FALCON is a different beast than the shipboard gravimeters. Shipboard gravimeters are -- in effect -- extremely well damped/shock absorbed/sprung/mechanically

FALCON is a different beast than the shipboard gravimeters. Shipboard gravimeters are -- in effect -- extremely well damped/shock absorbed/sprung/mechanically isolated standard spring-stretching gravimeters. Essentially the same idea as Lacoste-Romberg machines from post WWII. The damping is to ameliorate the accelerations from the ship moving through the ocean. Similar systems are flown in aircraft, but they both face the same exact problem: How the hell do you get rid of the background accelerations to measure something akin to a geological signal? Falcon is a gradiometer. There are accelerometers at the end of a spinning arm -- at least that's my mental picture. Perhaps it's a flat plate with two sets of accelerometers at 90 degrees from each other to measure two gradient components simultaneously? In any case, it is designed to "reject the common mode" between the paired accelerometers. If that rejection is done "successfully enough", the difference in the accelerometers' readings samples the spatial gradient of the gravity field at that place and time. A whole lot of ingenious engineering, a lot of on-device processing, and a lot of data massaging afterwords yields an estimate of the local gravity gradient. It's a very impressive piece of kit, and my hat's off to whoever dreamed up the idea in the first place -- even if it was buried under security classification prior to release in the '90s.