How hard would it be to but Global Positioning Systems (GPS) on Near Earth Asteroids?

It wouldn’t do much good, even if we could locate all of the relevant masses and place a device (or many, because they may rotate, too, so you’d have to have all faces covered). The “near-Earth asteroids” are in orbits that take them far out of range of the GPS satellite signals. Even at 22,000 miles above Earth those satellites are “very near”, and the asteroids can have orbits wider than Earth’s. That is, they can be hundreds of millions of miles from Earth, except when they’re about to intersect or fly by our orbit.

By the time the GPS satellites had them in range, everyone on Earth who was interested would already be getting an update on what was going to happen or likely to happen.

It’s cheaper and easier to just track their orbits. There are far too many to do what you suggest.

The Global Positioning System is only useful for locating objects on Earth, because of the way it works. A GPS works by knowing where the satellites should be at any given time, and listening for the Doppler effect on the satellite’s signals as they pass overhead. They are designed to be used on Earth’s surface (inside the satellite’s orbit). Once you get outside of the orbit, GPS units won’t work right.

One problem is that Earth is moving also. On Earth, the satellites are always orbiting around us, and we seem to be standing still. From the point of view of an asteroid, the satellites are moving around Earth, which is itself moving around the Sun, which makes the exact location in space of the satellite much more complicated to find.

We are already tracking and predicting the orbits of hundreds of asteroids, including several near-earth asteroids. GPS units won’t tell us anything that we don’t already know. Also, imagine the cost of installing GPS units on hundreds of asteroids.

@PhiNotPi Actually, GPS works by measuring the time it takes for a signal from at least 4 tracking satellites to reach the receiver. The GPS then takes the difference in time and the known positions of the satellites to calculate a location.