The Solar Isotope Spectrometer for the Advanced Composition Explorer |
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Authors: | Stone EC Cohen CMS Cook WR Cummings AC Gauld B Kecman B Leske RA Mewaldt RA Thayer MR Dougherty BL Grumm RL Milliken BD Radocinski RG Wiedenbeck ME Christian ER Shuman S von Rosenvinge TT |
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Institution: | (1) California Institute of Technology, Pasadena, CA, 91125, U.S.A.;(2) Jet Propulsion Laboratory, Pasadena, CA, 91109, U.S.A.;(3) NASA/Goddard Space Flight Center, Greenbelt, MD, 20771, U.S.A. |
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Abstract: | The Solar Isotope Spectrometer (SIS), one of nine instruments on the Advanced Composition Explorer (ACE), is designed to provide
high- resolution measurements of the isotopic composition of energetic nuclei from He to Zn (Z=2 to 30) over the energy range
from ∼10 to ∼100 MeV nucl−1. During large solar events SIS will measure the isotopic abundances of solar energetic particles
to determine directly the composition of the solar corona and to study particle acceleration processes. During solar quiet
times SIS will measure the isotopes of low-energy cosmic rays from the Galaxy and isotopes of the anomalous cosmic-ray component,
which originates in the nearby interstellar medium. SIS has two telescopes composed of silicon solid-state detectors that
provide measurements of the nuclear charge, mass, and kinetic energy of incident nuclei. Within each telescope, particle trajectories
are measured with a pair of two-dimensional silicon-strip detectors instrumented with custom, very large-scale integrated
(VLSI) electronics to provide both position and energy-loss measurements. SIS was especially designed to achieve excellent
mass resolution under the extreme, high flux conditions encountered in large solar particle events. It provides a geometry
factor of ∼40 cm2 sr, significantly greater than earlier solar particle isotope spectrometers. A microprocessor controls the
instrument operation, sorts events into prioritized buffers on the basis of their charge, range, angle of incidence, and quality
of trajectory determination, and formats data for readout by the spacecraft. This paper describes the design and operation
of SIS and the scientific objectives that the instrument will address.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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