The National Aeronautics and Space Administration (NASA) issues this Announcement of Opportunity (AO) for the purpose of soliciting proposals for investigations to be implemented through its Heliophysics Explorers Program. All investigations proposed in response to this solicitation must support the goals and objectives of the Heliophysics Explorers Program, must be implemented by Principal Investigator (PI) led investigation teams, and must be implemented through the provision of complete spaceflight missions.
 
Since the early 1990s, the Explorers Program has provided several classes of flight opportunities for addressing heliophysics 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."