Defensive driving at 30,000 miles per hour as probe zooms toward Pluto

Less than three weeks from a historic flyby of the dwarf planet Pluto, operators of the New Horizons spacecraft are poring over images and data streaming in from the probe to determine if any final trajectory adjustments will be necessary to steer safely past Pluto and its moons on July 14. Their window for such maneuvers is quickly closing.

“What we’re looking for in the imagery are new moons, new potential sources of particles or debris,” New Horizons’ Pluto Encounter Mission Manager Mark Holdridge said.

Rocks as small as grains of rice floating around Pluto or its moons could spell big trouble for a spacecraft traveling at a relative speed of more than 30,000 miles per hour, he said. So these last minute hazard observations have been part of the plan from the beginning.

The team even went as far as to outfit the spacecraft in its own Kevlar “bulletproof” vest, strong enough to stand up to a pelting by space dust without significant worry. And if imagery shows larger rocky debris in the probe’s path, they can make minor course adjustments to avoid them — but only up to a point.

“The latest that we could make a correction based on the hazard observations would be about 14 days out,” said Holdridge said. “If we had a problem with that maneuver, we could correct it 10 days out. That’s truly the final date for a trajectory correction maneuver.”

But New Horizons’ Principal Investigator Alan Stern is not too worried.

“We have a very good knowledge already that the system is not full of dust and debris,” he said. “There may be a low-level threat, but measurements made by ground-based telescopes and by the Hubble have already allowed us to establish that the estimated probability of loss of mission is about one in 10,000. That’s a pretty good set of odds.”

The July 14 Pluto flyby will be the culmination of a nine-year, 3-billion-mile journey to the edge of the solar system. The spacecraft is traveling so fast it will spend just 12 hours in close proximity to Pluto and its five known moons. At closest approach, it will pass just 7,750 miles from Pluto’s surface. All the while, a suite of onboard cameras and other scientific instruments will snap pictures and gather data.

“We are on Pluto’s doorstep,” New Horizons’ Stern said. “We want it. We worked designing the spacecraft, building the spacecraft and testing it, getting it launched, flying it — an epic journey across the entirety of the solar system. Now, we’re here and the data is flowing and we are revealing something completely new to human knowledge, and the energy level is just electric.”