How the Moon Landing Was Filmed
Landing on the moon was arguably the greatest achievement in human history, but filming the feat was a technological wonder, too. In the July 1969 issue of Popular Mechanics, released shortly before Neil Armstrong and Buzz Aldrin stepped onto the lunar surface, our editors previewed the historic spacewalk soon to come—including just how the heck everyone back on Earth would be able to watch it from their living rooms. As part of our Apollo Week, here’s the reprinted article explaining the Moon-to-TV setup—as remarkable now as it was 50 years ago.
Moving with caution, the bulky, helmeted astronaut descends the ladder one rung at a time. He reaches the last rung, about 18 inches above ground level, and pauses for a full minute. Then he lowers a heavily booted foot until it touches moon soil, the first man in history to take that giant step.
That scene will be viewed on TV in homes across America and in many other lands if our astronauts follow the Apollo 11 “script” and if no gremlins get into the act between the launch at Kennedy Space Center and arrival at the moon.
The ability to send back clear TV pictures from space was impressively demonstrated during the Apollo 8 mission. The highlight came Christmas Eve, 1968, when Frank Borman, Jim Lovell, and Bill Anders sent greetings some 230,000 miles to Earth. Viewers were amazed and perhaps a bit puzzled. They may have wondered how it was that local programs, beamed with 50,000 watts, sometimes didn’t come in as well as the pictures from the reaches of space. How could a tiny 20-watt transmitter push a good signal so far?
Four technological accomplishments, in addition to all those that made the flight itself possible, made a reality of what many NASA technicians had feared might be a disappointing failure. The first of these was an RCA television camera so small it weighs only 4.5 pounds. Filled with row upon row of integrated circuits, each smaller than a pinhead but capable of functions which a few years ago would have required several pounds of vacuum-tube circuits, the tiny instrument became a space-borne eye for more viewers than had ever before been served by a single TV camera.
Another factor, perhaps even more vital, was a new high-gain antenna aboard Apollo 8. Tucked into the side of the spacecraft during liftoff, the antenna popped into position on command and turned its four 30-inch steerable dishes toward earth, now just a basketball in space, and began to pour out its S-band transmissions.
This brought a cheer from the people back at Mission Control.
In the vacuum of space, radio waves and other forms of electromagnetic energy flash straight across the voids. There are no hills to deflect them or metallic rocks to absorb them, as on Earth. The signals that left Apollo 8 as 20 watts arrived at Earth only slightly diminished.
There, the third key element came into play-85-foot, S-band receiving antennas spaced 120 degrees apart around the globe so that at least one of them has the moon in "view" at all times. The big dishes are located at Goldstone, Calif.; Canberra, Australia, and Madrid.
Apollo 8’s TV signal required processing. Here on Earth, the TV spot flashes across our screens at a rate of 30 frames per second, 60 fields per second, covering 525 lines each time. This makes for flicker-free, sharp viewing. But such an operating mode requires heavy, high-powered equipment.
The camera system RCA designed for Apollo 8 produces only 10 frames per second, made up of only 320 lines—not quite as clear, nor quite as sharp as commercial TV, and prone to jerkiness when either astronauts or camera move too rapidly. It was, however, eminently viewable.
The Apollo TV system and commercial systems are not electronically compatible. That is, one can’t simply be plugged into the other without fouling up the picture.
RCA solved this problem with “scan conversion” equipment—the fourth key technological accomplishment. A commercial vidicon camera was set up in front of a slow-scan monitor, its output linked to a magnetic disc recorder (the same kind used for “stop motion” football plays). The disc recorder did the trick by repeating the 10-frames-per-second Apollo pictures enough times to make up the 60 fields needed for commercial TV. For each second of broadcast there were changes of image; the others were repeats.
Scan conversion equipment was installed at Goldstone and Madrid. Goldstone sent the converted signal through regular coaxial cable channels to Mission Control in Houston. From there the broadcasts were distributed through conventional channels across the United States.
In Spain, a similar operation was carried out. Converted images were sent by coaxial cable to London for distribution to all of Europe and Asia.
But Apollo 8 was really just a beginning. Apollo 9 roared into Earth orbit with even more sophisticated television equipment aboard. The camera on Apollo 9, slated for later use during the actual moon landings, is designed to function both in bright sunlight and in the nearly total darkness of the lunar night.
Key to this capability is a secondary electron conduction (SEC) tube invented by scientists at the Westinghouse Research Laboratories in Pittsburgh and installed in the 7.25-pound camera. SEC tubes convert light into electrical signals which then are amplified hundreds of times before being converted back into visible images. In scientific terms, the Westinghouse camera has a light range of from 0.007 to 12,600 foot-lamberts. On the moon, that means from bright sunshine to dim earthshine.
While the camera’s main use will be to let us watch from Earth as astronauts walk about the moon’s surface, it can also be used for scientific purposes. A fine-detail, slow-scan rate of 58 frames per second will transmit moon views to Earth with a resolution of 1280 lines. That approaches the quality associated with standard photographic camera systems.
The Apollo missions have dramatically demonstrated that the days of solitude in space are over. Thanks to TV, we’re all space travelers now.
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