New Horizons is a NASA unmanned spacecraft designed to fly by Pluto and its moon Charon and transmit images and data back to Earth. It will then continue on into the Kuiper Belt where it will fly by a number of Kuiper Belt Objects and return further data. The primary objectives are to characterize the global geology and morphology of Pluto and Charon, map the surface composition of Pluto and Charon, and characterize the neutral atmosphere of Pluto and its escape rate. Other objectives include studying time variability of Pluto's surface and atmosphere, imaging and mapping areas of Pluto and Charon at high-resolution, characterizing Pluto's upper atmosphere, ionosphere, and energetic particle environment, search for an atmosphere around Charon, refine bulk parameters of Pluto and Charon, search for additional satellites and rings, and characterize one or more Kuiper Belt Objects.

Mission Profile

New Horizons is planned for launch on January 9 2006 on an Atlas V 551 booster with a Star 48B third stage and will proceed to a Jupiter gravity assist in February 2007. (There are backup launch opportunities in February 2006 and February 2007.) The flyby will come within about 43 (±5) Jovian radii of Jupiter and will be the center of a 4 month intensive Jupiter system observation campaign. The flyby will put the spacecraft on a trajectory towards Pluto, about 2.5 degrees out of the plane of the solar systems. During cruise to Pluto New Horizons may be targeted to fly by a Centaur object (an escaped Kuiper Belt Body) if a suitable target can be identified. Flyby of Pluto will occur in July 2015. The encounter period begins 6 months prior to closest approach. Long range imaging will include 40 km mapping of Pluto and Charon 3.2 days out. This is half the rotation period of Pluto-Charon and will allow imaging of the side of both bodies that will be facing away from the spacecraft at closest approach. New Horizons will fly within 9600 km of Pluto at a relative velocity of 11 km/s at closest approach and will come as close as 27,000 km to Charon. During the flyby the instruments should be able to obtain images with resolution as high as 25 m/pixel, 4-color global dayside maps at 1.6 km resolution, hyper-spectral near-infrared maps at 7 km/pixel globally and 0.6 km/pixel for selected areas, characterization of the atmosphere, and radio science results. After passing by Pluto, New Horizons will be headed out to the Kuiper Belt where multiple Kuiper Belt Objects on the order of 50-100 km in diameter are expected to be targeted for encounter and similar measurements to those made at Pluto. This phase of the mission will last from 5 to 10 years.

Spacecraft and Subsystems

The spacecraft has the shape of a thick triangle with a cyclindrical radiothermal generator (RTG) protruding from one vertex in the plane of the triangle and a 2.5 m radio dish antenna affixed to one flat side. Communication will be via X-band at a rate of 768 bps from Pluto to a 70-m Deep Space Network dish. The RTG will provide 228 W at encounter in 2015. Hydrazine monopropellant is used for propulsion, a delta-V capability of 290 m/s will be available after launch. The spacecraft has both 3-axis stabilized and spin-stabilized modes. Star cameras are mounted on the side of the spacecraft for navigation. The spacecraft's on-orbit dry mass will be 463 kg.

The spacecraft will carry five scientific instruments. The Long Range Reconnaissance Imager (LORRI) consists of a visible light, high-resolution CCD Imager. The Pluto Exploration Remote Sensing Investigation (PERSI) is composed of three parts, a visible CCD imager (MVIC), a near-infrared imaging spectrometer (LEISA), and an ultraviolet imaging spectrometer (ALICE). The plasma and high energy particle spectrometer suite (PAM) consists of SWAP, a toroidal electrostatic analyzer and retarding potential analyzer, and PEPSSI, a time-of-flight ion and electron sensor. The Radio Science Experiment (REX) will use an ultrastable oscillator to conduct radio science investigations. A student-built dust counter (SDC) will also be onboard to make dust measurements in the outer solar system.

Total mission cost is planned to be under 550 million dollars. It replaces the cancelled Pluto Kuiper Express mission.

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