Noun
(aerospace) A component of a satellite that is released once in orbit
(celestial dynamics) A satellite that orbits another satellite
Source: en.wiktionary.orgAfter Young and Duke rejoined Mattingly in lunar orbit, the crew released a subsatellite from the Service Module (SM). Source: Internet
The burn to alter the CSM's orbit to that desired for the subsatellite had been cancelled; as a result, the subsatellite lasted half of its anticipated lifetime. Source: Internet