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After 9 years, New Horizons reaches Pluto’s doorstep

Moons around Pluto diagram
Image: New Horizons mission design - Yanping Guo, Robert W. Farquhar


After 9 years in flight the New Horizons mission is on Pluto’s doorstep. That journey was made possible in part by a gravity assist from massive Jupiter in 2007 which accelerated the baby-grand-piano-sized spacecraft to a speed of over 83,600 km/h (52,000 mph) away from the Sun, New Horizons will fly by Pluto and its system of five known moons on July 14, 2015, returning science to help unlock the secrets of the outer solar system.

Exploring the Pluto system and on into the Kuiper Belt is an archeological dig of sorts, into the earliest moments of the outer solar system. These objects have been held in a “deep freeze” for billions of years. Their pristine chemistry is expected to reveal clues about the history of the outer solar system. 

New Horizons’ science objectives include:

  • Map the surface and composition of Pluto and its moon Charon 
  • Study the composition, structure and escape rate of Pluto’s atmosphere. 

Lower priority objectives include measurement of surface temperatures, topographic mapping, and the search for an atmosphere around Charon as well as a search for additional moons or even rings around Pluto.

To achieve these objectives, New Horizons will pass within 12,500 kilometers (about 7,750 miles) of the surface of Pluto, using the most capable suite of science instruments ever launched on a first reconnaissance mission to an unexplored planet:

  • Ralph: Visible and infrared imager/spectrometer; provides color, composition and thermal maps.
  • Alice: Ultraviolet imaging spectrometer; analyzes composition and structure of Pluto’s atmosphere and looks for atmospheres around Charon and Kuiper Belt Objects (KBOs).
  • REX (Radio Science EXperiment): Measures atmospheric composition and temperature; passive radiometer.
  • LORRI (Long Range Reconnaissance Imager): Telescopic camera; obtains encounter data at long distances, maps Pluto’s far side and provides high-resolution geologic data.
  • SWAP (Solar Wind Around Pluto): Solar wind and plasma spectrometer; measures atmospheric “escape rate” and observes Pluto’s interaction with solar wind.
  • PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation): Energetic particle spectrometer; measures the composition and density of plasma (ions) escaping from Pluto’s atmosphere.
  • Venetia: Measures the space dust peppering New Horizons during its voyage across the solar system. Built and operated by students at University of Colorado; named for Venetia Burney, who suggested the name for Pluto as an 11-year-old in 1930.

Images returned by the mission will average about 500 times better resolution than the best provided by the Hubble Space Telescope.

After the brief encounter with the Pluto system and the months of transmitting the images and data gathered back to Earth, New Horizons’ mission doesn’t have to end. With NASA approval, New Horizons will continue into the Kuiper Belt, a billion miles beyond Neptune’s orbit, to study a much smaller icy world — a planetesimal. The science team already has a few candidate targets in mind.

You can learn more about New Horizons encounter with the Pluto system and what we hope to learn in a free presentation, Friday, July 17, 2015, beginning at 7:30 p.m. in the Morehead Planetarium and Science Center GSK Fulldome Theater.

Tony Rice is a NASA/JPL Ambassador who speaks frequently throughout North Carolina on spaceflight and astronomy. Most recently, his passion for sharing the night sky led him to the American Meteorological Society Conference, where he shared naked-eye astronomy tips with broadcast and other meteorologists from around the world.