Spatial Heterodyne Spectroscopy of NASA Deep Impact Encounter With Comet Tempel 1

Comets are the oldest and least modified bodies orbiting the sun, and investigations into their composition are a key to understanding the development of the early solar system. Studying the daughters of photochemical reactions occurring within a comet's coma provides information concerning the composition and other important properties, such as density and temperature. These can eventually be inverted to give a formation location within the solar nebula. The surface of comet 9P/Tempel 1 is highly evolved by the short-period comet's many revolutions around the sun, rendering it relatively inactive. However, the objective of the NASA mission Deep Impact is to discover what occurs when a manmade projectile impacts upon the nucleus of comet 9P/Tempel 1 and exposes fresh, pristine material. We report here on observations of diagnostic volatile species obtained from 9P/Tempel 1 using a spatial heterodyne spectrometer at the McMath-Pierce solar telescope on Kitt Peak, including C3, CN, and OI. SHS is a new technology, ideal for the study of faint diffuse targets at high spectral resolution, due to its ability to combine the latter quantity with a large field of view and consequently a high etendue. Two prototype instruments were used in the Kitt Peak program to study coma emissions from multiple volatile species over a two arc minute field of view and a spectral resolution of from 80000 to 180000. We present the first evaluation of the spectra obtained and the performance of these instruments, especially in the context of their ability to observe comets and the effects of a collision on gas production.