The wide use of satellites for both civilian and military purposes promise significant economic, social and security benefits. However, the rapidly evolving ecosystem and much lower barriers to entry have justifiably resulted in concerns for the cyber security of these systems. A number of threat actors have been identified and it is likely that space systems have already been compromised. As such it is important and timely that appropriate risk assessment is undertaken, and risk management strategies developed to ensure resilience of this part of the critical national infrastructure. While there have been some early forays into exploring cyber security of space systems, the issue remains a significant challenge. In this paper we discuss the challenges in assessing and managing cyber risk, and focus on those arising in space systems. We draw upon the discussion from a targeted workshop conducted in January 2019 as well as reviewing the academic literature.