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New Horizons Readied for Flight

With liftoff scheduled for January, the New Horizons mission to Pluto and Charon (and, if we are lucky, at least one flyby of a more distant Kuiper Belt object) continues to generate excitement in the scientific community. The spacecraft is now at the Kennedy Space Center and will be moved to the launch pad in December, with liftoff planned for January 11. Major testing on the science payload is complete. The next round of major instrument calibrations and testing won’t occur until the early months of the journey as New Horizons moves toward a 2007 flyby of Jupiter for a gravity assist to Pluto.

How do you package enough instrumentation for good science at the edge of the Solar System into a payload that draws only 28 watts of power? The science payload work was led by the Southwest Research Institute (SwRI), whose recent news release lists the seven instruments that will explore these icy worlds:

  • Alice, an ultraviolet imaging spectrometer that will probe the atmospheric composition and structure of Pluto. (Led by SwRI; PI Dr. Alan Stern)
  • Ralph, a visible and infrared camera that will obtain high-resolution color maps and surface composition maps of the surfaces of Pluto and Charon. (Led by Ball Aerospace and SwRI; PI Dr. Alan Stern)
  • LORRI, or Long Range Reconnaissance Imager, will image Pluto’s surface at football-field sized resolution, resolving features as small approximately 50 yards across. (Led by APL; PI Dr. Andrew Cheng)
  • SWAP, or Solar Wind Around Pluto, will measure charged particles from the solar wind near Pluto to determine whether it has a magnetosphere and how fast its atmosphere is escaping. (Led by SwRI; PI Dr. David McComas)
  • PEPSSI, or Pluto Energetic Particle Spectrometer Science Investigation, will search for neutral atoms that escape the planet’s atmosphere and subsequently become charged by their interaction with the solar wind. (Led by APL; PI Dr. Ralph McNutt)
  • SDC, or Student Dust Counter, will count and measure the masses of dust particles along the spacecraft’s entire trajectory, covering regions of interplanetary space never before sampled. (Led by the University of Colorado; PI Dr. Mihaly Horanyi)
  • REX, or Radio Science Experiment, a circuit board containing sophisticated electronics that has been integrated with the spacecraft’s radio telecommunications system, will study Pluto’s atmospheric structure, surface thermal properties, and make measurements of the mass of Pluto and Charon and KBOs. (Led by Stanford University and APL; PI Dr. Len Tyler)
  • Centauri Dreams‘ take: a critical part of New Horizons mission will take be the continuous operation, during the ten-year cruise to Pluto, of a dust counter that will trace the distribution of dust particles throughout the Solar System. We’ve had some data on this already — Voyager 2 measured dust impact on the spacecraft’s skin with its plasma wave instrument as it moved past Uranus and Neptune. But the Voyager measurements were taken with a device designed specifically to measure charged particles inside the magnetic fields of these gas giant planets, not one optimized for dust.

    Learning how much dust can affect spacecraft will become more and more significant as the speed of our missions increases. At 10 percent of light speed, a grain of sand could destroy an interstellar probe, so a thorough analysis of dust out past the Kuiper Belt and eventually into the Oort Cloud will one day be needed to see what kind of shielding such vehicles would demand.

    For more on the problems of interplanetary dust, see see Eberhard Grun, Harald Kruger, and Markus Landgraf, “Dust Measurements in the Outer Solar System,” available at the arXiv site. The specifics on Voyager’s dust measurements are examined in D. A. Gurnett et al., “Micron-sized Dust Particles Detected in the Outer Solar System by the Voyager 1 and 2 Plasma Wave Instruments,” Geophysical Research Letters Vol. 24 (1997): pp. 3125–28.