NASA’s New Horizons spacecraft, which flew by Pluto in July of 2015, woke up today from hibernation mode in preparation for its next rendezvous with a space rock at the edge of the Solar System. The vehicle came out of its slumber 3.7 billion miles from Earth, as it’s speeding toward an icy body nicknamed Ultima Thule that orbits the Sun way beyond Neptune. Now that the spacecraft is awake, the mission team has a very full schedule through 2018: the flyby will take place on January 1st, 2019.
New Horizons has been in and out of hibernation mode twice since April of 2017. While in hibernation, the spacecraft basically runs on autopilot, with only its essential components and a few of its instruments powered on. The probe also works off a long list of commands that get uploaded to the spacecraft’s memory before it snoozes off. All of this helps to save wear and tear on the spacecraft, as well as minimize the amount of work that the mission team has to do from the ground.
“We have a small team and when we put the spacecraft into hibernation, it takes less time for us” to operate New Horizons, Alice Bowman, New Horizons’ mission operations manager, tells The Verge. “We can be spending it on developing the command set for the flyby, which is what we were doing.”
The New Horizons mission team sent the commands to wake the vehicle from its six-month hibernation on June 4th, and early this morning, the spacecraft sent back a signal confirming that it was officially up and ready for action. For the next two and a half months, Bowman says they’ll be doing housekeeping on the spacecraft, such as running tests and uploading new software. This also includes downloading any science collected during hibernation and any data leftover in the vehicle’s recorder.
Then on August 13th, the New Horizons team will take the spacecraft out of its spin state, which helps to keep the probe stabilized. And in mid- to late-August, they will try to use one of the New Horizons’ cameras to image the vehicle’s target, Ultima Thule. The space rock is located in the Kuiper Belt — the large cloud of icy bodies beyond Neptune. “We believe that’s when we’ll first be able to see it,” says Bowman.
After August, New Horizons will be on its final approach to Ultima Thule, and that’s when the team will be in crunch time. They’ll be planning and refining the exact commands needed for the spacecraft’s flyby sequence. And that’s going to be tough, given the target: Ultima Thule is small, just about 20 to 23 miles in diameter, or nearly twice as long as the island of Manhattan. (For comparison, Pluto is nearly 1,500 miles in diameter.) It’s a dark body set against a bright field of stars, so it’s hard to see. And the team wants to fly closer to Ultima Thule than they did with Pluto. “We have a lot to do,” says Bowman. “It’s going to be very challenging.”
Adding to the challenge is that New Horizons is incredibly far from Earth right now, which makes communicating with the spacecraft a lengthy process. A radio signal takes about 12 hours to travel to and from the spacecraft — three hours longer than the round-trip signal time at Pluto. Over the next six months, the spacecraft will be collecting a lot of data, too. The mission team will be uploading commands every couple of weeks, instructing the vehicle to compress and erase the data to make room on the vehicle’s computer. That means they’ll have a lot of work and a lot of waiting to do.
Then in October, New Horizons will fire its thrusters and perform the first of seven maneuvers to change is trajectory. The last one is scheduled for December 22nd, and then on Christmas Day, its flyby sequence will begin. So today’s milestone is just the beginning of many exciting things to come for New Horizons. Or, as Bowman says, “It’s the start of something grand.”