Apollo 11 Missing Tapes - Background

Background

Only limited 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, so video of the Apollo 11 moonwalk was transmitted from the Apollo TV camera in a SSTV format of 10 frames per second at 320 lines of resolution. These SSTV signals were received by radio telescopes at Parkes Observatory, the Goldstone tracking station and Honeysuckle Creek tracking station. The format as received on Earth was incompatible with existing NTSC, PAL and SECAM television standards, so a conversion was needed for worldwide broadcast. This live conversion was crude: Simply put, the raw unconverted SSTV signal was split into two branches, with one branch sent to an analog data tape recorder where it was recorded onto fourteen-inch reels of one-inch-wide, fourteen-track analog magnetic data tapes at 120 inches per second. Each of the three tracking stations would have used approximately 15 tapes for recording telemetry during the moonwalk. The other SSTV signal branch, rather than being electronically processed and converted, was sent to a high-quality video monitor where a conventional television camera (using the NTSC broadcast standard of 525 lines resolution at 30 frames per second) merely re-photographed its screen. Optical limitations of both monitor and camera significantly lowered contrast, brightness and resolution of the original SSTV video whilst also putting noise in the broadcast. The video seen on home television sets was further degraded in quality by the very long and noisy analog transmission path through which the converted signal was sent, first by satellite from the receiving ground stations to Houston, Texas and thence by microwave relay transmission to New York, from where it was broadcast live to the United States and the world.

This low quality optical conversion of the Apollo 11 moonwalk video images, made with a TV camera taking pictures of a video monitor, is what was widely recorded in real-time onto videotape and kinescope. Recordings of this conversion were not lost and have long been available to the public (along with much higher quality video from later Project Apollo missions). If the SSTV tapes were to be found, modern technology would easily allow the production of higher quality television pictures from the Apollo 11 moonwalk than have ever been seen, other than by the few technicians and others who watched the SSTV transmission on video monitors as it was received. An amateur 8 mm film movie of about 15 minutes of Apollo 11 SSTV images, taken from another monitor before the conversion step, was rediscovered in 2005 and is available on DVD.