Wiktionary
subsatellite
n. A component of a satellite that is released once in orbit
Wikipedia
Subsatellite
Subsatellite is a satellite (artificial or natural) that orbits a natural satellite, i.e. a "moon of a moon". There are no known natural subsatellites in the Solar System. In most cases, the tidal effects of the primary would make such a system unstable.
Usage examples of "subsatellite".
The subsatellites still squirted over her head, darting this way and that like busy metal gnats, unable to comprehend the fact that the giant ship that had brought them here was gone.
As they went, each released a swarm of subsatellites like golden butterflies, expanding their observation baseline.