The Space Carbon Observatory (SCARBO) concept: assessment of X CO 2 and X CH 4 retrieval performance

[摘要] Several single-platform satellite missions have beendesigned during the past decades in order to retrieve the atmosphericconcentrations of anthropogenic greenhouse gases (GHG), initiating worldwideefforts towards better monitoring of their sources and sinks. To set up afuture operational system for anthropogenic GHG emission monitoring, bothrevisit frequency and spatial resolution need to be improved. The SpaceCarbon Observatory (SCARBO) project aims at significantly increasing therevisit frequency of spaceborne GHG measurements, while reachingstate-of-the-art precision requirements, by implementing a concept of smallsatellite constellation. It would accommodate a miniaturised GHG sensornamed NanoCarb coupled with an aerosol instrument, the multi-anglepolarimeter SPEXone. More specifically, the NanoCarb sensor is a staticFabry–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 X CO 2 and X CH 4 ).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 X CO 2 and X CH 4 directly from synthetic NanoCarb truncated interferograms and provide their systematic and random errors, column vertical sensitivities, and degrees of freedom as a function of fivescattering-error-critical atmospheric and observational parameters. We showthat NanoCarb X CO 2 and X CH 4 systematic retrieval errors can be greatly reduced with SPEXone posterior outputs used as improved prioraerosol constraints. For two-thirds of the soundings, located at the centreof the 200 km NanoCarb swath, X CO 2 and X CH 4 random errors span 0.5–1 ppm and 4–6 ppb, respectively, compliant with their respective 1 ppmand 6 ppb precision objectives. Finally, these Level 2 performance resultsare parameterised as a function of the explored scattering-error-criticalatmospheric and observational parameters in order to time-efficientlycompute extensive L2 error maps for future CO 2 and CH 4 fluxestimation performance studies.

[学科分类] 内科医学