New Horizons took a Fourth of July nap

New Horizons, now just one week away from closest approach to Pluto, suffered some sort of event on the Fourth of July.  At 1:54 PM EDT (12:54 PM CDT, or 15:54 UTC), controllers at Johns Hopkins University’s Applied Physics Lab in Maryland lost contact with the probe.   Downlink from the probe resumed about an hour and twenty minutes later, and indicated that a problem had been detected and New Horizons had switched to its backup computer, booting it into a safe mode and transmitting telemetry so controllers could decide what to do next.  The problem was traced to a timing flaw in a command sequence that will not be executed again before the encounter, so the team has allowed New Horizons to resume full operations starting tomorrow.  When the encounter comes, safe mode will be temporarily suppressed, as the data is of such high value that they are willing to jeopardize the spacecraft for it.  (Or, in other words, if it suffers a fault that would normally trigger safe mode, they will have lost the prime objective anyway, so recovery won’t really matter much.)

Some science observations were of course lost during the day that New Horizons was in safe mode, but they do not impact the primary objectives and only modestly impact secondary objectives.  The team is again on track for a good encounter next Monday.Talking of the encounter, remember to be patient for the pictures.  😉  New Horizons will be loading its memory banks full, and then spending months downlinking the results.  We’ll get a picture or two fairly quickly after the encounter, but we shall all have to be patient for the good stuff.New Horizons Plans July 7 Return to Normal Science Operations

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