US Commercial US and Russian Satellites
Collide in Orbit

JOHN MATSON / Scientific American 11feb2009

A commercial satellite collided with a Russian satellite over Siberia yesterday, yielding a cloud of fragments, according to a NASA scientist tracking space debris. The collision between the commercial satellite, belonging to the American communications firm Iridium, and the Russian satellite, believed to be defunct based on its advanced age, was the first of its kind, says Nicholas Johnson, chief scientist at the NASA Orbital Debris Program at Johnson Space Center in Houston. (A spokesperson for Iridium said a statement on the incident would be released shortly.)*

"In the past almost 20 years, there have been three other accidental collisions between objects in orbit, but they've all been very minor," Johnson says. "The most debris ever produced in an event was like four debris, and this is two intact spacecraft colliding, and we have hundreds of debris out there. We don't know exactly how many yet."

According to Johnson, the military sky-watchers who track satellites in orbit picked up the collision 490 miles (790 kilometers) above Earth Tuesday. "One of the things that they discovered yesterday afternoon ... was all of a sudden, where two satellites used to be, there were two clouds of debris," he says. The actual crash appears to have occurred just minutes before noon, Eastern Standard Time.

Johnson says NASA has already determined that the debris cloud poses "no significant new risk to the International Space Station." The next space shuttle mission, which may launch as early as February 22, should be in the clear as well, according to the space agency.

Such a collision between two intact spacecraft may be unprecedented, but it is not completely unexpected. "There are no rules of the road in space," Johnson says. "Anybody can fly anywhere they want." Even concerted efforts to track and guide spacecraft in orbit are subject to some uncertainty in trajectory estimates. At seven miles (11 kilometers) per second, Johnson says, "a little error means a lot."

*UPDATE (7:10 P.M.): Iridium's statement confirms the loss of the satellite, calling the crash an "extremely unusual, very low-probability event." The company says its network of 66 satellites plus in-orbit spares "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."

source: 11feb2009

Debris Spews Into Space in Collision of Satellites

WILLIAM J. BROAD / New York Times 12feb2009

For decades, space experts have warned of orbits around the planet growing so crowded that two satellites might one day slam into one another, producing swarms of treacherous debris.

It happened Tuesday. And the whirling fragments could pose a threat to the International Space Station, orbiting 215 miles up with three astronauts on board, though officials said the risk was now small.

“This is a first, unfortunately,” Nicholas L. Johnson, chief scientist for orbital debris at the National Aeronautics and Space Administration, said of the collision.

It happened some 490 miles above northern Siberia, at around noon Eastern time. Two communications satellites — one Russian, one American — cracked up in silent destruction. In the aftermath, military radars on the ground tracked large amounts of debris going into higher and lower orbits.

“Nothing to this extent” has ever happened before, Mr. Johnson said. “We’ve had three other accidental collisions between what we call catalog objects, but they were all much smaller than this,” the objects always very small and moderate in size.

The communication satellites, he added, “are two relatively big objects.”

The American satellite was an Iridium, one of a constellation of 66 spacecraft. Liz DeCastro, corporate communications director of Iridium Satellite, based in Bethesda, Md., said that the satellite weighed about 1,200 pounds and that its body was more than 12 feet long, not including large solar arrays.

In a statement, the company said that it had “lost an operational satellite” on Tuesday, apparently after it collided with “a nonoperational” Russian satellite.

“Although this event has minimal impact on Iridium’s service,” the statement added, “the company is taking immediate action to address the loss.” The company’s hand-held phones can be used anywhere around the globe to give users voice and data communications.

Mr. Johnson said the Russian satellite was presumably nonfunctional. Officials at the Russian Embassy in Washington could not be reached for comment.

Mr. Johnson said the United States military’s tracking radars had yet to determine the number of detectable fragments. “It’s going to take a while,” he 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.”

At a minimum, Mr. Johnson added, “I think we’re talking many, many dozens, if not hundreds.”

