[meteorite-list] Two Satellites Collide in Orbit

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 12 Feb 2009 09:57:11 -0800 (PST)
Message-ID: <200902121757.JAA12417_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/news/n0902/11iridium/

Two satellites collide in orbit
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
February 11, 2009;
Updated _at_ 5 p.m. with Iridium statement;
Updated _at_ 5:45 p.m. with STRATCOM interview

In an unprecedented space collision, 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."

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 LLC operates a constellation of some 66 satellites,
along with orbital spares, to support satellite telephone operations
around the world. The spacecraft, 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, those
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.
Received on Thu 12 Feb 2009 12:57:11 PM PST