When you imagine all the incredible hurdles mankind will have to eventually overcome if we plan on sending humans to other planets or, even better, other star systems, knowing what time it is probably doesn’t rank high on the list. For NASA, however, ensuring that missions deep into space have accurate readings of time is incredibly important, and it’s so vital that the agency actually launched an atomic clock into space back in April.

A few days ago, the clock’s handlers back on Earth flipped the switch and successfully activated the new timekeeping gadget, paving the way for such technology to play a major role in future deep-space missions.

The mission, called simply the Deep Space Atomic Clock, is largely a proof of concept in that NASA will use it for the next year to test how well it works before deciding how to proceed. Engineers will test its accuracy while it endures the same conditions it would while riding along with a crewed spacecraft.

Atomic clocks are used during space missions because they’re incredibly accurate. Firing a signal between two points and then measuring the time it takes for the signal to complete the trip gives scientists the ability to map the path of a spacecraft with precision, but for a crewed mission, waiting for those time readings to be relayed from clocks based on Earth would cause unacceptable delays.

Because of this, NASA wants future spacecraft to bring their own atomic clocks along for the ride, giving spacecraft crew the ability to navigate without having to wait for location information to arrive from Earth.

“The goal of the space experiment is to put the Deep Space Atomic Clock in the context of an operating spacecraft — complete with the things that affect the stability and accuracy of a clock — and see if it performs at the level we think it will: with orders of magnitude more stability than existing space clocks,” Todd Ely of NASA’s Jet Propulsion Laboratory said in a statement.

One of the major issues with building an atomic clock into a spacecraft is the size. The clocks used by NASA on Earth are huge — the size of a refrigerator, according to JPL — so shrinking things down a bit and ensuring the hardware can handle conditions in space are both high priorities for NASA.