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Question about TV and the moon-landings!


#1

Story point here but at what time would NASA have had the tech to send a broadcast back from the moon? I’m guessing some years before 1969.

MM


#2

The Apollo 8 mission at the end of 1968 (December 21-27) broadcast live pictures from the moon’s orbit, so at least by then.

Edit: wiki’s page on the Apollo TV Camera suggests that NASA set the initial specifications for the system much earlier, in 1962, so presumably that’s when the technology became plausible.


#3

The first television signal bounced off a satellite was in 1962, the Telstar 1 satellite, over the Atlantic. If you can send a picture via a satellite, you can send it from the Moon using exactly the same principles. So 1962 is a good ballpark year, though I think it could have been technologically possible even earlier.


#4

Thanks!

MM


#5

It doesn’t matter as the landings were obviously faked…


#6

However, would the receivers be as important or more important as far as broadcasting over that distance? For the Apollo Moon Landing there were at least three primary radio dish antennae/telescopes. The Goldstone antenna in California, one at Honeysuckle Creek and the one at Parkes both in Australia. I think they would date back to the late 50’s.

i seem to recall there was a movie about the one at Parkes.

http://www.parkes.atnf.csiro.au/news_events/apollo11/one_giant_leap.html

Receiving the TV pictures:

The giant dish of the Parkes Radio Telescope was fully tipped over to its zenith axis limit, waiting for the Moon to rise and ready to receive the television pictures once the TV circuit breakers in the LM were pushed in. John Bolton realised that the TV would begin during the ten-minute coverage period of the off-axis receiver. By turning a dial on the control desk, he turned the feed rotator and positioned the off-axis receiver so that it lay directly above the main, on-focus, receiver. This gave it its maximum field-of-view below the main beam.

As the moment approached, dust was seen racing across the country from the south. The giant dish, being fully tipped over, was at its most vulnerable. Two sharp gusts of wind exceeding 110 kph (70 mph) struck the dish, slamming it back against the zenith angle drive pinions, and causing the gears to change face. The telescope was subjected to wind forces ten times stronger that it was considered safe to withstand. The control tower shuddered and swayed perceptively from this battering, creating concern in all present. John Bolton rushed to check the strain gauges around the walls of the control room. The atmosphere in the control room was tense, with the wind alarm ringing and the telescope ominously rumbling overhead. Fortunately, cool heads prevailed and as the winds abated the Moon rose into the off-axis beam of the telescope just as Aldrin activated the TV at 12:54:00 p.m. (AEST).

Both John Bolton and Fox Mason were riveted to the controls of the telescope at this most critical period. John operated the feed rotator while Fox moved the dish. Tracking a radio source with an off-axis receiver was a tricky and complicated procedure. Essentially, it involved turning the feed rotator so that the off-axis receiver was directly above the main receiver. This gave the off-axis receiver its maximum field-of-view below the main beam. Then by slowly moving the telescope in azimuth angle, while simultaneously turning the feed rotator, one could keep the off-axis beam centred on the radio source. A signal strength indicator (a voltmeter), located on the top of the control panel, was used to determine the pointing of the off-axis beam on the source. If they tracked off the source, then the signal strength indicator would register a drop in voltage. The telescope would then be moved appropriately to centre the beam on the source and maximise the signal strength again.

Once the off-axis beam was level with the main, on focus, beam, the telescope was moved quickly in azimuth to lock onto the radio source and track it in the main beam of the telescope. This, then was the procedure employed to receive the pictures of Armstrong’s first step on another world, by the Parkes Radio Telescope.

Japser Wall recalls:

“There were no cheers amongst us; just the sudden realization that Bloody Hell there’s a man on the moon. We could see all the data, like heart monitors on the astronauts, and in fact there was so much information that what was really going on was hard to discern. Nevertheless none of us present will ever forget it.”

John Bolton was a pioneer of radio astronomy, and an expert in optically identifying radio sources in the sky. His success in acquiring the Apollo 11 TV signal in very trying conditions, even before the source had risen in the main beam of the telescope, was surely one of the most breathtaking examples of his expertise in action.


