August 29, 2014

New Horizons Commanded into Last Pre-Pluto Slumber

Rest up, New Horizons – you have a busy 2015 ahead.

NASA’s Pluto-bound spacecraft was put into hibernation this morning, following a successful 10-week annual checkout period. Mission controllers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, verified that New Horizons entered hibernation at 9:21 a.m. EDT. With New Horizons now beyond Neptune’s orbit – more than 2.75 billion miles from Earth – that signal needed just over four hours to reach the mission operations center through NASA’s Deep Space Network.

“This is the final hibernation period on the flight to Pluto,” says Principal Investigator Alan Stern, of the Southwest Research Institute. “When we wake up in December, it’s to prepare for encounter, which begins the following month!”

Final checkout

This summer marked New Horizons’ final annual systems checkout and instrument calibration before Pluto arrival. “The checkout went very well,” says Chris Hersman, New Horizons mission systems engineer from APL. “The spacecraft is healthy and in great shape to begin Pluto encounter activities in early 2015.”

Did you know? Before New Horizons enters hibernation, its main antenna is pointed to where Earth will be the next time the spacecraft wakes up. This allows operators to gather data on the spacecraft’s condition immediately upon wakeup, without having to fire thrusters to reposition New Horizons.

Checkout work ranged from refreshing the processors on the spacecraft’s computers, to testing the sun sensors New Horizons uses to automatically determine its position in space, to uploading the final version of the autonomy software that will guide collection of and protect the data New Horizons collects during Pluto close approach.

The team also checked the spacecraft’s primary and backup operating systems as well as all seven scientific instruments – and calibrated the instruments to gather “cruise science” data that includes a distant examination of the surfaces of Pluto and its moons early next year. Last month the Long Range Reconnaissance Imager was used for the first optical navigation campaign – snapping images that helped the team home in on Pluto – and the navigation team continued to track the spacecraft to refine its orbit.

A small trajectory correction maneuver on July 15 – the mission’s first in four years – corrected the spacecraft’s arrival time at the precisely intended aim point through the Pluto system next July. New Horizons’ traversing of Neptune’s orbit on Aug. 25 officially marked its entry into “Pluto space.”

“It’s great to get through the last annual checkout,” says Mission Operations Manager Alice Bowman, of APL. “Now, our main focus is the Pluto encounter. We’ve guided this spacecraft for more than eight years to get to this point, and we’re almost there. This is what we trained for.”

New Horizons is scheduled to come out of hibernation on December 7; it then stays awake for two years of Pluto encounter preparations, flyby operations, and data downlinks. Distant-encounter operations at Pluto begin January 4, 2015.

Flight controllers Mike Conner and Josh Albers, in the New Horizons Mission Operations Center at the Johns Hopkins Applied Physics Laboratory, await the signal confirming the spacecraft’s entry into hibernation on August 29; (inset) mission operations manager Alice Bowman keeps an eye on spacecraft telemetry and the communications link between New Horizons and NASA's Deep Space Network.