Other instruments gathering data before the mother ship crashed onto the Moon were a gamma ray spectrometer to measure overall lunar chemical composition and a radar altimeter. The radar altimeter was to give a signal ejecting the landing capsule and its solid-fueled braking rocket overboard from the Block II mother ship. The braking rocket was to slow and the landing sphere to a dead stop at above the surface and separate, allowing the landing sphere to free fall once more and hit the surface.