Posts Tagged ‘Collision’

Cosmic Collision Over Siberia

 
 
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NEWS BLOG by Kelly Beatty
Space is mostly empty, but sometimes it isn’t empty enough.

Two days ago a pair of orbiting satellites collided 480 miles (780 km) up over Siberia. One was Cosmos 2251, a defunct communications satellite launched in 1993 by the Russian Ministry of Defense. The other was named Iridium 33, one of several dozen spacecraft in a globe-girding commercial communications network.

It’s not yet clear exactly how many satellite shards the smashup created; more than 600 have already been logged by the U.S. military’s worldwide satellite-tracking network. A more accurate debris census — and, more importantly, how they’re distributed in orbit — will take a week or so to sort out.

Satellite snapshot
A snapshot of the thousands of satellite circling Earth in low-altitude orbits.
NASA / Johnson Space Center

This unplanned meeting in orbit is unprecedented, but it was bound to happen sooner or later. Ground-based cameras and radar currently keep tabs on more than 13,000 orbiting objects, everything from fragments the size of tennis balls to the International Space Station.

Speaking of ISS, it doesn’t appear to be in imminent danger. It orbits quite a bit lower, typically 220 miles (350 km). There’s a little more worry concerning the Hubble Space Telescope, currently circling at a height of 350 miles (565 km). Both of the colliding spacecraft had high-inclination orbits (Cosmos 2251 at 74°, Iridium 33 at 86°), and depending on their post-crash speeds, some of the 1½ tons of fragments might end up either much higher or much lower.

The February 10th collision was an accident: the Russian craft was inoperable, and the Iridium, though apparently equipped with a maneuvering rocket, hadn’t known it was going to be hit. As worrisome as all this might seem, it totally pales compared to an intentional space smashup that occurred two years ago.

Let’s not forget that on January 11, 2007, the People’s Republic of China launched a ballistic weapon that struck and destroyed Fengyun 1. The resulting fragments created more space shards than any other event in the history of satellite exploration, creating a hazardous cloud that has spread to altitudes ranging from 300 to 2,500 miles.

According to a recent newsletter from NASA’s Orbital Debris Office, pieces of Fengyun 1 and its annihilator now total nearly 2,400, accounting for more than 25% of all the objects being tracked at low orbital altitudes. And the estimated count of smaller bits, 1 to 5 cm across, exceeds 150,000. Some of these will remain aloft for decades, others for more than a century.

Accidents will happen, but to knowingly put so many other spacecraft at risk is unconscionable. Remarkably, five years earlier China’s National Space Administration (CNSA) had signed a United Nations agreement to help reduce the amount of space debris.

Posted by Kelly Beatty, February 13, 2009

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Close Encounters of the Worst Kind: How Safe Are We from Killer Asteroids?

Features –  February 12, 2009

Largest near-Earth objects are already well characterized, but smaller ones could surprise

By John Matson


In 1998, the year Deep Impact and Armageddon dueled for the attentions of apocalypse-from-the-heavens moviegoers, Congress tapped NASA to prevent such a cosmic cataclysm from becoming reality. The space agency was charged with cataloguing over the next decade the vast majority of nearby space objects larger than 0.62 mile (one kilometer) in size—those asteroids, and more rarely comets, capable of inflicting catastrophic damage to Earth.

Eleven years later—just behind schedule—the task appears to be nearly complete. Congress had requested that 90 percent of these large near-Earth objects (NEOs) be catalogued, and around 800 of them, roughly 80 to 85 percent of the entire population, have been tallied. (Astronomers can estimate how much of the lot has been surveyed by studying the gradual drop-off in discovery rates.) According to NASA’s impact-threat catalogue, only two of the kilometer-size NEOs so far identified pose a very slim risk in the next century; the more threatening of the two has a one in 116,000,000 chance of colliding with Earth. (That object, known as 2009 CR2, was just discovered last week; with further observation it may prove not to be a threat at all.)

