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Welcome, visitors from NASA's Apollo 11 Onboard Audio page.

Much of the information on this page was originally published on a NASA CD-ROM of the mission transcript scanning process. I've added additional information, diagrams and photos to put the recorders in context — Eric Hartwell

The Mission Transcript Collection

By Glen E. Swanson

Flight controllers often used downloaded data and voice transmission tapes for real-time analysis during a mission. Shown here at NASAs Manned Spacecraft Center (MSC) Mission Control Center (MCC) is Eugene F. Kranz (left), Flight Director for the Gemini VII White Team, and George M. Low, MSCs Deputy Director, reviewing a transmission tape received on December 9, 1965 from the Gemini VII spacecraft. In the background wearing glasses is flight controller Manfred von Ehrenfried. Crew members for the record-breaking 14-day flight of Gemini VII were astronauts Frank Borman, command pilot, and James A. Lovell Jr., pilot. (NASA Photo S-65-61513.)

Aboard every U.S. human spacecraft, from Mercury through Apollo, engineers installed tape recorders that, as part of their data-saving function, captured astronaut intercom communications. These recordings were made during critical phases of each flight when the preservation of all data was essential. These tapes and their resulting transcripts reveal a different side to America’s space program; one in which its astronauts are professional and profane, calm and excited, confident and nervous, healthy and sick—in a word, "human."

All transcripts are available online
from the Johnson Space Center:
Communications Transcripts:
Mercury Through Apollo

The Collection

Gathered in this special collection are 80 transcripts totalling nearly 45,000 pages of text that cover every US human spaceflight from the first human Mercury mission through the last lunar landing flight of Apollo 17.

Users will note that the quantity and type of transcripts made for each mission vary.

For example, the Mercury flights each had one transcript whereas the Gemini missions produced several. Starting with the Gemini flights, NASA produced a Public Affairs Office (PAO) commentary version, as well as at least one "technical" air-to-ground transcript version, per mission.

Most of the Apollo missions produced four transcripts per flight. These included the onboard voice data recorder transcripts made from the Data Storage Equipment (DSE) on the Command Module (CM), and the Data Storage Electronics Assembly (DSEA) onboard the Lunar Module (LM), in addition to the PAO commentary and air-to-ground technical transcripts.

Some of the transcripts include a detailed explanation of their contents and how they were made. Also included in this collection is a listing of all the original air-to-ground audiotapes housed in NASA’s archives from which many of these transcripts were made. We hope you find this collection of transcripts interesting and useful.


Beginning with Alan Shepard’s first flight into space and continuing through the early Space Shuttle Program, NASA Public Affairs employed legions of typists stationed in telephone booth-sized rooms whose single job was converting voice to paper. Armed with reel-to-reel tape players, electric typewriters, and reams of paper, these individuals hammered out transcripts within hours of when the astronauts first spoke the words.

Aboard every U.S. human spacecraft, from Mercury through Apollo, engineers installed tape recorders that, as part of their data-saving function, captured astronaut intercom communications. These recordings were made during critical phases of each flight when the preservation of all data was essential. These tapes and their resulting transcripts reveal a different side to America’s space program; one in which its astronauts are professional and profane, calm and excited, confident and nervous, healthy and sick—in a word, "human."

The Mercury spacecraft carried into space a combined onboard voice and data recorder. During the relatively short duration of each Mercury mission, these recorders ran continuously during launch and descent, capturing the voice of their precious human cargo. During orbital flights, the onboard recorders were set to automatic mode where they were on one minute then off three minutes. The onboard astronaut could override this automatic mode at any time by simply pressing the PUSH-TO-TALK switch. The tapes were then recovered after each mission, analyzed, and the voice data transcribed.

During the longer and more sophisticated follow-on two-person Gemini missions, onboard crew voice recordings were made using a small tape recorder mounted inside the spacecraft cabin between the pilot’s seat and the right-hand side wall. This unit allowed the crew to record their personal observations on removable tape cartridges which were recovered after each flight for transcription.

The resulting transcripts from these onboard voice recorders served to supplement existing air-to-ground narratives, filling in holes in the dialogue caused by periodic communication blackouts. Onboard recordings also were made during reentry since the blazing stream of ionized gas, which engulfed the spacecraft as it fell back through the Earth’s atmosphere, effectively blocked all radio communications with the ground, making direct communication impossible.

