New Horizons Payload Ready for Flight
10.19.05

The science payload for NASA's New Horizons mission completed its last major preparations for flight last week. The probe will be the first to visit Pluto and its moon, Charon. The spacecraft carries a payload of seven science instruments for examining the geology, composition, surface, temperature and atmospheric structure of the planet and its moon. Flybys of one or more of the icy objects in the Kuiper Belt may be scheduled during a possible mission extension.

Southwest Research Institute (SwRI) led the development of the science payload, which recently completed a series of spacecraft environmental tests in Maryland at NASA's Goddard Space Flight Center and the Johns Hopkins University Applied Physics Laboratory (APL), where the instruments were also integrated with the spacecraft.

The New Horizons payload is incredibly power efficient, with the instruments collectively drawing only about 28 watts. The payload consists of three optical instruments, two plasma instruments, a dust sensor and a radio science receiver/radiometer. The individual instruments are:

• Alice, an ultraviolet imaging spectrometer that will probe the atmospheric composition and structure of Pluto.
• Ralph, a visible and infrared camera that will obtain high-resolution color maps and surface composition maps of the surfaces of Pluto and Charon.
• LORRI , or Long Range Reconnaissance Imager, will image Pluto's surface at football-field sized resolution, resolving features as small approximately 50 yards across.
• 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.
• 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.
• 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.
• 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.

Principal investigator Dr. Alan Stern of SwRI believes the powerful suite of instruments will revolutionize our knowledge of Pluto, its large moon Charon and bodies farther out in the Kuiper Belt.

The spacecraft will be moved to the launch pad in December, at which time the science team will perform "aliveness" tests to verify the instruments communicate properly with spacecraft computers. Pending final launch approval, liftoff is scheduled for Jan. 11, 2006 , aboard an Atlas V rocket.

Beginning about one month after launch, the various instruments will be turned on to begin testing and ensure they and their power supplies are operating properly. Instrument calibrations are planned throughout the early and middle portions of 2006, in anticipation of the mission's early-2007 Jupiter flyby on the way to Pluto.