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After a wait, spacecraft confirms that it survived its close pass of Pluto

Joel Achenbach

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July 14, 2015

NASA’s New Horizons spacecraft phoned home Tuesday night, reporting that it had made it to Pluto and beyond after crossing the solar system for 9 1/2 years. To the immense relief of the men and women who had built it and then flung it into deep space, the robotic probe sent a brief stream of data, received shortly before 9 p.m., confirming that it had survived the close pass of the dwarf planet.

“We have a healthy spacecraft. We’ve recorded data in the Pluto system. And we’re outbound from Pluto,” Alice Bowman, the mission operations manager, announced to her thrilled colleagues in the control room at the Johns Hopkins University Applied Physics Laboratory, the home of New Horizons. In a nearby auditorium, hundreds of people who had been watching the video feed stood and gave the team a standing ovation.

On its approach to Pluto, the spacecraft obtained the most arresting image yet of the dwarf planet. Pluto is not a bland and featureless ball of ice, but rather a complex, variegated, mottled world with broad snowfields, structures that look like cliffs or fault lines, and a strikingly bright heart-shaped area that could be the eroded remnant of a giant impact crater.

Cheers erupted at 7:50 a.m. Tuesday as a countdown clock ticked to zero, signifying the spacecraft’s closest approach to Pluto’s surface, about 7,750 miles.

Instantly the “My Other Vehicle Is On Its Way to Pluto” bumper stickers on the team members’ cars became obsolete.

“Pluto has now been explored!” exulted Alan Stern, the mission’s principal investigator.

The members of the New Horizons team then spent the rest of the day waiting for the crucial signal that their spacecraft was intact. Traveling at more than 31,000 miles per hour, New Horizons could potentially have been disabled by a collision with debris, or perhaps in some way overloaded or discombobulated by its frenetic schedule of observations of Pluto and its five moons.

New Horizons crossed the face of Pluto in just three minutes and continued on its way through the realm of small ice-worlds in the outer solar system, destined ultimately for interstellar space.

The New Horizons spacecraft hadn’t been heard from since 11:17 p.m. Monday, when it ceased to transmit any information about its location or operations. That was all part of the plan, because New Horizons had so many duties to perform. The seven instruments on board were programmed to conduct a dizzying series of observations of Pluto and its moons.

Pluto is three billion miles from Earth, and so even at the speed of light it takes 4.5 hours for instructions to cross that distance. As a result, the spacecraft is flying autonomously, following a program loaded onto the main computer last Monday.

That “encounter load” called for 433 separate scientific observations over nine days and requiring roughly 600 spacecraft maneuvers. The New Horizons team chose to remain in the dark during the encounter so that the spacecraft could focus entirely on Pluto and its moons and thereby maximize its science yield.