In aerospace, Assembly, Test, and Launch Operations (ATLO), also known as Mission System Integration and Test (MSIT) is the phase of a spacecraft project that comprises building the spacecraft, testing it, and getting it launched.
Pictured to the right is John Wirth (left) and Kieran McKay (right) at Kennedy Space Center with ISS-RapidScat, the radar scatterometer which was built at JPL. Specifically, they were testing the rotating radar's capabilities at the Space Station Processing Facility.