of the Retroreflector In-Space (RIS) for the Advanced Earth Observing Satellite (ADEOS), which is planned for launch in February of 1995. RIS is a cube-corner retroreflector for earth-satellite-earth laser longpath absorption measurements of atmospheric trace species such as ozone, CFC 12, carbon dioxide and methane. In the RIS measurement, a laser beam is transmitted from a ground station, reflected by RIS and received at the ground station. The absorption spectrum of the atmosphere is measured by scanning the laser wavelength. The density of the trace species are obtained by analyzing the spectrum. RIS has a single-element hollow structure and has an effective diameter of 0.5 m. The mirror shape for RIS was newly designed to optimize the intensity pattern of the beam reflected by RIS in orbit. A slightly curved surface is used for one of three mirrors forming the retroreflector to overcome the velocity aberration of the reflected beam. The effect of the curved surface on the intensity pattern of the reflected beam was investigated by a computer simulation. The parameters of the surface curvature were determined by optimizing the reflected beam intensity at the ground station.