The NASA SWAS was launched in 1998 on a two-year mission to observe mainly interstellar dust clouds at submillimeter wavelengths from 487 GHz to 557 GHz (540-620 ^m, 16.2-18.6 cm-1). The wavelength region was chosen to search for emission lines of water vapor and SWAS detected water in almost every dust cloud that it observed, a key indicator in the cooling process of these clouds that eventually leads to their collapse to form stars. In addition to these observations, SWAS also observed water vapor emission lines from Jupiter (Lellouch et al., 2002).
SWAS was launched into a 600 km altitude near-polar orbit; its primary mirror was 0.68 x 0.58 m in size and its total mass was 288 kg. Hence, SWAS was a reasonably small spacecraft, but provided a valuable precursor to future far-IR/submilli-meter missions such as the Herschel Space Observatory, described in Chapter 8.
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