SIMBAD references

The Submillimeter Wave Astronomy Satellite (SWAS), launched in 1998 December, is a NASA mission dedicated to the study of star formation through direct measurements of (1) molecular cloud composition and chemistry, (2) the cooling mechanisms that facilitate cloud collapse, and (3) the large-scale structure of the UV-illuminated cloud surfaces. To achieve these goals, SWAS is conducting pointed observations of dense [n(H₂)>10³ cm^–3] molecular clouds throughout our Galaxy in either the ground state or a low-lying transition of five astrophysically important species: H₂O, H₂¹⁸O, O₂, C I, and ¹³CO. By observing these lines SWAS is (1) testing long-standing theories that predict that these species are the dominant coolants of molecular clouds during the early stages of their collapse to form stars and planets and (2) supplying previously missing information about the abundance of key species central to the chemical models of dense interstellar gas. SWAS carries two independent Schottky barrier diode mixers–passively cooled to ∼175 K–coupled to a 54x68 cm off-axis Cassegrain antenna with an aggregate surface error ∼11 µm rms. During its baseline 3 yr mission, SWAS is observing giant and dark cloud cores with the goal of detecting or setting an upper limit on the water and molecular oxygen abundance of 3x10^–6 (relative to H₂). In addition, advantage is being taken of SWAS's relatively large beam size of 3'.3x4'.5 at 553 GHz and 3'.5x5'.0 at 490 GHz to obtain large-area (∼1°x1°) maps of giant and dark clouds in the ¹³CO and C I lines. With the use of a 1.4 GHz bandwidth acousto-optical spectrometer, SWAS has the ability to simultaneously observe either the H₂O, O₂, C I, and ¹³CO lines or the H₂¹⁸O, O₂, and C I lines. All measurements are being conducted with a velocity resolution less than 1 km.s^–1.