Japanese- U.S. Satellite Ushers in Golden Era of X-ray Astronomy

Dolores Beasley

Headquarters, Washington, DC

(Phone: 202/358-1753)

Nancy Neal

Goddard Space Flight Center, Greenbelt, MD

(Phone: 301/286-0039)

RELEASE: 00-18

Astro-E, the Japanese-U.S. X-ray spacecraft poised for a Feb.
8 launch, will showcase an entirely new technology in X-ray
detection that not only will serve as a test bed for future
missions but also will earn the distinction of being the coldest
known object in space.

“This new mission allows us to apply a piece of whiz-bang new
technology to the exploration of the Universe,” said Dr. Alan N.
Bunner, Science Director of NASA’s Structure and Evolution of the
Universe program.

The new instrument is the X-ray Spectrometer (XRS), developed
jointly by NASA’s Goddard Space Flight Center, Greenbelt, MD, and
Japan’s Institute of Space and Astronautical Science (ISAS). The
XRS measures the heat created by individual X-ray photons, as
opposed to converting X-rays to electrical charges and then
collecting that charge, which is the mechanism in other X-ray
detectors.

Using this new technique, it is possible to measure the
energies of individual X-rays with a precision approximately 10
times greater than with previous X-ray sensors. To sense the heat
of a single photon, however, the XRS detector must be cooled to an
extremely low temperature, only 0.060 degrees Kelvin, or about –
460 degrees Fahrenheit.

This essentially makes the XRS detector the coldest object in
space. The absence of all heat, called absolute zero, is 0.0
degree Kelvin; the coldest reaches of space are a balmy three
degrees Kelvin.

“This increased precision for measuring X-rays should allow
fundamental breakthroughs in our understanding of essentially all
types of X-ray emitting sources, especially material very close to
black holes and the X-ray emitting gas in the vast spaces between
the individual galaxies that make up clusters of galaxies,” said
Dr. Richard Kelley, XRS Principal Investigator at Goddard.

Astro-E’s targets include: clusters of galaxies; supermassive
black holes; neutron stars; supernova remnants; stellar coronae of
stars 10,000-times more active than our Sun; and a study of the
history of how chemicals are made throughout the Universe.

Astro-E is primarily a spectroscopy mission, which means the
satellite’s instruments will study the “colors” of X-ray light,
much like a prism breaks visible light into the colors of the
rainbow. While the recently launched Chandra X-ray Observatory
excels in producing X-ray images, Astro-E excels in producing
spectra. In this regard, Astro-E complements Chandra, analyzing
the light that Chandra sees and determining the temperature,
velocity and composition of the gas producing those X-rays.

Along with the XRS are four X-ray Imaging Spectrometer (XIS)
instruments, a collaboration among Japanese universities and
institutions and the Massachusetts Institute of Technology Center
for Space Research, and the Hard X-Ray Detector (HXD), built by
the University of Tokyo and ISAS. Both the XRS and XIS
instruments will analyze X-ray photons focused by individual X-ray
telescopes, built at Goddard by a team led by Dr. Peter J.
Serlemitsos.

The imaging instrument utilizes detectors similar to those
flown on ASCA, Astro-E’s precursor, yet with twice the collection
efficiency at certain X-ray wavelengths. The Hard X-Ray Detector
will extend Astro-E’s observation ability into the “hard” or
higher-energy X-ray wavelengths with the highest sensitivity ever
achieved.

Astro-E will be launched on an M-V rocket from the Kagoshima
Space Center, located on the southern tip of the Japanese island
of Kyushu. The observatory’s expected mission lifetime is five
years (two years for the X-Ray Spectrometer, with the depletion of
cryogenic gases). Astro-E will attain a near-Earth circular orbit
of approximately 341 miles (550 kilometers). Its payload weighs
3,630 pounds (1,650 kilograms), and measures 20.8 x 17.28 x 6.72
feet (6.5 x 5.4 x 2.1 meters).

With its official name to be bestowed after deployment,
Astro-E will join the recently launched European X-ray Multi-
Mirror Mission and NASA’s Chandra X-ray Observatory, ushering in
what many experts are calling the decade of X-ray astronomy.
Astro-E is the fifth in a series of Japanese satellites devoted to
studying celestial X-ray sources. Previous missions are Hakucho,
Tenma, Ginga, and ASCA. ASCA, launched Feb. 20, 1993 and
formerly known as ASTRO-D, is still active.

More information on the Astro-E mission can be found on the
Internet at: