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New Horizons: A ‘Timing Flaw’ Scare Resolved

You get to expect the unexpected when writing about space probes, but somehow what New Horizons did to my weekend completely blind-sided me. Running a routine check of email before (I thought) sliding into the rest of a relaxing work break, I found messages about the glitch on the Pluto-bound spacecraft. Sunday turned into an all-screens-on exercise in checking multiple feeds and waiting for news.

The problem with New Horizons brought to mind a short story I wrote many years ago about an unmanned probe sent to Epsilon Indi on a 90-year journey. The probe is within a month of encounter when all goes silent and Earth controllers can only wait to see what happens.

The point of the story (it was called “Merchant Dying,” published in Charlie Ryan’s Aboriginal Science Fiction in the July/August 1987 issue) was that spacecraft going to another star are going to need autonomous repair capabilities we can only dream of today. New Horizons is a long way out, but we can still work with it through the Deep Space Network, and a check this morning shows DSN’s 70-meter Canberra dish working New Horizons as I write. But space is teaching us all about backup computers and autonomy one step at a time.

The ‘anomaly’ occurred on July 4 and led to a loss of communications with Earth. New Horizons’ autonomous systems were able to switch to the critical backup computer while placing the spacecraft in ‘safe mode’ and re-starting communications. Emily Lakdawalla reports here that the New Horizons Anomaly Review Board met at 1600 EDT yesterday to analyze the situation. The subsequent NASA statement was reassuring, and I’ll quote its latest update in its entirety:

NASA’s New Horizons mission is returning to normal science operations after a July 4 anomaly and remains on track for its July 14 flyby of Pluto.

The investigation into the anomaly that caused New Horizons to enter “safe mode” on July 4 has concluded that no hardware or software fault occurred on the spacecraft. The underlying cause of the incident was a hard-to-detect timing flaw in the spacecraft command sequence that occurred during an operation to prepare for the close flyby. No similar operations are planned for the remainder of the Pluto encounter.

“I’m pleased that our mission team quickly identified the problem and assured the health of the spacecraft,” said Jim Green, NASA’s Director of Planetary Science. “Now – with Pluto in our sights – we’re on the verge of returning to normal operations and going for the gold.”

Preparations are ongoing to resume the originally planned science operations on July 7 and to conduct the entire close flyby sequence as planned. The mission science team and principal investigator have concluded that the science observations lost during the anomaly recovery do not affect any primary objectives of the mission, with a minimal effect on lesser objectives. “In terms of science, it won’t change an A-plus even into an A,” said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute, Boulder.

Adding to the challenge of recovery is the spacecraft’s extreme distance from Earth. New Horizons is almost 3 billion miles away, where radio signals, even traveling at light speed, need 4.5 hours to reach home. Two-way communication between the spacecraft and its operators requires a nine-hour round trip.

Status updates will be issued as new information is available.


So we’re less than ten days out from Pluto/Charon and a knuckle-whitening moment seems to have passed with little loss of data. With observations re-starting on Tuesday, here’s imagery from July 1, with the inset showing an enlarged Pluto. Features as small as 160 kilometers are visible at this point (credit: NASA/JHUAPL/SWRI). Onward and outward…

Update: More news this afternoon, as per NASA:

NASA will host a media teleconference at 3 p.m. EDT (19:00 UTC) today to discuss the New Horizons spacecraft returning to normal science operations after a July 4 anomaly. The mission remains on track to conduct the entire close flyby sequence as planned, including the July 14 flyby of Pluto…

Audio of the teleconference will be streamed live at http://www.nasa.gov/newsaudio


Comments on this entry are closed.

  • djlactin July 6, 2015, 9:50

    Event happens on the Fourth of July.

    “Planetologist’s interpretation”: piece of grit?
    “Programmer’s interpretation:” Oops!
    “Physicist’s interpretation”: stray photon from a firework struck something important?
    “Cynic’s interpretation”: a stunt to grab public attention?
    My interpretation: Choose any three.

  • Alex Tolley July 6, 2015, 12:15

    Let’s hope they are right and this is a very minor glitch. Trying to fix things with a 9 hour round trip must be frustrating. With Lightsail-1, communication was all bust instantaneous with a few orbits between tries.

