Hard X-Ray Telescope Up For Final NASA Review

http://pr.caltech.edu/media/Press_Releases/PR12644.html

Hard X-Ray telescope up for final NASA review; project will be led
by Caltech's Fiona Harrison

Caltech News Release
February 1, 2005

PASADENA, Calif.--If all goes well with a technical study approved by
NASA for this year, an innovative telescope should be orbiting Earth by
the end of the decade and taking the first focused high-energy X-ray
pictures of matter falling into black holes and shooting out of
exploding stars. Not only will the telescope be 1,000 times more
capable
of finding new black holes than anything previously launched into
space,
but it will also give us an unprecedented look at the origins of the
heavy elements we're all made of.

Named the Nuclear Spectroscopic Telescope Array--or NuSTAR, for
short--the project has just been pegged by NASA for detailed study in
the competitive Small Explorer Program (SMEX), which seeks out new
technologies and new proposals for space missions that can be launched
at low cost. NASA announced earlier this week that an unrelated mission
called the Interstellar Boundary Explorer will be launched by 2008, and
that NuSTAR will be given an up-or-down decision by next year for
launch
in 2009.

According to California Institute of Technology astrophysicist Fiona
Harrison, the principal investigator of the NuSTAR project, an April
high-altitude balloon flight in New Mexico should help to demonstrate
whether the advanced sensors invented and built at Caltech are ready
for
space.

The balloon phase of the project sports the intuitive acronym HEFT (for
High-Energy Focusing Telescope), and will mark the first time that
focused pictures at "hard X-ray" wavelengths will have been returned
from high altitudes. In fact, the HEFT data from the balloon is
expected
to be superior to any data returned so far from satellites at high
X-ray
energies.

NuSTAR will be much better than the balloon experiment, Harrison
explains, because it's necessary to get above Earth's atmosphere for
extended periods to get a good view of the X-ray sky. NuSTAR will orbit
Earth at an altitude of about 300 miles or so for at least three years.

The reason that the new technology will be superior to that employed by
existing X-ray satellites for certain observations is that high-energy,
or hard, X rays, tend to penetrate the gas and dust of galaxies much
better than the soft X rays observed by NuSTAR's forerunners. Thus,
NuSTAR will get the first focused hard X-ray images for three basic
science goals:

--The taking of a census of black holes at all scales. NuSTAR will not
only count them, but will also measure the "accretion rate" at which
material has fallen into them over time, and the rate supermassive
black
holes have grown.

--The detecting and measuring of radioactive stuff in recently exploded
stars. These remnants of supernovae will provide a better idea of how
elements are formed in supernova explosions and then mixed in the
interstellar medium, which is the space between stars. NuSTAR will be
especially good at observing the decay of titanium to calcium, which
tends to be produced in the region of a supernova where material either
is ejected forever from the explosion or falls back inward to form a
compact remnant of some sort. NuSTAR will thus be an especially good
probe of this region, and the data returned will contribute directly to
NASA's "Cycles of Matter and Energy" program.

--The observing and imaging of the highly energetic jets that stream
out
of certain black holes at nearly the speed of light. Coupled with
observations from the Gamma-Ray Large-Area Space Telescope (GLAST),
NuSTAR will provide data to help scientists explain this
still-enigmatic
but powerful phenomenon.

The technical difficulties of obtaining hard X-ray images has been
overcome with groundbreaking work in various Caltech labs, including
that of famed inventor Carver Mead, who is the Moore Professor of
Engineering and Applied Science, Emeritus, at Caltech. Both HEFT and
NuSTAR will rely on an array of coaligned conical mirrors that will
focus X rays from about 20 to 100 kilo-electron-volts on a pixel
detector made of cadmium zinc telluride. The sensor is segmented into
squares of about half a millimeter each, and these will take thousands
of individual readings of X-ray photons and turn them into electronic
signals.

"With this mission, we'll open the hard X-ray frontier and look at
things never seen before," says Harrison, who is an associate professor
of physics and astronomy at Caltech.

In addition to Caltech, the other participating organizations and
universities are the Jet Propulsion Laboratory (managed by Caltech for
NASA), Columbia University, the Stanford Linear Accelerator (SLAC), the
Lawrence Livermore National Laboratory, Sonoma State University, the
University of California at Santa Cruz, and the Danish Space Research
Institute. NuSTAR's spacecraft will be built by General Dynamics
Spectrum Astro.

JPL handles project management, the metrology system, and the
extensible
mast, and is involved in the mission's science. The mast is based on a
previous JPL mission, the Shuttle Radar Topography Mission.

The selected proposals were among 29 SMEX and eight
mission-of-opportunity proposals submitted to NASA in May 2003. They
were in response to an Explorer Program Announcement of Opportunity
issued in February 2003. NASA selected six proposals in November 2003
for detailed feasibility studies.

The Explorer Program is designed to provide frequent, low-cost access
to
space for physics and astronomy missions with small to mid-sized
spacecraft. NASA has successfully launched six SMEX missions since
1992.
The missions include the Reuven Ramaty High Energy Solar Spectroscopic
Imager, launched in February 2002, and the Galaxy Evolution Explorer,
launched in April 2003 and led by Caltech physics professor Chris
Martin.

NASA's Goddard Space Flight Center, Greenbelt, Md., manages the
Explorer
Program for the Science Mission Directorate.
Contact: Robert Tindol (626) 395-3631