As America moved closer to achieving President Kennedy’s goal of landing Americans on the Moon, the size and complexity of the spacecraft needed to accomplish this task grew, and with it came a host of new requirements to capture data. Apollo introduced not only a three-astronaut crew to each new spaceflight, but two separate spacecraft—the bug-like Lunar Module (LM) that allowed two crew members to land on the Moon and return, and the gumdrop-shaped Command Module (CM) attached to the large cylindrical Service Module (SM), collectively referred to as Command and Service Module (CSM). The purpose of the CSM was to safely transport its three-member crew first to lunar orbit then back home, where the CM would separate, reenter the Earth’s atmosphere, and splashdown for recovery.

While in lunar orbit, one astronaut waited patiently aboard the CSM while his two crewmates explored the lunar surface. Each time the spacecraft passed behind the Moon, all radio communications were blocked, putting the astronauts out of touch with Mission Control. During these periods of loss of signal (LOS), important flight performance characteristics would be lost along with any onboard crew dialogue and observations. As a result, NASA introduced a new type of voice and data recorder that, for the first time, allowed ground controllers to periodically perform "tape dumpings" of voice as well as data during the course of an actual mission. A tape dumping involved downloading, via radio telemetry from the spacecraft, the onboard tape contents for either immediate or delayed playback on the ground.

Apollo CM DSE: NASA Photo S66-22993
Apollo LM DSEA: NASA Photo S73-37047
DSEA inside LM S70-30949
DSEA: Tape cartridge loader tool

Handling the recording of voice and data aboard the Command Module was a very sophisticated unit referred to in NASA parlance as the Data Storage Equipment (DSE). This self-contained device included two eight-inch reels that spooled through read-write heads approximately 2,250 feet of one-inch Mylar magnetic tape. The 14-track tape had a storage capacity of over four hours of voice and data. Subsystem information, normally sent directly from the spacecraft, was recorded by the DSE along with voice at a high or low bit rate and could then be transmitted to the ground by Mission Control. The DSE was used during the critical Lunar Orbit Insertion (LOI) burn performed by the CSM while on the far side of the Moon when the spacecraft was out of communication with the Earth. During this period, the DSE recorded crew voices, along with important engine and system parameters, that were then dumped to the ground for engineering analysis as soon as the vehicle flew into Earthrise and regained radio communication with Mission Control.

The ever weight conscious engineers designed a much simpler and lighter data storage unit for use onboard the LM. This unit, called a Data Storage Electronics Assembly (DSEA), used a single-speed, four-track, magnetic tape recorder to record up to 10 hours of voice communications from inside the LM. While the LM was on the far side of the Moon, data was sent live over VHF circuits and saved on a special track of the CM’s DSE. Even before the LM came back over the lunar horizon, engineering parameters of the critical first firing of the descent engine during the LM’s Descent Orbit Insertion (DOI) burn were being studied on the ground via a tape dump from the DSE.

The controls division of the Leach Corporation in Azusa, California, built both the DSE and DSEA for each Apollo spacecraft. Their managers reported to NASA’s instrumentation subsystem manager at the Manned Spacecraft Center in Houston. David E. O’Brien was the manager for the units aboard each LM. The instrumentation subsystem included the timers, the transducers, a signal conditioning electronics assembly, a caution and warning system, and the DSEA. The recorder system originally included telemetry data, which was the same as that for the CM, but due to weight restrictions its role was reduced to recording voice only.

A few problems were associated with the LM’s tape recorder. Originally, the DSEA’s 10-hour tape duration lasted longer since the unit would start recording only when the astronaut spoke. It would then automatically shut down when there was no sound, only to start back up again when the astronaut resumed speaking. This method helped conserve tape, capturing more voice and less dead air during each mission. Because the automatic voice activation (VOX) keying was not good enough to catch the start of an astronaut’s voice, engineers decided to use the tape in a continuous record mode, which made the 10 hours of available recording time a carefully husbanded resource. In each mission’s flight plan, a table was included which listed for the astronauts, exactly what was to be recorded.

Another problem associated with the DSEA centered upon the delicate cartridge containing the recording tape. The original plan was to use several tapes that the astronauts would load and unload during their mission. Getting the tape cartridges in and out of the unit, however, proved difficult and crews often damaged the tapes in the process. As a result, engineers designed a special tool to help the crew load and unload the tapes correctly. After numerous simulations, the astronauts found that even with the tool, it took far too long to change a tape. Engineers eventually settled on just having one tape in the unit, thus eliminating the tape change-out requirement. In addition, the revised mission plans called for bringing the whole unit, tape and all, back to the ground for removal, playback, and transcription. As a result, the special loader tool was never employed except as a very useful ground-handling tool.

