On Eagle's Wings: The Story of the Parkes Apollo 11 Support
Television from the Moon

The Apollo lunar television camera:

The lunar television camera was a black-and-white, slow-scan TV (SSTV) with a scan rate of 10 frames-per-second at 320 lines-per-frame. It weighed 3.29 kg (7.25 lb) and drew 6.5 watts of 24-32 volts of DC power. The camera body was 26.9 cm long, 16.5 cm wide and 8.6 cm deep (10.6 x 6.5 x 3.4 inches). The bayonet lens mount permitted lens changes by a crewman in a pressurised suit. Two lenses were provided: a wide-angle lens for close-ups and large areas, and a lunar day lens for viewing lunar surface features and activities in the near field of view with sunlight illumination.

Photo NASA: Neil Armstrong working at the MESA. This is the only high resolution photo of Neil on the Moon.
The camera was stowed in an instrument pallet known as the MESA (Modular Equipment Stowage Assembly) in the LM descent stage. The MESA was to the left of the ladder as viewed from the front of the LM. When Armstrong was at the top of the ladder, he pulled a lanyard to swing open the MESA, which was hinged at the bottom. The TV camera, which was attached to it, would also swing down. It was mounted upside-down so as to secure it firmly to the MESA with vibration isolators and to also simplify its removal by the astronaut. Aldrin then switched on the camera by pushing in the TV circuit breaker in the cabin of the LM. The camera was pointing at the ladder of the LM, so that TV pictures of Armstrong's initial steps on the Moon could be relayed to the world. Later, after Aldrin had descended to the surface, Armstrong mounted the TV camera on a tripod, and placed it some 10 metres from the LM. The camera was left unattended to cover the crew's activities during the remainder of the moonwalk.

The camera was also capable of operating in a high resolution mode which was 5/8 frames per second with 1280 lines per frame (non-interlaced). This mode was designed to telecast a high resolution image in case the astronauts were not able to return to Earth with photographs. The camera had a switch located on the top surface that would allow the astronauts to operate it in either mode. Back on Earth, 10-inch monitors with yellow-green high persistence phosphor screens were equipped with Polaroid cameras for shooting directly off the screens. However, because of time constraints this high resolution mode was never used in flight.

The Apollo lunar television camera was built by Westinghouse Electric Corp., Aerospace Division, Baltimore, Md., USA.

Scan-converting the TV pictures:

The TV pictures from the Moon were narrow band slow-scan TV, that is, 10 frames per second (non-interlaced) and 320 lines per frame. In order to broadcast them to the waiting world, the pictures had to first be converted to the commercial TV standards. In the US, the standard was the EIA (NTSC) standard of 30 frames per second (60 interlaced fields per second) at 525 lines per frame. In Australia, the standard was the higher resolution, CCIR 25 frames per second (50 interlaced fields per second) at 625 lines per frame.

Photo Hamsh Lindsay: The Honeysuckle Creek RCA scan-converter. Ed von Renourd is at the desk. The toggle switch can be seen directly above his head.
For Apollo 11, an RCA scan-converter was used, which operated on an optical conversion principle. The pictures were displayed on a 10-inch black-and-white monitor and a Vidicon TK22 camera was pointed at the screen. As each frame of the 10 frames per second picture was received, it was displayed on the monitor. The camera was gated to scan a single field at the EIA (NTSC) rate of 1/60th of a second, that is it did not take a picture until the 10-inch monitor had completed displaying a full frame. The output of the camera was transmitted and simultaneously recorded on magnetic disc. The disc recording was then played back a further five times and transmitted. While the disc recorder was playing back, the monitor screen was blacked out and the next frame started displaying. The monitor had enough persistence that it retained the picture, and RCA built special circuits to adjust for any loss of brightness between the top and bottom of the picture. In this way, a 30 frames per second (60 interlaced fields per second) TV was produced - with only one in six fields being live.

While the TV camera was upside-down in the MESA, the pictures were also upside-down. When Armstrong removed the camera to plant it on the lunar surface, the pictures would be the right way up again. A simple technique was employed to invert the images during the scan-conversion process on the Earth. This involved modifying the scan-converter by installing a toggle switch on its front panel. The switch was connected to the deflection coils of the Vidicon camera by means of a relay, which then inverted the picture by the simple expedient of reversing the vertical scans. Richard Holl, who was a Bendix Field Engineering Corporation engineer responsible for television ground support, helped design and implement the inverter switch.

