Spinning wheel. We heard about the spinning wheel in front of the moon TV cameras. Mechanical TV was back to open another technical outback! The electronics brought us the black-and-white part of the picture. But the color wheel brought us the hues.
Not the CBS color TV system. Newspaper stories mentioned that this mechanical color system was really the CBS color system: The very same system that the US had abandoned in 1951. Quaint, but inaccurate. The CBS color TV system didn't really go to the moon. A CBS color set couldn't lock the moon color picture. In fact, a CBS converter couldn't even lock a monochrome picture from the moon. With a CBS color TV, at best, all you'd see would be flipping streaks. Because the CBS system didn't transmit color burst signals, the streaks wouldn't even appear in color.
FACT: Apollo moon TV was really Col-R-Tel.
Terrestrial Col-R-Tel
What is Col-R-Tel? By Col-R-Tel, I mean NTSC field-sequential color. The Col-R-Tel brand color converter debuted in 1955. That was four years after the demise of the CBS system. For several more years, Color Converter, Inc., a small Indiana company, manufactured Col-R-Tel kits. At $150, the kits allowed do-it-yourselfers to convert their black-and-white TV sets for color reception.
Only the wheel. Col-R-Tel adopted the CBS color wheel, the CBS system's most distinctive feature. This disc is the point of confusion between the two color systems. Despite the disc, Col-R-Tel electronics differ markedly from CBS system circuits. On screen, the difference is obvious: Col-R-Tel can reproduce standard, off-air, NTSC color TV signals. The CBS system can't. CBS electronics are proprietary. Col-R-Tel electronics are a unique design, too, but that design borrows heavily from NTSC color. (NTSC stands for National Television System Committee.) With considerable help from industry engineers at various companies, RCA invented our NTSC color system. In 1953, the FCC (Federal Communications Commission) approved this system. NTSC broadcasts began in December, 1953. To this day, US stations continue to broadcast in this format.
Color TV signals have many components. For this discussion, the most important signals are hue, saturation and brightness. The Col-R-Tel converter provides hue and saturation. Your black-and-white set already detects and reproduces brightness values.
The mechanical part of a Col-R-Tel kit is a plastic color wheel. Six transparent, colored wedges make up the wheel. You mount the wheel in front of the picture tube. Viewers watch the picture through the spinning wheel. As the wheel spins, it adds hues to the picture.
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Col-R-Tel electronics add color saturation values to the picture. Normally, CRT brightness (luminance) is an average of three color values. The kit's color saturation values add or subtract from this average. Of course, the display is still monochrome. Yet when the viewer watches through the color disc, he perceives true color pictures. Another circuit alters incoming NTSC-standard color signals to produce field-sequential color signals. The electronics also keep the wheel in step with station color signals. |
Lunar Col-R-Tel
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Westinghouse cameras. For the early Apollo missions, Westinghouse designed and supplied monochrome and color cameras. As the Westinghouse-Apollo TV camera program manager, Stanley Lebar led the camera development group. Larkin Niemyer directed engineering efforts on the color cameras. Beginning with Apollo 10, lunar missions included a color model for the Command Module. |
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On Apollo 10, astronaut Thomas Stafford enthusiastically promoted the cabin color camera. The results from the Westinghouse field-sequential color system were nothing but spectacular. After the mission, NASA decided to include color cameras on future missions. Apollo 12 was the first mission to deploy a color camera on the lunar surface. Yet due to an operator error early in the mission, Apollo 12's surface camera failed. Apollo 13 developed serious equipment problems, and couldn't land. Apollo 14 achieved the first successful color TV transmissions from the lunar surface.
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RCA cameras. RCA supplied color cameras for Apollo 15, 16 and 17. One of RCA's important contributions was that it corrected the picture gamma (brightness in relation to signal strength). |
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Less blooming. The result of this change was less blooming or clipping of bright picture details. Gone were the Smurf-like astronaut pictures! Since Mission Control could remotely operate the RCA camera, the camera could follow the lunar liftoff. RCA dubbed the camera the Ground-Controlled Television Assembly or GCTA. Soon after the camera's introduction, astronauts shortened the name to "gotcha." Robert G. Horner managed the engineering design team. Sam Russell was RCA's project engineer for the Apollo cameras. A link to his story appears at the end of this page.
Moon color wheel. Moon cameras include a small color wheel in front of the camera lens. This wheel measures some three inches across. The wheel is practically the same as the terrestrial Col-R-Tel wheel. The main difference is that moon wheels have broader borders between color wedges. Otherwise, both terrestrial and lunar Col-R-Tel wheels resemble the original, CBS wheel. Stanley Lebar tells me that the mooncams even scanned the tube in R-B-G order. This is the order that CBS inventor Peter Goldmark specified. Col-R-Tel also follows this CBS spec. Yet in both terrestrial and lunar Col-R-Tel, the electronics differ from the CBS electronics.
Moon color wheel differences. I mentioned the moon color wheel's broad borders between color wedges. These opaque borders allow time to finish scanning one color video field. Afterward, the next color filter swings into place. Anyway, the colors scan across the camera at the standard NTSC vertical frequency, 59.94 Hz.
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