were mated on March 28, 1972, and the testing of the spacecraft began that month. The CSM was placed in a vacuum chamber at Kennedy Space Center, and the testing was conducted under those conditions. The LM was also placed in a vacuum chamber; both the prime and the backup crews participated in testing the CSM and LM. During the testing, it was discovered that the LM's rendezvous radar assembly had received too much voltage during earlier tests; it was replaced by the manufacturer, Grumman. The LM's landing radar also malfunctioned intermittently and was also replaced. The front and rear steering motors of the Lunar Roving Vehicle (LRV) also had to be replaced, and it required several modifications. Following the July 1972 removal from the vacuum chamber, the LM's landing gear was installed, and it, the CSM and the SLA were mated to each other. The combined craft was moved into the Vehicle Assembly Building in August for further testing, after which it was mounted on the launch vehicle. After completing testing, including a simulated mission, the LRV was placed in the LM on August 13. Erection of the stages of the launch vehicle began on May 15, 1972, in High Bay 3 of the Vehicle Assembly Building, and was completed on June 27. Since the launch vehicles for Skylab 1 and Skylab 2 were being processed in that building at the same time, this marked the first time NASA had three launch vehicles there since the height of the Apollo program in 1969. After the spacecraft was mounted on the launch vehicle on August 24, it was rolled out to Pad 39-A on August 28. Although this was not the final time a Saturn V would fly (another would lift Skylab to orbit), area residents reacted as though it was, and 5,000 of them watched the rollout, during which the prime crew joined the operating crew from Bendix atop the crawler. At Pad 39-A, testing continued, and the CSM was electrically mated to the launch vehicle on October 11, 1972. Testing concluded with the countdown demonstration tests, accomplished on November 20 and 21. The countdown to launch began at 7:53 a.m. (12:53 UTC) on December 5, 1972. Lunar surface science ALSEP The Apollo Lunar Surface Experiments Package was a suite of nuclear-powered experiments, flown on each landing mission after Apollo 11. This equipment was to be emplaced by the