Preprints
https://doi.org/10.5194/amt-2021-224
https://doi.org/10.5194/amt-2021-224

  12 Oct 2021

12 Oct 2021

Review status: this preprint is currently under review for the journal AMT.

The Space CARBon Observatory (SCARBO) concept: Assessment of XCO2 and XCH4 retrieval performance

Matthieu Dogniaux1, Cyril Crevoisier1, Silvère Gousset2, Étienne Le Coarer2, Yann Ferrec3, Laurence Croizé3, Lianghai Wu4, Otto Hasekamp4, Bojan Sic5, and Laure Brooker6 Matthieu Dogniaux et al.
  • 1Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Institut Polytechnique de Paris, Sorbonne Université, École Normale Supérieure, PSL Research University, 91120 Palaiseau, France
  • 2Institut de Planétologie et d’Astrophysique de Grenoble, Université Grenoble-Alpes, 38058 Grenoble, France
  • 3ONERA/DOTA, BP 80100, chemin de la Hunière, 91123 Palaiseau, France
  • 4SRON Netherlands Institute for Space Research, Utrecht, the Netherlands
  • 5NOVELTIS, 31670 Labège, France
  • 6Airbus Defence and Space, 31 rue des Cosmonautes, 31402 Toulouse, France

Abstract. Several single-platform satellite missions have been designed during the past decades in order to retrieve the atmospheric concentrations of anthropogenic greenhouse gases (GHG), initiating worldwide efforts towards better monitoring of their sources and sinks. To set up a future operational system for anthropogenic GHG emission monitoring, both revisit frequency and spatial resolution need to be improved. The Space CARBon Observatory (SCARBO) project aims at significantly increasing the revisit frequency of spaceborne GHG measurements, while reaching state-of-the-art precision requirements, by implementing a concept of small satellite constellation. It would accommodate a miniaturized GHG sensor named NanoCarb coupled with an aerosol instrument, the multi-angle polarimeter SPEXone. More specifically, the NanoCarb sensor is a static Fabry-Perot imaging interferometer with a 2.3 × 2.3 km2 spatial resolution and 200 km swath. It samples a truncated interferogram at optical path differences (OPDs) optimally sensitive to all the geophysical parameters necessary to retrieve column-averaged dry-air mole fractions of CO2 and CH4 (hereafter XCO2 and XCH4). In this work, we present the Level 2 performance assessment of the concept proposed in the SCARBO project. We perform inverse radiative transfer to retrieve XCO2 and XCH4 directly from synthetic NanoCarb truncated interferograms, and provide their systematic and random errors, column vertical sensitivities and degrees of freedom as a function of five scattering error-critical atmospheric and observational parameters. We show that NanoCarb XCO2 and XCH4 systematic retrieval errors can be greatly reduced with SPEXone posterior outputs used as improved prior aerosol constraints. For two thirds of the soundings, located at the centre of the 200 km NanoCarb swath, XCO2 and XCH4 random errors span 0.5–1 ppm and 4–6 ppb, respectively, compliant with their respective 1-ppm and 6-ppb precision objectives. Finally, these Level 2 performance results are parameterized as a function of the explored scattering error-critical atmospheric and observational parameters in order to time-efficiently compute extensive L2 error maps for future CO2 and CH4 flux estimation performance studies.

Matthieu Dogniaux et al.

Status: open (until 16 Nov 2021)

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Matthieu Dogniaux et al.

Matthieu Dogniaux et al.

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Short summary
The Space CARBon Observatory concept proposes a constellation of nano-satellites that would carry a miniaturized Fabry-Perot imaging interferometer named NanoCarb, and an aerosol instrument named SPEXone. In this work, we assess the performance of this concept for the retrieval of the total weighted columns of CO2 and CH4, and show the interest of adding the SPEXone aerosol instrument to improve the CO2 and CH4 column retrieval.