Advanced Extremely High Frequency (AEHF) satellites will be able to keep the U.S. military in communication even after a nuclear attack.

They're also more resistant to electronic jamming, which is a growing concern as tensions with China and Russia heat up.

In the war of the future, nations may try to physically destroy other nations' satellites to disrupt communications and navigation.

Your phone is not going to work on the day nuclear war starts. But the U.S. President, National Security Council, and combat commanders count on being able to communicate. This doomsday connection relies on what we call Advanced Extremely High Frequency (AEHF) satellites that sit in geostationary orbit.

“We need systems that work on the worst day in the history of the world,” says Todd Harrison, director of the Aerospace Security Project at the Center for Strategic and International Studies.

There are four AEHF sats in orbit today. The proposed 2019 U.S. Air Force budget shows about $29.8 million in funding to complete two more, which would launch in 2019 and 2020. Air Force staffers say more money has been set aside in 2019 to ready the software and databases for the pair of new sats.

The Air Force talks about the AEHF satellites as part of its new focus on modernizing America's nuclear abilities. “We must concurrently modernize the entire nuclear triad and the command and control systems that enable its effectiveness,” says Air Force Secretary Heather Wilson. The Trump administration has its eye on nuclear weapons, but these satellites also sit at the nexus of another big defense trend: Space warfare.

The Department of Defense is also investing in new jam-resistant GPS satellites. It is pouring money into future satellite programs, including AEHF, to the tune of $677 million for research and development in 2019. As orbital threats grow, new potential users—especially the U.S. Army—are taking interest in what the doomsday spacecraft can do. Preparing for post-apocalyptic communication may be just the beginning.

Can You Hear Me Now?

Nuclear weapons: They're bad for living things, and bad for spacecraft, too. After air- or ground-burst nuclear detonations, the atmosphere would fill with charged particles that emit energy across the electromagnetic spectrum. Ordinary signals from space won’t cut through this clutter. “In that kind of environment, all bets are off,” Harrison says.

AEHF sats send multiple beams toward the ground, improving the chances that information will get through. The phased array antenna hops across frequencies so the signal can jump to an unjammed frequency to get through, like a car swerving into an empty lane to avoid traffic.

“We need systems that work on the worst day in the history of the world"

The tactics that enable doomsday communications can also defeat intentional jamming from enemies, making these secure satellites useful as more than just a hotline for the White House. The sats surge their signal strength to overwhelm any noise from an enemy trying to jam them, while nulling antennas pinpoint the attack and dampen the signal with counter-noise.

Harrison says that only 7 percent of the military bandwidth is now carried on protected systems, leaving plenty of communications vulnerable to enemy jamming. Lockheed Martin, which builds AEHF sats, and Northrop Grumman, which builds the payloads, want to change that.

Grumman is promoting a new "Low Cost Terminal" for AEHF. “It was designed for easy operation and low maintenance and training costs to make it truly affordable for tactical users needing highly protected anti-jam, low probability of detection communications,” Cyrus Dhalla, Grumman’s vice president of communications systems, said in a release.

The terminals could be available by the end of 2018. This is the first time that a completely industry-funded and developed terminal has been allowed to access the doomsday satellites, the company says. In theory, by stripping away the physical protection that a terminal needs to survive a nuclear attack the Low Cost Terminal could be small and cheap enough to put inside a vehicle.

The Air Force did not respond to questions about using the terminals more broadly than its nuclear mission, but AEHF sats are shared by all U.S. military services and some allies. And the sats have attracted suitors. “We continue to field calls from interested customers,” Grumman spokesperson Jessica Brown says. “The Army has shown interest in a small transportable EHF terminal."

Dogfights in Orbit

Jamming is one major threat to satellites, but there is another looming danger, one that even AEHF cannot defend against: physical attacks in space. Back in 2007, both the U.S. and China destroyed defunct satellites in orbit to show that they could do it. The technique is to fire a hunter/killer into the vicinity, fix the location of the enemy sat with infrared sensors, and use thrusters to collide with it and blow it up.

So far, most anti-satellite tests have at aimed targets in low earth orbit, up to 1,200 miles above the planet. But other tests show space weapons can reach higher. The AEHF doomsday sats live in geostationary orbit (GEO), a higher plane that matches the spin of the earth, enabling the spacecraft to loiter over one spot. What could kill sats in GEO, which are 22,500 miles up?

“In that kind of environment, all bets are off.”

In 2013 China launched an experiment that, according to some analysts, showed great potential for sending a weapon to GEO. The launch didn’t deposit anything into orbit. Instead, the payload reached space and released a puff of telltale gas to prove it was there, then reentered the atmosphere.

Suspicion over the launch increased when the U.S. government confirmed that the payload went higher than the Chinese admitted. “The launch appeared to be on a ballistic trajectory nearly to geostationary orbit,” according to the U.S. Air Force. Civilian analysts used commercially available satellite imagery to show the test had launched from a mobile rocket launch system. (Credit is due to analyst Brian Wheedon for his sleuthing in 2014.)

Facing that kind of threat—a "shoot and scoot" direct-ascent space weapon that fires at targets when they're overhead—it makes sense to increase the number of AEHF sats. The upcoming increase from 4 to 6 is a way to protect the ability to communicate no matter what.

As far as fighting back against these space attacks, it won't be easy, but it's possible. Proposed methods include adding thrusters so sats can dodge the incoming hunter/killers, or arming satellites with lasers or their own kinetic projectiles. Not of these technologies appear ready for prime time.

All this hardware is just the start of a strange new world of space war, where the political and diplomatic implications of what's happening are even less clear than the engineering. Is jamming an AEHF satellite an act of war? Does hosting such a communication system on another nation’s payload make that spacecraft a legitimate target in a shooting war?

“The challenges of warfighting in this domain are not really understood,” Harrison says. “We don’t have any history to go on.”

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