Engineers discovered an unexpected, and beneficial, capability of the DSEA: the recording system had a circuit that would automatically pull up low sounds. This turned out to be a bonus. "We could hear the ground communications loud and clear, which wasn’t supposed to happen," said O’Brien. "We thought we had a configuration problem, but it was just the pickup from the astronaut’s earphones in the background!"

Only one recorder ever malfunctioned during the Apollo Program. On Apollo 11 several of the 26-gauge wires leading to the recorder broke resulting in reduced audio levels and a constant background 400hz tone. Because the entire DSEA unit from the mission was brought back, engineers were able to carefully study the hardware, deduce the problem, and develop a fix. They were also able to extract Armstrong and Aldrin’s comments from the noise, incorporating their words into the command module’s final DSE transcript.

Why was voice recording so important? An obvious need was the requirement by engineers for data to help with their systems analysis.

"At the conclusion of every mission, all subsystem managers gathered and assembled their data to evaluate problems," said James Gibbons, a retired NASA Johnson Space Center employee who served as test engineer and data manager in the Test and Evaluation Division of the Apollo Spacecraft Program Office (ASPO). "The transcripts were used to cross-check against the mission data to try and determine what happened at any one given point in time during the mission. In addition, both astronauts and flight controllers used the transcripts to help them recall key events." The press also made extensive use of the words to help its readers experience events in the space program as they unfolded.

There were detractors who questioned the need for transcripts. After all, it was an expensive and time-consuming process to transcribe each and every word spoken during each mission. One of the transcripts for Apollo 17, the last lunar landing mission and the longest in the Apollo Lunar Program, numbers over 2,000 pages. In addition, more than one astronaut was unhappy over having his every word, and perhaps every mistake, recorded, transcribed, and laid bare for all the world to see. Owen Morris, the LM spacecraft manager, also initially felt that the tape recorders represented excess weight on the spacecraft.

Overall, however, the transcripts proved very useful to the astronaut crews, technical support staff on the ground, journalists, and students. As the verbatim record of some of NASA’s greatest achievements, the transcripts are a valuable permanent reference.

The NASA Air-To-Ground Audio Tape Archives

The original mission control audio tapes from the Mercury through Apollo programs consist of audio gathered from different flight controller console stations at NASA’s Mission Control Center (originally based at Cape Canaveral Florida then moved to Houston). Each console fed an audio loop into a 30-track Soundscriber tape recorder which recorded audio from up to 30 different flight controller console positions per mission. Copies of these audio tapes are currently housed in the public affairs office vault at NASA’s Johnson Space Center in Houston, Texas.

Examples of loops recorded during a mission include audio from the flight director, capsule communicator (CAPCOM), and public affairs officer. The flight director loop includes all audio from the flight director such as queries, status checks, and commands given to other flight controllers. The CAPCOM loop includes all air-to-ground communications between the CAPCOM and the astronauts in their spacecraft. The PAO commentary loop includes mission status updates and other observations given by the public affairs officer who monitored each mission from his console in Mission Control. The resulting PAO commentary transcript was made available to the media during and after each mission.

At the close of the Apollo program, the 1-inch 30-track tape was replaced by a newer 1/4-inch 2 and 7 track format which is still in use by NASA today. With the retirement of the 1-inch 30 track tapes, the original hardware that supported this format was no longer needed. Since there no longer was a requirement to support this older equipment, the original Soundscriber tape recorder fell into disrepair.

Even though the requirement to record mission audio on the older 1-inch 30-track format was replaced by a newer system, there remained a historical need to capture and preserve the original audio. NASA recognized this need and soon came to realize that the only way to preserve the older audio was to transfer the 1-inch 30-track tapes to a newer format.

Enter Greg Wiseman, an audio engineer with JSC’s public affairs office. Wiseman led the task of dubbing the remaining 1-inch 30 track mission audio tapes containing audio from the Mercury through Gemini missions, as well as tapes from the Apollo-Soyuz Test Project (ASTP). The challenge Wiseman faced was to try and coax the only remaining machine capable of playing these tapes back into operation. "We found another machine underneath a subfloor in the same building," said Wiseman, adding that the found unit was "in pretty bad shape so we ended up taking parts from it to make the other one work." With spare parts plus a little spit, glue, and bungee cords, Wiseman proceeded to dub the remaining tapes.

