NEW YORK -- An
international team of astronomers is eagerly awaiting the launch of a new
orbital observatory that hopefully will
shed light on the most powerful explosions in the universe.
NASA's Swift spacecraft is being readied for a
mission to scan the sky for gamma-ray bursts, cosmic explosions that can burn
with the intensity of billions of suns in less than a second. Researchers hope
the mission will identify the events that trigger the bursts.
"I'm very
anxious to get up there and start doing the science," said Swift principal
investigator Neil Gehrels, a scientist
at NASA's Goddard Space Flight Center in Greenbelt, Md. "It's one of the most exciting things of my life."
As its name
implies, the Swift mission is designed for speed. Equipped with three
telescopes, the spacecraft is designed to automatically detect
the first flash of a gamma-ray burst and then target itself toward the event in about one minute to make detailed
observations.
That's
faster than any other satellite or ground-based system to date.
Swift "is the most autonomous spacecraft NASA has ever
built," Tim Gehringer, Swift's
deputy project manager at Goddard, said during a Nov. 1 prelaunch
mission briefing. "It's a smart,
capable spacecraft."
The
spacecraft, built by General Dynamics C4 Systems in Gilbert, Ariz., currently is slated launch from Cape Canaveral Air
Force Station, Fla., Nov. 17 aboard a Delta 2
rocket. NASA, the
Italian Space Agency and the Particle Physics and Astronomy Research Council in
the U.K shared the mission's total cost of about $250 million.
Gamma-ray
bursts can be as long
as a few minutes or as short as a few milliseconds, shedding intense gamma-rays
in the initial explosion with an afterglow of X-rays and optical light that fades over hours or weeks.
From
Earth's vantage point such bursts occur about once a day or so, and researchers
believe the explosions are the death knells of massive stars that can
subsequently collapse into neutron stars or black holes.
"We think
these bursts are the birth cries of black holes," Gehrels
said, adding that studying the connection
between gamma-ray bursts and black holes is one of
Swift's primary goals. "If you had gamma-ray glasses and looked out at the sky,
gamma-ray bursts would dominate your experience."
Gamma-ray bursts also could be triggered by more exotic means, such as the merging of two neutron
stars or a pair of black holes in orbit
around one another.
Swift researchers hope their
spacecraft will detect about one or two bursts a week, or about 100 a year.
"We have
now only been able to observe a couple of dozen or so bursts," Swift mission operations director John Nousek, of Pennsylvania State University, said during the briefing.
Researchers
hope Swift ultimately will detect about 500
bursts. The
spacecraft's nominal mission spans two years, though it has a potential orbital lifetime of between eight and possibly 15
years, Gehrels said in an interview.
To find the
gamma-ray burst trigger, Swift will use its primary Burst Alert
Telescope -- which has 32,000 detectors. The telescope will scan one-sixth of the sky at any one time for explosions.
Once a
burst is detected, the spacecraft can determine the location in space and reorient itself accordingly in 20 to 75 seconds. Swift then will use its X-ray telescope and optical-ultraviolet instrument
for more detailed measurements.
"We have more than 40 observatories, space- and
ground-based, to work with the Swift team to distribute this information," Nousek said. "This rapid response is imperative."
The
spacecraft will be in continuous contact with ground controllers and relay data through the Gamma-ray Burst Coordinates Network for
distribution to telescope facilities, researchers and the public-at-large.
"This
mission will generate the most comprehensive data set that we've ever had" on
gamma-ray bursts, Gehrels said.