    Is it just me, or does Pluto currently look like Lowell’s Mars? Just add some canals…

  • Paul Gilster July 6, 2015, 13:14

    Looks like Barsoom, right? I couldn’t agree more with the comparison.

  • Charley July 6, 2015, 14:06

    The cause of the problem was a timing flaw in the final batch of software uploaded to the spacecraft, NASA said in a status report late Sunday. The mission will provide the first up-close observations of Pluto when it passes within 7,800 miles (12,550 km) of the icy planet at around 7:50 a.m. ET (1350 GMT) on July 14.

    Notice said it was UPLOADED, not even something that was already in the system and at the last moment too. It really look like the expensive mission was lost for a while. This reminds me of the problems that they were going to face if they ever decided to send a space probe to a distant star, i.e. Project Daedalus. There, the computer would REALLY be on its own. The time for light signal to reach it would amount to months to even years. A long, lonely voyage for the automated system – and actually no one around to help it if it got in to trouble!

  • Charley July 6, 2015, 14:09

    The problem with New Horizons brought to mind a short story I wrote many years ago about an unmanned probe sent to Epsilon Indi on a 90-year journey. The probe is within a month of encounter when all goes silent and Earth controllers can only wait to see what happens.
    You wrote a story? You should do us a favor and reprint it here so that we can see it

  • Michael July 6, 2015, 14:23

    Looks a lot like Ganymede to me, I can’t wait for the close ups.


  • J. Jason Wentworth July 6, 2015, 14:44

    Better having that hiccup occur now than just before periapsis! (Cassini’s Huygens Titan probe was discovered to have a problem that the ESA flight controllers had to work around, although they had months or years to do so.) I believe that dark region on Pluto may be what enabled the 6.4 Earth day rotation rate to be determined (I’d always imagined Pluto as having a feature like that, which would give it such a light curve).

  • Andrew Palfreyman July 6, 2015, 15:18

    It’s Monday 1500 EDT and new “spectacular” pix are due to be released in about one hour. Heads up!

  • RobFlores July 6, 2015, 15:24

    I wonder if horizons uses the multi-computer ‘board of governors’
    the space shuttle main computer systems used to have. A computer spews out nonsense it gets tossed out. It doesn’t sound like it since probably it would not have glitched, unless the instruction set sent to the coder contractors had the same timing flaw.
    It would have been interesting to see mission control activity when the loss
    of communications occurred. (the scene from Apollo 13 after the initial event and controllers getting data they couldn’t believe comes to mind, bit of organized chaos)

  • Paul Gilster July 6, 2015, 16:50

    Charley writes:

    You should do us a favor and reprint it here so that we can see it.

    Can’t do that for reasons of copyright, I’m afraid. At least I assume that’s the case, but I need to find out what the situation is now that Aboriginal is no longer with us.

  • Alex Tolley July 6, 2015, 17:08

    July 3 images even clearer. And like Mariner images of Mars, the image of Pluto no longer looks like Barsoom.

    @Michel – it does look more like Ganymede at the moment.

  • ljk July 7, 2015, 9:42

    Latest information on New Horizons glitch from TPS including a list of what science data was lost during the down time:


    To quote:

    Precisely what we gave up:

    We lost 16 LORRI images, 3 of which were for navigation.

    We lost 4 Ralph color observations.

    1 Ralph composition spectroscopy measurement.

    4 Alice atmospheric observations — but the Alice team does not expect to detect the Pluto system until July 12, these were just being taken for due diligence.

    We lost a “plasma roll” in which SWAP, PEPSSI and radio science collaborate to measure planetary environment.

    We lost 3 days of SWAP, PEPSSI, and SDC background monitoring. We don’t have any evidence that any of these have detected the Pluto system yet anyway.

    That’s 30 observations out of a total of 496 to be made between July 4 and end of close approach observations. So about 6% of observations by count, but scientifically we weight observations by how close they are to the planet. These are not nearly as important as the ones we’ll make from 100 times closer. While we’d prefer this hadn’t occurred, it’s a speed bump in terms of total return.