2026 Astrophysics Small Explorer (APSMEX)

NASA has released the Final Announcement of Opportunity (AO) for the 2026 Astrophysics Small Explorer (SMEX) program, solicitation NNH26ZDA011O. This cycle introduces a single-step competitive process, replacing the previous two-step evaluation method and moving selected projects directly into a combined Phase A&B. Mandatory milestones include a virtual pre-proposal conference and the submission of a Notice of Intent (NOI). The Science Mission Directorate manages this procurement, with all formal documentation and submission portals hosted on NSPIRES. The final proposal deadline is September 9, 2026, following the completion of mandatory pre-submission requirements. This SMEX cycle replaces the traditional two-step selection process with a single-step competitive process. Evaluation and selection will lead directly into a combined Phase A&B, which changes the proposal requirements compared to previous SMD Explorers Program AOs. The APSMEX program supports PI-led space science investigations under the Science Mission Directorate. Research focuses on the origin and destiny of the universe, the evolution of galaxies and stars, and the search for life on exoplanets. Investigations must align with objectives such as probing dark matter, dark energy, or exoplanet habitability.