Equatorial airglow observations


Yi Chung Chiu1, Loren Chang1, J.B. Nee2


1Institute of Space Science, National Central University.

                           2Department of Physics, National Central University


Airglow is a phenomenon caused by chemical reactions in the mesosphere and thermosphere, which emit visible light at specific wavelengths. Airglow can act as a tracer for certain chemical species, and can be used to infer temperature and wind velocity. As preparation for long term ground-based airglow observations in Taiwan, OH airglow near the mesopause (630 nm wavelength) observed by the ISUAL (Imager of the Sprites and Upper Atmospheric Lightning) instrument on board FORMOSAT 2 is analyzed. The satellite is sun-synchronous and ISUAL CCD camera is limb view scan, so we can use these properties to study the vertical structure of the upper atmosphere in detail. In order to avoid noise from sunlight, the scanning region must avoid the summer hemisphere. Due to this reason, the observations in the middle and low latitudes are much better than the regions approaching the pole. OH airglow is at about from 80~90 km altitude, so we can study the phenomenon in mesosphere and lower thermosphere (MLT) region via OH airglow research.

To prepare our long term observation, we combine a photomultiplier tube (PMT), 6 channel filter wheel and Cassegrain reflector into a photometer. Our calibration system includes an integration sphere, monochrometer, and illuminometer to make sure the value we use from photometer is reliable. We will use the airglow data to develop a simple model to measure the concentration of different species chemical elements in upper atmosphere.