Physics
Scientific paper
Apr 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja.....8128m&link_type=abstract
EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #8128
Physics
Scientific paper
MESSENGER is a NASA Discovery mission to reach Mercury and orbit that planet for an Earth year, gathering data with a miniaturized scientific payload. The MESSENGER project is now entering the integration and test phase as the spacecraft is assembled and the instruments are calibrated and delivered to the spacecraft. The Gamma-Ray and Neutron spectrometer (GRNS) and X-Ray Spectrometer (XRS) experienced detector changes in order to increase the signal-to-noise ratio (based upon more experience with similar instrumentation on the Near Earth Asteroid Rendezvous, NEAR-Shoemaker, mission and on Mars Odyssey). The gamma-ray portion of GRNS uses a high-purity germanium crystal cooled to ˜90K and surrounded by an active shield to detect characteristic gamma-rays from the planet. The neutron spectrometer uses Li-glass and plastic scintillators to detect and separate thermal, epithermal, and fast neutrons. The XRS spectrometer uses three gas-filled proportional counters looking at the planet and a solar monitor to measure X-ray fluorescence lines from the planet's surface. These instruments thus provide information on elemental abundances. The optical remote-sensing instruments map the planet in several spectral bands (Mercury Dual Imaging System -- MDIS), measure surface spectral reflectance in the visible and infra-red and exospheric emission lines in the ultraviolet and visible (Mercury Atmospheric and Surface Composition Spectrometer -- MASCS), and measure surface topography (Mercury Laser Altimeter -- MLA). The combination of altimetry with MLA and radio-science (RS) measurements will allow maps of the gravitational field of the planet and inference of the planet's obliquity and physical amplitude. The combination of boom-mounted magnetometer (MAG) and combined Energetic Particle and Plasma Spectrometer (EPPS) allows internal and external sources of magnetic field to be separated, providing knowledge of both Mercury's internal structure and its magnetosphere and interaction with the solar wind. These scientific instruments are optimized to deal with the extreme thermal environment while answering the science questions that frame the MESSENGER mission to the innermost planet. Based upon implementation of proven near-term technologies, MESSENGER remains on track for its launch to Mercury in March 2004 and its insertion into Mercury orbit in April 2009.
Gold Robert
McNutt Ralph
Solomon Sean
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