NASA to Launch 'Deep Space Atomic Clock' Into Orbit Aboard SpaceX Falcon Heavy Rocket

In three day's time, NASA is launching a host of unique science experiments into space aboard a SpaceX Falcon Heavy rocket as part of the Department of Defense's Space Test Program-2 (STP-2) mission.

Among the payloads inside the rocket—which is set to take-off from the Kennedy Space Center, Florida, sometime after 11:30 p.m. EDT on June 24—is a technology which has the potential to revolutionize navigation in space and usher in a new era of exploration to far-flung worlds.

The toaster-sized Deep Space Atomic Clock (DSAC)—built by NASA's Jet Propulsion Laboratory (JPL)—will be sent into orbit and tested for one year in preparation for future missions to the moon, Mars and beyond.

Essentially, the technology works in a similar way Global Positioning Systems, or GPS. When we navigate on Earth using a phone for example, GPS satellites can locate where we are based on the time it takes for the signal to travel between the phone and the satellite. Spacecraft, however, communicate with atomic clocks located on Earth to navigate rather than orbiting satellites.

"Our ability to navigate spacecraft throughout deep space is driven by the ability to very accurately measure the length of time it takes a signal to travel from a ground antenna to the spacecraft—knowing how fast that signal travels and how long that trip took, we can compute the distance to the spacecraft," Jill Seubert, Deputy Principal Investigator with the DSAC project, wrote in a Reddit AMA thread. "Collecting these data points over time allows navigators to reconstruct the spacecraft's trajectory, and predict where it's going."

However, current atomic clock technology has several drawbacks for space navigation, thus researchers are looking to develop techniques so that a spacecraft can work out its position immediately with an onboard system.

"Today, the atomic clocks that can measure that signal travel time accurately enough to safely navigate spacecraft are big—up to the size of a refrigerator, too big to send into deep space," Seubert said. "Because of this, we currently have to send the signal from the ground antenna to the spacecraft and then back to the ground antenna, which is known as 'two-way tracking.'"

"The Deep Space Atomic Clock will give us that accurate and stable time-keeping capability in a package small enough and robust enough to fly into space—which means now we can use 'one-way tracking,' in which the signal is sent directly from the ground antenna to the spacecraft, or vice versa from the spacecraft to the ground antenna. This is an amazing advancement in navigation; it lets us use the existing Deep Space Network more efficiently, it enables autonomous onboard spacecraft navigation—'self-driving spacecraft'—and even enables GPS-like navigation systems at other planets and moons."

The DSAC uses ions (charged atoms or molecules) of mercury to keep time incredibly accurately—to about a tenth of a trillionth of second. This means that even after 10 million years, the clock will lose just one second. In the high-precision world of space navigation, this level of accuracy is essential. But adapting this kind of technology for deep space throws up several challenges.

"The main challenges in designing/building a space atomic clock are making it handle the high level of vibration during launch and the usually more extreme environment of space while maintaining a high level of performance," Eric Burt, a developer of the DSAC at JPL, wrote in the AMA thread.

"For instance, to protect the clock against large variations in the external magnetic field—this could be 100 times larger than variations found on Earth—usually requires heavy magnetic shielding, but at the same time we must keep the mass down.

"Another example would be temperature: for a clock on the ground one can usually control the temperature to less than 1 degree Celsius whereas in space we expect swings of 10 degrees Celsius," he said. "The easiest way to solve this is by putting the clock inside an 'oven,' which would keep the temperature constant. However this would also require a lot of power that we don't have available. We must also protect the clock from radiation. Finally, the clock must be able to operate autonomously for many years without human intervention."

The STP-2 mission will also include several other experimental payloads which could help to improve future spacecraft technology. Among these are a small satellite that will test a non-toxic propulsion system and an experiment designed to look into the issue of how to protect satellites in space.