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SWAS mission graphic

Submillimeter Wave Astronomy Satellite

Phase: Past

Launch Date: December 06, 1998

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Program(s):Astrophysics Explorers, Explorers

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The Submillimeter Wave Astronomy Satellite (SWAS) was launched from a Pegasus-XL vehicle into low Earth orbit. A small Explorer Program (SMEX) mission originally planned for two-year, SWAS made observations until July 21, 2004. The goal of the mission was to gain a greater understanding of star formation by determining the composition of interstellar clouds and establishing the means by which these clouds cool as they collapse to form stars and planets.

SWAS was a complete radio telescope in space. It had a 55 x 71 cm elliptical off-axis Cassegrain telescope with a beam width of 4 arcminutes at its operating frequencies. The submillimeter radiometers were a pair of passively cooled subharmonic Schottky diode receivers, with receiver noise figures of 2500-3000 K. The outputs of the two SWAS receivers were combined to form a final intermediate frequency, which extends from 1.4 to 2.8 GHz.

Science Highlights

After over six years of science observations, SWAS achieved and exceeded its original scientific goals. It made detailed 1 degree x 1 degree maps of many giant molecular and dark cloud cores. It observed the atmospheres of Mars, Jupiter, Saturn and several comets. Other SWAS discoveries include:

  • Water, a key component for life, is prevalent throughout space. Water was detected in almost every dust cloud in space observed. High amounts of water were found in warm gas, while very low amounts of water were seen in cold dense gas.
  • Provided the most precise measurements of water vapor in interstellar clouds and established the tightest limits on the maximum amount of molecular oxygen that might be in these clouds.
  • A swarm of comets were discovered evaporating around an aging red giant star.
  • In June 2005, the spacecraft was reactivated for a 3 month period after a year of stand-by operation. SWAS observed the effects of the Deep Impact probe's collision with Comet P/Tempel 1. Measurements indicated that the comet was ejecting about 730 pounds of water per second.

Last updated: June 3, 2015