Athena (Advanced Telescope for High Energy Astrophysics) is the X-ray observatory mission of the European Space Agency (ESA) to address the scientific theme 'Hot and Energetic Universe'. The scientific payload will have three key elements: an X-ray telescope, an X-ray Integral Field Unit for high-spectral resolution imaging and a Wide Field Imager (WFI) for high count rate, wide field imaging and spectroscopy. Within the ESA’s Science Program related to the Athena, VTT MIKES investigated the possibility of using graphene-based thermal straps for cooling the scientific instrumentation on board the satellite, specifically the Wide Field Imager.
Graphene has excellent properties for use as a cooling material: it’s lightweight, flexible and highly thermally conductive. Therefore, we designed and developed a thermal strap based on graphene (figure 1) for cooling the WFI and in thorough tests tried to find out if it has potential to replace the current WFI cooling design relying on heat pipes.
Characterisation of the developed graphene-based thermal strap showed that it exhibits extraordinary properties with respect to lightweight, flexibility and thermal conductance when compared to conventional metal-based solutions. We performed comprehensive testing of the mechanical, thermal and cleanliness properties and durability of the developed strap and related materials to verify that the strap conforms to the various requirements set by ESA in relation to the Athena space mission, specifically for thermal management of the WFI. The thermal conductance value was found to even exceed the best commercial solution. Novel test setups and procedures for thermal (figure 2), vibrational and particulate testing were developed to increase confidence in the test results. In order to reach Technology Readiness Level 5 (TRL 5 — technology validated in relevant environment), critical functions and performances were verified on a Breadboard in a relevant environment for the WFI application.
The developed strap was shown to be excellent for cooling and the design can be applied, and if needed re-dimensioned, for other space and non-space applications where similar properties are desired.
The next step will be to patent and commercialize the technology together with an industrial partner.