After a voyage of nine years and five billion kilometers, NASA’s New Horizons spacecraft is literally on Pluto’s doorstep, on schedule, in good health, and on course.
This is an artist’s concept of NASA’s New Horizons during its planned encounter with Pluto and its moon, Charon: the craft’s miniature cameras, radio science experiment, ultraviolet and infrared spectrometers and space plasma experiments would characterize the global geology and geomorphology of Pluto and Charon, map their surface compositions and temperatures, and examine Pluto’s atmosphere in detail; the spacecraft’s most prominent design feature is a nearly 2.1-m dish antenna, through which it would communicate with Earth from as far as 7.5 billion km away. Image credit: Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute / JHUAPL / SwRI.
NASA’s New Horizons spacecraft was launched on January 19, 2006. It passed Jupiter for a gravity boost and scientific studies in February 2007, and will reach Pluto and its moons in July 2015.
Generally, the probe seeks to understand where Pluto and its moons fit in with the other objects in the Solar System.
Planetary scientists currently classify the planets into groups: Earth, Mars, Venus and Mercury are the terrestrial planets, which are mostly rocky objects; Jupiter, Saturn, Uranus and Neptune are the gas giants. Pluto belongs to a third category that could be called ice dwarfs. They have solid surfaces but, unlike the terrestrial planets, a significant portion of their mass is icy material.
Pluto and Charon are also widely considered to be among the largest objects in the Kuiper Belt, a vast reservoir of icy objects located just outside of Neptune’s orbit and extending out to about 50 astronomical units from the Sun.
The Kuiper Belt is thought to be the source of most short-period comets – those with orbits shorter than two centuries – so scientists really want to compare the composition and surface properties of Pluto and its moons to those of cometary nuclei.
Pluto and its moons are truly part of the current frontier in planetary science; no spacecraft has ever explored them.
On December 6, 2014, New Horizons came out of hibernation for its 2015 encounter with the Pluto system. It is currently about 261 million kilometers from Pluto and more than 4.7 billion kilometers from Earth.
The New Horizons team used hibernation to save wear and tear on spacecraft components and reduce the risk of system failures.
During hibernation mode, the onboard flight computer monitored system health and broadcast a weekly beacon-status tone back to Earth. Onboard sequences sent in advance by mission controllers woke the spacecraft 2-3 times each year to check out critical systems, calibrate instruments, gather some science data, rehearse Pluto-encounter activities, and perform course corrections.
“Technically, this was routine, since the wake-up was a procedure that we’d done many times before. Symbolically, however, this is a big deal. It means the start of our pre-encounter operations,” said Dr Glen Fountain, New Horizons project manager.
The team will spend the next several weeks checking out the spacecraft, making sure its systems and science instruments are operating properly.
They’ll also continue to build and test the computer-command sequences that will guide the spacecraft through its flight to and reconnaissance of Pluto and its moons.
With a seven-instrument science payload that includes advanced imaging infrared and ultraviolet spectrometers, a compact multicolor camera, a high-resolution telescopic camera, two powerful particle spectrometers and a space-dust detector, New Horizons will begin observing the Pluto system on January 15, 2015.
Its closest approach to Pluto will occur on July 14, 2015, but plenty of highlights are expected before then, including, by mid-May, views of the Pluto system better than what the Hubble Space Telescope can provide of the dwarf planet and its moons.
