Cygnus CRS OA-4 S. S. Deke Slayton II

After Antares was grounded by the Orb-3 pad explosion, Orbital ATK bought a series of Atlas V flights from United Launch Alliance to keep CRS deliveries on schedule while Antares was redesigned around new first-stage engines. Cargo included the MinXSS-1 cubesat — a soft X-ray spectrometer for studying solar flare plasmas — and the first batch of Planet Flock-2e imaging satellites.