The moon landings transported humanity to a new frontier. This grand
also offered a personal scale. Each viewer shared the astronauts' observations.
Each of us beheld the lunar landscape for himself. For the worldwide audience, the Apollo
astronauts became our Apollo astronauts. As they spoke with us, we all
joined Mission Control. We saw what they saw. We delighted in their
personal words and thoughts. Newsmen and engineers explained to us technical
details that college physics students had never heard. For a brief moment, each
of us had a seat on the world's most powerful spacecraft.
Only through television could this event be possible. Here's a true example
of television, not as a box of electronics, but as illusion generator.
The Apollo astronauts took a rocket to the moon and back. Via television, the rest
of us soared through 500,000 miles of virtual space. Illusion generator
though it was, television was our true distant vision. Television portrayed
the moon as it grew close. At the television, we drew a sigh of relief
as our LEM touched down. And by television, we matched our footfalls to the
first steps on the lunar surface. Our friend with the camera was there. And
this camera brought us all along. In television history, we have found no more
compelling use for the medium.
Moon tech. Apollo moon television differs from the TV that we
watched in our homes on Earth. NASA briefed the media on the differences.
Spinning wheel. We heard about the spinning wheel in front of color
moon TV cameras. Electronics brought us the black-and-white part of the picture.
But the color wheel brought us the hues. Mechanical TV had returned to open another
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 set
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.
What is Col-R-Tel? Let's define some terms and recount some related
TV technical history...
1955 Col-R-Tel converter from back of TV. (Luckett, 1955,
Col-R-Tel (for our purposes, terrestrial Col-R-Tel)
is field-sequential color TV that operates at NTSC scanning rates.
This is standard black-and-white TV with a non-standard, color
switching circuit. When you view the TV through a color wheel, the picture
comes out in full color. The Col-R-Tel brand color converter debuted in 1955.
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.
Apollo mooncams that produced color pictures first flew on Apollo 10.
Astronaut Tom Stafford promoted the use of these cameras. After Apollo 10,
every Command Module carried a color mooncam. Starting
with Apollo 12, every Lunar Module carried a hardened color camera for use on
the lunar surface.
Compatible with Col-R-Tel. These moon cameras produced a field-sequential,
color signal that was compatible with the 1955 Col-R-Tel output. Apparently
Westinghouse and RCA developed their mooncams independently of and without
knowledge of Col-R-Tel (Lebar, 2006). Despite this fact, Col-R-Tel and Apollo
mooncams are parallel and compatible technologies.
Field-sequential color is a form of TV where colors play across the
screen one by one, instead of simultaneously. The CBS color TV system,
Col-R-Tel and color mooncams all use field-sequential color technology.
CBS color is a color TV method that Peter Goldmark invented in the 1940s. The FCC
approved the final version in 1950. CBS became the U.S. color TV standard
in 1951. Yet after only a few months, it flopped commercially. The CBS system is
a field-sequential color system that operates at non-NTSC scanning rates.
This system is incompatible with NTSC TV. The most famous
features of the CBS system are the color wheels (scanning discs) at both
the TV camera and TV receiver.
NTSC stands for National Television System Committee. With
considerable help from industry engineers at various companies, RCA invented our NTSC
color system. NTSC color TV is compatible with black-and-white TV. In NTSC color,
combinations of three primary colors, red, green and blue, make up all the colors in
a picture. The three primaries transmit simultaneously. In 1953, the FCC (Federal
Communications Commission) approved this system. NTSC broadcasts began in December,
1953. NTSC remained the U.S. system of television until digital TV took over in 2009.
Connections. There are several connections
between Col-R-Tel and the color mooncams that debuted some 14 years later...
Like terrestrial Col-R-Tel, mooncams (lunar Col-R-Tel) produce
field-sequential pictures. These pictures are compatible with the output of
Both terrestrial Col-R-Tel and the mooncams conserve picture bandwidth and
equipment complexity. (For our purposes, bandwidth is the amount of
data that can simultaneously pass through the system.)
The cost of the Col-R-Tel process (whether on Earth or the moon) is a
decrease in image quality. The resulting picture is dim and flickers slightly.
The mooncams pose another problem: Normal TV sets can't properly decode and
display mooncam pictures.
Apollo downlink stations solve the display problem with complex electromechanics: The
downlinks contain equipment that converts the R-B-G (red-blue-green) sequential
signal to NTSC. This NTSC is viewable on a home TV. Fortunately the conversion process
eliminates both the dimness and flicker problems of terrestrial Col-R-Tel
pictures. Conversion takes 12 seconds and slightly blurs the edges of moving objects.
(Spacecraft Films, Men On the Moon, “TV Transmission 33:59 GET”
and “Probe & Drogue TV.”)
Only the wheel. Col-R-Tel adopted the CBS color wheel, the CBS
system's most distinctive feature. The CBS system uses one wheel before the studio
camera. A matching and synchronized wheel rotates in front of the home receiver,
painting colors over the TV picture.
