Pluto Probe Prepares for 9000 mph Boost from Jupiter
February 5, 2007
By Rachel C.F. Lentz, science writer
New Horizons is the fastest human craft ever sent into space, going nearly 44,000 miles per hour now, a year after launch, and planning to cover the 3 billion miles (4.8 billion kilometers) to Pluto in less than ten years. To help it on its way, the probe is approaching a rendezvous with Jupiter to use that giant planet as a gravity-based slingshot. The five-month flyby will induce a tremendous burst of speed, accelerating the spacecraft by 9000 mph up to a whopping 52,000 mph. At that speed, you could fly from Los Angeles to New York in three and a half minutes!
Last year’s still-debated demotion of diminutive Pluto to a “dwarf planet” by the International Astronomical Union certainly has not diminished the enthusiasm surrounding the first mission to that world. New Horizons will be the first human spacecraft to visit Pluto, the last planet to be explored in our multi-decade tour of the solar system. Missions to Pluto have been proposed for 20 years in one form or another, but the cost of reaching such a far distant world seemed a major stumbling block. Finally, in 2001, New Horizons was approved and, after several false funding starts, was launched on January 19, 2006. Arrival at Pluto is anticipated to be July 2015, and if all goes well, the probe will then continue on into the outer reaches of the solar system to explore another icy body of the Kuiper belt, thought to be the source of short-period comets.
New Horizons reaches its first big milestone, closest approach to Jupiter, on February 28, but already the first new images of the giant planet have been transmitted, demonstrating the added opportunity for making new observations and measurements of the Galilean system.
“We set out for Pluto-Charon and the Kuiper belt thinking of Jupiter as little more than a gravity assist target and a testing ground in preparation for the real meat and potatoes that lies ahead,” declares Alan Stern, Principal Investigator for New Horizons from Southwest Research Institute in Boulder, Colorado. “Yet, even our first Jupiter system observations are revealing new things about the solar system's largest planet. And those first images were taken more than 35 times farther than we will be at closest approach.”
During the Jupiter flyby, the New Horizons team will use all the onboard instruments to carry out many procedures planned for the more critical flyby of the Pluto/Charon system. This will be a way to discover any problems in the mechanical and operational systems now, when there is time to fix them.
The instrument package includes a visible and infrared spectrometer to produce high-resolution color and compositional maps of planetary (or moon) surfaces (Ralph); an ultraviolet spectrometer (Alice) and passive radiometer (REX) to investigate atmospheric composition and temperature; a long-range imaging system (LORRI); a solar wind analyzer (SWAP); and an energetic particle spectrometer (PEPPSI). In addition, there is a student-produced instrument, the Student Dust Center (SDC), that will measure the sizes of dust particles throughout the mission.
At Jupiter, the mission team plans over 700 scientific observations of the planet system including scans of Jupiter’s atmosphere, magnetosphere, and ring system. New Horizons will also make compositional and topographical maps of the four largest moons, as well as survey Io’s current volcanic activity, which was detailed so amazingly by the Galileo mission earlier this decade.
Studies of Jupiter’s atmosphere will focus on the Little Red Spot (a small storm raging to the southest of the Great Red Spot) and a usually turbulent region to the northwest of the Great Red Spot. Early images returned in mid-January show that turbulence in that area has calmed to nearly nothing since the Galileo mission last imaged the giant planet in 1998.
Great turbulence was seen in high-level clouds to the northwest of Jupiter’s Great Red Spot. First spotted by the Galileo mission (left), the same area recently imaged by New Horizons (right) appears much less turbulent.
“It seems the skies are clear over a much larger fraction of the planet than has been typically encountered by these other spacecraft,” reports Dr. Kevin Baines, a science team member from NASA’s Jet Propulsion Laboratory in Pasadena, California. “But if Jupiter remains relatively quiet, this might give us a valuable opportunity to effectively plumb the obscure depths of Jupiter below the ammonia clouds.”
The other unique opportunity of the flyby is the investigation of Jupiter’s magnetosphere. The magnetosphere of a planet is the area where charged particles (ions and electrons) are trapped by the magnetic field of the planet. The shape of the magnetosphere ends up looking more like a raindrop than a sphere, though, with the solar wind blowing the charged particles into a long tail “downwind” of the planet. After New Horizon receives its gravity assist from Jupiter, the resulting trajectory will take the spacecraft down the length of the magnetospheric tail allowing for a detailed examination of the strongest planetary magnetosphere in the solar system.
During the five months of this Jupiter flyby (January–June), there will be a flurry of activity, taking advantage of the chance to update our knowledge about Jupiter, the largest planet, and its moons. But ultimately, its primary importance is to be a dress rehearsal for the even more intriguing five-month flyby of Pluto and its moons.
New Horizons is the first mission in NASA's New Frontiers Program of medium-class spacecraft exploration projects. Stern leads the mission and science team as principal investigator. APL manages the mission for NASA's Science Mission Directorate and is operating the spacecraft in flight. The mission team also includes Ball Aerospace Corporation, the Boeing Company, NASA Goddard Space Flight Center, NASA Jet Propulsion Laboratory, Stanford University, KinetX, Inc., Lockheed Martin Corporation, University of Colorado, the U.S. Department of Energy, and a number of other firms, NASA centers, and university partners.
All images are courtesy of Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Last updated January 30, 2008