Atmosphere-Space Transition Region Explorer (ASTRE) is a mission concept proposed in 2011 to NASA's Medium-Class Explorers program (MIDEX) to study the interaction between the Earth's atmosphere and the ionized gases in outer space in an effort to understand how space-induced currents in electric power grids originate, as well as improve satellite drag models.[1] The spacecraft would measure ionized gases within the transition region/boundary layer between 150–250 km altitude.[2][3] The concept was not selected for development at that time.
The Principal Investigator is Robert F. Pfaff from the Goddard Space Flight Center in Greenbelt, Maryland.[1]