Mark Brown is Safety Critical Systems contributor to the Xen FuSa working group. Mark has worked with a range of operating systems, type-1 hypervisors, and chip/system architectures to address a variety of high assurance concerns, including cybersecurity and flight safety. He first worked with Xen source code in a DARPA-funded collaboration with Galois. In that project, we evaluated single event effects (SEE) for spacecraft that relied on Xen on x86. Since then, he has worked at Siemens, Lynx Software, and Collins Aerospace to promote modularly-updateable solutions.