New Horizons
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- New Horizons is also the name of computer game Uncharted Waters 2
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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 may possibly fly by a Kuiper Belt Object 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 possibly characterize one Kuiper Belt Object.
Mission profile
New Horizons is planned for launch in January 2006 on an Atlas V (551) booster fitted with an additional Star 48B third stage to achieve a high escape velocity. It will then proceed to a Jupiter gravity assist in February 2007. There are backup launch opportunities in February 2006 and February 2007, which would involve the spacecraft flying a slower trajectory directly to Pluto, as only the first 23 days of the 2006 launch window allow a Jupiter flyby. 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 system. During the cruise to Pluto New Horizons will perform a distant flyby of a Centaur (an escaped Kuiper Belt Object), 83982 (2002 GO9), in 2010.
The flyby of Pluto will occur in July 2015. The observations will begin 6 months prior to closest approach, exceeding for 150 days Hubble space telescope's resolution, and last another two weeks after the flyby. 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. It is planned for New Horizons to fly within 9600 km of Pluto at a relative velocity of 11 km/s at closest approach and to come as close as 27,000 km to Charon, although these parameters may easily be changed during the mission flight time. 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 continue out into the Kuiper Belt, where one or more Kuiper Belt Objects on the order of 50-100 km in diameter can be targeted for encounter and measurements similar to those made at Pluto. As maneuvering capability is limited, this phase of the mission is contingent on suitable KBOs close to New Horizon's flight path being identified. In 2004, it was reported that this mission phase was in jeopardy due to a shortage of Plutonium-238, caused by the 2004 temporary shutdown of Los Alamos National Laboratory (where the Plutonium for the mission was being produced). However, this issue was resolved, and while New Horizons will fly with less than its originally-specified power generation capacity, margins will be sufficient for a full mission. A full load would have provided approximately 202 watts at Pluto, the actual expected power will be slightly over 190 watts. Given that RTG output declines over time, this should allow spacecraft operations to continue until approximately 2025, by which point New Horizons will have reached a distance of 50-60 Astronomical Units.
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 bit/s from Pluto to a 70 m Deep Space Network dish (38 Kbit/s at Jupiter). The RTG will provide about 190 W at encounter in 2015. Hydrazine monopropellant is used for propulsion, a minimal delta-V capability of 290 m/s will be available after launch. The spacecraft has both three-axis stabilized and spin-stabilized modes. Star cameras are mounted on the side of the spacecraft for navigation. The spacecraft's on-orbit mass including fuel will be 465 kg for a Jupiter fly-by trajectory and 445 kg for a direct flight to Pluto. This means less fuel for later Kuiper Belt operations and is caused by the launch vehicle performance limitations for a direct-to-Pluto flight.
The spacecraft will carry seven scientific instruments. The Long Range Reconnaissance Imager (LORRI) consists of a visible light, high-resolution CCD Imager. The Pluto Exploration Remote Sensing Investigation (PERSI) contains of two instruments, Ralph telescope with two separate channels: a visible CCD imager (MVIC) and 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 expected to be around 650 million dollars, over the lifetime of the primary mission and including the cost of launch. It replaces the cancelled Pluto Kuiper Express mission.
External links
- Official site (http://pluto.jhuapl.edu/)
- NSSDC page (http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=NHORIZONS)
- Space.com: News report on New Horizon's decreased fuel allowance (http://space.com/spacenews/businessmonday_041004.html)
- www.unmannedspaceflight.com: Very informative discussion on New Horizons including the plutonium problem and report on its resolution (http://www.unmannedspaceflight.com/index.php?showtopic=675)de:New Horizons