Greek participation to Solar Orbiter development

Greece, via its PRODEX membership intends to meaningfully participate to the instrument development of a flagship ESA mission, the Solar Orbiter (SolO). This involvement pertains to hardware development for SolO´s Spectrometer/Telescope for Imaging X-rays (STIX), namely, STIX´s movable attenuator. SolO will allow close-up and high-latitude studies of our mother star, the Sun, based mostly on remote-sensing measurements (imaging). STIX is a critical SolO instrument, enabling one of its major science goals: understanding and acceleration of electrons at the Sun and their transport into interplanetary space. The attenuator, or shutter, that will be developed by the Greek team, is a critical component of the STIX instrument. Attenuators are dictated by the substantial dynamical range of incident X-ray fluxes from solar flares: the largest X-ray flares can give as many as 10⁵ more count rates in X-ray photons compared to those of the smallest microflare that STIX can detect. lt is proposed that two mechanisms are developed for a comparative study. First, a mechanism based on sensitive Shape Memory Alloy actuators and, second, one based on a piezoelectric actuator module. Both mechanisms will be designed and manufactured and then tested in vacuum and alternating high-low temperature conditions. Evaluation of reliability and accuracy in assembly and operation will follow. A vibrating table will be used for the dynamical analysis of the mechanism and independent strength tests of the various parts of the mechanism will follow.