Investigation of spacecraft surface charging for a telecommunication satellite at geosynchronous orbit

Abstract

Telecommunication satellites encounter with high density energetic plasma environment during events originated from the Sun and some major anomalies could arise in the forms of surface and deep dielectric charging concepts. The anomalies which develop in the spacecraft in orbit may affect the power and data subsystems, can change the spacecraft attitude in terms of orientation, can modify satellite operational modes and prevent the satellite operators to conduct regular operations which may lead to catastrophic failures in flight. There are numerous incidents which have previously been encountered by satellite operators on geosynchronous orbit during space weather events that have lead to system and subsystem level spacecraft failures. Surface charging on geosynchronous orbit should be monitored continuously by in-situ measurements and predicted by realistic models. In this context, plasma properties parametrization and effects on surface charging is investigated, behaviors of surface elements under the worst-case space eenvironments are analyzed and a realistic surface charging estimation approach is proposed by driving a 3D particle-in-cel (PIC) simulation with a realistic electron and proton populations with inner-magnetosphere model. Comprehensive InnerMagnetosphere Ionosphere (CIMI) Model is a inner magnetosphere model which develops electron and ion fluxes up to 10 RE behind the Earth on the nightside. This model is a time dependent model which is driven with the solar wind observations made by Lagrange 1 (L1) spacecrafts such as ACE and WIND, then solves the particle transport principles considering advanced advection-diffusion equation for solving particle phase distribution function (fs). As a result of CIMI simulations, several major MLT locations (00:00, 06:00, 12:00 and 18:00) are chosen to study the spacecraft surface charging. Electron and proton density and energy data were obtained from CIMI for selected three large geomagnetic storms events; November 2003, May 2005 and March 2015 substorms. These model outputs later are used as inputs for SPIS simulatons to obtain spacecraft charging levels for our hytpotehtical spacecraft at geosyncronous orbit. For 21 November 2003 09:59 UT, 15 May 2005 19:49 UT and 19 March 2015 16:44 UT, electron and proton populations are fitted into triple-Maxwellian and mono-Maxwellian distributions respectively and SPIS simulations are produced with these plasma properties obtained from CIMI simulation results. Realistic solar declination angle is introduced with respect to day of year and varying solar array configuration with respect to spacecraft attitude with corresponding Magnetic Local Time (MLT) orientation of the Earth pointing telecommunication satellite is considered in simulations for improved accuracy in surface charging estimation results. The study shows how main plasma parameters, population energies and densities, affect the surface charging phenomena; moreover, telecommunication satellites in GEO orbit experiencing the electron belt could be charged up to several negative tens of kV's of frame potentials and up to several kV's of differential potentials on dielectric surface materials. Eclipse conditions are quite dangerous for surface charging phenomena to occur since the absolute and differential potential values develop even further. The worst-case environmental investigation approach was used for the extreme case study simulations implemented in SPIS with the same satellite configuration. The results of this experiment showed that the worst-case space environments create appropriate conditions for high surface potentials on the critical materials. CMG material builds an absolute potential up to around -5 kV for reasonable space environments and differential potential up to around 3 kV which is over the critical arcing and discharge thresholds. The realistic surface charging estimation proposal was analyzed as well for three selected storm cases where the surface potential of dielectrics could develop quite negative values around local midnight through dawn sectors which is expected and validated by the simulation results. The satellite flight configuration could change the surface charging slightly due to the fact that incoming solar flux will create a differential and unequal satellite charging as the spacecraft fly on its trajectory with respect to the Sun. In this study, the CIMI model outputs are used for the first time as SPIS program surface charging simulation inputs. Widely used and numerous worst-case space environments were analyzed together for comprehensive and diverse investigation of surface charging phenomena. By changing the orientation of solar panels according to the MLT configuration, the accuracy of simulations was increased and the effects of the main MLT sector locations of surface charging were examined.