[Updated: 27 April 2004]: Click here to view a comparison of the image quality from the Parkes SSTV Monitor and the broadcast images captured on commercial black-and-white TV monitors.

The images at Goldstone and Honeysuckle Creek were scan-converted on-site to the EIA (NTSC) standard TV (Honeysuckle Creek only ever had US standard equipment of any kind). The Parkes pictures were scan-converted in Paddington, Sydney, to the NTSC standard also.

When Sydney Video selected the Parkes or Honeysuckle Creek pictures for Houston, the selected signal was split and sent to the ABC Gore Hill studios in Sydney for electronic standards conversion to the Australian CCIR standard. The ABC then distributed the pictures to all Australian networks for broadcast to an estimated audience of 10 million.

In Houston, NASA introduced a six second delay before releasing the TV worldwide. This was to give NASA enough time to cut the broadcast in case an accident occurred to the astronauts - NASA didn't want the world to witness a disaster. The ABC on the other hand didn't have this delay; it broadcast the TV live. Also, because the signal for the Australian broadcast did not have to travel to Houston (via satellite) and then back again as it did for the rest of the world, a further delay of 300 milliseconds was avoided. As a result of these, Australian audiences saw the pictures some 6.3 seconds before the rest of the world.

[Updated 25 February 2009: The six second delay was not in place during the Apollo 11 mission. This statement is now known to be incorrect. The six second delay was in fact introduced during the Apollo 16 and 17 missions and was due to the time required for improving the TV. The 300 millisecond transmission delay was of course in place, so the correct statement should read "Australian audiences saw the pictures some 0.3 seconds before the rest of the world."]

Photo CSIRO: The 2 inch video tape recorders at Parkes.
As the video and telemetry downlink was being received at Parkes, it was recorded onto 1/2 inch magnetic tapes on a Mincom M22 instrumentation recorder at a rate of 120 inches per second. These tapes had to be changed every 15 minutes during the whole period of the moonwalk. The scan-converted commercial NTSC standard television at Sydney Video was recorded on an Ampex VR660 two-head helical recorder using 2-inch tape.

Image Artefacts:

A number of peculiar image artefacts were seen on the images broadcast to the world. One set of artefacts was produced by sunlight reflecting off the astronauts and the LM, directly onto the lens of the lunar TV camera. One prominent bright streak appeared to the right of the US flag. It was a reflection of the bright, sunlit, rear leg of the LM. Whenever the astronauts walked in front of the portion of the picture that coincided with the bright streak, it appeared to be visible through them. These reflections produced the ghostly effects remembered by the public.

Another set of prominent artefacts were small 'white spots' seen in the images scan-converted from the Goldstone and Parkes pictures. These were a result of the optical conversion system. According to John Bolton, following tests of the system the 10-inch monitors were left on and burned spots on their screens. However Ed von Renouard, the Honeysuckle Creek video operator, suggested they may have been reflections from ceiling lights that somehow got into the matte black enclosures of the scan-converters through cracks and other areas. Bill Wood, the Goldstone lead video engineer, thinks they were defects in the targets of the Vidicon camera tubes and Richard Holl, the Parkes scan-converter designer and operator, agrees with him. Whatever their origin, when the images from Goldstone and Parkes were scan-converted, the spots were always present. The Goldstone pictures had a white spot located just below the centre of the screen, whereas the Parkes pictures had the spot located just above the middle of the right hand edge of the screen. The author has not been able to find any such spots on the pictures from Honeysuckle Creek. This has been fortuitous, since it has enabled the author to easily identify the sources of the pictures in the broadcasts of the moonwalk.

An Explosion in the Scan-converter:

Photo Richard Holl: (L-R) Ted Knotts, Dick Holl and Elmer Fredd standing in front of the Parkes Scanconverter at OTC Paddington following the mission.
A few weeks before the launch of Apollo 11, the scan-converter at OTC Paddington exploded when it was switched on by Richard Holl following a test. The explosion occurred because the scan-converter was wrongly rewired one evening. Weeks of frantic work by Richard Holl and his team resulted in the scan-converter being completely rebuilt. It wasn't until a few days into the mission that their work was completed in time for the historic broadcast. Richard Holl explains:


Comments to: John Sarkissian