"Bungee cords were not factory equipment" said Wiseman with a grin. "We had to add them in order to provide the necessary pressure between the pinch roller and capstan. Without it, the tape speed over the read/write heads wouldn’t stay constant. It may look strange, but it works."

After nearly a year, Wiseman’s patience paid off as he succeeded in transferring the 20 remaining Mercury through Gemini 1-inch 30-track tapes and the 36 tapes left over from the Apollo-Soyuz Test Project. "We now have all of the older format mission audio tapes transferred" said Wiseman. "We’ll still keep around the Soundscriber just in case we find any other older format tapes that need to be transferred, but I’m pretty sure we got them all."

As part of the dubbing project, Wiseman assembled a detailed database listing every mission audio tape from Mercury through Apollo housed in JSC’s PAO vault collection. The tape database is an invaluable historical reference tool as it lists in column form (left to right) the following information:

YR -
MO -
DA -
Year of the original audio
Month of the original audio
Day of the original audio
Tape number
Catalog number
Description of tape contents
Greenwich Mean Time (Start)
Greenwich Mean Time (End)
Mission Elapsed Time (Start)
Mission Elapsed Time (End)
Local Time Start (a conversion of GMT)
Local Time End (a conversion of GMT)

Researchers can use the mission transcript scans on this CD to search particular words or phrases spoken during a mission, find the GMT or MET when they were said, and use the tape database to then find the actual audio tape.

The story behind the "Beep"

Those fortunate enough to listen to any of the actual mission control air-to-ground audiotapes will notice a high-pitched beep emitted before and after every air-to-ground communication between mission control and the astronauts. This sound is called a Quindar tone. Steve Schindler, an engineer with voice systems engineering at NASA’s Kennedy Space Center, offers the following history of its origins.

"Quindar tones, named after the manufacturer of the tone generation and detection equipment, are actually used to turn on and off, or "key," the remote transmitters at the various tracking stations (Merritt Island Launch Area–now Kennedy Space Center, Bermuda, Australia, etc.) that were used to communicate with the Mercury through Apollo spacecraft and, in some cases, are still used with the Space Shuttle. A one-half second tone burst is generated when someone in a control room depresses the push-to-talk (PTT) button of their headset. The decoder at the remote transmitter site detects this tone and keys the transmitter. When the PTT button is released a different frequency tone burst is generated. When the decoder detects this second tone, it unkeys the transmitter. Because the telephone lines between the control rooms and the remote transmitters were originally designed to carry only voice frequencies, the tones had to be in the voice frequency range ("in-band signaling") and thus audible to humans. The tone signaling could have been done on a separate phone line, but to keep costs down, signaling and audio were done on the same line."

"Although it usually worked well, there were a couple of peculiarities with this system. If the transmitter was keyed and the telephone line connection broken, the transmitter would never get the tone to turn off. To prevent this there was a "transmitter on" light at each remote site that would come on when the transmitter was keyed. Someone was supposed to monitor the circuit and if the audio dropped, but the "transmitter on" light was still on, they would have to manually unkey the transmitter. Also, just before communications was handed over to a new tracking station, the key-unkey tone pair was sent 10 times to ensure that everything was functioning correctly. This was done before the audio was patched to the tracking station’s line so it wasn’t heard in the control room or on NASA Select audio.

The Quindar system was actually built from a piece of equipment that was used to put multiple teletype circuits on a single phone line by means of frequency domain multiplexing. Because replacement parts are no longer available, an "out-of-band signaling" system was installed in 1998 for the transmitters located in the U.S. This system uses a continuous tone that is below the normal audio frequency range. When the tone is present, the transmitters are keyed. When the tone is not present, the transmitters are unkeyed. It worked fine, but the Astronaut Office complained about the lack of tones which everyone had become accustomed to as an alert that a transmission was about to start. So, the Quindar tone generator, which was still installed in case it was necessary to key the transmitters at an overseas site, was re-enabled.

Photos and Technical Specifications

The following photos depict both the Data Storage Equipment (DSE) used aboard the Command Module (CM) and the Data Storage Electronics Assembly (DSEA) that was used aboard the Lunar Module (LM) during the Apollo program.


