This topic might have a better name.
The Time Almanac spells it "Gedes", and it sounds closer to "Gedes" than to "Galis" in the Tardisode itself.
Talk about it here.
The Galis Expedition was the first mission sent to find the planet Krop Tor. They found that it did indeed exist and orbited K37 Gem 5 as if it were a star rather than a black hole. The Galis Expedition brought back artefacts, including a notebook and some ancient pottery. (WC: Tardisode 8)
The Galis Expedition was followed by the Walker Expedition. (TV: The Impossible Planet)