Comment on amt-2021-224

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.

Authors 10

1. Matthieu Dogniaux

   Centre National de la Recherche Scientifique · École Polytechnique · Université Paris Sciences et Lettres · École Normale Supérieure - PSL · Sorbonne Université · Laboratoire de Météorologie Dynamique · Institut Polytechnique de Paris

   Affiliation as printed

   Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Institut Polytechnique de Paris, Sorbonne Université, École Normale Supérieure, PSL Research University, 91120 Palaiseau, France

2. Cyril Crévoisier

   Centre National de la Recherche Scientifique · École Polytechnique · Université Paris Sciences et Lettres · École Normale Supérieure - PSL · Sorbonne Université · Laboratoire de Météorologie Dynamique · Institut Polytechnique de Paris

   Affiliation as printed

   Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Institut Polytechnique de Paris, Sorbonne Université, École Normale Supérieure, PSL Research University, 91120 Palaiseau, France

3. Silvà ̈re Gousset

   Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes

   Affiliation as printed

   Institut de Planétologie et d’Astrophysique de Grenoble, Université Grenoble-Alpes, 38058 Grenoble, France

4. Étienne Le Coarer

   Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes

   Affiliation as printed

   Institut de Planétologie et d’Astrophysique de Grenoble, Université Grenoble-Alpes, 38058 Grenoble, France

5. Yann Ferrec

   Office National d'Études et de Recherches Aérospatiales · Département Optique et Techniques Associées

   Affiliation as printed

   ONERA/DOTA, BP 80100, chemin de la Hunière, 91123 Palaiseau, France

6. Laurence Croizé

   Office National d'Études et de Recherches Aérospatiales · Département Optique et Techniques Associées

   Affiliation as printed

   ONERA/DOTA, BP 80100, chemin de la Hunière, 91123 Palaiseau, France

7. Lianghai Wu corresponding Aachen SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Netherlands Institute for Space Research, Utrecht, the Netherlands

8. Otto Hasekamp corresponding Aachen SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Netherlands Institute for Space Research, Utrecht, the Netherlands

9. Bojan Sič

   Noveltis (France)

   Affiliation as printed

   NOVELTIS, 31670 Labège, France

10. Laure Brooker

    Airbus (France)

    Affiliation as printed

    Airbus Defence and Space, 31 rue des Cosmonautes, 31402 Toulouse, France