Jeffrey LewisBlinding Satellites

The Pentagon often issues dire sounding warnings like :

  • “The Soviets have … at least one ground-based laser, also at Sary Shagan, that may have sufficient power to damage some unprotected satellites in near-earth orbits.”
  • “China already may possess the capability to damage, under specific conditions, optical sensors on satellites that are very vulnerable to damage by lasers.”

The Pentagon refuses to comment on the specifics. Typical is Maj. Gen. Franklin J. Blaisdel, who told reporters “As to the specifics of that, you know, we’re getting down into the weeds in the tactical side of that; I’d prefer not to do that.”

Well, let’s get in the weeds for a second.

The qualifications, especially in the reference to China, clearly indicate that DOD is talking about the vulnerability of satellites that use optical sensors to detect light. I know the Bush Administration isn’t big on science but that vulnerability is how the damn things work. As Allen Thomson has written of imaging satellites, their “very functioning depends on concentrating incident light on a small, sensitive detector.”

Consider an series of incidents in 1975 with missile warning satellites, which detect infrared light:

Infrared sensors on board an early warning satellite stationed over the Indian Ocean, which monitors Soviet ICBM silos, were illuminated Oct. 18 from sources in the western part of the USSR. The energy level was 10-1,000 times the intensity obtained from an ICBM launch or from natural sources such as a forest fire or volcano. Five such incidents have occurred since Oct. 18, and the strong radiation persisted for more than 4 hr. on at least one occasion. No permanent damage was experienced by the spacecraft sensors, so far as is known. …

However, on Nov. 17 and Nov. 18, two other USAF satellites in highly elliptical Molniya-type orbits also experienced similar incidents with their infrared horizon sensors while over the USSR.

The initial judgment of many in the Department of Defense was that the Soviet Union was experimenting with lasers. Then, cooler heads prevailed:

In his first meeting with the press as Defense secretary, Donald H. Rumsfeld sought to discount earlier Defense Dept. reports that tended to support the view that the Soviets used laser devices to blind the U.S. satellites. … Shortly after the Rumsfeld meeting, background material from the Pentagon wasmade public that said the cause was believed related to breaks in gas pipelines in the USSR. [Emphasis mine.]

Gas fires may generate enough infrared light to temporarily blind satellites. Why? Because missile launches and other natural phenomena, which the satellites must be sensitive enough to detect, are 10-1,000 times less bright that these gas fires. The satellite has to be sensitive.

DOD is taking a trivial statement that is true (optical sensors are sensitive to light) and using it as a warrant for the claim, as summarized by one story, that “China appears to be sharpening its war fighting space skills.”

Calm down people.

Sources:

“The Soviets have …” Department of Defense, Soviet Military Power 1990 (Washington, DC: Government Printing Office, September 1990) 61.

“China already may possess …” Department of Defense, Report to Congress Pursuant to the FY2000 National Defense Authorization Act, Annual Report On The Military Power Of The People¬ís Republic Of China, (Washington, DC: Government Printing Office, July 2003) 32.

“Infrared sensors on board …” Philip J. Klass, “Anti-Satellite Laser Use Suspected,” Aviation Week & Space Technology (December 8, 1975) 12.

“In his first meeting …” “DOD Continues Satellite Blinding Investigation,” Aviation Week & Space Technology (January 5, 1976) 18.

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