2026 Astrophysics Small Explorer (APSMEX)

The National Aeronautics and Space Administration (NASA) Science Mission Directorate (SMD) is soliciting Principal Investigator (PI)-led space science investigations for the Small Explorer (SMEX) opportunity under the Astrophysics Explorers Program. The proposal due date is September 9, 2026. • The AO text is available for download from the NASA Solicitation and Proposal Integrated Review and Evaluation System (NSPIRES) at https://nspires.nasaprs.com. • A virtual Preproposal conference will be held prior to the proposal due date. • A MANDATORY Notice of Intent (NOI) must be submitted prior to the proposal due date. • Questions and comments about the AO should be addressed via email to the primary and alternative points of contact. • The Q&A period for the SMEX 2026 AO ends 14 days before the proposal due date.