In late 2017, the National Academies of Sciences, Engineering, and Medicine finalized the report of the 2017-2027 decadal survey of Earth Science and Applications from Space. This was the second such Earth science survey and it converged to a final, small set of Science and Applications Priorities and Observing System Priorities starting from a large number of community-provided inputs. Emerging from these were a set of eight designated observables (DO’s) declared to be of highest priority for the decade. Observations of aerosol (A) and separately clouds, convection and precipitation (CCP) were recommended as two of these designated observables. Since the science of each significantly overlap the other, NASA proposed these be combined into a single (ACCP) DO study, now renamed AtmOS. This talk reviews the principal outcomes of the DO study that has now defined AtmOS, its architecture and the main elements of the AtmOS program. Speaker Bio: Graeme Stephens was a distinguished professor at Colorado State University (now emeritus) and currently is co-director of JPL’s Center for Climate Sciences. He is also a member of the U.S. National Academy of Engineering, Fellow of the Royal Society (UK), and until May this year was the co-chair of the Scientific Steering Group (SSG) for the Global Energy and Water Exchanges (GEWEX) project of the World Climate Research Programme (WCRP). Stephens serves as principal investigator of the NASA CloudSat mission, is project scientist of Libera, and served on the steering committee of the NRC 2017-2027 Decadal Survey. Originally presented as an online talk for JPL Center for Climate Sciences Friday Seminar Series, June 25, 2021.