If the US does not protect its Earth-orbiting satellites, the equivalent of a car bomb in space could take the economy back to the 1950s, according to witnesses testifying in Washington DC earlier this week.
"We are at an unusually good moment for the US in space, and it won't last," Brookings Institution fellow Michael O'Hanlon told the US House armed services subcommittee on Tuesday. "It can't last."
US Global Positioning System satellites and commercial telecommunications satellites already face jamming from low-tech weapons on the ground. But a looming threat, said witnesses, is a weapon launched into space to directly attack a satellite or to detonate a nuclear device that could fry the electronics of many satellites at once
Such an attack could cripple US military capability and also affect day-to-day civilian life. For example, credit card transactions are authorised through satellite communications links, and most cable channels are beamed down to Earth through satellites. "We don't worry as much about nuclear attacks on our satellites as we used to, and I think that's a mistake," O'Hanlon says.
The Outer Space Treaty of 1967 bans nuclear weapons in space. But in a wartime situation, a country might put a bomb into low Earth orbit and detonate it with a timer or remote control. Any satellite within tens of kilometres would probably be destroyed and any unprotected satellites within hundreds of kilometres would risk being damaged or disabled.
Over time, the blast would feed additional charged particles into the Van Allen radiation belts that surround Earth, ruining the operation of most satellites in low Earth orbit within a month, O'Hanlon argues in written testimony.
"I think most countries could pull off an anti-satellite strike on the first try," O'Hanlon says. "You don't have to get that close to destroy something." But it would be considerably more difficult to explode a nuclear weapon in the higher geosynchronous orbit, where many communications and military satellites orbit.
Another potential threat is small satellites that could ram into larger satellites or carry conventional explosives. "Some countries have had anti-satellite weapons in the past," said air force lieutenant-general Robert Kehler. "We're watching that today."
A potential response to the threat of attack is to "harden" satellites to make their electronics less vulnerable. The US military already hardens some of its satellites.
But if US companies were asked to harden their satellites, they would have a tougher time competing with international companies that did not have such a requirement, noted Edward Morris, director of the office of space commercialisation for the National Oceanic and Atmospheric Administration.
O'Hanlon recommended improved monitoring of satellites so the US would know whether its satellites were being attacked. Some satellites, including National Reconnaissance Office imaging satellites, already have warning systems, while air force radar can track boosters or other objects in space.
Another way to deal with a satellite attack is to jam the attacker's communications. "We have in fact deployed some of our own terrestrial-based counter-communication capabilities so we can be in a position to deal with an adversary," Kehler said.
Kehler said more a likely threat in the near term was an attack to the ground stations that communicate with military satellites. The armed forces have had to increase security at these installations, he said. "But you can only build so many fences," Kehler added, so there should be back-up stations too.
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