45 Years Ago Today…Apollo 11 Begins The Trip Home: Day 7

Here is the seventh of eight daily articles written for Eyes Of A Generation by Jodie Peeler on this historic event, complete with videos. Enjoy and share!
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While television from Earth orbit had been demonstrated as early as Gordon Cooper’s May 1963 Mercury flight, television from beyond Earth orbit posed several challenges.

Television cameras (about which we’ll learn more tomorrow) were carried on every Apollo flight starting with Apollo 7. The television signals, along with all other communications signals to and from the spacecraft, were routed simultaneously through a Unified S-Band system developed for the Apollo program. It had to compress seven components (voice, telemetry, television, biomedical data, ranging, emergency voice and emergency key) into a 3 MHz allotment. Priority was given to voice and telemetry, leaving only about 700 KHz for everything else.

Early Apollo missions used a monochrome 320-line system with a 10 fps scan rate, which only demanded about 500 KHz for transmission. On Earth, ground stations split the raw signal into two branches. One branch recorded the unprocessed signal, while the other sent it to a scan converter developed by RCA (which incorporated a TK-22 camera) that produced the extra 20 frames per second needed for a satisfactory, flicker-free television picture. The converted picture was sent from the receiving stations via satellite to Houston, and from Houston it was relayed to the networks.

Better television started to come along on the Apollo 10 mission, which finally also brought support for the Command Module’s second 3 MHz USB system. (Apollo 10 also saw the debut of a color television camera developed by Westinghouse; more on it tomorrow.)

Oddly, flying to the Moon allowed more opportunities for television coverage; while NASA’s worldwide tracking network had some areas of sparse or nonexistent coverage for Earth orbit, deep space allowed more continuous coverage. The Manned Space Flight Network (MSFN, pronounced “miss-fin”) had three prime 26-meter stations in Canberra, Australia; Goldstone, California; and Madrid, Spain. All were equipped with slow-scan converters. These stations made it possible for Apollo 8 to send a total of 90 minutes of broadcasts during its six-day mission to lunar orbit in December 1968.

For Apollo 11 NASA had 64-meter antennas, at Goldstone, California and Parkes, Australia, added to the coverage in order to receive weaker signals that couldn’t be picked up by the 26-meter antennas. NASA also had backup arrangements made at Goldstone’s Pioneer Deep Space Network station, and Parkes had additional equipment installed in case of failure at the Honeysuckle Creek Prime station. NASA used Honeysuckle Creek as its Australian hub for spacecraft communications. Both Parkes and Honeysuckle Creek could receive television signals; they would be sent via microwave to Sydney Video, where technicians would decide whether the video from Parkes or Honeysuckle Creek would be sent on to Houston. Sydney Video would also provide the video to the Australian Broadcasting Commission’s network (unfortunately, the only recording of the Australian version that still exists appears to be several minutes of motion picture film taken from a monitor; all the more a loss, given that NASA’s long-sought “raw” tapes of the Moon walk were probably wiped during a tape shortage in the ’70s).

Television transmissions from Apollo 11 were sent both in color (using the Command Module’s color camera) and black and white (using the system in the Lunar Module). Signals from Eagle were being sent through the S-band antenna atop Eagle. As Neil Armstrong climbed down the LM’s ladder for his first steps on the Moon, Houston’s picture was coming from Goldstone. Initially it was inverted, and when that was corrected the contrast was still too high. Houston saw that the video from Honeysuckle Creek was better and switched to that signal. A few moments later, what looked like an improved picture from Goldstone came in, so there was a switch back to Goldstone. Once the stronger Parkes station began tracking, Sydney Video advised Houston that Parkes was providing the best picture. It was so good that Houston stayed with Parkes for the rest of the Moon walk.

Later Apollo missions would bring new innovations and improvements, and by Apollo 17 the television pictures from the Moon would be an entire world removed from the ghostly images of three years before. But while those pictures may be better, the crude monochrome images from Apollo 11 will be the ones most remembered, and most often played and replayed.

This account draws heavily on several sources, notably Bill Wood’s excellent 2005 account “Apollo Television,” available here:
http://www.hq.nasa.gov/alsj/ApolloTV-Acrobat7.pdf

The story of the support lent by Parkes in the Apollo 11 broadcasts is told here:
http://www.parkes.atnf.csiro.au/news_events/apollo11/

A fictionalized account of Parkes’ role in Apollo 11 formed the basis of the movie “The Dish.”

This isn’t an easy story to boil down, and I’ve drawn heavily on these and other sources. Still, I imagine I’ve gotten some things wrong and oversimplified others, and those errors are my own. Please forgive me; I’m not an engineer, only a historian.

Tomorrow, we’ll take a look at the television cameras used aboard Apollo 11, then wrap up coverage on Thursday with a safe landing in the Pacific on live television.

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