As many checks as possible were made to the LM within the time available before it was allowed to fly free and continue to the surface. While these were being carried out, the CMP mounted cameras in brackets to monitor the upcoming departure of the lander through the CM windows. A television camera would then allow live pictures to be sent to Houston and the world, though on Apollo 11, the opportunity was missed. A 16-mm movie film of the event would also be taken using the lightweight Maurer cameras carried on all Apollo missions.
These 16-mm cameras have provided much of the best motion documentation of the Apollo flights, yet their official NASA designation implied that history and posterity were far from the thinking behind their inclusion on the trip. NASA called them data acquisition cameras (DACs) and used them in precisely that way - to gather data on the performance of its vehicles. For example, one of the most familiar Apollo scenes is a short shot of a lunar rover being driven around the Apollo 16 landing site at Descartes, with John Young at its controls and a great rooster-tail of dirt rising from its wheels. This wonderful film was shot only because engineers wanted to see how the rover performed in its designed environment. Since the TV camera was mounted on the rover itself, it was unable to provide such coverage.
With a DAC mounted in a command module window, the first moments of the lunar module's flight were recorded, including its pirouette to allow the landing gear to be inspected. The DAC also filmed the LM's ascent stage as it returned from the Moon. Another DAC mounted in the right-hand lunar module window filmed the approaching landscape throughout the entire descent, and again as the ascent stage rose from the surface.
The DACs have played their part in distorting the historical record, not in terms of image, but of time. NASA instructed the crews to shoot at frame rates that were often much slower than normal. Conventionally, movie film is shot at 24 frames per second and subsequently projected or transferred to TV at about the same rate. The Maurer cameras could also shoot at 1, 6 or 12 frames per second, and much of what was shot on Apollo used these slower rates to conserve film. When replayed on conventional equipment at the higher frame rate, the recorded events would be portrayed at twice, four times or even 24 times their actual speed. Eventually those transfers found their way into documentaries and influenced the public's notion of the Apollo spacecraft. It was only with the advent of advanced video processing technology in later years that careful researchers were able to restore a true sense of the speed of the Apollo films. In the long run, while the television coverage suffered from the degradation inherent with the technology of the time, the movies shot by the DACs have stood as a clear, high-quality record of the achievements of Apollo.
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