Author: theLogBook.com

NASA’s New Horizons abruptly loses contact with Earth-based ground controllers and then signals that it has gone into safe mode, ten days before its closest flyby of Pluto. In this mode, the spacecraft gathers no scientific data, and awaits intervention from Earth, but its distance from Earth – four billion miles away – means that signals transmitted to or from New Horizons take four and a half hours to reach their destination (and any reply takes just as long). A timing error is located in New Horizons’ automatic event sequencer, a vital part of its mission since it will need to operate independently to conduct hundreds of observations of Pluto and its satellites with no contact from Earth until later, and the probe is rebooted within 48 hours. Though the probe’s automatic switch to failsafe mode has cost the mission some scientific observations, most of the high-value data will not be collected until within 24 hours of closest approach on July 14th.

Nine years after its launch from Earth, NASA’s New Horizons space probe passes within 8,000 miles of the surface of Pluto, and within 18,000 miles of Pluto’s largest moon, Charon. Detailed images and observations are obtained of both of these bodies, with less detailed data gathered on Pluto’s four smaller, outermost moons. Cruising through the Pluto system at 30,000 miles per hour, New Horizons must break contact with Earth for nearly a full day to aim its cameras and other instruments at their targets. It’s not until some 12 hours after the point of closest flyby that New Horizons re-establishes contact with Earth, reporting that it has successfully completed the encounter with no problems.