Dr. Llewellyn is head of the InfraRed Group in the Institute of Space and Atmospheric Studies at the University of Saskatchewan. He is also the Principal Investigator for the OSIRIS instrument on the Odin satellite. Dr. Llewellyn's research specialization and expertise is optical aeronomy, with particular emphasis on the use of airglow emissions to derive atmospheric state parameters, and on the interaction of spacecraft in low Earth orbit with the atmosphere. He is a co-Investigator for the WINDII instrument on the UARS spacecraft. He was a co-discoverer (with Drs. W.F.J. Evans, D.M. Hunten and A. Vallance Jones) of the upper ozone layer; together with Drs. R.G.H. Greer, G. Witt, J. Stegman and B.H. Solheim he developed the idea that both the oxygen green line and the low energy molecular oxygen states are excited by energy transfer. Together with Dr. I.C. McDade he has developed a set of mechanistic rate constants that can describe the airglow excitation of oxygen. He has also developed, with Dr. McDade, a new description of the processes controlling the collisional relaxation of vibrationally excited OH. Another aspect of that collaboration has been the development of a tomographic analysis system that can improve our understanding of airglow distributions.

While Dr. Llewellyn has been extensively involved with research intended to improve our understanding of the excitation mechanisms for the various airglow emissions most of the current research efforts are directed toward Odin and in particular the OSIRIS instrument, an optical spectrograph and infrared imager, on that satellite. The infrared imager will make observations that will allow the application of tomographic techniques to the measurement of the oxygen infrared atmospheric bands. However, as the Odin satellite measurements must also be validated there is an on-going research effort to provide the appropriate measurements. New instrumentation is being developed to measure the twilight sky spectrum in order to determine the atmospheric temperature profile and aerosol content. This instrumentation will also be used to study impact of the Ring effect on some of the atmospheric absorption bands. column. Other related work is involved with the design of new instrumentation that can be used to make spectral tomographic measurements that provide improved knowledge of the atmospheric state parameters.

Low altitude spacecraft and rockets are frequently enveloped in a vehicle induced glow and, following the discovery that the glow brightness is both species and temperature dependent, Dr. Llewellyn has been involved in an on-going program to use the glow signals as an indicator of the atomic oxygen content of the mesosphere and lower thermosphere. This work is continuing through the inclusion of photometers on a number of sounding rocket payloads.