Gigascale antenna arrays (3 to 4 orders of magnitude more elements than the largest ever built) are a critical component of proposed space-based solar power (SBSP) systems. The transmitting antenna arrays in orbit are expected to be up to 3 km 2 , while the receiving arrays on Earth have been proposed at up to 77 km 2 . There are many challenges and risks in the design, modelling, operation and deployment of the gigascale antenna arrays in the SBSP system. This paper highlights these challenges and risks, reviews existing solutions and proposes novel approaches.