The debris could threaten the space station and its astronaut crew, he said.

“There are actually debris from this event which we believe are going through space station altitude already,” he said. The risk to the station, Mr. Johnson added, “is going to be very, very small.” In the worst case, he said, “We’ll just dodge them if we have to. It’s the small things you can’t see that are the ones that can do you harm.”

In Houston, International Space Station controllers have often adjusted its orbit to get out of the way of speeding space debris, which can move so incredibly fast that even small pieces pack a destructive wallop.

John Yembrick, a NASA spokesman in Washington, said the agency now judged the risk of collision with the speeding fragments to be “very small.” The threat, he added, is defined and acceptable.

Mr. Johnson, who works at the Johnson Space Center in Houston, said the new swarms of whirling debris might also eventually pose a threat to other satellites in an orbital chain reaction.

“What we’re doing now is trying to quantify that risk,” he said. “That’s a work in progress. It’s only been 24 hours. We put first things first,” meaning the station and preparing for the next shuttle mission.

William Harwood contributed reporting.

source: 11feb2009

Big satellites collide 500 miles over Siberia 

MARCIA DUNN / AP  12feb2009

CAPE CANAVERAL, Fla. – Two big communications satellites collided in the first-ever crash of its kind 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.

This was the first high-speed impact between two intact spacecraft, NASA officials said.

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 that 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 said the loss of the satellite was causing brief, occasional outages in its service and that it expected to have the problem fixed by Friday.

Iridium also said it expected to replace the lost satellite with one of its eight in-orbit spares within 30 days.

"The Iridium constellation is healthy, and this event is not the result of a failure on the part of Iridium or its technology," the company said in a statement.

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.

source: 11feb2009

NASA Alert as Russian and US Satellites
Crash in Space at 25,000mph

BOBBIE JOHNSON / The Guardian (UK) 12feb2009

NASA scientists are closely monitoring the skies after two satellites crashed into each other over Siberia, in what experts have said is the first collision of its kind.

The accident, which took place more than 400 miles above the earth's surface on Tuesday, has left a large cloud of debris drifting in space. NASA officials are keeping watch to see if the wreckage could endanger other spacecraft, although they said it was unlikely that the International Space Station could be damaged.

"It will be weeks at least before the true magnitude of these clouds are known," NASA said in an alert message. "The risk to the space station is considered to be very small and within acceptable limits."

The agency said that it was more concerned about the threat to an array of monitoring satellites, which it said were of "highest interest for immediate consideration".

Air Force Lieutenant Colonel Les Kodlick of the US strategic command, said: "We believe it's the first time that two satellites have collided in orbit." The command's joint space operations centre was tracking 500 to 600 new bits of debris, some as small as 10cm (3.9 inches) across, in addition to the 18,000 or so other man-made objects it has catalogued, he said.

The incident is thought to have involved a 12-year-old satellite belonging to the US company Iridium and a defunct Russian Cosmos satellite that was put into orbit in 1993. The craft, which weighed 560kg and 950kg respectively, apparently smashed into each other at a speed of 420 miles per minute (25,000mph). Both satellites were used for telecommunications, with the US satellite an active part of Iridium's network of 66 craft which provide satellite telephone access to more than 250,000 people worldwide.

It is unclear what caused the crash, but the Russian satellite is thought to have shut down some time ago and would have had no steering mechanism.

Although there have been collisions in the past, they only involved spent rocket parts or small satellites. The scale of this crash, said officials, was unprecedented.

"In the past almost 20 years there have been three other accidental collisions between objects in orbit, but they've all been very minor," said Nicholas Johnson, chief scientist at NASA's orbital debris programme. "The most debris ever produced in an event was four … this is two intact spacecraft colliding and we have hundreds of debris out there."

In the past abandoned or dysfunctional satellites have caused problems, with some pushed into extremely wide "graveyard" orbits that move them out of the way of other spacecraft. In several cases, rogue satellites have been shot out of the sky to prevent them crashing to Earth.

source: 11feb2009