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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 miniaturised GHG sensor named NanoCarb coupled with an aerosol instrument, the multi-angle polarimeter SPEXone. More specifically, the NanoCarb sensor is a static Fabry–Pérot imaging interferometer with a 2.3×2.3 km 2 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 CO 2 and CH 4 (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 parameterised 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 CO 2 and CH 4 flux estimation performance studies. [ABSTRACT FROM AUTHOR]

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 x 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. [ABSTRACT FROM AUTHOR]

The SCARBO project (Space CARBon Observatory) aims at solving a key challenge of anthropogenic greenhouse gases (GHGs) monitoring from space: improving the temporal revisit over the various sites of interest while meeting the accuracy and spatial resolution requirements (as per the EU guidelines on anthropogenic GHGs monitoring). To do that a novel miniaturized static spectrometer concept called Nanocarb is currently being developed to be included on a constellation of Small Satellites and coupled with aerosol sensors and high-end reference instruments. NanoCarb is an imaging interferometer dedicated to the measurement of CO2 concentration in the atmosphere. It is based on the ImSPOC concept (invented by ONERA and by IPAG). This concept combines a multipath imager (lens array in front of single 2D detector) and an array of static Fabry-Perot filters (FP). The lens array forms a collection of thumbnail images of the scene at the focal plane, and each step of the interferometer is placed in front of a lens from the lens array. The specificity of NanoCarb is to measure only few optical path differences (as many as Fabry-Perot filters), that is only a partial interferogram. This specificity leads to a paradigm shift, since it is impossible to retrieve the spectrum from a partial interferogram. Therefore, the estimation of the CO2 (and CH4) column concentration has to be done directly from these partial interferograms. Such a strategy implies that the spectral band and the optical path differences must be chosen very carefully. This is done through the development of an inversion algorithm, coupled with an optimization over instrumental parameters. This step is essential since on the one hand it includes a contribution to the SCARBO overall performance analysis tool: inversion from level 1 products (calibrated partial interferograms) to level 2 products (estimated geophysical parameters), and on the other hand it will also be used for the definition of the instrument and the prototype.In this paper, after a presentation of Nanocarb and its inversion tool, first elements of performance analysis will be presented. [ABSTRACT FROM AUTHOR]