#7

I’m no expert, but I’m guessing you probably need both. :wink:


#8

I’m just thinking there was nothing particularly special about the camera as far as broadcast signal strength. they’ve had television cameras since the 40’s (maybe even the 20’s) and I imagine Apollo’s was state of the art, but it was still an analog signal from a TV tube camera. However, the ability to pick up a signal from the moon seemed to require a radio telescope and those, of the kind that were used, would not have existed until the late 50’s and early 60’s. Also, I think the science for radio astronomy that allowed them to figure it out probably dates to that time as well.


#9

Yeah, sorry for my glib response, I can see what you’re getting at.

Either way, it sounds like the early-sixties era is still about right.


#10

interesting article: Apollo 11 missing tapes

It sounds like they didn’t really have the technology even when they did the broadcast. They just used the technology they had to come up with a solution.

Background:

**Limited radio bandwidth was available to transmit the video signal, which needed to be multiplexed with other communication and telemetry channels beamed from the Lunar Module back to the Earth. Therefore, Apollo 11’s moonwalk video was transmitted from the Apollo TV camera in a monochrome SSTV format at 10 frames per second (fps) with 320 lines of resolution, progressively scanned.These SSTV signals were received by radio telescopes at Parkes Observatory, the Goldstone tracking station and Honeysuckle Creek tracking station. The camera’s video format was incompatible with existing NTSC, PAL and SECAM broadcast television standards. It needed to be converted before it could be shown on broadcast television networks. This live conversion was crude, essentially using a video camera pointing at a high-quality 10-inch TV monitor.

Video signal processing
Since the camera’s scan rate was much lower than the approximately 30 fps for NTSC video,[Note 1] the television standard used in North America at the time, a real-time scan conversion was needed to be able to show its images on a regular TV set. NASA selected a scan converter manufactured by RCA to convert the black-and-white SSTV signals from the Apollo 7, 8, 9 and 11 missions.

When the Apollo TV camera radioed its images, the ground stations received its raw unconverted SSTV signal and split it into two branches. One signal branch was sent unprocessed to a fourteen-track analog data tape recorder where it was recorded onto fourteen-inch diameter reels of one-inch-wide analog magnetic data tapes at 3.04 meters per second. The other raw SSTV signal branch was sent to the RCA scan converter where it would be processed into an NTSC broadcast television signal.

The conversion process started when the signal was sent to the RCA converter’s high-quality 10-inch video monitor where a conventional RCA TK-22 television camera — using the NTSC broadcast standard of 525 scanned lines interlaced at 30 fps — merely re-photographed its screen. The monitor had persistent phosphors, that acted as a primitive framebuffer.[6] An analog disk recorder, based on the Ampex HS-100 model, was used to record the first field from the camera. It then fed that field, and an appropriately time-delayed copy of the first field, to the NTSC Field Interlace Switch (encoder). The combined original and copied fields created the first full 525 line interlaced frame and the signal was then sent to Houston. The disk recorder repeated this sequence five more times, until the camera imaged the next SSTV frame. The converter then repeated the whole process with each new frame downloaded from space in real-time. In this way, the RCA converter produced the extra 20 frames per second needed to produce flicker-free images to the world’s television broadcasters.

This live conversion was crude compared to early 21st-century electronic digital conversion techniques. Image degradation was unavoidable with this system as the monitor and camera’s optical limitations significantly lowered the original SSTV signal’s contrast, brightness and resolution. If the scan converter’s settings were incorrectly set, as they were at the Goldstone station during the first few minutes of Apollo 11’s Moonwalk, the negative impact on the image could be very obvious. When Armstrong first came down the Lunar Module’s ladder, he was barely visible because the contrast and the vertical phase were not set correctly by the scan converter operator. The video seen on home television sets was further degraded by the very long and noisy analog transmission path. The converted signal was sent by satellite from the receiving ground stations to Houston, Texas. Then the network pool feed was sent by microwave relay to New York, where it was broadcast live to the United States and the world.


#11

I think I read an article on this a while back. Didn’t some of the tape resurface in less than pristine shape not too long ago?


#12

Whenever I feel a bit down and want to make myself feel a bit better I remember the time Buzz Aldrin punched that “the moon landings didn’t haopen” conspiracy guy in the face.


#13

I love Buzz Aldrin,

Mike Collins, too.