NASA’s New Horizons spacecraft to fly past Jupiter on way to Pluto-Charon system

by William Atkins

Tuesday, 16 January 2007

On January 19, 2006, the NASA New Frontiers space mission called New Horizons was launched from Cape Canaveral, Florida, for its mission to the planet Pluto and its moon Charon. Now about one year later, astronomers are preparing for its flyby of the planet Jupiter before it reaches dwarf planets Pluto and Charon. Scientists estimate that its closest approach to Jupiter will be at approximately 06:00 UTC (coordinated universal time) on February 28, 2007, which is 1:00 a.m. eastern standard time.

When New Horizons (officially called Pluto-Kuiper Belt Mission) flies by Jupiter, the fifth planet from the Sun and the largest within the solar system, at 47,000 miles per hour (21 kilometers per second) it will send back images of the gigantic planet through its almost 7-foot (2.1-meter) dish antenna. The images sent back to Earth, which were first transmitted on September 4, 2006, will help astronomers to better calculate the orbits of the inner moons of Jupiter, measure physical characteristics of the active volcanoes on moon Io, and study the four Galilean moons (Callisto, Europa, Ganymede, and Io) in greater detail than ever before.

If its trajectory is near to what was recently calculated, New Horizons will travel within 1.4 million miles (2.3 million kilometers) of Jupiter. Besides taking images of Jupiter and many of its 60-plus moons, the spacecraft’s trajectory around Jupiter will raise its speed so that it arrives in the vicinity of Pluto about three years earlier than if it had not passed near Jupiter.

This flyby of Jupiter, which is called a Jupiter gravity assist, increases the speed of New Horizons by almost 9,000 miles per hour (about 4 kilometers per second). A gravity assist is an orbital mechanical technique used to obtain extra energy for a spacecraft by using the gravitational field of a body, such as Jupiter, to change the speed (as is in this case) or the shape of a spacecraft’s orbit.

At the time of the launch, Pluto was the only planet in the Earth’s solar system that had not been visited by a spacecraft. However, seven months afterwards, Pluto was demoted to a dwarf planet (per the official definition of the International Astronomical Union), leaving the solar system with only eight major planets. About two-thirds the size of the Earth’s Moon, relatively little is known about distant Pluto when compared to closer neighbors of the Earth.

The New Horizons mission will be the first exploration of a probe to the distant Pluto-Charon system. The spacecraft, built by the Southwest Research Institute (Texas) and the Johns Hopkins Applied Physics Laboratory (Maryland), is expected to fly within 6,200 miles (10,000 kilometers) of Pluto and as close as 6,800 miles (27,000 kilometers) of Charon. The scientific instruments aboard New Horizons—including cameras, ultraviolet and infrared spectrometers, and radio science and space plasma experiments—will study (as its primary mission) the geology, geomorphology, and surface compositions and temperatures of both Pluto and Charon. In addition, the instruments will study the atmosphere of Pluto.

After leaving Pluto and Charon, the spacecraft will fly on to explore rocky objects in the Kuiper Belt. New Horizons may also view two newly discovered moons of Pluto. Discovered by the Hubble Space Telescope in 2005, Nix and Hydra are about two to three times further away from Pluto that Charon. Observations of Kuiper Belt Objects past Pluto should happen between 2016 and 2020.

Information about NASA’s New Horizons (Pluto-Kuiper Belt Mission) can be found on Web site: http://pluto.jhuapl.edu/.

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