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Published 1998 | public
Journal Article

The solar isotope spectrometer for the Advanced Composition Explorer


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 cm^2 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.

Additional Information

© 1998 Kluwer Academic Publishers. This research was supported by the National Aeronautics and Space Administration at the Space Radiation Laboratory (SRL) of the California Institute of Technology (under contract NASS-32626 and grant NAGW-1919), the Jet Propulsion Laboratory (JPL), and the Goddard Space Flight Center (GSFC). We wish to thank the many individuals and organizations who contributed to the development of SIS: J. H. Marshall III of Radcal Corp., J. Gill and B. Mitchell of Harris Corp., and R. McKenzie of Teledyne Corp. played major roles in the design, development, and fabrication of the custom stack VLSI chips and hybrid circuits, while G. Stupian and M. Leung of Aerospace Corp. provided their microfocus X-ray facility for hybrid screening. S. Kleinfelder helped design the custom matrix VLSI chip which was fabricated by UTMC. C. Wilburn and his staff at Micron Semiconductor Ltd. fabricated the silicon detectors. D. Aalami of Space Instruments was responsible for the design of the power supplies and also contributed to the design, fabrication, and testing of the other electronic assemblies. W. Blanchard of Falcon Services provided all of the board layouts except for the logic and matrix boards, which were provided by J. Stelma of Design Solutions. Electronic assembly was carried out at Caltech and JPL by N. Neverida and T. Ngo Luu of JPL with the help ofT. Dea, who also assisted during conformal coating and environmental testing at JPL. V. Nguyen of Caltech was responsible for most of the subassembly testing. W. Morris of Caltech received and kitted parts and J. Valenzuela of Space Instruments assisted in PCB production and technical document control. B. Williams and J. Krein of JHU/APL were responsible for thermal design and support. L. Stillman of the same institution was responsible for the mechanical design of the door mechanism. At Caltech, B. Sears, R. Selesnick, J. Cummings, and L. Sollitt provided calibration and analysis support, G. Allbritton was responsible for detector testing, G. Flemming contributed to the flight software, J. Burnham provided engineering support, F. Spalding was responsible for project administration, and D. Kubly and R. Kubly performed a variety of secretarial tasks. In addition, M. Calderon, A. Davis, and T. Garrard assisted with computing issues, R. Paniagua and R. Borup provided support in the Caltech Physics shop, and B. Wong helped with a variety of laboratory tasks. We thank H. Issaian and A. Jefferson for their help with neutron calibrations and R. Kavanaugh for use of the Am-Be neutron source. J. Lopez Tiana and E. Friese provided purchasing and contract support. At JPL, J. Rice and C. Cruzan provided assistance with wire bonding of the detectors, B. Potter assisted in expediting the VLSI build at Harris Corp., D. Cipes Cwik and R. Hill carried out the hybrid inspections at Teledyne, N. Silva contributed to the assembly of the telescope modules and instrument card cage, as well as development of specifications for magnetics parts, W. Powell served as instrument expediter, K. Evans provided advice on parts, J. DePew provided technical support for calibrations and laboratory testing, and M. Salama and T. Scharton assisted with mechanical design issues along with P. Rentz of EER Systems Corporation. R. Pool consulted on contractual issues. At GSFC, B. Fridovich provided administrative support, M. Madden and B. Nahory were responsible for detector testing, and S. Hendricks of Swales and Associates, Inc. assisted with mechanical design issues. Some accelerator testing of the SIS detectors was made possible by N. Anantaraman, R. Ronningen, and the staff of the MSU/NSCL, while H. Specht, D. Schardt, and the staff of the GSI heavy ion accelerator in Darmstadt, Germany made possible the heavy ion calibrations of the SIS instrument. R. Koga provided access to the 'Aerospace' chamber at the Lawrence Berkeley Laboratory's 88" Cyclotron where additional detector calibrations and IC latch-up testing took place. The spacecraft team at JHU/APL provided assistance in many areas while SIS was being integrated and tested on the spacecraft. Finally, we thank A. Frandsen, G. Murphy, H. Eyerly, M. Breslof, C. Rangel, and M. McElveney of the ACE Payload Management Office for their untiring support and assistance, and D. Margolies, J. Laudadio, and the ACE Project Office at GSFC for their help in all phases of the SIS development.

Additional details

August 19, 2023
October 17, 2023