Here is the full list of all 21 Space Explorers: Lunar Mission trophies - there are 6 bronze, 6 silver, 8 gold and 1 platinum.
Moon Master
Albategnius
Bailly
Outpost2
Hydroponic
Lunar Post
Solar Panels
Antenna
Comm Tower
Signal Post
Silo Pack
Clavius
Fra Mauro
Humboldt
Janssen
Langrenus
Maginus
Petavius
Rheita
Seleucus
Tycho