The value of darkness
The passage of time brings the oncoming darkness; the 8th of February marked the end of eternal light with the official start of twilight at Davis.
The atmospheric research group runs several experiments in the dark. Most of these focus on the hydroxyl layer in the upper atmosphere. This area of the atmosphere glows very faintly green but also more strongly in the infrared spectrum. By the use of specialist instruments and filters we can observe this glow and determine information about that region of the atmosphere.
A significant experiment is the Czerny Turner Spectrometer which has been measuring the temperature of the hydroxyl layer since 1993. This experiment was disabled during the summer for calibration and improvements and has now started back up.
Another experiment, UWOSCR (University of Western Ontario Scanning Radiometer), was installed in 1998 after spending several years in France. It scans the sky +/- 8 degrees from the zenith recording the light intensity of the hydroxyl layer to record images of the horizontal structure. Due to the sensitivity of the camera it's covered each summer and only operates after dark.
We also have two CCD camera based systems which are running this year. One is part of the collaboration with the German based IAP (Leibniz-Institute of Atmospheric Physics).
The other in collaboration with Utah State University. Both of these are looking to study gravity waves propagating through the layer.
Our last experiment, the Fabry-Perot Spectrometer, in collaboration with La Trobe University, requires a little more darkness before it can operate.
(Photo: David Tulloh)