At the end of their service life, the majority of satellites suffer from orbital decay and are destroyed by the heat of atmospheric entry.
Zombie satellites, however, maintain a stable orbit but are either partially or completely inoperable, preventing operators from communicating with them consistently.
[3][4] AMSAT-OSCAR 7 is an amateur-radio communications satellite which was launched into Low Earth Orbit on November 15, 1974, and remained operational until a battery failure in 1981.
In April 2010, only five years into a planned 15-year mission, its operator, Intelsat, lost control of the satellite and it drifted out of its orbital slot.
It was a zombie satellite until Scott Tilley, an amateur radio operator living in Canada tracked it down in January 2018.