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In 1841, Swiss physicist Jean-Daniel Colladon at the University of Geneva demonstrated to his students that light could be guided through total internal reflection.
In 1841, Swiss physicist Jean-Daniel Colladon at the University of Geneva demonstrated to his students that light could be guided through total internal reflection.
This phenomenon occurs when a ray of light repeatedly bounces within a transparent substance, following its contours instead of escaping.
Colladon illustrated this by focusing sunlight through a lens into a tank and then directing the beam into a jet of water flowing out of the tank.
The light remained trapped within the flowing water, guided along its curve by repeated internal reflections at the boundary between the water and the surrounding air.
The water appeared to glow like a luminous glass pipe, demonstrating how total internal reflection can guide light along a curved path.
Colladon later described the experiment, titled “On the reflections of a ray of light inside a parabolic liquid stream,” in a brief note to the French Academy of Sciences, published in Comptes Rendus Oct. 24, 1842 (Volume 15, pages 800 to 802).
In it, he wrote, “I managed to illuminate the interior of a stream in a dark space. I have discovered that this strange arrangement offers in results one of the most beautiful, and most curious experiments that one can perform in a course on Optics.”
Colladon’s experiment showed that light can be guided, the same basic principle behind today’s fiber-optic cables, where light travels through ultra-thin glass strands about the width of a human hair.
By the 1960s, this light-guiding idea had moved from the lecture hall into space-age hardware.
When Apollo 11 touched down on the moon July 20, 1969, it brought along a Westinghouse television camera with a fiber-optic element inside its imaging tube, using total internal reflection to direct light.
Westinghouse both designed and manufactured this fiber-optic component for the Apollo 11 lunar TV camera.
The project was overseen at their Defense and Space Center in Baltimore, MD, while the SEC (secondary electron conduction) tube’s fiber-optic faceplate was produced at Westinghouse’s electron tube division.
The Manned Spacecraft Center in Houston, TX, issued an acceptance test plan for the Lunar Television Camera March 12, 1968, classifying its fiber-optic section as confidential.
This designation was tied to security controls surrounding the SEC image tube technology in the camera, a proprietary low-light imaging design.
The test plan said that any camera with the fiber-optic part had to be treated as classified if it was taken out for repair or maintenance, and that it had to be kept in a secure place when not in use.
Only authorized and supervised staff could handle the camera because of its classified fiber-optic assembly inside the SEC image tube.
The camera required secure handling, controlled access, and supervised maintenance for any unit that included the classified fiber-optic portion.
The Apollo 11 lunar camera, weighing about 7.25 pounds, captured video on the moon that was transmitted to Earth receiving stations, where its signal was converted into a standard format for broadcasting.
In NASA photo AS11-40-5907, you can see the television camera set up on the lunar surface for the Apollo 11 mission.
The camera sent a slow-scan black-and-white picture at about 320 lines and 10 frames per second, which seems crude today but was state-of-the-art in 1969.
Because the lunar module’s radio system could not transmit standard broadcast television, the camera sent a slow-scan video signal to Earth.
At NASA’s ground receiving stations, specialized scan-conversion equipment converted the slow-scan signal into a standard television format for broadcast over televisions on Earth.
On the Apollo 11 lunar module descent stage, the camera was stowed in the Modular Equipment Stowage Assembly, or MESA.
The MESA was a fold-down storage compartment on the lunar module that carried tools, scientific equipment, and the lunar surface television camera.
The Apollo 11 lunar module Eagle landed on the moon at 3:17:40 p.m. CDT (Central Daylight Time, Minnesota time) July 20, 1969.
That evening, astronaut Neil Armstrong opened the hatch of the lunar module and pulled a cord next to the ladder to release the MESA.
This step set up the television camera so it could show his descent live as he climbed down the ladder.
A TV cable linked the camera to the lunar module, providing power and sending the video signal through the lunar module’s communication system to be broadcast to Earth.
Inside the lunar module, astronaut Buzz Aldrin verified that the TV circuit breaker was in.
Later during the moonwalk, Armstrong removed the camera from its MESA mount, carried it about 30 feet from the lunar module, and set it on a tripod, keeping the cable connected so the signal could be sent back to Earth.
The following excerpts are from NASA’s official “Apollo 11 Technical Air-to-Ground Voice Transcription.”
Mission transcript times have been converted to Central time (CDT).
Key: CDR, Commander Neil A. Armstrong; LMP, Lunar Module Pilot Edwin E. Aldrin Jr.; CapCom, capsule communicator in Mission Control Center, Houston; TV, television camera in the lunar module’s Modular Equipment Stowage Assembly (MESA) bay.
9:52:58 p.m. CDR: “Okay. Can you pull the door open a little more?”
9:53:00 p.m. LMP: “All right.”
9:53:03 p.m. CDR: “Okay.”
9:53:07 p.m. LMP: “Did you get the MESA out?”
9:53:09 p.m. CDR: “I’m going to pull it now.”
9:53:18 p.m. CDR: “Houston, the MESA came down all right.”
9:53:22 p.m. CapCom: “This is Houston, Roger. We copy. And we’re standing by for your TV.”
9:53:39 p.m. CDR: “Houston, this is Neil. Radio check.”
9:53:42 p.m. CapCom: “Neil, this is Houston. Loud and clear. Break. Break. Buzz, this is Houston. Radio check, and verify TV circuit breaker in.”
9:53:54 p.m. LMP: “Roger. TV circuit breaker is in, and read you five square.”
9:54:00 p.m. CapCom: “Roger. We’re getting a picture on the TV.”
9:54:09 p.m. LMP: “You got a good picture, huh?”
9:54:11 p.m. CapCom: “There’s a great deal of contrast in it, and currently it’s upside down on our monitor, but we can make out a fair amount of detail.”
9:54:28 p.m. LMP: “Okay. Will you verify the position, the opening I ought to have on the camera?”
9:54:34 p.m. CapCom: “Stand by.”
9:54:48 p.m. CapCom: “Okay. Neil, we can see you coming down the ladder now.”
When the lunar landing mission ended, the camera was left at the Apollo 11 landing site, with its classified fiber-optic portion inside the camera’s housing.
Jean-Daniel Colladon was born Dec. 15, 1802, and died June 30, 1893.
