GHGSat-C1 - Initial Results, Design, and Characterization

GHGSat Inc. is launching its second satellite - GHGSat-C1 or "Iris" - in summer 2020. We present first results from GHGSat-C1, including measurements taken during the commissioning phase and during the first weeks of nominal operation.

Iris is based on the same spectrometer concept as GHGSat's demonstration instrument (GHGSat-D or "Claire" launched in 2016): the wide-angle Fabry-Perot (WAF-P). Both units fit the same cost-effective form factor and have imaging resolution in the tens of meters , designed to provide a ctionable information to operators by identifying specific facilit ies or piece s of equipment responsible for methane emissions.

Compared with Claire, Iris's design improvements should lead to approximately an order of magnitude lower error levels in the methane column retrievals (down to 2% of background or better) which will lower the detection threshold by a similar factor and enable emissions monitoring of a much wider range of sources. Key improvements include: reduction of stray light from outside the field of view and from unwanted reflections inside the payload; an on-board detector calibration to mitigate the effects of radiation damage to our pixel array; a re-optimized WAF-P and spectral bandpass to maximize sensitivity to local methane enhancements; and a slightly reduced focal length to give a moderate boost in per-pixel signal at the expense of spatial resolution. The nominal ground sampling distance will be 33 m - this is slightly higher than GHGSat-D's 23 m. However, GHGSat-C1's spatial resolution will be pixel-size-limited, unlike GHGSat-D that was limited to ~50 m due to aberrations.

As well as showing initial on-orbit observations, we present critical component-level characterization data that illustrates the improvements realized on GHGSat-C1. Finally, we provide a brief update on the GHGSat constellation, including GHGSat-C2 ("Hugo"), also launching in 2020.