Differences. Unlike the CBS system, Col-R-Tel only needs a color
wheel at the receiver. 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.
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.
Col-R-Tel kit electronics add color saturation values to the picture.
Normally, CRT brightness (luminance) is the sum of three color values. The kit's
color saturation values add or subtract from this sum. Of course, the display
is still monochrome. Yet when watching through the color disc, the viewer
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
Mooncams must travel through space, pulling multiple G-forces during takeoffs and
landings. They must operate over a 500-degree temperature range. Despite all this abuse,
mooncams must be reliable. And there's more: Mooncams have to use as little power and
bandwidth as possible. Mooncams must be lightweight and portable. They can't be temperamental.
Complicated tube alignment and optical balancing procedures are out of the question. With all these
requirements, no studio color camera of the 1960s can measure up. Eventually Westinghouse
designers find a solution in field-sequential technology, the stuff of Col-R-Tel and the CBS
color system. This technology only requires one tube, so out go the tube-alignment procedures.
Meanwhile, the weight and power requirements drop to one-third or one-fourth. Bandwidth reduction
is possible, since only one color transmits at a time. (Mooncams don't transmit chroma, burst, or
separate monochrome signals.) Specialized camera tubes (the SEC from Westinghouse and the SIT
from RCA) can operate in extreme lighting conditions. Special reflective coatings protect the
cameras from the temperature extremes of lunar days and nights. New integrated circuits and
transistors shrink the electronics. And like Col-R-Tel, every color mooncam sports a color
Westinghouse Moon cameras. For the early Apollo missions, Westinghouse
designed and supplied monochrome and color cameras. At Westinghouse, the
TV camera program manager for Apollo was Stanley Lebar. Stan 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.
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. These missions transmitted color TV pictures
from Westinghouse (WEC) cameras in their command modules. 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.
Left: Stan Lebar holds the Westinghouse color camera for
use onboard the Command Module.
SEC Tube. Westinghouse (WEC) used a type WL30691 SEC (Secondary Electron Conduction)
pickup tube in its TV mooncams. According to Westinghouse, SEC advantages include “...its size, weight,
power requirements, ruggedness, stability, and simplicity of operation.” Low-light capability and lack of
lag are particularly important characteristics of the SEC. “Lag is a problem when viewing a moving scene,
generally resulting in a loss of resolution...” (Niemyer paper, 5)
Right: Mechanical drawing of SEC tube from color mooncam manual, as retouched by
the author (Westinghouse, Manual, 3-8)
Moon color wheel. Moon cameras include a small color wheel in front of
the camera lens. This wheel measures some three inches across. It rotates at 599.94 rpm.
To the left of the wheel you can see the three-to-one driver wheel. The driver rotates in
the reverse direction (clockwise here, from behind the lens) at 1799.82 rpm. The motor shaft,
rotating counterclockwise, appears to the left of the driver. The color 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 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 color order spec. (CBS
research with test audiences proved that R-B-G was the preferred order.) Yet in both
terrestrial and lunar Col-R-Tel, the electronics differ from the CBS electronics.
See the photo at top-right, above: This is the back of the Westinghouse color wheel
assembly from an Apollo mooncam. This part of the color wheel faces the camera body.
The photo originally appeared in “The Color
War Goes to the Moon” by Stanley Lebar. Note: The colors on this wheel
appear to be cyan, yellow and magenta. As Stan explained to me, these are
the complements of the filtered colors red, blue and green. The glass dichroic filters
reflect complements and pass filtered colors. Notice the six filter wedges on the
color wheel: The convex sides of each filter wedge are the leading edges. This disc would turn
counterclockwise. A retouched negative picture shows the actual filter colors. To see these colors,
click the photo.
Goldmark's CBS patent (U.S.
patent 2,304,081) includes his color wheel drawing, bottom-right, above. Note the
similarity to the mooncam color wheel. Goldmark's color wheel turns counterclockwise, the same way
as the Lebar wheel does. (See the direction arrow in the center.) To view a color version of
Goldmark's wheel, click the drawing.
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. Colors scan across
the camera at the standard NTSC vertical frequency, 59.94 Hz.
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).
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 article.
Right: RCA GCTA camera for Apollo missions 15 - 17. The moon rover
telecasts used this type of camera.
Image Transform received a NASA contract to reduce noise in lunar video.
This extra processing smoothed and sharpened mooncam pictures during Apollo 16 and 17. Image
Transform was a North Hollywood, California concern. In nearly real time, it polished video
feeds from lunar surface EVAs (extravehicular activities). After this processing, the
video returned to Houston for dissemination to worldwide TV networks.
Right, above: Mechanical drawing of SIT tube from RCA color mooncam
manual. Retouched by the author (RCA, Manual, 1-23)