Submillimeter Wave Astronomy Satellite
Illustration of SWAS
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| Names | Explorer-74, SMEX-3 |
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| Mission type | Submillimeter astronomy |
| Operator | NASA / Goddard |
| COSPAR ID | 1998-071A |
| SATCAT no. | 25560 |
| Website | https://www.cfa.harvard.edu/swas/ |
| Mission duration | Planned: 2 years Final: 6 years, 8 months and 26 days |
| Spacecraft properties | |
| Manufacturer | NASA / Goddard |
| Launch mass | 288 kg (635 lb) |
| Payload mass | 102 kg (225 lb) |
| Dimensions | 1.63 × 1.02 m (5.3 × 3.3 ft) |
| Power | 230 W |
| Start of mission | |
| Launch date | December 6, 1998, 00:57 UTC |
| Rocket | Pegasus XL |
| Launch site | Stargazer, Vandenberg AFB |
| Contractor | Orbital Sciences |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Low Earth |
| Semi-major axis | 6,968.1 km (4,329.8 mi) |
| Eccentricity | 0.0005458 |
| Perigee | 586.2 km (364.2 mi) |
| Apogee | 593.8 km (369.0 mi) |
| Inclination | 69.8979° |
| Period | 96.4833 min |
| RAAN | 85.8457° |
| Argument of perigee | 74.6613° |
| Mean anomaly | 285.5145° |
| Mean motion | 14.9254 rev/day |
| Epoch | September 9, 2015, 13:11:43 UTC |
| Revolution no. | 90902 |
| Main telescope | |
| Name | Submillimeter Wave Telescope |
| Type | Cassegrain |
| Diameter | 55 × 71 cm (22 × 28 in) |
| Wavelengths | 540-610 μm |
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The Submillimeter Wave Astronomy Satellite (SWAS) is a NASA submillimeter astronomy satellite, and is the third spacecraft in the Small Explorer program. It was launched on December 6, 1998 (UTC), from Vandenberg Air Force Base aboard a Pegasus XL rocket. The telescope was designed by the Smithsonian Astrophysical Observatory and integrated by Ball Aerospace, while the spacecraft was built by NASA's Goddard Space Flight Center. The mission's principal investigator is Gary J. Melnick.
SWAS was designed to study the composition and structure of interstellar clouds and investigate the processes of stellar and planetary formation. Its sole instrument is a telescope operating in the submillimeter wavelengths of far infrared and microwave radiation. The telescope is composed of three main components: a 55 × 71 cm (22 × 28 in) elliptical off-axis Cassegrain reflector, two Schottky diode receivers, and an acousto-optical spectrometer. The system is sensitive to frequencies between 487–557 GHz (538–616 μm), which allows it to focus on the spectral lines of molecular oxygen (O2) at 487.249 GHz; neutral carbon (C i) at 492.161 GHz; isotopic water (H218O) at 548.676 GHz; isotopic carbon monoxide (13CO) at 550.927 GHz; and water (H2O) at 556.936 GHz.
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