At the end of the Jupiter flyby, New Horizons entered safe mode. I remember at that time a question being asked "What would happen if this happened during the Pluto flyby", and the answer was that safe mode was going to be disabled for a few weeks around the time of the flyby. I can't remember very precisely the time period.

Flash forward, New Horizons entered safe mode less than 2 weeks before the flyby. I can't find the original source of my knowledge. Deos anyone out there know what the plan was 8 years ago to disable safe mode around the time of the Pluto encounter?


1 Answer 1


You remember correctly:

On Sunday, ground controllers planned to relay a final batch of instructions to New Horizons to prepare for its July 14 flyby of Pluto, the only major body in the solar system that has not yet been visited by a robotic spacecraft.

The “encounter program” includes software to prohibit the very type of automated safe mode that New Horizons executed Saturday afternoon.

“Encounter mode short-circuits the on board intelligent autopilot so that if something goes wrong, instead of calling home for help, which is what most spacecraft do and what New Horizons does during cruise flight, it will just stay on the timeline. It will try to fix the problem, but it will rejoin the timeline because if it ‘went fetal,’ as we say, if it just called home for help, it could miss the flyby,” New Horizons lead scientist Alan Stern told Discovery News before Saturday’s problem.

  • $\begingroup$ I wish I could find the quote from years ago, but it's good to know I'm not completely crazy (At least on this account...) Still, it would be nice to get the quote from back then... $\endgroup$
    – PearsonArtPhoto
    Jul 6, 2015 at 14:43

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