The spacecraft was put in hibernation mode starting June 28, 2007, during which time the spacecraft’s onboard computer kept tabs on mission systems, transmitting special codes indicating that operations were either nominal or anomalous. During hibernation, most major systems of New Horizons were deactivated and revived only about two months every year. The second, third, and fourth hibernation cycles were Dec. 16, 2008, Aug. 27, 2009, and Aug. 29, 2014.
See Also
Why Is Pluto No Longer a Planet?