Now sky sentries are turning their gaze to smaller NEOs. In 2005 Congress asked NASA to extend its survey to include objects as small as 460 feet (140 meters) across—not dinosaur-killers but still big enough to outdo the largest nuclear weapon ever tested if they ever cross paths with Earth. “The objects that people who have studied the risk from this sort of thing are worried about are the 300-meter [1,000-foot] class of objects,” says astronomer Edward Beshore, co-investigator for the Catalina Sky Survey (CSS) at the University of Arizona, currently the most prolific NEO-finding program. “They could create regional destruction. A 300-meter object landing off the western coast of the U.S. could inundate coastal cities” with a massive tsunami, Beshore adds.

The task will be complicated by the sheer number of such objects and by their diminished brightness—smaller asteroids and comets reflect less light and so more easily escape detection. “Like gravel in a stream bank, there are more smaller objects than there are larger objects,” Beshore says. “And so we expect to find something on the order of 50,000 to 60,000 [near-Earth] objects down to 140 meters in size.” So far, only 4,000 or so NEOs in that size range have been tracked down.

Astronomer Donald Yeomans, manager of NASA’s Near-Earth Object Program office, says officials are studying the best way to tackle the 140-meter challenge: Should efforts be focused on ground-based observations, as they have been in the kilometer-size census? Or, would a space-borne infrared telescope be more effective? Whatever the case, Beshore says, better instruments are needed to meet Congress’s request that 90 percent of the smaller group be tracked by 2020. “With the systems that are currently online,” he says, “you’d be looking at decades before you could begin to approach finishing that problem.”

An even more intractable problem would be locating the plentiful NEOs in the 30-meter-plus range, which probably number in the millions. According to Clark Chapman, a space scientist at the Southwest Research Institute in Boulder, Colo., the odds of our planet encountering one of those bodies in the next century might be as high as 50 percent. Such an object would not impact the ground but would produce a multimegaton airburst in the lower stratosphere, Chapman says. Over a populated area with flimsy structures, that could be deadly, but in the more likely event of an explosion over the ocean, the effects would be relatively minor.

At present, the most threatening known asteroids all have a relatively low probability of ever striking Earth. One small body called 2007 VK184, which is 130 meters (425 feet) in diameter, has about a one in 3,000 chance of smacking into the planet in 2048. A much larger asteroid known as 1999 RQ36, 560 meters (1,800 feet) across, packs a more significant impact probability of one in 1,400, but not for another 160 years. It’s worth noting that over time these odds of impact are often revised, sometimes negating the objects’ threat entirely, as further observations better define NEO orbits or as those orbits are deformed by the gravitational pull of celestial bodies.

“That’s one of our main problems—as soon as you make a very close approach to a planet, including Earth, the subsequent motion gets much less certain,” Yeomans says. “The small errors you have in the orbit get magnified as a result of the close approach.”

One tiny asteroid that did strike, burning up on entry, provided a test of CSS and NASA’s efforts. In October, a CSS observer picked up a relatively common two-meter (six-foot) object at close range, and astronomers correctly predicted that it would disintegrate over northern Africa the next night. Although last-minute discovery of a larger NEO would be problematic for evacuations, Yeomans notes that being able to pinpoint the location of a brilliant fireball even hours in advance can have great geopolitical value. Armed with accurate NEO information, scientists can warn “countries that might be arguing with one another that this kiloton blast in the sky is not a man-made event,” he says. “What if this thing were spotted over the border between Pakistan and India? It could have been a real problem had it not been predicted ahead of time.”

For larger inbound NEOs, of course, early detection might allow human intervention to skirt catastrophe. Fulfilling lawmakers’ mandate for tracking 90 percent of 140-meter objects would “retire 99 percent of the risk to Earth from all objects of all sizes,” Yeomans says. “By retire, I mean, if we know they’re coming and they pose a threat, we have the technology to deal with it”—options include detonation or disrupting the object’s orbit by ramming into it or tugging it off-course with a nearby spacecraft. “There’s any number of ways to mitigate,” he says, “but you have to find them well in advance of a threatening encounter in order to undertake any of them.”

