The European Space Agency has issued an intriguing Intended Invitation To Tender, “Weak GNSS Signal Navigation on the Moon.” The study will investigate use of weak-signal GPS/GNSS — and of course ESA is interested primarily in the use of Galileo — for real-time position, navigation and timing information to various future lunar assets such as automated landers, rovers, Earth-Moon transportation vehicle, in-situ navigation, and so on.