Result: Ultraviolet remote sensing techniques for planetary aeronomy

This paper presents an overview of the principles of the study of planetary atmospheres at vacuum ultraviolet wavelengths. Ultraviolet (UV) remote sensing is a powerful technique for investigating the chemistry, dynamics, energetics, and composition of planetary atmospheres. In the last fifteen years optical aeronomy has undergone a profound change. The field has begun the transformation from initial spectroscopy, in which the radiating species and their signatures are identified, to remote sensing in which the signatures are used to provide quantitative information on a global basis. This transformation has occurred as UV spectra of nearly all major planetary bodies have been obtained, either by flyby spacecraft or Earth-orbiting observatories, and the basic composition of their atmospheres is now known. We present an historical overview to show how improvements in technology have led to improved measurements. The UV is an ideal region of the spectrum for remotely sensing planetary atmospheres due to the large absorption cross sections exhibited by most of the major species and the prevalence of emission features. The flight of lightweight, compact sensors permits sensitive measurements of the upper atmospheres of the major planets and Titan, and the thin atmospheres of Mercury and Pluto as well as several planetary satellites.