A team led by the Naval Observatory is preparing to launch a new optical space
telescope intended to increase substantially what is known about millions of
stars-and their major planets-within the neighborhood of Earth's own galaxy.
The National Aeronautics and Space Administration (NASA) agreed earlier this
year to launch the telescope, known as the Full-Sky Astrometric Mapping Explorer
(FAME), in 2004, from its facility at Cape Canaveral, Fla., at a cost of $162
million.
During a 2.5 year mission, the new telescope will provide the most detailed
information yet about the positions, distances, motions and colors of stars
in the vicinity of the sun, said P. Kenneth Seidelmann, director of astrometry
at the Naval Observatory and chairman of the FAME science team.
Seidelmann-pushing away from a cluttered desk in a spacious office in the observatory's
century-old facility near Embassy Row in Washington, D.C. took time recently
to explain the project.
FAME, he said, "will be the most accurate astrometric catalog in history."
Astrometry-the oldest branch of astronomy-is the science of determining the
position of stars, Seidelmann said. Astrometric measurements determine the positions
of stars in the sky. By measuring a star's parallax-the apparent change in its
position during the Earth's yearlong revolution around the sun astronomers also
can determine the distance from the Earth to that star.
The FAME telescope, 30 times as accurate as previous position-measuring spacecraft,
is designed to obtain precise position and brightness data for 40 million stars,
said Seidelmann. This rich database, he said, should allow astronomers to:
- Determine the distance to all of the stars on this side of the Milky Way galaxy.
- Detect large planets and planetary systems within 1,000 light years of the
sun.
- Measure the amount of dark matter in the galaxy from its influence on stellar
motion.
- Help resolve questions about the age and size of the universe.
- Improve the ability of NASA and the armed services to control satellites and
to navigate ships, airplanes and spacecraft.
FAME is a collaborative effort by the observatory; the Naval Research Laboratory,
of Washington, D.C.; Lockheed Martin Missiles and Space Advanced Technology
Center, of Palo Alto, Calif., and Smithsonian Astrophysical Observatory, of
Cambridge, Mass.
The observatory, the project's lead organization, was founded in 1830, to provide
the Navy, the Defense Department and the public with information about astrometry
and time. Its mission includes maintaining the Master Clock for the United States,
determining precise time, measuring the Earth's rotation, and providing astronomical
data, including the positions and motions of the Earth, sun, moon, planets,
stars and other celestial objects.
Keys to Navigation
Precise timing information and astrometry, or star position, are the foundations
of navigation, Seidelmann said.
For this reason, FAME-unlike NASA's successful, decade-old Hubble Space Telescope,
which studies the farthest and faintest reaches of the cosmos-will focus on
the stars relatively close to this solar system.
FAME project leaders hope to avoid the kinds of problems that plagued Hubble
in its early years. For one thing, it is smaller. While Hubble was placed into
orbit by the Space Shuttle Discovery, FAME will be launched at the top of a
far simpler Delta II rocket. Also, Hubble was plagued initially by a flaw in
its main mirror, which had to be replaced in another shuttle flight.
Said Seidelmann: "Our optical system is much simpler."
FAME is a successor to the European Space Agency's (ESA) Hipparcos telescope,
which mapped stars from 1989 to 1993. But FAME has an innovative design to enable
it to observe "a lot more stars, with a lot more accuracy," Seidelmann
said. It employs a solar sail that uses pressure from sunlight to change the
orientation of the spacecraft, allowing the telescope to scan the entire sky.
The telescope looks in two directions at the same time, and rotates every 40
minutes.
FAME will be able to detect the "wobbling" of stars caused by companion
objects, such as other stars, brown dwarfs-substellar objects that have formed
like a star, but lack enough mass to sustain nuclear fusion processes and giant
planets.
"We don't expect to be able to detect Earth-size planets," Seidelmann
said.
"The accuracy isn't that good-not yet. The portion of a star's motion
caused by a planet is very small.
"FAME will detect Jupiter-size planets and larger. It can detect smaller
stuff around a star, but it can tell whether it is made up of small planets,
asteroids or just space dust."
Scientists hope that FAME will tell them much about the sun and its solar system,
Seidelmann said. "We will observe a lot of stars like the sun. That should
be an excellent source for studying the sun, how it functions, how planets form,
and are the classical theories correct?"
Although FAME has a planned mission life of 2.5 years, the data that it gathers
will be studied for years afterwards, Seidelmann noted.
Also, scientists planning their own missions in space will be watching to see
whether FAME succeeds or not. The Europeans, for example, are planning another
space telescope, costing perhaps as much as $600 million, to be launched around
2009.
The observatory, meanwhile, is excited about the project. "This is our
business," Seidelmann said. "This is the first time that we will be
doing it from space.
"The good news is it's going to be fun. The bad news is this: We've proposed
this project, and now, we've got to make it work."