NASA’s Jet Propulsion Laboratory has been trying to perfect a clock for 20 years because accurate timekeeping is very important to navigation in space. The Deep Space Atomic Clock or DSAC is being built for deep space exploration. The space agency has said that it’s going to test this atomic clock later this year.
Most missions currently use antennas on the ground paired with atomic clocks for navigation. They send narrowly focused signals to the spacecraft which return the signal. The time difference between sending the signal and receiving a response is used to calculate the spacecraft’s velocity, location, and path.
This method has been used for a long time and while it’s reliable, NASA feels that it can be made more efficient. Since a ground station has to wait for the spacecraft to return a signal, it can only track one spacecraft at a time. This, in turn, binds the spacecraft to wait for navigation commands from Earth instead of making the decisions onboard in real-time.
NASA’s DSAC project will is about ensuring that future missions have accurate onboard timekeeping. Spacecraft that use this new technology will no longer have to rely on two-way tracking. It could use the signal sent from Earth to calculate position without having to first return the signal and then wait for a command from the ground, a process that normally takes up to a few hours.
Not only with this innovation enable ground stations to track multiple spacecraft at once, it will also enable the spacecraft to focus on mission objects instead of having to adjust its position to point antennas earthward or close to a link or two-way tracking.
The DSAC prototype is a small, low-mass atomic clock that’s base on mercury-ion trap technology and it’s about the size of a four-slice toaster. NASA says that it could be made smaller for future missions.
It will be launched later this year with General Atomic’s Orbital Test Bed spacecraft. NASA aiming to confirm in the test that the DSAC can maintain time accuracy to better than two nanoseconds(.000000002 seconds) over a day, the goal is to achieve a 0.3 nanosecond accuracy.