All spacewalks have had the astronauts tethered to their spacecraft except for seven spacewalks by the United States (six in 1984 using the Manned Maneuvering Unit, and one in 1994 testing the SAFER rescue device). All moonwalks were performed with astronauts untethered, and some of the astronauts traveled far enough to lose visual contact with their craft (they were up to 7.6 km away from it using the Lunar Roving Vehicle). One lunar EVA was not a moonwalk, but rather a stand-up EVA partially out the top hatch of the LM, where it was thought that the extra height would help with surveying the area prior to conducting the moonwalks. Only three deep-space EVAs have ever been conducted, where the activity was neither on the lunar surface nor in low Earth orbit, but far away from both the Moon and the Earth.