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Far Ultraviolet Spectroscopic Explorer
From Wikipedia, the free encyclopedia
 FUSE |
|
| Organization | Johns Hopkins University APL, NASA |
|---|---|
| Wavelength regime | 90–120 nm |
| Orbit height | 773 km |
| Orbit period | 100.06 minutes |
| Launch | June 24, 1999 on a Delta II |
| Launch site | Cape Canaveral |
| Deorbit date | |
| Mission duration | 3 years [1] |
| Mass | 1360 kg (launch), 580 kg (dry) |
| Webpage | http://fuse.pha.jhu.edu/ |
| Physical characteristics | |
| Telescope style | |
| Diameter | |
| Collecting area | |
| Focal length | |
FUSE, the Far Ultraviolet Spectroscopic Explorer, is a space-based telescope run by the Johns Hopkins University. FUSE was launched on a Delta II rocket on June 24, 1999, as a part of NASA's Origins project, and as of October 2006 is still functioning [2]. Its Explorer designation is Explorer 77. FUSE is in a low-earth orbit, roughly 475 miles up with an inclination of 25 degrees and 100 minute orbital period.
FUSE looks at light in the far ultraviolet portion of the electromagnetic spectrum, between 90 to 120 nanometers, which is unobservable with other telescopes. Its primary mission is to characterize universal deuterium, in an effort to learn about the stellar processing times of the deuterium left over from the Big Bang.
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 cm by 35 cm 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 the performance over the entire spectral range.
Each mirror has a corresponding astigmatism-corrected, holographically-ruled diffraction grating, each one on a curved substrate so as to produce four 1.65 meter Rowland circle spectrographs. The dispersed ultraviolet light is detected by two microchannel plate intensified double delay-line detectors, whose surfaces are curved to match the curvature of the focal plane.
Over 400 scientific papers have been written using data from FUSE [3], with subjects ranging from cool stars to the intergalactic medium. One of the primary science goals of FUSE was to study the abundance of deuterium, an isotope of hydrogen. Because of the large number of atomic absorption and emission lines in the far-ultraviolet, FUSE enabled many studies of Galactic, extragalactic and intergalactic chemistry and chemical evolution.