Optical design of a compact spectrometer for space applications: depolarizers analysis

ANSER Atmosphere (AT) is the second mission of INTA's SmallSat constellation program. Its main objective is the study and monitoring of greenhouse gases, air quality and polar ozone by absorption spectroscopy. It is composed of a cluster of four CubeSats flying in formation, each of them comprised of 6U. The main payload of each CubeSat consists of a catadioptric telescope (1U) and a refractive spectrometer (2U) each of them working in a different spectral range from UV to SWIR. The optical design of the spectrometer, which spectrally disperses and analyses the energy collected by the telescope, is based on a reflective diffraction grating with a slit at the entrance. Due to the fact that this is an atmospheric observation mission and the precision required for the measurements, it is necessary to eliminate the polarization of the incoming light. For this reason, depolarizers have been included in the instrument design.