Pentagon seeks to detect laser attacks on satellites

Oct. 1, 1995
Lasers are double-edged swords in the minds of Pentagon officials. Lasers in the hands of a US enemy could cause major headaches for American military forces. But at the same time, under the right circumstances, lasers can be enormously powerful and cost-effective weapons for the United States military. Recent events in the Department of Defense illustrate both lines of thought.

Lasers are double-edged swords in the minds of Pentagon officials. Lasers in the hands of a US enemy could cause major headaches for American military forces. But at the same time, under the right circumstances, lasers can be enormously powerful and cost-effective weapons for the United States military. Recent events in the Department of Defense illustrate both lines of thought.

The Pentagon has been quietly conducting space experiments to try to develop ways to detect laser attacks on its satellites. Military spacecraft are considered among the most vital of US military assets because they are used to warn of any impending nuclear attacks on the USA by an enemy. In the depths of the Cold War, US officials worried that the Soviet Union was developing a ground-based laser that could blind or disable US military satellites at a crucial moment. That never happened, but now some rogue nation might do the same thing, thanks to the ever-widening availability of laser technology.

Weather-satellite experiment

Right now, when a satellite dies unexpectedly in orbit, Pentagon officials have few ways to diagnose what might have happened and to determine whether the satellite may have been attacked by an enemy. A newly disclosed experiment on an Air Force weather satellite is seeking to determine if laser attacks on a satellite can be detected.

The Air Force never officially announced the laser experiment, called Special Sensor Z, but a few sketchy details were disclosed in the in-house newsletter of The Aerospace Corporation (El Segundo, Calif.), which built the device for the US Air Force. However, Air Force officials are reluctant to see the project publicized, and company officials declined to be interviewed by Laser Focus World.

But the newsletter says that Special Sensor Z is attached to a weather satellite called Defense Meteorological Satellite Program Spacecraft F-13, which was launched March 24 into an orbit that loops over the Earth's north and south poles (see photo). The sensor is "a proof-of-concept project that uses novel optical technology to detect the presence of a ground-based laser illuminating the satellite," says the newsletter article. The sensor uses a Fabry-Perot interferometer to separate laser light from other radiation striking the sensor. Presumably researchers are testing the sensor's capabilities by shining a laser on the satellite from the groundbut the newsletter article steers clear of any details.

The major technological challenge was making sure the interferometer would stay properly aligned despite the vibration during the launch and expansion and contraction caused by extremes of hot and cold of space. The sensor package includes a laser source that is used to check the interferometer`s alignment.

John Pike, a space policy analyst at the Federation of American Scientists (Washington DC), says the Air Force is barking up the wrong tree. Potential US foes are more likely to try to use a space rocket to attack a US satellite than a laser, he says. "Of all the ways that Iraq might try to poke out our eyes, a laser is lowest on the list."

On-board reporting system experiment

But Special Sensor Z isn't the military`s only foray into this field. Three months after that experiment was sent into space, the Pentagon's Ballistic Missile Defense Organizationthe "Star Wars" officetried to fly another laser-sensor experiment on a military scientific satellite known as STEP-3.

The experiment, called the Satellite Attack Warning and Flight Experiment (SAWAFE), would have used a "smart skin" that could detect when a satellite was under attack by a variety of weapons. Unfortunately for the Pentagon, the rocket carrying the satellite veered out of control seconds after its June 23 launch and was ordered to self-destruct over the Pacific Ocean, blowing SAWAFE to smithereens.

The SAWAFE smart skin included thin-film pyroelectric sensors that were designed to detect when a laser was being trained on the satellite, fiberoptic cables that would have registered x-rays hitting the satellite from an enemy nuclear explosion meant to knock out the satellite, and a spiral-shaped antenna that would have detected microwaves aimed at the satellite.

Of course, Pentagon officials didn't think that anyone would have attacked the STEP-3 satellite. But they wanted to move beyond laboratory tests of the sensors to trying them out in the real environment of space, so that they could be tuned to accurately identify attacks.

Meanwhile, Air Force officials continue to be excited about the prospect of developing laser weapons of their own. These would not be used against satellites but against missiles: the Airborne Laser, which would fly in a converted Boeing 747 aircraft, would destroy enemy short-range ballistic missiles seconds after they were launched.

Two teams of aerospace companies, led by Boeing and Rockwell, are developing competing designs for the Airborne Laser. General Ronald Fogelman, chief of staff of the Air Force, told reporters in August that the service remains bullish on the project and plans to spend $5 billion to purchase seven of the laser aircraft.

The Navy and Army are developing new defensive missiles that would shoot down enemy missiles in flight, but Air Force officials believe that the laser is a more cost-effective way to provide missile defense. The irony, of course, is that one arm of the Air Force is rushing to develop the laser weapons just as another is worrying about attacks by them.

About the Author

Vincent Kiernan | Washington Editor

Vincent Kiernan was Washington Editor for Laser Focus World.

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