NASA's New Horizons space probe is set to make the history books when it flies past Pluto on July 14. Currently, the probe looking closely at the little dwarf planet as it looks for anything that could cause problems for the craft during the final months of its historic mission.
In an effort to make sure its path remains clear, New Horizons has begun searching the system for anything that might get in its way. Currently, the probe is searching for previously undiscovered moons or may even an unknown ring system that could surround the dwarf planet.
You know how Curiosity had its 'seven minutes of terror?'" said New Horizons principal investigator Alan Stern, of the Southwest Research Institute (SwRI) in Boulder, Colorado, referring to the NASA Mars rover's harrowing "sky crane" landing in August 2012. "Well, we call this 'seven weeks of suspense.'"
New Horizons was the fastest craft ever launched from Earth and it is now rocketing along at a fast pace of 32,570 miles per hour (52,416 kilometers per hour). At this speed, even a collision with a piece of debris that is only a few millimeters wide could prove fatal to the craft even if you consider it is protected by a Kevlar vest.
"New moons might be shedding dust into the system, into a place where we can encounter it," said New Horizons science team member John Spencer, also of SwRI, who is leading the hazard search. The odds of actually slamming into a newfound moon are extremely small, he added.
So what will New Horizons do if it does detect a possible hazard? There are two main options available to the craft. One option is to point New Horizons' high-gain antenna forward, using it like a shield as the probe passes through the field of debris.
"That change would hurt our science significantly, because we wouldn't have the freedom to point in all the directions we'd like," Spencer said.
The other option is to change course. Mission team members have mapped out three alternate trajectories, two of which are merely slight adjustments while the third would send the craft even closer to the dwarf planet and far inside the orbit of one of Pluto's moons, Charon.
"If we fly that very close one, we cannot fly the nominal sequence," Spencer said. "We have to fly the sequence that has the antenna pointing forward, because things are just in too much of a different direction than they would be on the nominal sequence."
In addition, photos taken very close to Pluto probably would not be as clear as those snapped from a nominal trajectory.
"Our cameras are designed to work from a certain distance, with things moving at a certain rate of speed through the system," Spencer said. "If you're speeding along a highway," he explained by way of analogy, "it's hard to read the sign on the front of a business that's right next to the road."
All of this being said, New Horizons' current trajectory appears to be quite safe, Stern and Spencer stressed.
"All the models say that the odds of losing the spacecraft due to a debris impact are far less than 1 percent," Stern said. "So, I really don't lose any sleep over it."
