This notice is a justification for other than full and open competition supporting a sole-source award for NASA’s HelioSwarm Medium-Class Explorers mission. The mission is intended to explore three-dimensional, dynamic mechanisms controlling plasma turbulence throughout the heliosphere and plasma universe. The required period of performance is November 1, 2026 through April 30, 2027. NASA/ARC awarded the work to Southwest Research Institute as the only responsible source capable of continuing vital HelioSwarm requirements and supporting mission objectives already selected and funded by NASA HQ.