Traveling out of the Solar System is tiring work. Having visited Pluto in July 2015, and now half way to its next target, NASA’s New Horizons spacecraft has entered a period of hibernation.
It officially went to sleep at 3.32pm EDT (8.32pm BST) on Friday, April 7 at a distance of 5.7 billion kilometers (3.5 billion miles) from Earth. It will remain asleep for 157 days until September 11, when it will be woken up to begin studying the Kuiper Belt at the edge of the Solar System in earnest.
New Horizons is currently half way in both time and distance to 2014 MU69, an object in the Kuiper Belt it is heading towards. It will fly past briefly and study this remnant of the early Solar System, no more than 45 kilometers (30 miles) across, on January 1, 2019. This will be the most distant object from Earth ever visited by humanity.
Prior to going into hibernation, the spacecraft had been “awake” for about two and a half years, since December 6, 2014. Since it launched in January 2006 it has entered hibernation 18 times to save power, but this 852-day period of being awake was its longest yet, required to not only observe Pluto but also send back all of its data over 16 months.
It won’t be entirely asleep during this upcoming period, though. While most of the spacecraft will be unpowered, its onboard flight computer will continue to monitor the spacecraft’s health and send back a weekly beacon-status tone to Earth. Onboard sequences sent by mission controllers will eventually wake the spacecraft up.
"We're looking forward taking advantage of the reduced mission operations workload during this hibernation, as well as one early next year, to plan much of the MU69 flyby," said Alice Bowman, New Horizons mission operations manager, from the Johns Hopkins University Applied Physics Laboratory, in a statement.
Bowman told The Verge that the team would now be working on preparing for the flyby, which will require a sequence of commands to be performed from December 25, 2018 to January 3, 2019. The team also needs to work out exactly where MU69 is.
Once New Horizons does make this flyby, it’ll continue to make its way out of the Solar System, communicating with Earth for as long as possible until it runs out of power.