Mars flyby and rendezvous with the flyby segment transferring the crew over. (see also Mars Excursion Module (MEM)) Alternately, a flyby-only human mission is also possible, without detaching at Mars, but to slingshot around Mars and back to Earth. In July 1965, Mariner 4 achieved a flyby of Mars with a return of data, providing the public and scientists with dramatically closer images of Mars. During the flyby Mariner 4 took 21 pictures amounting to about 1% of the surface of Mars. Mars was not globally mapped until the Mariner 9 orbiter, which over the course of 1972 to 1973 took thousands
Space-based radar and, thus, the unwanted echo from other surface objects. The first radar sounder flown was ALSE (Apollo Lunar Sounder Experiment) on board Apollo 17 in 1972. Other sounder instruments flown (in this case around Mars), are MARSIS (Mars Advanced Radar for SubSurface and Ionosphere Sounding) on board the European Space Agency's Mars Express probe, and SHARAD (mars SHAllow RADar sounder) on JPL's Mars Reconnaissance Orbiter (MRO). Both are currently operational. A radar sounder is also used on the Japanese Moon probe SELENE, launched September 14, 2007. A similar instrument (primarily devoted to ionospheric plasma probing) was embarked on the Japanese