GHGSat-C1 – Initial Results, Design, and Characterization

Abstract:

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 actionable information to operators by identifying specific facilities or pieces 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.