<!–Original Article and Photos

U.S. and Russian satellites collide

February 11, 2009 3:47 PM PST
In a commercial Iridium communications satellite and a defunct Russian satellite ran into each other Tuesday above northern Siberia, creating a cloud of wreckage, officials said today. The international space station does not appear to be threatened by the debris, they said, but it’s not yet clear whether it poses a risk to any other military or civilian satellites.

“They collided at an altitude of 790 kilometers (491 miles) over northern Siberia Tuesday about noon Washington time,” said Nicholas Johnson, NASA’s chief scientist for orbital debris at the Johnson Space Center in Houston. “The U.S. space surveillance network detected a large number of debris from both objects.”

g of an Iridium satellite near earth.

A rendering of an Iridium satellite near earth.

(Credit: Iridium Satellite)

Air Force Brig. Gen. Michael Carey, deputy director of global operations with U.S. Strategic Command, the agency responsible for space surveillance, said initial radar tracking detected some 600 pieces of debris. He identified the Russian spacecraft as Cosmos 2251, a communications relay station launched in June 1993, and said the satellite is believed to have been non-operational for the past 10 years or so.

“As of about 12 hours ago, I think the head count was up (to around) 600 pieces,” Carey told CBS News late today. “It’s going to take about two days before we get a solid picture of what the debris fields look like. But you, I think, can imply that the majority of that should be probably along the same line as the original orbits.”

He said U.S. STRATCOM routinely tracks about 18,000 objects in space, including satellites and debris, that are 3.9 inches across or larger. Tracking priority and “conjunction analysis”–identifying which objects may pose a threat to manned spacecraft–is the first priority.

“It’s going to take a while” to get an accurate count of the debris fragments, Johnson said. “It’s very, very difficult to discriminate all those objects when they’re really close together. And so, over the next couple of days, we’ll have a much better understanding.”

Asked which satellite was at fault, Johnson said “they ran into each other. Nothing has the right of way up there. We don’t have an air traffic controller in space. There is no universal way of knowing what’s coming in your direction.”

Iridium Satellite operates a constellation of some 66 satellites, along with orbital spares, to support satellite telephone operations around the world. The spacecrafts, which weigh about 1,485 pounds when fully fueled, are in orbits tilted 86.4 degrees to the equator at an altitude of about 485 miles. Ninety-five Iridium satellites were launched between 1997 and 2002 and several have failed over the years.

“Yesterday, Iridium Satellite LLC lost an operational satellite,” the company said in a statement. “According to information shared with the company by various U.S. government organizations that monitor satellites and other space objects (such as debris), it appears that the satellite loss is the result of a collision with a non-operational Russian satellite.

“Although this event has minimal impact on Iridium’s service, the company is taking immediate action to address the loss. The Iridium constellation is healthy, and this event is not the result of a failure on the part of Iridium or its technology. While this is an extremely unusual, very low-probability event, the Iridium constellation is uniquely designed to withstand such an event, and the company is taking the necessary steps to replace the lost satellite with one of its in-orbit spare satellites.”

Johnson said the collision was unprecedented.

“Nothing to this extent (has happened before),” he said. “We’ve had three other accidental collisions between what we call catalog objects, but they were all much smaller than this and always a moderate sized objects and a very small object. And these are two relatively big objects. So this is a first, unfortunately.”

As for the threat posed by the debris, Johnson said NASA carried out an immediate analysis to determine whether the space station faced any increased risk. The station, carrying three crew members, circles the globe at an altitude of about 220 miles in an orbit tilted 51.6 degrees to the equator.

“There are two issues: the immediate threat and a longer-term threat,” he said. “It turns out, when you have a collision like this the debris is thrown very energetically both to higher orbits and to lower orbits. So there are actually debris from this event which we believe are going through the space station’s altitude already. Most of it is not, most of it is still clustered up where the event took place. But a small number are going through station’s altitude.

