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| Titel |
Sensitivity studies for a space-based methane lidar mission |
| VerfasserIn |
C. Kiemle, M. Quatrevalet, G. Ehret, A. Amediek, A. Fix, M. Wirth |
| 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 ; 4, no. 10 ; Nr. 4, no. 10 (2011-10-18), S.2195-2211 |
| Datensatznummer |
250002118
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| Publikation (Nr.) |
 copernicus.org/amt-4-2195-2011.pdf |
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| Zusammenfassung |
| Methane is the third most important greenhouse gas in the atmosphere after
water vapour and carbon dioxide. A major handicap to quantify the emissions
at the Earth's surface in order to better understand biosphere-atmosphere
exchange processes and potential climate feedbacks is the lack of accurate
and global observations of methane. Space-based integrated path differential
absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote
Lidar Mission (MERLIN) on a small satellite in polar orbit was proposed by
DLR and CNES in the frame of a German-French climate monitoring initiative.
System simulations are used to identify key performance parameters and to
find an advantageous instrument configuration, given the environmental,
technological, and budget constraints. The sensitivity studies use
representative averages of the atmospheric and surface state to estimate the
measurement precision, i.e. the random uncertainty due to instrument noise.
Key performance parameters for MERLIN are average laser power, telescope
size, orbit height, surface reflectance, and detector noise. A modest-size
lidar instrument with 0.45 W average laser power and 0.55 m telescope
diameter on a 506 km orbit could provide 50-km averaged methane column
measurement along the sub-satellite track with a precision of about 1%
over vegetation. The use of a methane absorption trough at 1.65 μm
improves the near-surface measurement sensitivity and vastly relaxes the
wavelength stability requirement that was identified as one of the major
technological risks in the pre-phase A studies for A-SCOPE, a space-based
IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity
and temperature sensitivity at this wavelength position will enable accurate
measurements in tropical wetlands, key regions with largely uncertain
methane emissions. In contrast to actual passive remote sensors,
measurements in Polar Regions will be possible and biases due to aerosol
layers and thin ice clouds will be minimised. |
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