The promise and perils of LEO constellations

The Pentagon already created an acronym — PLEO — for its plans to deploy satellites in proliferated low Earth orbit constellations.

DoD’s Space Development Agency is leading the way as it prepares to put up a communications transport layer and a surveillance and tracking layer for hypersonic missile defense.

The Pentagon’s staunchest proponent of PLEO, undersecretary of defense for research and engineering Mike Griffin, has argued that the Pentagon must reduce its dependence on large, billion-dollar satellites in geosynchronous orbit that are vulnerable to anti-satellite weapons.

The case for proliferated constellations in low Earth orbit is based on the idea that it provides a resilient space infrastructure. Smaller satellites would be cheaper and easier to replace than geostationary systems if they were destroyed by anti-satellite weapons. That approach should work in theory. A key question is whether satellites and launch vehicles can be made cheap enough to make the cost of taking down a LEO system not worth it.

Changing the “cost equation” for an enemy will be a key challenge for DoD and the U.S. Space Force, says Michael Martindale, a former U.S. Air Force space operator and currently the director of space education for the Space Force Association.

As much as DoD worries about GEO satellites becoming targets of China’s orbital weapons, LEO systems are much easier to hit — no sophisticated in-space weapons required. So-called direct-ascent weapon such as ordinary surface-to-air missiles and anti-ballistic missile interceptors are far more likely to be used against low-orbiting satellites than space-based weapons, Martindale says.

A recent study by Todd Harrison of the Center for Strategic and International Studies points out that China and Russia, despite their rhetoric about wanting to ban weapons in space, are building arsenals of anti-satellite weapons on the ground. This is sending a message to other countries that ground-based anti-satellite weapons are fair game, Harrison notes. “With its 2019 ASAT test, India made clear that it believes kinetic Earth-to-space ASAT weapons are a legitimate means of self-defense by deterrence.”

A space-arms control proposal that for years has been pushed by China and Russia says nothing about prohibiting ground-based weapons. That speaks loudly about what their intentions are, says Martindale. “Their behavior says they’re only interested in banning the capabilities that they don’t already have.”

With more LEO systems about to be deployed by DoD — and by U.S. companies that aim to provide services to DoD — the growth of direct-ascent weapons challenges U.S. space superiority, which military doctrine defines as the ability to conduct space operations “without prohibitive interference from terrestrial or space-based threats.”

Space superiority, one of the missions the Space Force inherited from Air Force Space Command, “was always a given,” Martindale says. “Now it’s contested.”

The Space Force can’t possibly protect every satellite so it must figure out ways to deter countries from even attempting to take one down.

The deterrence doctrine of massive retaliation works in the nuclear realm because no one wants to be nuked. But it might not be as effective with space because the United States has more to lose than anyone else if satellites become targets in the event of war. Martindale says the key is to make it too costly for an enemy to mount an attack. “You have to reduce the value of each individual target.”

Direct-ascent weapons aren’t cheap enough to take out LEO constellations comprising dozens or hundreds of small, widely space satellites. “If I want to deny the U.S. its space capabilities, the cost equation is easy for expensive GEO satellites,” he says. But if there are hundreds of targets, and the enemy knows that the U.S. can replenish those assets quickly, the cost equation changes and using missiles is not as effective.

To ensure the PLEO satellite architectures envisioned by Griffin and the Space Development Agency provide their own deterrence, DoD would need a ready supply of replacement satellites and rapid access to launch services so constellations can be replenished quickly and inexpensively.

“That is one of the most important things they can do: change the space-lift equation,” he says.

Right now, it generally takes years to get a DoD satellite off the ground. One of the Space Force’s challenges, Martindale said, will be to make space launch more like Air Force air operations, where the time line from identifying a target to launching an airstrike is usually measured in minutes or hours.

Maybe that’s not realistic in space, says Martindale. But it should be days or weeks. It can’t be years.