from the LM by about 30 feet, after which Young visually inspected the LM from the CSM. The CSM performed another separation burn, this time separating the two spacecraft by about . The LM crew thereafter performed the descent orbit insertion maneuver by firing their descent engine for 27.4 seconds at 99:46:01.6, and tested their craft's landing radar as they approached the altitude where the subsequent Apollo 11 mission would begin powered descent to actually land on the Moon. Previously, the LM's landing radar had only been tested under terrestrial conditions. While the LM executed these maneuvers, Young monitored the location and status of the LM from the CSM, standing by to mount a rescue of the LM crew should it become necessary. Cernan and Stafford surveyed ALS-2, coming within of the lunar surface at a point 15 degrees to its east, then performed a phasing burn at 100:58:25.93, thrusting for just under 40 seconds to allow a second pass at ALS-2. Reporting on his observations of the site from the LM's low passes, Stafford indicated that ALS-2 seemed smoother than he had expected and described its appearance as similar to the desert surrounding Blythe, California, but that Apollo 11 could face rougher terrain downrange if it approached off-target. Based upon Apollo 10's observations from relatively low altitude, NASA mission planners became comfortable enough with ALS-2 to confirm it as the target site for Apollo 11. The next action was to prepare to separate the LM ascent stage from the descent stage, to jettison the descent stage and fire the Ascent Propulsion System to return the ascent stage towards the CSM. As Stafford and Cernan prepared to do so, the LM began to gyrate out of control. Alarmed, Cernan exclaimed into the hot mic being broadcast live, "Son of a bitch!", which, combined with other language used by the crew during the mission, generated some complaints back on Earth. Stafford discarded the descent stage about five seconds after the tumbling began and fought to regain control manually, suspecting that there might have been an "open thruster", or a thruster stuck firing, and did so in time to be able to orient the spacecraft properly to send Snoopy to rejoin Charlie Brown. The problem was traced to a switch controlling the mode of the abort guidance system; it was to be moved as part of the procedure, but each of the