Primary missions often carry smaller, independent probes to perform specialized measurements or act as communications relays. Once the main spacecraft establishes its trajectory or orbit, it ejects the subsatellite using a spring-loaded mechanism or robotic arm. These secondary units typically lack their own propulsion and rely on the initial deployment velocity to maintain a safe distance from the mother ship.
Heard on the job
We'll deploy the subsatellite on the third orbit to begin the magnetic field mapping.