Charging Monitor Aboard the Geostationary Satellite GK2A at 128.2° E Longitude

A simple internal charging current monitor has been developed to monitor the penetration of energetic particles within spacecraft in geostationary orbits. The instrument, known as a charging monitor (CM), is a component of a suite of space weather instruments aboard the geostationary satellite GEO-KOMPSAT-2A (GK2A), that was successfully launched on December 4, 2018, with a final longitude of 128.2° E. The instrument measures the integral fluxes of charged particles through a 1-mm-thick aluminum wall, along with another 1-mm-thick aluminum plate, effectively collecting electron and proton currents with energies approximately above 0.6 and 13.1 MeV, respectively. Great care has been exercised in the design of the instrument to extend the lifetime of the analog electronics of the detector, which may easily become vulnerable to the harsh radiation environment of the outer electron belt in geostationary orbits. Comparisons of measurements from the CM have been made with those from particle detectors with a more sophisticated design from the same suite. Initial results of the CM operation for the first four months are presented, including a period of moderate geomagnetic storms. The comparisons clearly show that the CM is sufficiently capable of monitoring the enhanced levels of electrical currents from the penetration of high-energy charged particles in the context of space weather research with a minimal spacecraft resources cost and design efforts.