Analysis of radiation damage of a satellite in GTO orbit: system level design

Analysis of radiation damage of a satellite in GTO orbit: system level design

The space environment includes different types of particles originating from both within and without the solar system. They can categorize depending on their origin (cosmic-galactic, solar, and Van Allen belts), and can cause severe damage to electronic components or functional failure of the equipment. Therefore, the radiation environment is an important concern in the system-level design of a satellite. The correct evaluation of radiation effects should occur as early as possible in the design procedure, and be upgraded as necessary throughout the development of project phases.

The space radiation environment varies dramatically with the latitude, longitude, and altitude of the orbit, and also varies significantly with time. Satellite in the geosynchronous transfer orbit (GTO) faces significant amounts of particles including the high-energy electrons and protons trapped in the Van Allen belts (extend from an altitude of about 640km to 580000km). These particles are the source of three kinds of damage to electronic equipment (total ionizing dose (TID), displacement damage (DD), and single event effects (SEE)).

In this article, the flux of the different energetic particles in the GTO is obtained by employing SPENVIS web-based software. SPENVIS is developed by a consortium led by the Royal Belgian Institute for space aeronomy for ESA’s space environments and effect section. Results show that the radiation fluxes have very drastic changes during every orbit time due to passing through the Van Allen Belts. The maximum flux of protons and electrons is in the range of 108. The sensitive electronic components can not tolerate the total ionizing dose made by this amount of flux density. Therefore, to reduce the dose below the specified limits by the manufacturer, an aluminum shield must be used. Fig. 1, shows that in order to decrease the dose below the 10krad, the thickness of the shield should be equal to 6mm. This amount of shield is much thicker than those are used in LEO (Low Earth Orbit), and increases the total mass of the satellite. Regarding electric power generated by solar panels of satellite, the results show that the solar panels efficiency benefiting AZUR SPACE solar cell (3G30) is less than 33% at the end of the mission life (see Fig. 2). So to support the subsystems and payloads over the whole mission life, the more solar panel is needed in comparison with satellites in LEO.



Fig. 1: The required shield to decrease the dose Fig. 2: Solar panel efficiency versus cover-glass thickness

Besides, the simulations show that with the increase of the thickness of the shielding from 4mm to 6 mm, the overall rate of single event upset (SEU) decreases from 3.7225E-06 /bit to 2.6556E-06 /bit (about 30%).