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| Titel |
The Orbiting Carbon Observatory (OCO-2): spectrometer performance evaluation using pre-launch direct sun measurements |
| VerfasserIn |
C. Frankenberg, R. Pollock, R. A. M. Lee, R. Rosenberg, J.-F. Blavier, D. Crisp, C. W. O'Dell, G. B. Osterman, C. Roehl, P. O. Wennberg, D. Wunch |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 1 ; Nr. 8, no. 1 (2015-01-14), S.301-313 |
| Datensatznummer |
250116053
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| Publikation (Nr.) |
 copernicus.org/amt-8-301-2015.pdf |
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| Zusammenfassung |
| The Orbiting Carbon Observatory-2 (OCO-2), launched on 2 July 2014, is a NASA
mission designed to measure the column-averaged CO2 dry air mole fraction,
XCO2. Towards that goal, it will collect spectra of reflected
sunlight in narrow spectral ranges centered at 0.76, 1.6 and
2.0 μm with a resolving power (λ/Δ λ) of
20 000. These spectra will be used in an optimal estimation framework to
retrieve XCO2. About 100 000 cloud free soundings of
XCO2 each day will allow estimates of net CO2 fluxes on
regional to continental scales to be determined. Here, we evaluate the OCO-2
spectrometer performance using pre-launch data acquired during instrument
thermal vacuum tests in April 2012. A heliostat and a diffuser plate were
used to feed direct sunlight into the OCO-2 instrument and spectra were
recorded. These spectra were compared to those collected concurrently from a
nearby high-resolution Fourier Transform Spectrometer that was part of the
Total Carbon Column Observing Network (TCCON). Using the launch-ready OCO-2
calibration and spectroscopic parameters, we performed total column scaling
fits to all spectral bands and compared these to TCCON results. On 20 April,
we detected a CO2 plume from the Los Angeles basin at the JPL site with
strongly enhanced short-term variability on the order of 1% (3–4 ppm).
We also found good (< 0.5 ppm) inter-footprint consistency in retrieved
XCO2. The variations in spectral fitting residuals are
consistent with signal-to-noise estimates from instrument calibration, while
average residuals are systematic and mostly attributable to remaining errors
in our knowledge of the CO2 and O2 spectroscopic parameters. A few
remaining inconsistencies observed during the tests may be attributable to
the specific instrument setup on the ground and will be re-evaluated with
in-orbit data. |
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