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

TL;DR

This paper presents the optical design of the Carbon-I Imaging Spectrometer, a space-based instrument capable of high-precision greenhouse gas measurements from Earth's orbit using advanced freeform optics and spectral sampling.

Contribution

It introduces a novel optical design combining a freeform three-mirror telescope with a Dyson-inspired spectrometer for enhanced spectral and spatial resolution.

Findings

Achieves spectral sampling of 0.7 nm per pixel.

Supports global and target modes with different GSDs.

Enables precise greenhouse gas concentration measurements.

Abstract

The proposed Carbon Investigation (Carbon-I) Imaging Spectrometer is designed to measure variations of greenhouse gases in 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 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.