As Pluto Recedes, the Wait for New Horizons’ Signal Begins

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LAUREL, Md. — While New Horizons passed by Pluto this morning, the science team, and the rest of the world, now have to wait the rest of the day to hear back from the spacecraft to find out how well it carried out its flyby.

New Horizons made its closest approach to the dwarf planet at 7:50 a.m. EDT, passing within 12,500 kilometers of the Pluto’s surface.

“We have a long day until we get to the ‘phone home’ signal,” said John Grunsfeld, NASA associate administrator for science, during a briefing at the Applied Physics Laboratory Tuesday morning shortly after the spacecraft’s closest approach.

The signal will come in no earlier than 8:53 p.m. EDT tonight. Mission operations manager Alice Bowman said they’ll first seek carrier lock with the spacecraft to confirm the spacecraft is broadcasting, then a telemetry lock. “Then we’ll start to get real-time data from the spacecraft,” she said, consisting of key information on the health of spacecraft systems. Controllers hope to get several cycles of data before the communications window closes.

These is, of course, a risk that they won’t hear from the spacecraft, either because of a technical glitch or because the spacecraft was damaged in a collision with debris in the Pluto system. Mission principal investigator Alan Stern played down those odds, though. “I don’t think we’re going to lose the spacecraft,” he said. “We set upper limits on the probability of loss at around 2 parts in 10,000. You could fly hundreds of New Horizons through the system and expect all of them to survive.”

In an interview after the briefing, Bowman said she had only one hour of sleep last night, having been up to see the final pre-flyby New Horizons communications session completed after 11 p.m. last night. What would she recommend until the spacecraft is due to communicate this evening? “Probably have some breakfast,” she said.