NASA hopes to mark the 30th anniversary of the Apollo moon landing Tuesday with a giant leap in X-ray vision. A crew of five astronauts led by Eileen Collins, the first female commander in U.S. space history, is scheduled to lift off aboard the shuttle Columbia just after midnight tonight to deploy the massive $1.55 billion Chandra X-ray observatory.
The 45-foot-long telescope is designed to study an array of the most violent and extreme phenomena in the universe in 10 to 100 times as much detail as ever before--in high-energy wavelengths of light invisible to human eyes. Scientists expect Chandra to zoom in on the "last millisecond" of mayhem around the event horizons of black holes and help identify the mysterious, unseen "dark matter" that makes up much of the mass of the universe.
"It's going to be much, much better than science fiction," said Harvey D. Tananbaum, head of the Chandra center in Cambridge, Mass.
The $2.78 billion mission, carrying the largest and heaviest payload in shuttle history, involves a high-stakes roll of the dice for the space agency as well as dozens of scientists who have devoted their careers to it.
Chandra is the third in a series of four planned orbital "great observatories" designed to cover all the wavelengths, or "colors" of electromagnetic radiation. The series began with the 1990 launch of the Hubble Space Telescope (which studies visible and ultraviolet light) and continued with the Compton Gamma Ray Observatory. The last observatory will study the infrared sky.
Chandra still has significant hurdles to clear. "This is not a trip to grandma's on a Sunday afternoon," said Edward Weiler, chief scientist of the National Aeronautics and Space Administration.
Beginning shortly after launch, the shuttle crew and teams in three control rooms across the country must execute a precisely timed sequence of operations, cutting the 43,000-pound mass of the observatory and its attached solid-fuel rocket booster off irreversibly from shuttle power and communications, and preparing it to be catapulted far beyond the reach of repair services or any other kind of rescue.
"If we don't finish our work quickly" during this period, said veteran astronaut and astronomer Steven Hawley, who in four previous missions helped deploy and service the Hubble, Chandra's batteries will be depleted and the telescope will freeze to death.
Columbia astronauts will take an emergency space walk if needed to accomplish the deployment manually. But once the shuttle tosses the telescope overboard, there will be no chance to retrieve it. This is because Chandra is designed to end up in an elliptical, or egg-shaped, orbit that will carry it 87,000 miles from Earth, about one-third of the distance to the moon, once during every 64-hour orbit. This represents a new strategy for a "great observatory," placing the craft far beyond the reach of shuttle repair crews.
The Hubble, by contrast, was designed for periodic maintenance and upgrades, enabling astronauts to perform a crucial in-flight fix on a devastating flaw discovered post-launch. The Chandra science team's members have gambled with their approach, hoping they will gain major advantages in efficiency over lower-orbiting telescopes. By swinging far from Earth, Chandra will be able to observe virtually any target in the cosmos most of the time, without the home planet blocking its view for much of every orbit. The path also carries Chandra's sensitive instruments beyond interference from Earth's radiation belts.
The telescope's barrel had to be as long as a big-rig truck for the one-ton mirror system to bounce, or reflect, the X-rays to the tiny focal point. If these extremely short-wave particles struck the mirror at anything but a shallow grazing angle, like stones skipping over a pond, they would be absorbed and disappear.
The X-ray universe is about a thousand times hotter than the one that appears in visible wavelengths. (Only gamma rays are more energetic.) By some estimates, Chandra could reveal 1,000 new X-ray sources in every moon-size patch of sky, according to Chandra scientist Martin Elvis, of the Harvard Smithsonian Center for Astrophysics.
Because light at this wavelength does not penetrate Earth's atmosphere, X-ray astronomy had to wait for the space age. The first X-ray satellite was launched in 1970. But the view of the X-ray sky up to now has been blurry, researchers say, because the instruments so far have been even less capable than the small optical equivalents used by backyard amateurs.
A throwback to the era of big-ticket mega-projects, the effort to build a giant U.S. X-ray observatory has consumed some three decades, scientists said. (The trend now is toward smaller, simpler spacecraft on short timetables that allow them to take maximum advantage of the latest technologies.) Formally proposed in 1976, the project, initially known as the Advanced X-Ray Astrophysics Facility (AXAF), has proceeded in fits and starts through a run of problems that included budget crunches and delays generated by the 1986 Challenger disaster. In 1992, its costs and complexity under fire, the design was scaled back by billions of dollars.
Mindful of the lessons of the Hubble telescope, Chandra program manager Fred Wojtalik of Marshall Space Flight Center in Huntsville, Ala., said the team has done extraordinary amounts of testing to ensure that the observatory will work. (Chandra, the nickname of the late Indian American Nobel laureate Subrahmanyan Chandrasekhar, an astrophysicist at the University of Chicago, also means "luminous" in Sanskrit.)
Now X-ray astronomers anticipate a virtual revolution in their infant science, with the European and Japanese space agencies poised to launch advanced X-ray telescopes next year. The pent-up demand for a powerful X-ray facility is such that the Chandra project received more than 800 scientific proposals for the first year, but could accommodate only 200, Tananbaum said.
Black holes are among the most bizarre objects known--concentrations of collapsed matter so dense that not even light can escape their gravitational power. Though themselves invisible, they can throw up spectacular fireworks when consuming material around them. By precisely determining the energy of the individual X-rays, Chandra is supposed to trace the motions of particles up to the instant they disappear forever from the known universe, enabling scientists to test theories about the gravitational warping of space around these monsters. Quasars, another target, are thought to be a variation on this theme--blazing beacons powered by super-massive black holes at the hearts of galaxies.
Chandra's subjects will also include flaring or exploding stars and vast clouds of multimillion-degree gas in galaxy clusters. By studying the gas, scientists theorize, they can assess the unseen sources of the extra gravity that keeps the clouds from dispersing and locate the cosmic "missing mass." And by studying expanding remnants of exploding stars, they hope to trace the dispersal through space of heavy elements manufactured inside stars--elements that made possible the existence of planets and, in at least one setting, life.
NASA's Super Scope
Chandra is the largest and most sophisticated X-ray observatory ever constructed. After it is launched into orbit around Earth from the space shuttle Columbia, Chandra will be able to detect X-ray sources that are billions of light years away and produce images 10 to 100 times sharper than the best previous X-ray telescope.
1. The observatory's telescope is pointed toward an X-ray source.
2. Nested mirrors focus X-rays onto a camera to produce an image.
The observatory is designed to be accurate enough to observe X-rays from particles up to the last second before they fall into a black hole.
Size: 45.3 feet x 64.0 feet
(solar arrays deployed)
Weight: 10,560 pounds
Life: minimum 5 years
SOURCES: NASA, Harvard