THE INFRARED and AERONOMY GROUP

Prof. Ted Llewellyn.

This group is involved in studies of atmospheric remote sensing, the airglow and the aurora in the terrestrial atmosphere. The airglow studies are primarily directed toward an interpretation of the observations of the emissions from atomic and molecular oxygen, in the altitude region between 40 and 110 km. The objective of the work is:

  1. to follow variations in the atomic oxygen density in the mesosphere/lower thermosphere interface region;
  2. to understand the reaction paths and kinetics responsible for these emissions in the airglow.
  3. to provide an improved understanding of ozone depletion at high altitude.

The necessary observations for these studies are obtained from satellites (Shuttle and WINDII on UARS), rockets (the ETON, OASIS and GEMINI campaigns) and from ground based photometric studies in the high Arctic. These latter observations use the airglow to provide a monitor of the high altitude ozone concentration, and to determine the altitude extent of the ozone depletion at high latitude. New work on ozone depletion at high latitudes that will use measurements from the ODIN satellite are also being undertaken. This Swedish satellite , which is scheduled for launching in 1998, includes a uv/visible spectrograph and IR imager (OSIRIS), provided by Canada, that will provide information on the concentrations of chemically active species. Dr. Llewellyn is the Principal Investigator (P.I.) for the OSIRIS instrument.

The auroral investigations are designed to enhance our understanding of the reaction/excitation mechanisms for the visible and near infrared emissions. In an effort to overcome the non-simultaneity of the optical and particle measurements the work also involves the on-going improvement of newly developed tomographic methods for non-stationary systems (i.e., a temporally varying aurora). These tomographic techniques are also being modified for use with the ODIN satellite.

The Infrared/Aeronomy group is also involved in studies of spacecraft interactions, notably spacecraft glow. An experiment designed to measure the effect of surface temperature on the glow intensity was flown on Shuttle mission STS-S2 in October 1992. The required man-rated instrumentation for this experiment was developed by members of the group. Some of our previous work on Shuttle glow has shown that much of the required interaction occurs in the gas phase plough cloud that is ahead of the Shuttle, and that the adsorption of the significant molecular species is strongly temperature dependent.

The group includes senior scientists (Drs. Ted Llewellyn, Nick Lloyd, Ildar Khabibrakhmanov and Bill Brooks), Instrumentation Engineers and several graduate students. There are on-going opportunities to develop and characterize new instrumentation for rockets and satellites that will assist in the improvement of required model atmospheres. The group is also responsible for the new CIRA reference model for atomic oxygen.