2019 Astrophysics Small Explorer (SMEX) AO and MO

The National Aeronautics and Space Administration (NASA) issues this DRAFT Announcement of Opportunity (AO) for the purpose of soliciting comments on the DRAFT AO for investigations to be implemented through its Astrophysics Explorers Program.
 
Since the early 1990s, the Explorers Program has provided several classes of flight opportunities for addressing astrophysics science objectives. These mission classes are defined by their cost caps and are designed to increase the number of flight opportunities in response to recommendations from the scientific community. The Explorers Program currently consists of larger stand-alone "full missions," and smaller investigations called "missions of opportunity."