New Horizons starts first phase of Pluto encounter
NASA’s New Horizons spacecraft began the first of several phases of its historic rendezvous with Pluto on Thursday, Jan. 15, exactly six months before its closest approach to the small planet. This early phase, after nine years and three billion miles of travel across the solar system, marks the beginning of optical navigation, when the spacecraft will, for the first time, take images of Pluto that will be used to navigate the flyby.
New Horizons was launched on Jan. 19, 2006 as the fastest spacecraft to leave our planet, to a destination 4.67 billion miles away. The following animation video shows the spacecraft’s trajectory as it left Earth, flew by Jupiter 13 months after launch for a gravity assist, and heads toward Pluto.
Video courtesy of NASA
As the mission progresses, scientists will refine their knowledge of Pluto’s exact position, so mission controllers can make any necessary course corrections required for precise timing of the July 14 encounter. The piano-sized probe is currently 32.39 Astronomical Units or AU (one AU equals the Earth-Sun distance, or 93 million miles) from Earth and 1.41 AU or 135 million miles from Pluto, traveling 27,000 miles per hour.
Long-distance observations of the Pluto system will begin on Jan. 25 via the spacecraft’s Long Range Reconnaissance Imager (LORRI), a long focal length telescopic instrument designed to obtain high-resolution photographs in visible wavelengths. Between now and early spring, LORRI will take hundreds of photographs of Pluto and its five moons, enabling mission scientists to obtain precise measurements of Pluto’s orbital position and the current distance between the probe and Pluto.
Mark Holdridge, New Horizons encounter mission manager at Johns Hopkins University Applied Physics Lab (JHUAPL) stressed the importance of knowing precisely where Pluto will be at the time of the flyby.
“The flyby timing has to be exact, because the computer commands that will orient the spacecraft and point the science instruments are based on precisely knowing the time we pass Pluto–which these images will help us determine,” he said.
Not only does New Horizons need to fly by Pluto in the best possible position for gathering data; it also has to steer clear of any debris that could destroy the swiftly flying spacecraft in an impact. This includes dust particles from any as yet undiscovered ring system or tiny moons. If deemed necessary, a course correction maneuver of the spacecraft might be carried out as soon as March. New Horizons will actually fly inside the orbits of Pluto’s moons during closest approach.
In addition to assisting with navigation and providing crucial information determining whether any course corrections are needed, LORRI will also conduct detailed observations of the dynamics between Pluto and its moons during this period.
Video courtesy of Griffin Observatory
Principal Investigator Alan Stern compares this first reconnaissance of an unknown world to the historic Voyager missions of the 1970s and 1980s, which gave humanity its first ever look at the solar system’s four gas giants.
“We’ve completed the longest journey any spacecraft has flown from Earth to reach its primary target, and we are ready to begin exploring,” Stern said.
LORRI’s early images will show Pluto and its moons only as bright dots. More detailed images will not come until the spring. By May, New Horizons’ cameras and spectrometers will be close enough to provide images of higher resolution than the most powerful Earth-based telescopes and even the Hubble Space Telescope.
At closest approach, the spacecraft will come within 7,700 miles of Pluto. Its instruments will take photographs of the planet’s surface and atmosphere at much higher resolution than those the Voyagers took of the giant planets. The best images of Pluto we have now are blurry and low resolution. Comparable images of Earth would not even reveal its continents.
In just six months, these will be replaced by detailed, high-resolution pictures that will reveal surface features such as mountains and craters. A spacecraft imaging Earth from this distance with these instruments would yield detailed photos of New York City, clearly showing the Hudson and East Rivers and even ponds in Central Park.
“What I am most excited about is taking this point of light and transforming it into a planet,” Stern emphasized.
New Horizons will be doing a great deal of science during this first approach phase, measuring high energy charged particles in the solar wind, collecting data on the environment of the Pluto system, and calculating the concentration of dust particles in the region. The results of these studies will provide data not just on Pluto’s environment, but also on the environment of the solar system’s third and most unexplored area, the Kuiper Belt, which may contain many as yet undiscovered small planets composed of rock and ice.
Studying this region filled with primordial material from the solar system’s earliest days will yield important clues to how the system formed. Software that will assist analysis of New Horizons’ data is being provided by the US Geological Survey’s Astrogeology Science Center in Arizona.
Will Grundy, a mission co-investigator and astronomer at Lowell Observatory in Flagstaff, Arizona, where Pluto was discovered in 1930, is working with Northern Arizona University professors Stephen Tegler, Randy Dillingham, and David Trilling growing methane-nitrogen ice in conditions simulating those on Pluto’s surface. Because Pluto’s surface is known to contain methane and nitrogen ice, Grundy plans to use the simulation to interpret New Horizons’ data in situ.
Jim Green, director of NASA’s Planetary Science Division, praised the New Horizons team for its “flawless” work in getting the spacecraft to this point.
“NASA’s first mission to distant Pluto will also be humankind’s first close-up view of this cold, unexplored world in the solar system,” Green noted.
Stern discusses the mission and its start of operations in an interview last week on “All Space Considered” with Dr. Laura Danly, curator of the Griffith Observatory in Los Angeles, California.
Video courtesy of Griffin Observatory
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.