Other
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21715705z&link_type=abstract
American Astronomical Society, AAS Meeting #217, #157.05; Bulletin of the American Astronomical Society, Vol. 43, 2011
Other
Scientific paper
We present initial results of combined lidar and all-sky thermal infrared camera measurements of transmission losses through clouds. Thermal IR observations in the 10 micron window have long been used at observatories to detect the presence of clouds by measuring the contrast in downwelling thermal radiation between clear and cloudy sky. The ability of these techniques to measure thin cirrus at high altitudes, the sort of clouds that typically ruin otherwise photometric conditions, has always been limited due to their low temperature and low emissivity. Lidar, on the other hand, is quite effective at measuring both the presence and optical depth of thin cirrus clouds, well below 1% transmission losses. A lidar can only operate in one direction at a time and thus is limited in its ability to measure transmission over wide fields of view. The combination of wide field thermal IR imaging plus lidar measurements of transmission hold significant promise for helping solve the time and field dependence of atmospheric transmission caused by clouds, especially sub-visual cirrus.
To test this instrumental combination, the LSST all-sky infrared camera was deployed for several weeks at the UNM Campus Observatory in Albuquerque, NM, the location of the Astronomical Lidar for Extinction (ALE). The two instruments were operated together under various cloud cover conditions and when conditions permitted, narrowband photometry of bright stars was simultaneously obtained to verify the temporal and spatial variation of extinction.
MAP atmospheric transmission research is supported by NIST Award 60NANB9D9121 and NSF Grant AST-1009878.
McGraw John T.
Sebag Julien
UNM Measurement Astrophysics MAP Research Group
Vorobiev D. V.
Zimmer Peter C.
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