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| Background Information | Spacecraft charging | |
| Spacecraft charging: data sets | ||
The charging data given here consist of two databases which are available at ESA. They contain ion and electron fluxes as measured by two satellites, Gorizont 91/2 (ADIPE) and CRRES (LEPA). The data that has been used is the data that was reported by Rodgers [1994] to contain charging events for the Gorizont satellite and by Rodgers and Johnstone [1994] for the CRRES data. The description below was taken from these references.
In the table, the times given and the potential reached are based on visual interpretation of the data plots and hence are subjective. Multiple charging events on the same day are listed separately where the spacecraft appears to return to its normal state in-between. The duration of the data in each file is listed in decimal hours but when two events are in the same file a dash replaces the duration for the second event. The eclipse flag is shown where the spacecraft was in eclipse for part of the charging event. In practice, there were often non-eclipse charging events on these days also, but the maximum potential usually occurred during the eclipse phase. The electron signature flag is set when electron charging was seen. In general, a distinct rise and fall in energy of the electron peak was required before being identified as being due to charging. Many intense bursts of electrons were seen at other times and it is not yet clear whether these are natural or the result of some differential potential. The electron potential is the maximum differential charging as deduced from the electron charging signature. When two simultaneous peaks were seen, maximum values for both are quoted. The electron potential was always lower than the ion charging potential.
The first graph is a panel plot showing five variables as a function of time. The two top panels are spectograms which show the temporal evolution of the plasma data (ions above and electrons below). The flux levels are represented by logarithmic colour scales. The fluxes shown are the fluxes along the spacecraft Z-axis. The next two panels show the parameters of a double Maxwellian fit to the electron spectra, and the last plot shows B/B0 and McIlwain's L parameter as a function of time. For the last plot, the UNILIB Library (developed by BIRA-IASB) was used. Links to tables with the fit parameters and magnetic coordinates are provided.
The next three graphs represent electron spectra taken at three different times. The first spectrum corresponds to conditions before charging occurs, the second one is taken at the beginning of the charging event and the third one near the maximum charging level. The spectograms also contain a SCATHA worst case plot and a double Maxwellian approximation of the spectrum. The parameters of the fitted function are given with each graph.
Two charging events on orbit 279 are listed separately. Some doubt still remains in the identification of the events on orbits 809 and 856 as charging events. The signature of a brief charging event appears to be present on these orbits but the background count rate was too high for the ion peaks to be clearly identified in both the perpendicular and parallel look directions.
The two most intense charging events were during eclipses on orbits 425 and 431. On these days eclipse occurred from 11:22:00 to 12:07:00 and 22:52:00 to 23:07:00, respectively. The duration of the charging events matched closely the duration of the eclipse. All the other events occurred in sunlight.
Rodgers, D. J. and A. D. Johnstone, Analysis of CRRES Charging Events, Chapter 3 in Final Report on Rider 2, Estec Contract No. 7989/88/NL/PB(SC), 1994.