these 'mascons' comes from small changes noted in the motion of Lunar Orbiter 5, when very precise radio Doppler
tracking was continued for 80 consecutive circuits of the moon....
The open-loop recording of radio Doppler
and signal spectrum transmitted by the NASA mission were stored on Mars Express and then downloaded to Earth.
The flyby, at a planned altitude of just 50 km, will collect very precise radio Doppler
data to help determine the moon's gravity field more accurately than ever.