Paper presented at the AAAS meeting, February 16, 1997, Seatle, WA, USA
The solar wind is an extension of the solar corona (the sun's "atmosphere") into interplanetary space and beyond. The first measurement of the composition of the solar wind was accomplished nearly 35 years ago. It was determined that the ion components consist of singly ionized hydrogen, doubly ionized helium, and trace abundances of other ions. These "other ions", usually designated as "minor ions", nonetheless hold a wealth of information on solar and heliospheric processes. The Charge, Element, and Isotope Analysis System (CELIAS) on the ESA/NASA Solar Heliospheric Observatory (SoHO) spacecraft uses advanced instrument techniques to provide unprecedented mass and temporal resolution for solar wind elemental and isotopic abundance measurements and minor ion charge state measurements. Spectroscopically, only the noble gases, carbon, and oxygen observations are available for solar isotopic abundances, hence the importance of having solar wind isotope abundances to compare to standard meteoritic values (commonly used as a baseline for isotope abundances).