With the
successful landing of space shuttle Atlantis this morning, U.S. Defense
Department officials said the window of opportunity is now open for attempting to
shoot down a wayward spy satellite.
But experts
question the stated motives and whether the potential benefits outweigh the
risks.
The
satellite USA-193, also known as NROL-21, was launched into orbit Dec. 14,
2006. Shortly after it reached orbit, ground controllers lost contact with it.
Though the satellite's objective is secret, many figure it is a high-resolution
radar satellite intended to produce images for the National Reconnaissance
Office (NRO).
The
Pentagon plans to shoot it down,
convinced its toxic hydrazine fuel poses an unacceptable risk to people on the
ground. Currently, three U.S. Navy ships — the cruiser USS Lake Erie and the
destroyers USS Decatur and USS Russell — are posted in the Pacific Ocean
waiting for an optimal time to launch. The Erie will get one 10-second window
each day over the next 10 days or so to fire one of its two SM-3 missiles
before the defunct satellite tumbles to Earth, according to the American Forces
Press Service. The Decatur is also fitted with an SM-3 missile.
But former
assistant secretary of defense Philip Coyle doesn't buy that rationale.
"The
spy agency doesn't want some part of the satellite to fall into the wrong
hands," said Coyle, now a senior advisor to the Center for Defense
Information. "I don't think that's being emphasized enough as a motivation
for NRO to want this thing to be shot down."
In order of
importance to the NRO, Coyle named two other reasons for the attempted
shoot-down:
"Number
two, poke the Chinese, because we're showing them not only that we can shoot
down a satellite in a test without creating a lot of debris like they did. But
we're also showing them we can do it any place in the world, because we're
doing it from the ocean," Coyle said, referring to a similar satellite
destruction by the Chinese. "And a third reason is to show off our
missile-defense capabilities such as this, though this is much easier than
hitting an enemy warhead."
Warheads
move more erratically and are much trickier targets than a predictably moving
satellite.
Toxic
tank
Even so,
there is a chance of missing the satellite all together, for one because it's
moving so fast.
"The
closing speed between the missile and the satellite is going to be very high,
much higher than they might have in a missile engagement," said Coyle, who
is also past director of the Operational Test and Evaluation program in the
Department of Defense. "So that's another reason why they might miss is
because they've never had experience trying to hit something moving so fast
before. Still I think it should be relatively straightforward."
The
satellite and missile would close on one another at a velocity of about 22,783
mph (36,667 kph).
Hitting the
bus-sized
target is just half the battle. To be completely successful, the missile
must also destroy the satellite's fuel tank, which holds about 1,000 pounds
(454 kilograms) of toxic hydrazine.
Pentagon
officials have argued that if the satellite were to fall through the atmosphere
with no missile interference the hydrazine tank could survive the fiery descent
to reach Earth's surface intact, spewing toxic gas over an area about the size
of two football fields. Those who inhaled it would need medical attention.
"In this
case, we have some historical background that we can work against for the tank
that contains the hydrazine," said Marine Gen. James E. Cartwright during
a Feb. 14 press briefing. "We had a similar one on Columbia that survived
re-entry. We have a pretty reasonable understanding that, if the tank is left
intact, it would survive the re-entry."
However,
destroying the fuel tank and dispersing the hydrazine requires a direct hit on
the possibly tumbling satellite. The high closing speeds for the satellite
intercept and the uncertainty of puncturing the fuel tank could make that goal
questionable, according to an analysis done by Geoffrey Forden, an MIT
physicist and space expert.
"If
they do shoot at it, even if they hit it, there's just a 30 percent chance that
the shrapnel connected by the intersection hits the hydrazine tank,"
Forden said.
What if the
missile misses?
"As we
reviewed the data, if we fire at the satellite, the worst that could happen is
that we miss," Cartwright said. "Then we have a known situation, which is where
we are today." He continued, "If we hit the hydrazine tank, then we've improved
the potential to mitigate that threat. The regret factor of not acting clearly
outweighed the regret factor of acting."
