Strawman design for a gas-filter correlation radiometer satellite instrument to measure the atmospheric CO2 column

Satellite-based remote sensing of atmospheric CO2 holds the promise to greatly improve our understanding of the processes which regulate atmospheric CO2 and the global carbon cycle. However, the required precision and resolution of such measurements needed to characterise sources and sinks of CO2 on regional scales presents strong instrument design challenges. One type of remote sensing instrument which has been proposed to measure the integrated-column concentration of CO2 is a Gas-Filter Correlation Radiometer (GFCR). As a technique, a GFCR is a radiometer which uses a sample of the gas of interest as a spectral filter for that gas in the atmosphere. In this paper we present a "strawman" design for a GFCR satellite instrument to remotely sense atmospheric CO2. This design, which includes multi-pass CO2 and O-2 gas cells with path lengths of up to 10 metres, demonstrates that such an instrument can be built within the constraints of a satellite environment.