We have designed a precision optical system which will be sent to the International Space Station (ISS) via a SpaceX Falcon 9 launch vehicle in 2014. The optical system is part of the Cloud-Aerosol Transport System (CATS) developed by NASA’s Goddard Space Flight Center. Mounted externally on the space station’s Japanese Experiment Module, CATS uses a Light Detection and Ranging (LIDAR) system to measure the location, composition and distribution of pollution, dust, smoke, aerosols and other particulates that impact global climate.