They also overwrote the EEPROM of the satellite computer before shutting it, because apparently they were concerned that the satellite would reawake, because it has multiple autonomous recovery modes.
> As part of its decommissioning, the names of around 1500 team members who contributed to its mission were used to overwrite some of the back-up software stored in Gaia’s onboard memory. Personal farewell messages were also written into the spacecraft’s memory, ensuring that Gaia will forever carry a piece of its team with it as it drifts through space.
[0]: https://www.esa.int/Enabling_Support/Operations/Farewell_Gai...