The New Horizons spacecraft is nearing the distant dwarf planet Pluto, after a flight nearly nine years long.
New Horizons was launched to Pluto on January 19, 2006, when the icy body was still considered a planet, the last one never visited by a spacecraft from Earth. Months after liftoff, astronomers reclassified Pluto as a dwarf planet, just the second-largest of all known objects in the Kuiper Belt, a collection of icy bodies in eccentric orbits, far from the Sun. Since its launch, the robotic explorer has journeyed three billion miles from our home planet to the outskirts of the Solar System.
New Horizons has been in hibernation mode for much of its flight. On December 6, 2014, mission controllers woke the craft from its slumber, preparing for its long-awaited encounter with the system of Pluto and its natural satellites. So far, astronomers know of five moons orbiting around the remote body.
New Horizons will begin observations of Pluto and its moons on January 15. As the spacecraft approaches the frozen bodies, observations will become more detailed. By the middle of May, images from the robotic observer are predicted to be more detailed than the best images of the dwarf planet ever taken by the Hubble Space Telescope. New Horizons will make its closest approach to Pluto on July 14, 2015.
The Kuiper Belt is one of the last unexplored regions of the Solar System. This feature, along with the similar, but even more distant, Oort Cloud, is believed to be an ultimate source of comets, which race toward the Sun.
"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," Hal Weaver of Johns Hopkins Applied Physics Laboratory said.
The journey to Pluto is the greatest distance NASA has ever covered on the way to a spacecraft's primary target. The vehicle is so far away from the Earth that it takes radio waves, traveling over 186,000 miles a second, four-and-a-half hours to travel between the craft and mission on our planet.
During hibernation, most of the electronics on-board the vehicle were shut down, saving wear and tear on the systems. The vehicle was awakened two to three times a year for course corrections, to gather science data, practice approach procedures, and to calibrate instruments. New Horizons sent a signal, once a week, back to mission controllers, reporting on the condition of the vehicle.
"The final hibernation wake up Dec. 6 signifies the end of an historic cruise across the entirety of our planetary system. We are almost on Pluto's doorstep!" Alan Stern of the Southwest Research Institute, principal investigator on the New Horizons mission, said.