Geostationary Emission Explorer for Europe (G3E): mission concept and initial performance assessment
The Geostationary Emission Explorer for Europe (G3E) is a concept for a geostationary satellite sounder that aims to constrain the sources and sinks of greenhouse gases carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>) for continental-scale regions. Its primary foc...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-11-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/8/4719/2015/amt-8-4719-2015.pdf |
| Summary: | The Geostationary Emission Explorer for Europe (G3E) is a concept for
a geostationary satellite sounder that aims to constrain the sources
and sinks of greenhouse gases carbon dioxide (CO<sub>2</sub>) and methane
(CH<sub>4</sub>) for continental-scale regions. Its primary focus is on
central Europe. G3E carries a spectrometer system that collects sunlight
backscattered from the Earth's surface and atmosphere in the near-infrared
(NIR) and shortwave-infrared (SWIR) spectral range. Solar absorption spectra
allow for spatiotemporally dense observations of the column-average
concentrations of carbon dioxide (XCO<sub>2</sub>), methane (XCH<sub>4</sub>), and carbon
monoxide (XCO). The mission concept in particular facilitates sampling of the diurnal variation with several measurements per day during summer.
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Here, we present the mission concept and carry out an initial performance
assessment of the retrieval capabilities. The radiometric performance of the
4 grating spectrometers is tuned to reconcile small ground-pixel sizes
(~2 km × 3 km at 50° latitude) with short
single-shot exposures (~2.9 s) that allow for sampling
continental regions such as central Europe within 2 h while providing
a sufficient signal-to-noise ratio. The noise errors to be expected for XCO<sub>2</sub>,
XCH<sub>4</sub>, and XCO are assessed through retrieval simulations for a European
trial ensemble. Generally, single-shot precision for the targeted XCO<sub>2</sub> and
XCH<sub>4</sub> is better than 0.5 % with some exception for scenes with low
infrared surface albedo observed under low sun conditions in winter. For XCO,
precision is generally better than 10 %. Performance for aerosol and
cirrus loaded atmospheres is assessed by mimicking G3E's slant view on Europe
for an ensemble of atmospheric scattering properties used previously for
evaluating nadir-viewing low-Earth-orbit (LEO) satellites. While retrieval
concepts developed for LEO configurations generally succeed in mitigating
aerosol- and cirrus-induced retrieval errors for G3E's setup, residual errors
are somewhat greater in geostationary orbit (GEO) than in LEO. G3E's
deployment in the vicinity of the Meteosat Third Generation (MTG) satellites
has the potential to make synergistic use of MTG's sounding capabilities e.g. with
respect to characterization of aerosol and cloud properties or with respect
to enhancing carbon monoxide retrievals by combining G3E's solar and MTG's
thermal infrared spectra. |
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| ISSN: | 1867-1381 1867-8548 |