After a journey of more than 5 billion kilometers (3 billion miles) over nine years, the New Horizons spacecraft is now only a week away from becoming humanity’s first ever visitor to Pluto on July 14.
So when the spacecraft suddenly went dark over the weekend and entered safe mode, it probably wasn’t the best of times for all of the scientists involved. At 6:54 p.m. BST (1:54 p.m. EDT) on Saturday July 4, the mission operations team at the John Hopkins University Applied Physics Laboratory in Maryland temporarily lost contact with the unmanned probe. Scientists were eventually able to regain contact but, with a two-way communication time of nine hours owing to the vast distances involved, they remained unsure of what had happened for most of the weekend.
Fortunately, the spacecraft has now returned to normal operations and the problem appears to have been resolved, meaning that very minimal actual science was lost. No images had been planned for the weekend, so the anomaly will not be a huge setback for the mission.
"In terms of science, it won’t change an A-plus even into an A," New Horizons Principle Investigator Alan Stern at the Southwest Research Institute in Boulder, Colorado said in a statement.
Pluto and its largest moon Charon are seen here in this image from New Horizons on July 1, 2015. Features as small as 160km (100 miles) across are visible. NASA/JHUAPL/SWRI.
The problem, according to NASA, seems to have been a "hard-to-detect timing flaw" in the spacecraft’s command sequence. The team had performed an operation to prepare it for the close flyby of Pluto when the glitch occurred. The spacecraft switched to its backup computer and placed itself into safe mode as a result of the glitch, transmitting information back to engineers so that they could solve the problem. Thankfully, this operation does not need to be performed again and the issue was not a hardware or software fault, meaning that the mission should – fingers crossed – continue unabated.
"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, in a statement. "Now – with Pluto in our sights – we’re on the verge of returning to normal operations and going for the gold."
Despite the huge journey time, the actual flyby of Pluto will last just slightly more than two hours on July 14, beginning at 12:49 p.m. BST (7:49 a.m. EST), and ending at around 3.15 p.m. BST (10.15 a.m. EDT). Thus, if even one thing goes wrong, crucial science could be missed. With no other mission to Pluto even being considered at the moment, this will be the only chance for many decades to find out exactly what Pluto looks like and examine some of its intriguing surface features, such as a series of large, dark spots along its equator.
No pressure, then.