After nearly a decade of planning and assembly, the Far Ultraviolet Spectroscopic Explorer satellite--planned, designed and built by Johns Hopkins--has taken the penultimate step toward its scheduled Feb. 18, 1999, launch.
The satellite was moved on Aug. 13 from the Applied Physics Laboratory in Laurel, where it was assembled, to the Goddard Space Flight Center in nearby Greenbelt, where scientists will subject the instrument to a series of environmental tests. If all goes as expected, the satellite will be shipped in December to Cape Canaveral, Fla., and readied for launch.
FUSE is the first large-scale space mission to be fully planned and operated by an academic department of a university. Hopkins will take control of the three-year scientific mission about 100 minutes after launch and will manage it from a mission control center in the Physics and Astronomy building on the Homewood campus.
FUSE began as a NASA-managed project in the mid-1980s. Later, when the budget ballooned to more than $300 million, the space agency sought a way to restructure the project. In 1995, Hopkins proposed to NASA a way to build the satellite faster, better and more cheaply than previously conceived. Hopkins assured NASA it could bring FUSE to the launch pad for about $100 million, and two years earlier than planned. And it has.
Warren Moos, a professor in the Department of Physics and Astronomy, is the principal investigator of the mission, which was developed with a group of global, corporate and academic partners. Other members of the Hopkins FUSE team are Dennis McCarthy, project manager; research professor William P. Blair, planning scientist and press liaison officer; research scientist Scott Friedman, FUSE project scientist; J.B. Joyce, mission operations manager; and associate research scientist Ken Sembach, press liaison officer.
FUSE was designed to study the origin and evolution of hydrogen and deuterium, the universe's lightest atoms, which were created shortly after the Big Bang. It also will investigate the forces and processes involved in the evolution of galaxies, stars and planetary systems.
It is the first satellite capable of viewing at high resolution galaxies and faint stars in a portion of the spectrum astronomers refer to as far-ultraviolet wavelengths, which can only be observed outside the Earth's atmosphere. Those wavelengths are particularly revealing about the characteristics of objects and processes in space. FUSE complements other NASA missions by detecting these far-ultraviolet wavelengths that are invisible to other telescopes, including the Hubble Space Telescope. FUSE will enable astronomers to learn more about the secrets of galaxy evolution and star formation by analyzing clouds of gases between stars in the Milky Way and nearby galaxies.
"FUSE will investigate a fossil nucleus of the universe, deuterium, which was created three minutes after the Big Bang," Moos said. "Others have investigated this, but these explorations have been like attacking a target from far more angles and providing information never before possible. So these explorations will allow us to place a big piece in a complex jigsaw puzzle."
Hopkins scientists will control about 50 percent of the observation time during the three-year mission. NASA will determine how the remainder of the observation window will be filled.
Other satellites and instruments have been used to observe ultraviolet light. The first to view the same wavelength range as FUSE was the Copernicus spacecraft, during the 1970s. But the pioneering spacecraft's view was limited to a small portion of the Milky Way galaxy, which astronomers suspect is not representative of the galaxy as a whole. FUSE is at least 10,000 times more sensitive than Copernicus was.
The Hubble Space Telescope has higher resolution than FUSE, but FUSE can see smaller wavelengths of light, which reveal important information about the composition and characteristics of objects in space. The Hubble can detect lower-temperature gases, and satellites sensitive to X-rays can detect higher-temperature gases, but no telescope has been able to explore the middle ground, which has remained a mystery to astronomers. FUSE will bridge that gap.
FUSE will be placed in low-earth orbit, at an altitude of about 775 km (480 miles). The 18-foot satellite is made up of two parts: a spacecraft and an instrument. The spacecraft contains the solar panels and power supply, the controls for pointing the satellite, the communications and computer hardware and other essential equipment.
The instrument, mounted on top of the spacecraft, contains all the optics for FUSE's four aligned telescopes. Light passes into the instrument and is focused by four curved mirrors onto four spectrograph gratings. The gratings are roughly one-foot-square pieces of glass that are etched with lines that separate the light into different bands, or wavelengths, like a prism splitting light into distinct colors. Each band reveals something about the composition or properties of objects in space. The band patterns of specific objects are recorded digitally for downlink to the ground and interpretation by scientists.
Because FUSE's orbit will straddle the equator, it will be out of direct communication range from Baltimore, so telephone lines will link the control center to a satellite dish in Puerto Rico. Scientists will communicate with FUSE while it passes over the automated ground station at the University of Puerto Rico, in Mayaguez. The automated station will be linked to the control center at Hopkins by an ISDN line.
FUSE will orbit the Earth every 100 minutes, making more than 14 complete orbits each day. But because the Earth is rotating under the satellite, not all of FUSE's orbits will carry it over Puerto Rico; consequently, satellite communications will be blacked out for about 12 hours each day. That means computers on FUSE must perform the important tasks of pointing the telescopes and making the observations.
One way Hopkins has been able to structure FUSE to meet NASA's directive for making exploration missions "faster, better, cheaper" has been to rely upon the expertise of Maryland's aerospace industry. By entering into partnerships with members of commercial industry to purchase existing hardware and software, Hopkins has infused about $96 million into the state's economy. Among the Maryland partners benefiting from the project are Orbital Sciences Corp., Germantown; Swales Aerospace, Beltsville; Interface Control Systems, Columbia; AlliedSignal Technical Services Corp., Columbia; Hopkins' Applied Physics Laboratory; NASA's Space Telescope Science Institute, located on the Hopkins Homewood campus; and NASA's Goddard Space Flight Center, Greenbelt.
Other scientific partners have come from universities and space agencies. Scientists at the University of California, Berkeley, designed and built the ultraviolet light detectors, which are essential components of the scientific instrument. They also helped design the ultraviolet instrument along with Hopkins and the University of Colorado, where scientists were also responsible for the assembly and alignment work on the spectrograph. The Canadian Space Agency provided the fine-error sensor, which is a guide camera essential for keeping the telescope locked onto its targets. The sensor constantly informs an onboard computer where the telescope is pointing. It was designed and built by ComDev, a Canadian aerospace company located in Cambridge, Ontario. CSA also provided the main computer--the Instrument Data System--which was designed by ComDev as well.
The French Space Agency provided the diffraction gratings, which perform the critical task of breaking the far-ultraviolet light into component wavelengths for analysis.
FUSE can be found on the Web at http://fuse.pha.jhu.edu.