NASA has identified the glitch that struck its Pluto-bound New Horizons spacecraft, mission scientists said during a press conference today. But the problem should be fixed in plenty of time for the Pluto flyby later this month.
The July 4th anomaly that set back the New Horizons spacecraft owed to a hardware error: The process of compressing data to clear room on the solid state drive for the flyby caused the processor to overload, NASA says. As a result, the spacecraft automatically entered safe mode, losing downlink with the Deep Space Network.
However, the team sees this as a minor bump in the road toward Pluto. New Horizons principal investigator Alan Stern said that the data blackout from Saturday to Monday resulted in a loss of 30 observations. None of it involved the principal science payload, although some spectroscopy and minor atmospheric observations were lost, as well as some data from a dust counter designed by a group of students.
After working through the weekend, though, NASA's engineers have the craft ready to go just in time for the beginning of its encounter with Pluto tomorrow.
"New Horizons is operating flawlessly, on course, and not only is the spacecraft operating flawlessly, but so are all the instruments in the payload," Stern said in a press conference. "We came a long way to explore pluto, and all the early indications are that Pluto is not going to let us down."
The safe mode process was automatically programmed into the craft, meaning it was just a matter of getting it back online. However, tomorrow it will be switched into "encounter mode," where the principal mission is observation, and the spacecraft is not designed to enter safe mode unless absolutely necessary. As the spacecraft only moves data at about 1 kilobyte per second, 99 percent of the data will remain on the spacecraft after the encounter, slowly downlinking with Earth.
"Those events will not happen concurrently again," Glen Fountain, project manager of New Horizons, said.
The first science data, post-flyby, is expected to start downlinking to Earth on July 15, including imaging. During the flyby on July 14, the craft will focus exclusively on observations during its 12 hour flyby. The relay time between the spacecraft and the Earth is about nine hours, as the craft is about 4.5 light hours away. Because of that long trip, a high degree of automation is necessary for the craft, which is why it was designed to enter safe mode many times prior to encounter mode.