The people in the Mission Operations Center — “the MOC” — had been tracking NASA’s New Horizons spacecraft for 9½ years as it journeyed the breadth of the solar system. It was just 10 days away from the dwarf planet Pluto when, at 1:55 p.m. on July 4, it vanished.
The disappearance of the spacecraft challenged the New Horizons team to perform at its highest level and under the greatest of deadline pressures. They did work efficiently and saved the mission. We all wish the New Horizons team the best as they approach the busiest time of the fly-by encounter. I have known and respected many of the engineers and scientist for more than 20 years and am happy to praise their skills.
The nature of the New Horizons mission did not permit any wiggle room, any delays, any do-overs, because it was a flyby. The spacecraft had one shot at Pluto, tightly scheduled: When it vanished, New Horizons was going about 32,000 miles per hour and on track to make its closest pass to Pluto, about 7,800 miles, at precisely 7:49 a.m. July 14.
But as the New Horizons team gathered in the control room on July 4, no one knew whether their spacecraft was still alive.
Because New Horizons is so far away, it takes 4 1/2 hours for a one-way message between the spacecraft and the MOC. That means whatever happened to New Horizons on July 4 had actually happened 4 1/2 hours before the people in Mission Operations knew about it.
The team figured out what had gone wrong. The spacecraft’s main computer had been compressing new scientific data for downloading much later. At the same time, it was supposed to execute some previously uploaded commands. It got overloaded; the spacecraft has an “autonomy” system that can decide what to do if something’s not quite right. That system decided to switch from the main to the backup computer and go into safe mode.
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Additional information about the start of the New Horizons mission and the key roles played by ATI instructors who worked (and are still working) on the New Horizons mission see