Launcher Plume effect on the Satellite

Launcher plume heat fluxes specified are often quite conservative and may result in local temperature exceedings during the ascent phase and if this is the case, thermal design measures would need to be implemented sometimes at a rather late phase of the project. Consequently the plume effect needs to be known to asses in an early design phase, if any measures are needed. The Sentinel-2 satellite has on-board external Coarse Earth and Sun Sensors (CESS), heat load sensors which are usually used as safe mode attitude sensors. The sensor serves as an ideal sensor to measure external heat fluxes, also originating from the plume. The satellite was launched successfully in summer 2015 with the Vega launcher, thus this was an opportunity to measure the actual heat flux on the satellite. The measured temperatures are used to determine the radiation source caused by the plume after fairing jettison. The launch took place in the eclipse, thus for the interesting phase of the ascent, the external heat fluxes were due to the plume and to the Earth Infrared heat fluxes only. By considering the satellite attitude during the phase after fairing jettison until Z9 separation, the impact of the Earth IR heat fluxes was assessed and the plume effect was determined. This paper describes the evaluation of the measured temperatures, correlation of the flight data and the thermal analysis approach. Finally a potential plume model is proposed which fits to the measured temperatures .