The looming U.S. Navy attempt to shoot down a dying satellite could demonstrate an anti-satellite capability for its missile defense system.
A successful kill would mark the first time the United States uses a tactical missile to destroy a spacecraft – assuming that the ship-based missile defense system can handle the high closing speed of more than 22,000 mph.
“Everything becomes much more stressful at these large closing speeds,” said Geoffrey Forden, MIT physicist and space expert. “But if they do hit it, that’d be very impressive, and that’d be proof that it has ASAT [anti-satellite] capability.”
How it would work
The Navy looks to rely on its Aegis Ballistic Missile Defense System based on U.S. cruisers and destroyers, which was developed to protect U.S. forces and allies against short- and medium-range ballistic missiles. The interceptors rely on kinetic energy from their combined mass and speed to smash into their targets.
Three naval ships stand ready in the North Pacific Ocean to each take a shot with a modified Standard Missile-3 (SM-3). If the first attempt misses, the other two ships can take turns as backups.
The modified SM-3 interceptors will supposedly be able to identify the falling U.S. spy satellite based on changes in their targeting software. However, Forden expressed caution as to whether the Aegis system can score a successful satellite kill at such high closing speeds – previous tests involved much slower-moving targets.
“I’ll be very surprised if it works,” Forden said, pegging the chances at “less than 50-50.”
The United States has managed to take out satellites with other weapon systems in the past. An F-15 Eagle fired a missile-launched kill vehicle that struck and destroyed a target satellite in 1985. SPACE.com’s Leonard David also noted a 1986 “Star Wars” test by the Strategic Defense Initiative Organization involving the first space-to-space intercept of a target.
The United States is not alone in its anti-satellite tests. China used a missile to shoot down an old weather satellite a year ago, leaving a cloud of debris that will present a low-risk threat to other satellites and space missions for up to 20 years.
A U.S. intercept of its falling spy satellite would happen low enough to avoid debris endangering the International Space Station, and would only occur after space shuttle Atlantis has safely landed.
Success for the United States would boost the perceived capabilities of the Aegis system, but could also heighten international concern over U.S. missile defense systems being used to target satellites.
“All along, other countries have said missile defense has offensive capabilities, and in fact is better suited for such,” noted Joan Johnson-Freese, Naval War College security expert, in an e-mail to SPACE.com. “While the U.S. has ignored/downplayed those concerns, this test will basically prove that those concerns were valid.”
Senior U.S. officials apparently tried to allay such concerns at the Feb. 14 press briefing by emphasizing that the missile modifications would be difficult to make on a fleet-wide basis.
Yet Johnson-Freese also observed that the U.S. Navy’s three potential attempts “equates to lots of target practice – without international condemnation,” because the U.S. has declared the falling satellite a threat to public safety. That still has not prevented China and Russia from expressing their concerns.
Forden pointed out that the U.S. interception attempt could also help legitimize the earlier Chinese anti-satellite test which was heavily criticized by the U.S. and other countries. Setting a precedent now could open the door for future anti-satellite tests by other countries, added Johnson-Freese.
A slight chance also exists that China might be tempted to test its proven anti-satellite capability again, should the U.S. attempts fail to destroy the falling satellite.
“China has said it would take preventive measures, and that’s the only thing that makes sense,” Forden said.
By Jeremy Hsu
posted: 20 February 2008, 06:22 am ET