WHEN, if all goes well, Apollo 17's lunar module Challenger makes the final approach for a landing on the moon, it will let down toward a dramatic landscape: a wide valley guarded by three massive, well-rounded mountains that tower as high as 7,000 ft. "Once we're there," insists Apollo 17's commander, Gene Cernan, "I'm going to get us down." He will have little margin for error: only a few miles downrange of Challenger's glide path are the towering Taurus Mountains; to the northeast lies the giant crater Littrow. Much as the landing site for America's sixth (and last) scheduled expedition to the moon's surface will test the astronauts' piloting skills, it should be even more of a scientific challenge. A combination of ancient highlands and a younger lowland valley, the Taurus-Littrow* site promises to provide the moon walkers with two major scientific prizes: the youngest and the oldest rocks yet found on the moon.
The route to Taurus-Littrow will be unusual. Because of the relative positions of the earth, moon and sun in early December, Apollo 17, following the standard trajectory of the moon, would remain in the moon's shadow for nine hours. The spacecraft would, in effect, experience a total solar eclipse, which would screen it completely from the sun's rays and deprive it of essential heat. Thus, to avoid damage to Apollo's systems, the spacecraft will be sent on a trajectory that shortens its "cold soak" to an acceptable two hours. The longer route will add half a day to the total flight time (85½ hours). That change—along with NASA'S requirements for the proper sun angle at the Taurus-Littrow site during landing—make it necessary to launch Apollo 17 at night. Early in the Apollo program, a night launch would have given NASA pause; in the event of an abort shortly after blastoff, the astronauts would have to be fished from the waters of the Atlantic in darkness. But NASA now has such confidence in its launch and recovery techniques that it considers a night pickup to be a relatively safe procedure.
Apollo is scheduled to swing into lunar orbit at 2:49 p.m. E.S.T. Sunday, Dec. 10. Next day, leaving Ron Evans behind in America, the command ship, Cernan and Jack Schmitt will climb aboard the lunar module Challenger, cast off two hours later and, at 2:54 p.m., touch down on the black dust of the Taurus-Littrow Valley. Less than four hours later, Cernan will emerge from Challenger's hatch. His descent down the lander's ladder and the familiar post-landing activities will not be seen on earth. To save weight for scientific experiments and fuel for hovering, mission planners eliminated both the TV connections to the side of the LM and the bulky tripod on which the camera was later mounted.
Picture transmission to earth will begin about an hour after the first EVA (for ExtraVehicular Activity) begins, when the Houston-controlled color TV camera is finally set up on its mounting at the front end of the lunar rover.