The Submillimeter Wave Astronomy Satellite

Abstract

The Submillimeter Wave Astronomy Satellite (SWAS) is a NASA Small-Explorer Class experiment whose objective is to study both the chemical composition and the thermal balance in dense (N_H2 > 10³ cm⁻³) molecular clouds and, by observing many clouds throughout our galaxy, relate these conditions to the processes of star formation. To conduct this study SWAS will be capable of carrying out both pointed and scanning observations simultaneously in the lines of four important species: (1) the H₂O (1₁₀–1₀₁) 556.963 GHz ground-state ortho transition, (2) the O₂ (3,3–1,2) 487.249 GHz transition, (3) the CI (³P₁ – ³P₀) 492.162 GHz ground-state fine structure transition, and (4) the ¹³CO (J = 5–4) 550.926 GHz rotational transition. These atoms and molecules are predicted to be among the most abundant within molecular clouds and, because they possess low-lying transitions with energy differences (ΔE/k) between 15 and 30K (temperatures typical of many molecular clouds), these species are believed to be dominant coolants of the gas as it collapses to form stars and planets. A large-scale survey in these lines is virtually impossible from any platform within the atmosphere due to telluric absorption.