Among the EUMETSAT various activities related to
EPS-SG, the timely and
efficient processing of the data down-linked from the orbiting platforms is of outstanding importance to the primary users.
To this end, it was necessary to simulate realistic data from the observation missions to be embarked upon for EPS-SG.
The 4MSDS project concerned the optical missions METimage and 3MI and the generation of appropriate test data to support the ground processor development. Given the EPS-SG orbit and instrument viewing geometries, top of the atmosphere (TOA) radiances for the full range of representative atmospheric and surface conditions were generated for each instrument.
For this purpose, full orbit propagation were performed based on 3 test orbits derived from EPS orbital parameters.
Observation geometries (sensor reference frame) for 3MI and METimage were simulated based on instrument sampling characteristics.
Geolocation and sampling geometries were used as input to radiative transfer simulator in which surface and atmosphere (clouds, aerosols, gas)
were realistically described based on ancillary information obtained for dates and time of required simulation (among which AVHRR products for clouds, MACC reanalysis for aerosols, ECMWF reanalysis for atmospheric state, MODIS BRDF parameters for land properties).
The simulated TOA radiances were generated at level 1b, equivalent to the calibrated and geolocated measurements.
The project was driven by the Laboratoire d'Optique Atmosphérique.
HYGEOS was in charge to develop and run the radiance simulator. The starting point was a set of ancillary data (e.g. cloud optical depth, effective radius and altitude, aerosol optical depth and type, surface BRDF parameters...) and a set of sun and view geometries. These were provided as geolocated 1b grid. The simulator then (i) read these input for each pixel, (ii) run the radiative transfer solving (using the ARTDECO package) and (iii) writes the result into a corresponding level 1b grid. The parallelization of that computation was necessary due to the high CPU demand of radiative transfer solvers in absorbing and scattering atmosphere.
3MI synthetic data. Left panel is 865 nm total intensity.
The Right panel is 865 nm polarized intensity. G, CB and BS stand for Glitter, Cloud Bow and Back-Scattering, respectively.
Contour lines show the scattering angle.
METimage synthetic data RGB. Left panel is a composite of 670 nm (red), 555 nm (green) and 443 nm (blue).
The Right panel is a composite of 2250 nm (red), 1630 nm (green) and 865 nm (blue).
METimage synthetic data RGB. Red is 670 nm , green is 555 nm and blue is 443 nm.
One tile appearing corresponds rougthly to 5 minutes observation.
Contact at Hygeos: Mathieu Compiègne