by Rafi Letzter, LiveScience
NASA has switched on a new, super-precise, space-based atomic clock that the agency hopes will one day help spacecraft drive themselves through deep space without relying on Earthbound clocks.
It’s called the Deep Space Atomic Clock (DSAC), and it works by measuring the behaviors of mercury ions trapped in its small frame. It’s been in orbit since June, but it was first successfully activated on Aug. 23. It’s not at all flashy — just a gray box about the size of a four-slice toaster and full of wires, Jill Seubert, an aerospace engineer and one of the leaders of the project at NASA, told Live Science. But that unassuming size is the point: Suebert and her colleagues are working to engineer a clock small enough to load onto any spacecraft and precise enough to guide complicated maneuvers in deep space without any input from its refrigerator-sized cousins on Earth.
You need a precise clock to find your way around space because it’s big and empty. There are few landmarks by which to judge your position or velocity, and most are too far away to offer precise information. So every decision to turn a ship or fire its thrusters, Seubert said, begins with three questions: Where am I? How fast am I moving? And in what direction?