Submillimeter Wave Astronomy Satellite

Submillimeter Wave Astronomy Satellite
Name	Submillimeter Wave Astronomy Satellite
Acronym	SWAS
Operator	NASA / Smithsonian Astrophysical Observatory
Mission type	Astronomy
Launch date	1998-12-05
Launch vehicle	Delta II
Launch site	Cape Canaveral Space Force Station
Orbit	Low Earth orbit
Mass	370 kg
Instruments	Submillimeter spectrometer

Submillimeter Wave Astronomy Satellite The Submillimeter Wave Astronomy Satellite was a small observatory developed by NASA in collaboration with the Smithsonian Astrophysical Observatory to perform high-resolution spectroscopy in the submillimeter band, focusing on interstellar chemistry and star formation. It complemented contemporary missions such as Hubble Space Telescope, Chandra X-ray Observatory, Far Ultraviolet Spectroscopic Explorer, and ground facilities like Atacama Large Millimeter/submillimeter Array and James Clerk Maxwell Telescope. The project drew on institutional expertise from Jet Propulsion Laboratory, Goddard Space Flight Center, and academic partners including Harvard University and California Institute of Technology.

Overview

SWAS was conceived amid advances in submillimeter technology pioneered at institutions such as Ball Aerospace, Jet Propulsion Laboratory, and Lockheed Martin, and it flew as a Small Explorer program mission overseen by NASA and operated by the Smithsonian Astrophysical Observatory. The satellite carried a heterodyne receiver designed to measure spectral lines of species including water, molecular oxygen, atomic carbon, and carbon monoxide, leveraging detector developments from laboratories at Massachusetts Institute of Technology, University of Chicago, and University of Arizona. The mission fit within a lineage of spaceborne observatories including Infrared Astronomical Satellite, COBE, and Infrared Space Observatory.

Mission Objectives and Scientific Goals

Primary goals emphasized astrochemistry and star formation research, aligning with thematic priorities set by panels from the National Academy of Sciences and the Astronomy and Astrophysics Decadal Survey. Objectives included measuring the abundance and distribution of water vapor in molecular clouds associated with regions such as Orion Nebula, Taurus Molecular Cloud, and Rho Ophiuchi Cloud Complex; probing cooling processes through lines seen in targets like Sagittarius B2 and the Galactic Center; and constraining chemical models developed at Princeton University, University of Cambridge, and Max Planck Institute for Astronomy. SWAS aimed to test predictions from theoretical frameworks advanced by researchers affiliated with California Institute of Technology and University of California, Berkeley.

Spacecraft Design and Instruments

The spacecraft bus combined components from firms like TRW Inc. and instrument subsystems built with contribution from teams at Johns Hopkins University and University of Maryland. The science payload centered on a submillimeter heterodyne spectrometer, employing mixers and local oscillator systems developed through partnerships with MIT Lincoln Laboratory and Rutherford Appleton Laboratory. The detector suite targeted spectral lines including the 557 GHz water line, transitions of carbon monoxide at millimeter wavelengths, and the fine-structure line of neutral atomic carbon, with calibration traceable to standards used at National Institute of Standards and Technology. Thermal and attitude control solutions leveraged heritage from missions such as Windsat and engineering practices from Goddard Space Flight Center.

Launch and Mission Timeline

SWAS launched on a Delta II rocket from Cape Canaveral Space Force Station in December 1998, alongside operational milestones coordinated with NASA Kennedy Space Center launch operations and mission planning at the Smithsonian Astrophysical Observatory. The satellite entered a low Earth orbit and completed an initial commissioning phase involving teams at Jet Propulsion Laboratory and the Massachusetts Institute of Technology. Routine science operations extended through the early 2000s, incorporating collaborative observation campaigns with ground arrays such as IRAM and space observatories including Herschel Space Observatory and Spitzer Space Telescope. Mission timelines were reported to advisory committees at the National Academy of Sciences and monitored by program offices at NASA Headquarters.

Scientific Results and Discoveries

SWAS produced seminal measurements of water vapor in cold molecular clouds, revealing unexpectedly low abundance in regions surveyed in Orion and Taurus, findings that informed chemical models created by groups at Harvard-Smithsonian Center for Astrophysics, Max Planck Institute for Radio Astronomy, and University College London. The detection limits for molecular oxygen helped reconcile discrepancies between theory and observations in papers from researchers at Princeton University and University of Cambridge. Measurements of atomic carbon and carbon monoxide cooling lines provided constraints used by teams at Caltech and University of Chicago in studies of cloud energetics and collapse. SWAS data contributed to multiwavelength campaigns with Hubble Space Telescope imaging and Chandra X-ray Observatory spectroscopy to study protostellar evolution in regions such as Perseus Molecular Cloud and Serpens Cloud. Results were cited in work by authors affiliated with Stanford University, University of Colorado Boulder, and University of Toronto.

Legacy and Impact on Submillimeter Astronomy

The mission paved the way for successor projects and influenced instrument design for missions like Herschel Space Observatory, ground facilities such as ALMA, and technology development at Ball Aerospace and Northrop Grumman. SWAS fostered collaborations linking institutions including Smithsonian Astrophysical Observatory, NASA Jet Propulsion Laboratory, Max Planck Society, and universities across the United States and Europe, and its datasets remain in archives accessed alongside surveys from Sloan Digital Sky Survey and Two Micron All Sky Survey. The mission advanced understanding in astrochemistry, informed proposals reviewed by panels at the National Science Foundation, and trained scientists now at institutions such as University of California, Santa Cruz and University of Michigan.

Category:NASA spacecraft Category:Space telescopes Category:Astronomy satellites