Statistical relationships between satellite anomalies at geostationary orbit and high-energy particles

A statistical evaluation of possible space weather impacts on space missions has been made using the NOAA database of geostationary (GEO) satellite anomalies for the period 1986-94. Measurements of protons and relativistic electrons by the geostationary monitors LANL and GOES and of solar protons by the extra-magneto spheric monitor IMP-8 were used. In addition to the raw data of measured relativistic electrons, we also used values recalibrated to noon fluxes because they provide homogeneous observations that exclude spatial variations. Correlation analyses were made using the anomaly probability function and the superposed epoch analysis technique. Both indicate the occurrence of space weather impacts on satellite missions. The results show that at different phases of the solar cycle the principal causes of space radiation that impact satellites are different. During the period of maximum solar activity, high fluxes of energetic solar protons are the main factor causing anomalies on geostationary satellites. During the growth and decline phases of solar activity (indicated by sunspot numbers), magnetospheric relativistic electrons are the main menace to GEO satellite systems. There are intervals with very low fluxes of solar protons and relativistic electrons, when satellite anomalies were related to fluxes of less energetic (similar to 100 keV) electrons. These patterns should be taken into account during consideration of measures to mitigate radiation hazards for future satellite missions. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.