New Horizons' first operational hibernation phase is off to a successful start! On commands transmitted from the Mission Operations Center at Johns Hopkins Applied Physics Laboratory (APL) in Maryland, through NASA's Deep Space Network, the spacecraft eased into hibernation mode in the early hours of June 27. Since then, New Horizons has twice broadcast "green" beacon tones back to Earth, indicating all systems are healthy and operating as programmed.

Hibernation - in which the spacecraft's redundant components and guidance and control system are powered off - is designed to reduce wear and tear on spacecraft electronics, lessen spacecraft-operation costs and free up Deep Space Network tracking resources for other missions. New Horizons will "sleep" in this spin-stabilized state for most of the remaining 8-year cruise to Pluto; operators will wake New Horizons for about two months out of each year for system checkouts and instrument calibrations.

During hibernation, New Horizons' onboard flight computer monitors system health and broadcasts a beacon tone through the medium-gain antenna. New Horizons will transmit a "green" coded tone if all is well, or a "red" tone if it detects a problem and requires help from the operations team. New Horizons is the first mission to make operational use of hibernation in flight and the associated beacon communications mode.

"We're looking forward to an uneventful spacecraft slumber," says New Horizons Mission Operations Manager Alice Bowman, of APL. She adds that to be sure everything is nominal, the team will check in on New Horizons seven times during this hibernation period, which lasts two weeks.