OPS-SAT 1 is a 3U CubeSat launched on December 18th, 2019. It was funded by the ESA General Support Technology Programme (GSTP) and built by Austrian, German, Polish and Danish industry. Its aim is to demonstrate the improvements in mission control capabilities that arise when satellites can fly more powerful on-board computers. Being in orbit for over three years, it has produced numerous publications and validated concepts that are now being adapted by big upcoming space missions. Its success has paved the way for further missions, in which the lessons learned are being incorporated.