Optical design and performance analysis of a CubeSat-sized limb sounder utilizing a spatial heterodyne spectrometer for the measurement of mesospheric temperature

A highly miniaturized limb sounder for the observation of the O₂ A-band to derive temperatures in the mesosphere and lower thermosphere is presented. The instrument consists of a monolithic spatial heterodyne spectrometer, which is able to resolve the rotational structure of that band. The SHS operates at a Littrow wavelength of 762 nm with a resolving power in the order of 10.000. Complemented by a front optics with an acceptance angle of less than +/-1 degree and a detector optics, the entire optical system fits into a volume of about 1.5 liters. This allows this instrument to be flown on a three or six unit CubeSat. In this paper, we introduce the optical design and computer simulations on the expected performance of the instrument. The laboratory characterization of a prototype instrument, which has been built on university level, and the lessons learned are discussed.