Far Ultraviolet Spectroscopic Explorer
FUSE in a pre-launch cleanroom
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| Names | Explorer 77 MIDEX-0 |
|---|---|
| Mission type | Ultraviolet astronomy |
| Operator | NASA / JHUAPL |
| COSPAR ID | 1999-035A |
| SATCAT no. | 25791 |
| Website | http://fuse.pha.jhu.edu/ |
| Mission duration | Planned: 3 years Final: 8 years, 3 months, 23 days |
| Spacecraft properties | |
| Manufacturer | Orbital Sciences / JHUAPL |
| Launch mass | 1,360 kg (3,000 lb) |
| Dimensions | 5.3 × 1.9 m (17.4 × 6.2 ft) |
| Power | Average: 520 watts Peak: 645 watts |
| Start of mission | |
| Launch date | 24 June 1999, 15:44 UTC |
| Rocket | Delta II 7320-10 |
| Launch site | Cape Canaveral AFS SLC-17A |
| End of mission | |
| Disposal | Decommissioned |
| Deactivated | 18 October 2007 |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Low Earth |
| Semi-major axis | 7,127.8 km (4,429.0 mi) |
| Eccentricity | 0.0010062 |
| Perigee | 742.5 km (461.4 mi) |
| Apogee | 756.8 km (470.3 mi) |
| Inclination | 24.9836° |
| Period | 99.8 minutes |
| RAAN | 129.8201° |
| Argument of perigee | 246.2689° |
| Mean anomaly | 113.6763° |
| Mean motion | 14.43 rev/day |
| Epoch | 18 April 2016, 11:52:03 UTC |
| Main | |
| Wavelengths | 90.5 to 119.5 nm (far ultraviolet) |
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The Far Ultraviolet Spectroscopic Explorer (FUSE) is a space-based telescope operated by the Johns Hopkins University Applied Physics Laboratory. FUSE was launched on a Delta II rocket on 24 June 1999, as a part of NASA's Origins program. FUSE detected light in the far ultraviolet portion of the electromagnetic spectrum, between 90.5-119.5 nanometres, which is mostly unobservable by other telescopes. Its primary mission was to characterize universal deuterium in an effort to learn about the stellar processing times of deuterium left over from the Big Bang. FUSE resides in a low Earth orbit, approximately 760 km (410 nmi) in altitude, with an inclination of 25 degrees and just less than a 100-minute orbital period. Its Explorer designation is Explorer 77.
On 12 July 2007, FUSE's final reaction wheel, which is required for accurately pointing a spacecraft, failed and efforts to restart it were unsuccessful. An announcement was made on 6 September that because the fine control needed to perform its mission had been lost, the FUSE mission would be terminated.
Although the original specification was to have a Wolter-type grazing incidence telescope, the final design of the FUSE telescope comprises four individual mirrors. Each of the four mirrors is a 39-by-35 cm (15.4-by-13.8 in) off-axis parabola. Two mirror segments are coated with silicon carbide for reflectivity at the shortest ultraviolet wavelengths, and two mirror segments are coated with lithium fluoride over aluminum that reflects better at longer wavelengths. This optimizes performance over the entire spectral range.
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