SCATHA (Spacecraft charging at high altitudes) was launched in January of 1979 into a near-geosynchronous orbit with apogee ~ 7.8 Earth radii, perigee ~ 5.3 Earth radii. The orbital period was 23.7 hours, and the orbit was inclined by 7.9 degrees.

In descriptions of the spacecraft instrumentation the ion composition experiment is referred to as "SC-8." A review of the SCATHA ion composition results can be found in Johnson, R. G., R. J. Strangeway, E. G. Shelley, J. M. Quinn and S. M. Kaye, Hot plasma composition results from the SCATHA spacecraft, in Energetic Ion Composition in the Earth's Magnetosphere (ed. R. G. Johnson), Terra Scientific Publishing Co., Japan, 1983.

The figure to the left is a thumbnail example of the plots available online. The plots are 24 hour summary plots showing the differential energy flux for the four primary species: Protons (H+), Alphas (He++), Helium (He+), and Oxygen (O+). The energy flux is shown as a function of energy and time, with energy going from 0.1 to 32 keV/q. In addition, the number densities, integrated over this energy range, are also shown. The energy fluxes and densities are 15 minute averages over all pitch angles sampled. For all the species except Oxygen the spectra are calculated using data from "Sweep mode", where the mass spectrometer sweeps through all the masses. This allows for a background count determination, and this background is subtracted from the data. The oxygen data are from "Lock mode", where the instrument locks onto the mass peak. Because of the background subtraction it is possible to get negative densities.

Robert J. Strangeway
Institute of Geophysics and Planetary Physics / UCLA
Los Angeles, CA 90095-1567
Telephone: (310) 206-6247
FAX: (310) 206-3051
Internet e-mail: strange@igpp.ucla.edu

UCLA/IGPP Space Physics Center home page     Bob Strangeway's home page

Last modified: February 27, 2007.