The Space Shot

Survey finds fewer near-Earth asteroids than once thought

Analysis of data collected by a NASA infrared space telescope shows there are fewer near-Earth asteroids than previously believed, scientists said today.

But the majority of the nearly 20,000 bodies between 330 and 3,300 feet wide have not yet been detected and it's not yet clear whether a reduced population also means a reduced number of midsize asteroids in orbits that could pose a threat to Earth.

"We find that there are fewer near-Earth asteroids out there," said Amy Mainzer, principal investigator with NASA's NEOWISE program. "However, it's very important to note that fewer does not mean none. And there are still tens of thousands that are out there that we need to find."

Using NASA's Wide-Field Infrared Survey Explorer--WISE--space telescope, researchers conducted a census of near-Earth objects, or NEOs, orbiting within 120 million miles of the sun. Scanning the entire sky twice between January 2010 and February 2011, the NEOWISE project observed more than 100,000 asteroids orbiting between Mars and Jupiter and nearly 600 that pass near Earth.

"With NEOWISE, we didn't go out and find every single asteroid that's out there, but we got a good representative sample, kind of like doing a census where you take a poll of a small subset of people that you think is representative of what everybody thinks," Mainzer said. "And so, that's what we've been able to do with NEOWISE."

She said the NEOWISE data, along with surveys conducted by ground-based instruments, show that more than 90 percent of the so-called "planet busters" six-tenths of a mile across and larger have now been identified, meeting a goal set by Congress in 1998.

Previous estimates put the population of large near-Earth objects at around 1,000. The NEOWISE survey indicates the actual number is around 981, of which 911 have been detected, including all of the very large bodies like the six-mile-wide asteroid that is believed to have wiped out the dinosaurs 65 million years ago. None pose any threat to Earth, at least for the next few centuries.

China launches prototype lab module for docking tests

In a major milestone for China's space program, a modified Long March 2 rocket boosted an unmanned prototype space station module, dubbed "Heavenly Palace," into orbit today to serve as a target for critical tests of automated rendezvous and docking systems needed before construction of a Mir-class space station later in the decade.

The Long March 2F T1 rocket, equipped with four liquid-fueled strap-on boosters for extra launch power, took off from the Jiuquan Satellite Launch Center in north central China at 9:16 a.m. EDT (GMT-4; 9:16 p.m. local time), majestically climbing away through a more

Dead satellite likely fell into Pacific Ocean--maybe

NASA's decommissioned 6.3-ton Upper Atmosphere Research Satellite, out of gas and out of control after two decades in space, plunged back into the atmosphere early Saturday, heating up, breaking apart, and presumably showering chunks of debris along a 500-mile-long Pacific Ocean impact zone.

Maybe.

U.S. Strategic Command radar tracking indicated re-entry would occur around 12:16 a.m. EDT (GMT-4) Saturday as the satellite was descending across the Pacific Ocean on a southwest-to-northeast trajectory approaching Canada's west coast. If re-entry occurred on or before the predicted time, any wreckage that survived atmospheric heating almost certainly fell more

Derelict NASA satellite falls back to Earth

NASA's Upper Atmosphere Research Satellite, out of gas and out of control after two decades in space, plunged back into the atmosphere early Saturday, heating up, breaking apart and presumably showering chunks of debris along a 500-mile-long downrange impact zone.

But NASA officials could not immediately confirm where or exactly when the satellite came down, saying only that re-entry occurred during a two-hour period.

"NASA's decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23, and 1:09 a.m. EDT Sept. 24," the agency said in a statement released more

Heads up! NASA satellite descends toward fiery doom

NASA's decommissioned Upper Atmosphere Research Satellite, out of gas and out of control, is not descending toward re-entry as rapidly as expected, officials say, likely delaying the satellite's kamikaze plunge to Earth by a few hours, to late Friday or early Saturday.

Experts expect more than two dozen chunks of debris to survive re-entry and hit the ground in a 500-mile-long footprint somewhere along the satellite's orbital track. But given the bus-size 6.3-ton's satellite's trajectory and the vast areas of ocean and sparsely populated areas UARS passes over, experts say it is unlikely any more

Patience, lots of luck needed to spot falling satellite

Armchair satellite trackers hoping to catch a glimpse of NASA's doomed Upper Atmosphere Research Satellite when it plunges back to Earth on Friday will need patience, access to the Internet, a clear sky, and a large helping of luck, experts say.

