Airglow In The Presence and Absence of Pmc As Observed With Osiris On Odin

The Odin research satellite [jointly funded by Sweden (SNSB), Canada (CSA), Finland (Tekes) and France (CNES)] was launched in February 2001 into a sun- synchronous terminator orbit with the ascending node at 1800LT. Since that time it has provided more than 3000 orbits of limb-scan data. Odin carries two instruments: a submm/mm radiometer and an Optical Spectrograph and Infrared Imaging System (OSIRIS). The Optical Spectrograph measures the atmospheric limb spectrum from 280 nm to 800 nm, every 1 - 2 seconds with a spectral resolution of 1 nm. Most of the time OSIRIS is operating in either the mesospheric or stratospheric mode, making continuous limb scans at a constant angular velocity over the altitude range 70 km U

100 km, and 6 km U 60 km respectively.

During Summer 2001 OSIRIS detected Polar Mesospheric Clouds (PMCs) in more than 200 scans over the northern polar region between 64 N and 82 N, and during the December 2001 U January 2002 period has detected many PMCs in the south-

ern hemisphere. The broad spectral range and the 1 nm spectral resolution of OSIRIS make it possible to measure many atmospheric absorption/emission features at differ- ent altitudes. These features include the oxygen A-band, the sodium emission line, the atomic oxygen green and red lines. This work presents the first results of the analy- sis of airglow emission features in the polar summer mesosphere, using the detected PMCs as an indirect indicator of the mesospheric temperature.