Optical Design and Performance of the Odin UV/Visible Spectrograph and Infrared Imager Instrument

Sweden's Odin international scientific small satellite is planned for launch into a sun synchronous low earth orbit in 1998. Odin's mission will be both astronomy and atmospheric science (aeronomy). Its principle aeronomy payload is a high performance, lightweight (12 kilograms) ultraviolet/visible imaging spectrograph and infrared imager, that will point at the limb of the earth's upper atmosphere and measure molecular species associated with ozone chemistry, detect aerosols and tomographically measure and map ozone. The Canadian Space Agency is funding this payload, which has the acronym "OSIRIS", and Routes Inc. is currently building the flight model. OSIRIS is effectively two optical instruments mounted in a common optical housing and supported by common electronics. The first instrument consists of three infrared telescopes, each with an Indium Gallium Arsenide (InGaAs) linear detector. The second part is a high precision imaging spectrograph with a wavelength range of 280 to 800 nanometers, which uses a UV-enhanced CCD. The imaging spectrograph uses compact reflective optics and an aspheric reflective ruled grating, and provides excellent spectral imaging performance and stray-light rejection. This paper first briefly describes the overall instrument and then describes the optical design and the Development Model optical and sky test performance results. This paper includes a brief description of how OSIRIS will obtain valuable new environmental information on the upper atmosphere, and the requirements this places on the instruments optical design.