Almost 9 years and 3 billion miles ago, NASA launched New Horizons -- a space probe with a big mission -- to boldly go where no space probe had gone before. Its destination was the solar system's most famous dwarf planet, Pluto, and its home, the asteroid-rich region called the Kuiper Belt.
In order to travel the distance, New Horizons -- launched from Earth on January 19, 2006 -- was put into hibernation for about two-thirds of its journey, or 1,873 days. As its long journey comes to an end, so too has that hibernation: at 9:53 p.m. EST, the John Hopkins University Applied Physics Laboratory confirmed that it had received the signal that indicated the pre-programmed "on" switch had toggled (a signal, NASA noted, that took 4 hours and 26 minutes in transit between New Horizons and the NASA Deep Space Network in Canberra, Australia). The space probe is awake.
"This is a watershed event that signals the end of New Horizons crossing of a vast ocean of space to the very frontier of our solar system, and the beginning of the mission's primary objective: the exploration of Pluto and its many moons in 2015," said New Horizons principal investigator Alan Stern.
New Horizons' stasis wasn't constant: the probe went into 18 separate sleeps on its journey, ranging between 36 and 202 days. This sleep cycle allowed the NASA team to monitor the probe while it was awake, and preserve it from wear and tear on its components, and reduce the risk of system failure, while it was asleep.
Its awakening was programmed by the team back in August.
"Technically, this was routine, since the wake-up was a procedure that we'd done many times before, said New Horizons project manager Glen Fountain. "Symbolically, however, this is a big deal. It means the start of our pre-encounter operations."
Before the probe begins surveying Pluto and its system on January 15, the team on Earth will spend the next several weeks checking New Horizons, making sure it is fully operational, testing commands and sequences. They'll also test the probe's array of sensors: infrared and ultraviolet imaging spectrometers, a compact multicolour camera, a high-resolution telescopic camera, two powerful particle spectrometers and a space dust detector.
The probe will be closest to Pluto on July 14, 2015, but there will be plenty to see, both before and after. The NASA team expects detailed views of the Pluton system by May; from July, it will be able to send detailed images of Pluto's moons, Charon, Hydra, Nix, Kerberos and Styx; after which, it will spend the next decade traversing the Kuiper belt.
If it's still operational, it is expected that New Horizons will be 100 AU from the sun by 2038, and hopefully able to send data about the outer heliosphere.
"New Horizons is on a journey to a new class of planets we've never seen, in a place we've never been before," says New Horizons project scientist Hal Weaver, of APL. "For decades we thought Pluto was this odd little body on the planetary outskirts; now we know it's really a gateway to an entire region of new worlds in the Kuiper Belt, and New Horizons is going to provide the first close-up look at them."