Ross said in the Extra-Vehicular Activity (EVA) debrief that the crew had tried to have the Manned Maneuvering Unit (MMU) manifested for use in the second spacewalk, because "for certain applications it would be very useful. In particular if you were building portions of a space station attached to the orbiter, then moving those portions farther than the manipulator arm could transport them." He added that the MMU could be used to attach cable runs and instruments in places out of reach of the shuttle's robotic arm (RMS). During the mission, astronaut Rodolfo Neri Vela accomplished a series of experiments, primarily related to human physiology. He also photographed Mexico and Mexico City as part of the mission's Earth observations. Astronaut Charles Walker again operated the Continuous Flow Electrophoresis System, the third flight of this larger and improved equipment, to produce commercial pharmaceutical products in microgravity. An experiment in Diffusive Mixing of Organic Solutions, or DMOS, was conducted successfully for 3M. The object of this experiment was to grow single crystals that were larger and more pure than any that could be grown on Earth. One Getaway Special canister stored in "Atlantis"' payload bay carried a Canadian student experiment, which involved the fabrication of mirrors in microgravity with higher performance than ones made on Earth. All the experiments on this mission were successfully accomplished, and all equipment operated within established parameters. "Atlantis" landed safely at Edwards Air Force Base at 16:33 EST on 3 December 1985, after a mission lasting 6 days, 21 hours, and 5 minutes. Atlantis landed one orbit earlier than planned due to lighting concerns at the Edwards AFB. Rollout distance on landing was 10,759 feet lasting 78 seconds. Two spacewalks were conducted during the STS-61-B mission to demonstrate assembly techniques which might be used in space station assembly. NASA began a tradition of playing music to astronauts during the Gemini program, and first used music to wake up a flight crew during Apollo 15. Each track is specially chosen, often by the astronauts' families, and usually has a special meaning to an individual member of the crew, or is applicable to their daily activities.