“Yesterday, we did an assessment of what the risk might be to station and we found it’s going to be very, very small. As time goes on, (that) debris will (come down) some over months, most over years and decades and as the big ones come down they’ll be tracked, we’ll see them and the worst-case scenario, we’ll just dodge them if we have to. It’s the small things you can’t see are the ones that can do you harm.”

Asked if other satellites might be at risk, Johnson said, “Technically, yes. What we’re doing now is trying to quantify that risk. That’s a work in progress. It’s only been 24 hours. We put first things first, which is station and preparing for the next shuttle mission.”

Most, if not all, of the debris is expected to eventually burn up in Earth’s atmosphere.

Bill Harwood is a space analyst for CBS News.

Original Article

2 big satellites collide 500 miles over Siberia

CAPE CANAVERAL, Fla. – Two big communications satellites collided in the first-ever crash of two intact spacecraft in orbit, shooting out a pair of massive debris clouds and posing a slight risk to the international space station.

NASA said it will take weeks to determine the full magnitude of the crash, which occurred nearly 500 miles over Siberia on Tuesday.

“We knew this was going to happen eventually,” said Mark Matney, an orbital debris scientist at Johnson Space Center in Houston.

NASA believes any risk to the space station and its three astronauts is low. It orbits about 270 miles below the collision course. There also should be no danger to the space shuttle set to launch with seven astronauts on Feb. 22, officials said, but that will be re-evaluated in the coming days.

The collision involved an Iridium commercial satellite, which was launched in 1997, and a Russian satellite launched in 1993 and believed to be nonfunctioning. The Russian satellite was out of control, Matney said.

The Iridium craft weighed 1,235 pounds, and the Russian craft nearly a ton.

No one has any idea yet how many pieces were generated or how big they might be.

“Right now, they’re definitely counting dozens,” Matney said. “I would suspect that they’ll be counting hundreds when the counting is done.”

As for pieces the size of micrometers, the count will likely be in the thousands, he added.

There have been four other cases in which space objects have collided accidentally in orbit, NASA said. But those were considered minor and involved parts of spent rockets or small satellites.

Nicholas Johnson, an orbital debris expert at the Houston space center, said the risk of damage from Tuesday’s collision is greater for the Hubble Space Telescope and Earth-observing satellites, which are in higher orbit and nearer the debris field.

At the beginning of this year there were roughly 17,000 pieces of manmade debris orbiting Earth, Johnson said. The items, at least 4 inches in size, are being tracked by the U.S. Space Surveillance Network, which is operated by the military. The network detected the two debris clouds created Tuesday.

Litter in orbit has increased in recent years, in part because of the deliberate breakups of old satellites. It’s gotten so bad that orbital debris is now the biggest threat to a space shuttle in flight, surpassing the dangers of liftoff and return to Earth. NASA is in regular touch with the Space Surveillance Network, to keep the space station a safe distance from any encroaching objects, and shuttles, too, when they’re flying.

“The collisions are going to be becoming more and more important in the coming decades,” Matney said.

Iridium Holdings LLC has a system of 65 active satellites which relay calls from portable phones that are about twice the size of a regular mobile phone. It has more than 300,000 subscribers. The U.S. Department of Defense is one of its largest customers.

The company has spare satellites, and it is unclear whether the collision caused an outage. An Iridium spokeswoman had no immediate comment.

Initially launched by Motorola Inc. in the 1990s, Iridium plunged into bankruptcy in 1999. Private investors relaunched service in 2001.

Iridium satellites are unusual because their orbit is so low and they move so fast. Most communications satellites are in much higher orbits and don’t move relative to each other, which means collisions are rare.Iridium Holdings LLC, is owned by New York-based investment firm Greenhill & Co. through a subsidiary, GHL Acquisition Corp., which is listed on the American Stock Exchange. The shares closed Wednesday down 3 cents at $9.28.___AP science writer Seth Borenstein in Washington and AP technology writer Peter Svensson in New York contributed to this report.___On the Net:NASA: http://www.nasa.gov

Link to Original Article