Even with last-minute updates from NASA and U.S. Strategic Command pinpointing when and where UARS will begin its final plunge, the sheer size of the planet, with its vast stretches of ocean and remote terrain, means the odds of catching a glimpse of the spacecraft's fiery demise--or of being anywhere near any falling debris--will be remote.

But as re-entry footage of the old Russian Mir space station and the more recent flaming fall of a European cargo craft show, satellite "decays" offer the public and experienced amateurs alike a chance to witness a fairly spectacular show.

The UARS re-entry "is nothing to be particularly worried about, and if you're very lucky and in the right place at the right time, you may see quite a nice little fireworks show from it. But it's highly improbable that you'll get even that much out of it," said Ted Molczan, a well-known satellite watcher whose computer analysis and predictions have helped sophisticated hobbyists around the world track down spy satellites and other challenging targets.

"You have to maintain reasonable expectations. And in this case, the right expectation is, 'I'm not going to see this.' On the other hand, if you stop there it becomes a self-fulfilling prophecy. So you do want to see it, you know you won't, but (if you make the effort) you might!"

Mars micro-rover Kapvik may tether to larger vehicles

Engineers at Carleton University in Canada have demonstrated a small-scale rover that could be used as a risk-assessment tool in explorations of the surface of Mars and the moon.

The Kapvik micro-rover is inspired by design concepts seen in NASA's Sojourner, Spirit, and Opportunity rovers. It has six wheels, weighs less than 66 pounds, and could be deployed by larger unmanned rovers to scout out specific areas.

One problem that has dogged Martian rovers is getting stuck in sand or other topographic features. The Kapvik, named for an Inuktitut term for "wolverine," has a tethering system for winching it up hills.

Yikes! ISS crew endures comms blackout during re-entry

A Russian Soyuz capsule carrying three of the International Space Station's six crew members suffered an unexpected communications blackout just before plunging back into Earth's atmosphere, completing a nail-biting descent in radio silence with repeated calls from flight controllers near Moscow going unanswered.

Finally, recovery crews spotted the Soyuz TMA-21's braking parachute, communications with ground crews were established and the spacecraft touched down in Kazakhstan at 9:59 a.m. local time Friday (8:59 p.m. PT Thursday), tipping over on its side as it closed out an expedition lasting 164 days since launch April 4 more

NASA spots first planet in binary star system

NASA's Kepler space telescope, searching for planets around distant suns, has discovered a Saturn-size world orbiting two stars 200 light years from Earth, a long-sought "circumbinary" planet reminiscent of the fictional world Tatooine in the Star Wars saga.

"This is the first definitive detection of a circumbinary planet and the best example we have of a Tatooine-type world," said Laurance Doyle, a researcher at the SETI Institute's Carl Sagan Center for the Study of Life in the Universe and lead author of a paper in the journal Science describing the discovery.

"Now, we don't expect Luke Skywalker more

Falling science satellite poses little risk, NASA says

A 6.3-ton NASA science satellite, decommissioned in 2005, is expected to plunge into Earth's atmosphere later this month, breaking up in a shower of debris. Experts said today they expect 26 components, the largest weighing more than 330 pounds, to survive re-entry heating to hit the surface somewhere between 57 degrees north and south latitude.

But a NASA space debris expert said the threat to the public is minimal and that statistically, the odds are good the debris will land in an ocean or some other sparsely populated area.

"We looked at those 26 pieces and how big they are and we've looked at the fact they can hit anywhere in the world between 57 north and 57 south and we looked at what the population density of the world is," said Nick Johnson, chief scientist with NASA's Orbital Debris Program at the Johnson Space Center in Houston.

"Numerically, it comes out to a chance of 1 in 3,200 that one person anywhere in the world might be struck by a piece of debris. Those are obviously very, very low odds that anybody's going to be impacted by this debris."

The centerpiece of a $750 million mission, the Upper Atmosphere Research Satellite, or UARS, was launched from the shuttle Discovery in September 1991. The solar-powered satellite was designed to address a wide variety of atmospheric questions, including the depletion of Earth's ozone layer 15 to 30 miles up, a trend blamed on the release of man-made chemicals called chlorofluorocarbons, or CFCs, used in refrigerants, foam products, and various solvents.

The long-lived satellite was decommissioned in 2005 and one side of its orbit was lowered using the last of its fuel to hasten re-entry. No more fuel is available for maneuvering and the satellite's re-entry will be "uncontrolled."