Nasa’s New Horizons spacecraft has got humanity’s first up-close look at Pluto, sending word of its triumph across nearly five billion kilometres to scientists waiting breathlessly back home.
Confirmation of mission success came 13 hours after the actual fly-by and, after a day of both jubilation and tension, allowed the New Horizons team to finally celebrate in full force.
Early indications had been encouraging and a cheering, flag-waving celebration swept over the mission operations centre in Maryland at the time of closest approach. But until New Horizons phoned home hours later, there was no guarantee the spacecraft had buzzed the small, icy far away – but no longer unknown – world.
The unprecedented encounter was the last stop on Nasa’s grand tour over the past half-century of the planets in our solar system.
New Horizons arrived at Pluto after an epic journey that began nine-and-a-half years ago, when Pluto was still considered a full-fledged planet.
According to Nasa, the spacecraft swept to within 13,390km of Pluto at 49,890kph. It was programmed to then go past the dwarf planet and begin studying its far side.
To commemorate the moment of closest approach, scientists released the best picture yet of Pluto, taken on the eve of the fly-by.
Even better images will start “raining” down on Earth later, promised principal scientist Alan Stern.
It takes four-and-a-half hours for signals to travel one way between New Horizons and Earth. The message went out late in the afternoon during a brief break in the spacecraft’s data-gathering frenzy. The New Horizons team kept up a confirmation countdown, noting via Twitter when the signal should have passed the halfway point, then Jupiter’s orbit.
The uncertainty added to the drama.
“This is true exploration,” warned Stern, a Southwest Research Institute planetary scientist.
“New Horizons is flying into the unknown.”
Among the possible dangers was cosmic debris that could destroy the mission. But with the chances of a problem considered extremely low, scientists and hundreds of others assembled at Johns Hopkins University’s Applied Physics Laboratory erupted in jubilation when the moment of closest approach occurred at 7.49am EDT (1.49pm local time).
The scene repeated itself a little before 9pm. This time, the flight control room was packed compared with earlier, when it was empty because New Horizons was out of touch and operating on autopilot.
“We have a healthy spacecraft. We’ve recorded data of the Pluto system and we’re outbound from Pluto,” announced mission operations director Alice Bowman. Joining in the day-long hoopla were the two children of the American astronomer who discovered Pluto in 1930, Clyde Tombaugh – some of his ashes are aboard the spacecraft.
New Horizons is also expected to beam back photos of Pluto’s big moon, Charon, and observe its four little moons. It will take 16 months, or until late 2016, for all the data to reach Earth.