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FS-1999 (03)-008-GSFC
Astronomers are embarking on a new study to understand the origin and history of the chemical elements in the Universe, thanks to the unique data which will be obtained by NASA’s Far Ultraviolet Spectroscopic Explorer (FUSE) mission. The FUSE satellite will investigate the lightest elements in the Universe - hydrogen and one of its isotopes, deuterium - created shortly after the Big Bang, and the processes involved in the evolution of the galaxies, stars and planetary systems.
Observations made with the FUSE satellite will enable astronomers to answer several fundamental questions about the Universe. What were the conditions shortly after the Big Bang? What are the properties of interstellar gas clouds that form stars and planetary systems? How are chemical elements made and subsequently dispersed throughout our galaxy?
These goals will be accomplished by recording the far ultraviolet spectrum of hundreds of stars and other astronomical objects. The far ultraviolet is one small portion of the electromagnetic spectrum, of which visible light is also a part. FUSE will be the only current telescope capable of observations at these wavelengths.
FUSE, one of NASA’s Explorer satellites, was built by the Johns Hopkins University (JHU), Baltimore, Md., in collaboration with the Canadien Space Agency and the French Space Agency (CNES), the University of Colorado, and the University of California, Berkeley. The project is managed by NASA’s Goddard Space Flight Center (GSFC), Greenbelt, Md. The FUSE mission and science control center is on the JHU Homewood campus in Baltimore.
The FUSE Mission is designed to address a number of scientific questions with broad applications to astronomy. Astronomers will use FUSE observations to:
* Understand the origin and history of the chemical elements in the Milky Way galaxy and other nearby galaxies, especially the Large and Small Magellanic Clouds;
* Help trace the history of deuterium, a special form of hydrogen, back to its origin in the Big Bang;
* Explore the origin and circulation of hot and cold gas in the Milky Way and the relationship of these gases with the formation of new generations of stars;
* Provide insight into the origin and evolution of our galaxy by studying a wide range of astronomical objects including: hot stars; solar-type stars; remnants of supernova explosions; active nuclei of galaxies and quasars; and planets and comets in the solar system.
The wavelength region FUSE will investigate (90.5-118.5nm) is largely unexplored. In the 1970’s, NASA’s Copernicus satellite opened the Far-UV universe to astronomers by obtaining spectra of bright nearby stars. FUSE, however, will be able to study sources more than 10,000 times fainter and more distant than those observed by the Copernicus mission.
The spectral window opened by FUSE will permit the study of many important atoms, ions, and molecules that cannot be investigated otherwise. The wavelength range that FUSE will explore is extremely rich in spectral lines essential for studying the gas clouds between the stars, the material from which stars and planets are formed.
The FUSE satellite consists of two sections: the spacecraft and the science instrument. The spacecraft contains all the elements necessary for powering and pointing the satellite including: the attitude control system, solar panels, batteries, and communications electronics and antennas. The FUSE spacecraft was built by Orbital Sciences Corp., Germantown, Md.
The science instrument consists of telescope mirrors, the spectrograph, and an electronic guide camera called the Fine Error Sensor (FES). The spacecraft and the science instrument each have their own computers which coordinate the activities of the satellite.
FUSE is designed for a very specialized and unique task which is complementary to other NASA missions. For instance, FUSE looks far into the ultraviolet portion of the spectrum of light extending to shorter ultraviolet wavelengths than can be observed by the Hubble Space Telescope. FUSE provides the combination of much greater sensitivity and higher resolving power than previous space instruments that have used this wavelength range.
FUSE incorporates a number of unique and unusual design features. For example, instead of a single telescope, FUSE uses four mirror sections to focus star light. Two mirrors are coated with a material that has superior reflectivity at the shortest ultraviolet wavelengths (silicon carbide), and two mirrors coated with a different material (lithium fluoride) that reflects better at the longer ultraviolet wavelengths.
These mirrors optimize performance over the entire spectral range of FUSE. Also, FUSE has two sophisticated electronic detectors to "see" the incoming ultraviolet light and record it digitally for transmission to the ground.
The ultraviolet light seen by FUSE is spread into a spectrum by four special optical components called gratings, one for the light from each of the four mirror segments. Each FUSE grating has been etched with over a million fine, parallel grooves. The large number of grooves spread the light into a spectrum and provides the high resolving power that allows FUSE to determine the amounts of the elements present in the direction of the object being studied. The FUSE gratings were built by the French Space Agency.
The FES cameras are the "eyes" of the satellite that provide the precision measurements which control the satellite’s pointing. The FES works in the visible light and images a region about one third of a degree in size surrounding the object being observed. (For comparison, the full moon is about one-half degree in size). The FES will be able to see stars over 10,000 times fainter than those seen with the unaided human eye on a clear night. The FES cameras were built by the Canadian Space Agency.
FUSE is a component of NASA’s Origins program. The Origins Program seeks to explore our galaxy and the Universe to address fundamental questions related to our origins. Some of these questions include:
* How did galaxies form in the early Universe and what role do galaxies play in the appearance of planetary systems and life?
* How do stars and planetary systems form, and are there life-sustaining planets around other stars?
* How did life originate on Earth and does it exist elsewhere in the Universe?
Satellite Dimensions: 1.2m x 1.8m x 5.5m
Weight: 1360 kg (3000lbs)
Launch Vehicle: Delta II rocket
Instrument: High Resolution Spectrograph
Orbit: Circular, 775 km altitude, 25 degree inclination
http://fuse.pha.jhu.edu
http://fusewww.gsfc.nasa.gov/fuse/
http://www.hq.nasa.gov/office/OSS/missions/index.html
http://eis.jpl.nasa.gov/origins/index.html
http://www.gsfc.nasa.gov