It was a moment nearly 10 years in the making. But for more than 13 hours, NASA scientists didn't know for sure whether the Pluto flyby had actually occurred.
The suspense ended just after 8:50 p.m. Tuesday, when the New Horizons spacecraft –- launched in January 2006 on a 3 billion mile journey to Pluto -– "phoned home," indicating that it had navigated just 7,700 miles from the dwarf planet.
"We have a healthy spacecraft," Mission Operations Manager (aka "MOM") Alice Bowman said with a sigh of relief. "Just like we planned it, just like we practiced. We did it."
"I have never been one to underplay the significance of this mission," said Chief Investigator Alan Stern, as his team chuckled. "Just wait -- One small step for new horizons and one giant leap for man kind!"
Tomorrow, New Horizons will beam back the closest pictures ever taken of Pluto.
Bowman admitted this morning that the wait was making her "a little bit nervous."
"Just like you do when you set your child off!" she said this morning, before the spacecraft had made the call home. "Even though we knew that that spacecraft wasn't going to be talking to us, we were there. We wanted to be with it as it went through this journey."
New Horizons was programmed to go silent for 22 hours during the flyby, focusing all its energy on gathering, rather than transmitting, scientific data.
Before going silent, the probe beamed back what NASA dubbed a "'love note' back to Earth" – a high-resolution image displaying a heart-shaped region on the planet's surface.
Researchers had calculated the "loss of mission" likelihood at 2 in 10,000. Still, NASA was a little jittery -- even a rice-sized spec of interstellar dust could have blown to bits the culmination of more than a decade of work.
"We always caution that we are flying into the unknown," Alan Stern cautioned at a press conference this morning.
But the discoveries are just beginning. New Horizons will spend the next 16 months transmitting data from this mission back to Earth.
"Everyone get some sleep," NASA Associate Administrator John Grunsfeld said at a press conference this evening. "Because tomorrow's going to get really exciting."