Developing a method of transmitting quantum information over global distances would open up applications such as provably secure communication through quantum key distribution. A promising option for doing this is to use quantum satellites that can directly communicate between distant users.
I will present a proposal for a series of missions to develop and test the components needed to perform quantum key distribution between two ground stations anywhere on Earth, via a low-earth orbit satellite. A key requirement is an on-board quantum memory, capable of storing quantum information for times comparable to the orbit time of the satellite. I will describe a memory technology based on rare-earth ion crystals, which have demonstrated coherence times of up to six hours.