The Optical Design of the Carbon Investigation (Carbon-I) Imaging Spectrometer

The proposed Carbon Investigation (Carbon-I) Imaging Spectrometer is designed to measure variations of green-house gases in the Earth's atmosphere. The instrument will survey the Earth from its own spacecraft at an altitude of approximately 610 km. It will use a coarse ground sampling distance (GSD) of <400 m in global mode for land and coastal monitoring and a finer 35 m GSD in target mode to sample key regions. The identification and quantification of greenhouse gases require continuous spectral sampling over the 2040–2380 nm wavelength range with <1 nm spectral sampling. The proposed design builds upon Jet Propulsion Laboratory's (JPL) experience of spaceflight Dyson imaging spectrometers to achieve spectral sampling of 0.7 nm per pixel. This paper presents the proposed Carbon-I optical design comprised of a freeform three-mirror anastigmat telescope that couples to a F/2.2, highly uniform Dyson-inspired imaging spectrometer. The high uniformity and throughput enables Carbon-I to measure Earth's greenhouse gas concentrations with unprecedented precision and spatial sampling.