They
wouldn't know for at least a day whether the tank had been destroyed, said
Pentagon Press Secretary Geoff Morrell.
Coyle, the
former Defense Department official, doesn't think the hydrazine tank is a big
enough safety issue in the first place, stating that the U.S. produces about 36 million pounds (about 16 million kilograms) of hydrazine each year.
"If
we're so worried about hydrazine we oughtn't to be trucking it around on U.S. highways and on rail cars the way we do, if that's really our concern," Coyle
told SPACE.com. "So if we're really worried about safety, putting a
few dollars into a school-bus crossing some place would probably be a better
investment than $60 million for this test."
Clouded
rationale
During a
Tuesday press briefing, Morrell denied that this is a test of the United State's anti-satellite capabilities.
"This
operation is designed to alleviate a threat to human beings on this planet.
There is a large tank of hydrazine fuel onboard that satellite that would pose
a significant threat to people within the immediate vicinity of it if it were
to hit land," Morrell said. "So not wishing to take that risk, the president
has asked — ordered — this department to shoot down that satellite."
The plan
comes on the heels of the intentional
destruction last year of China's Fengyun-1C weather satellite, which
produced a flurry of concern over the hostile-or-not nature of the firing as
well as a serious load of shrapnel littering Earth orbit. That debris is still
in space, frustrating mission managers and satellite operators forced to dodge
the potentially debilitating bits.
The U.S.
Defense Department plan, however, was made public to the international
community.
"This
announcement demonstrates openness about a sensitive subject that is
appropriate to a democratic society," said Ray Williamson, Executive Director
of the Secure World Foundation in Colorado.
However,
Williamson added, "I fear that using a ballistic missile in this manner after
the United States roundly chastised the Chinese government for its
anti-satellite (ASAT) test just over a year ago sends completely the wrong
message to the world community."
The
attempted shoot down of the satellite will undoubtedly send a political
message. Both Russia and China have expressed concerns regarding the U.S. attempt, with Russia labeling it a weapons test of the missile defense system.
"The
timing of it is very interesting, coming after [the Russia-China] proposal on
banning space weapons," said Roger Launius, National Air and Space Museum senior curator. He added that the U.S. attempt could be a response to China's anti-satellite test last year that "we can do this too," and take out
satellites if necessary.
"The
potential political cost of shooting down this satellite is high," said
Laura Grego, an astrophysicist with the Union of Concerned Scientist's Global
Security Program. "Whatever the motivation for it, demonstrating an
anti-satellite weapon is counterproductive to U.S. long-term interests, given
that the United States has the most to gain from an international space weapons
ban. Instead, it should be taking the lead in negotiating a treaty."
A U.S. attempt that fails to destroy the satellite could also send a message – although not one the U.S. would like. China and the rest of the world could assume the miss was a fluke, or they
could also see failure as evidence that the U.S. technological lead in space
has declined, according to Launius.
Weighing
the balance
The U.S. may find itself in a difficult position by going ahead with the attempt, even given
the real danger of the satellite's hazardous payload falling to Earth.
Forden
calculated the risks of the hydrazine tank killing or injuring someone at 3.5
percent if it survived re-entry. However, he stated his belief that the
political consequences of the attempted shoot-down could be worse, by further
opening up the international arena for future anti-satellite tests and possible
conflict in space.
"You
have to weigh the chance of [the satellite] killing or injuring someone against
legitimizing China's ASAT [anti-satellite] test," Forden said. "A
three percent chance of killing or injuring someone is large, but the
consequences of allowing China to go ahead...I still come down and say it's a bad
idea."
The future
of space as a battlefield could mean clouds of debris from destroyed
satellites. That would add to some 17,000-plus objects that are already being
tracked by the U.S. Space Surveillance Network. According to the NASA Orbital
Debris Program Office at the space agency's Johnson Space Center in Houston, Texas, for the past 45 years, the average number of cataloged object re-entries
has been one per day.
"Stuff
will hang up there until gravity brings it down," noted Launius. "If
you get enough of that up there, just getting through it could be an issue for
mission launches."
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