NSSDCA ID: 1978-071A-03
Mission Name: ESA-GEOS 2This instrument (ESA experiment S-303) measured the energy, angular distribution, and composition of positive ions using a cylindrical electrostatic analyzer (ESA) followed by a crossed electric and magnetic field analyzer (CFA) to select the energy and velocity. The energy (per unit charge) ranged from 0.001 to 17.2 keV in 32 steps with a delta E/E of 0.03 and a mass range of 1 to 140 u in 64 logarithmically spaced steps. There was a thermal mode in which a retarding grid in the entrance slit was used for analysis below 0.1 keV. All particles that overcame this grid voltage were accelerated to 3 keV before entering the ESA in its lowest energy step, where both the ESA and CFA were transparent. The device was aimed perpendicular to the spin or Z axis. For low-energy ions, the acceptance angles were plus or minus 6 deg in azimuth and plus or minus 30 deg in elevation (referenced to the Z axis). For the highest energies, these angles decreased to 3.5 and 7.1 deg, respectively. Three percent of the ions leaving the ESA were counted by a channeltron. The remaining 97% entered the CFA and the output was detected by an electron multiplier. This signal was pulse-height analyzed by one fixed and one variable discriminator to obtain better mass discrimination. The main purpose of this investigation was to identify the sources of low-energy particles in the magnetosphere. Time variations of the helium/hydrogen ratio, the degree of ionization of helium and oxygen, and the isotopic abundance ratio of helium 3/helium 4 could be measured to determine these sources. For additional details, see J. Geiss et al., Space Sci. Rev., v. 22, p. 537, 1978.
Questions and comments about this experiment can be directed to: Dr. H. Kent Hills
Name | Role | Original Affiliation | |
---|---|---|---|
Prof. Peter X. Eberhardt | Other Investigator | Universitat Bern | eberhardt@phim.unibe.ch |
Dr. David T. Young | Other Investigator | Los Alamos National Laboratory | dyoung@srwi.edu |
Prof. Hans R. Balsiger | Other Investigator | Universitat Bern | hans.balsinger@phim.berne.ch |
Dr. Arthur G. Ghielmetti | Other Investigator | Universitat Bern | gmetti@spasci.com |
Dr. Hans Loidl | Other Investigator | Max-Planck-Institut fur Extraterrestrische Physik | |
Dr. Helmut R. Rosenbauer | Principal Investigator | Max-Planck-Institut fur Aeronomie | rosenbauer@linmpi.mpg.de |
Prof. Johannes Geiss | Principal Investigator | Universitat Bern | geiss@issi.unibe.ch |