This post is also available in: heעברית (Hebrew)

About 70% of the US Army’s major combat systems depend on signals being beamed from space. The Pentagon is investing in a new generation of satellites that will provide the military with better accuracy and have better anti-jamming capabilities, but this is not enough.

“Our force structure today is built around the assumption that we have GPS and we have satellite communications,” said Colonel Richard Zellmann, commander of the 1st Space Brigade based in Colorado. “Militaries around the world have begun to understand the advantages that the US has enjoyed because of uncontested access to the space domain,” Zellmann recently told reporters, according to phys.org. Russia and China are both developing satellites capable of maneuvering through space, potentially allowing them to smash into another orbiting object. America, too, has acquired satellites that can move in orbit and inspect or monitor other space objects.

But Zellmann noted it is far cheaper and simpler for an enemy to disrupt or damage US military satellites than to develop their own orbital platforms. For instance, low-cost jammers placed at the right location can wreak havoc with incoming GPS signals, which are often quite weak.

Already, the Army has brought back training to keep soldiers current on how to read paper maps, and the Navy is teaching sailors how to navigate by the stars with the help of sextants. Army operations centers have map boards that show where troops are on the ground, so if a “Blue Force tracker” that watches soldiers with GPS is disrupted, “we still know where all of our units are,” Zellmann said.

The old-school, analog technologies are also being augmented by new science designed to replicate satellites, only from Earth.

DARPA (the military’s Defense Advanced Research Projects Agency) has stated it wants a new generation of precise navigation and timing tools that can work without GPS. One such system uses “pseudolites”—ground-based devices that beam GPS-like signals and are already being used in the commercial sector.

Another technology that is used in aircraft is an “inertial navigation system” that deploys a series of sensors and gyroscopes to calculate a plane’s—or a missile’s—location. The military is still trying to improve the accuracy of these systems.

President Donald Trump unveiled his first National Security Strategy, which specifically addressed the military importance of America’s space infrastructure.