DSE: NASA Photo S66-22991

DSE: NASA Photo S66-22994
DSE: NASA Photo S66-22993

DSE: NASA Photo S66-22992
DSEA: NASA Photo S73-37044

DSEA: NASA Photo S73-37046
DSEA: Photo S73-37045

DSEA: NASA Photo S73-37047
DSEA inside LM S70-30949

DSEA inside LM S72-35105
DSEA inside LM S72-35124

DSEA inside LM S72-35134

DSE_5 is a cutaway drawing showing the relative position of the DSE positioned in the lower equipment bay of the CM.

NASA Photo S66-22991 and NASA Photo S66-22994 are exterior shots of the DSE. Both NASA Photo S66-22993 and NASA Photo S66-22992 reveal the inside of the DSE unit showing one of the two eight-inch reels that would spool through the 14-track read-write heads of the 2,250-feet of one-inch Mylar magnetic tape. The unit can record over four hours of voice and data.

Copied excerpts containing detailed technical specifications of the DSE can be found in the following:


NASA Photo S73-37044 and NASA Photo S73-37046 are exterior shots of the DSEA. NASA Photo S73-37045 shows the DSEA with cover removed revealing the interior electronics and tape cartridge. NASA Photo S73-37047 shows the individual components along with a close-up of the tape cartridge loader tool.

DSEA: Tape cartridge loader tool

NASA Photo S70-30949 shows the DSEA mounted inside the LM behind the commander’s position. NASA Photo S72-35105, S72-35124, and S72-35134 show the DSEA inside LM-11 (Apollo 16’s LM "Orion"). These photos were taken by Grumman as part of the LM closeout sequence documentation.

A more detailed report on the malfunctioning Apollo 11 DSEA can be found in:

Copied excerpts containing detailed technical specifications of the DSEA can be found in the following:

About the Author

Glen E. Swanson is founder of Quest, the world's only publication focusing on the history of space flight. He currently works for NASA as the historian of the Johnson Space Center in Houston, Texas. During the summer he led a project to gather and scan nearly 80 mission transcripts, totalling some 45,000 pages of text.


We hope you enjoy this CD-ROM and find it helpful. Special thanks go to Glen Swanson, historian at NASA’s Johnson Space Center, who tracked down the transcripts, oversaw their scanning, and managed a group of over 50 Internet-based volunteers who collectively reviewed and edited nearly 50,000 pages of transcripts in less than three weeks. This group of volunteers, without their help this project would not have been possible, includes the following: Bill T. Bard, Robert Barton, Adam Bootle, Francis Breame, Todd G. Burns, Earl L. Cagle, Jr., Nancy Chabot, Jeff Cieszecki, Michael Cleaver, Stephanie DeClue, Armistead Dennett, Karl D. Dodenhoff, Eugene Dorr, Kevin M. Doyle, David Fisher, Thomas J. Frieling, Robert Gass, Ken Glover, Richard Glueck, Steve Goodey, David M. Harland, Marv Hein, Ronald Henry, Dana Holland, Mick Hyde, Kandy S. Jarvis, Chris Jones, Larry Kellogg, Suzanne Kinnison, Jason C. Koval, Jack A. Kozak, Ron Kuku, Brian Lawrence, Frances Lilly, Jonathan McDowell, Markus Mehring, Matthew A. Meineke, Michelle Mock, Des O’Neill, Jan Persson, John A. Pfannerstill, Jr., M. Pleau, Mike Poliszuk, Mark Richards, Joy Ritchie, Daniel Robino, Rod Rose, Mark Shavers, Mike Smithwick, Eugene G. Stansberry, Mark Strow, Charles Taylor, Ronald Wells, and Stephanie Wong. In addition, a special note of thanks to Paul Fjeld who helped track down and confirm details on the lunar module and its DSEA, as well as provided material for the introductory narrative. Thanks to Nancy Hutchins, Susan McDonald, and Mary Russell for sharing reminiscences of their transcript days working the tape recorders and typewriters at NASA JSC Public Affairs. Mike Gentry, Mary Wilkerson, David Sharron, and Allen Bond did a fantastic job in helping track down the necessary images used in this project. The many hours of scanning was expertly done by Travis Shelton, whose demonstrated skill and patience with an often temperamental scanning machine was nothing short of magic. Long time NASA JSC contractor Robert Legler, along with civil servants Jared Woodfill and David O’Brien, helped provide details on how the voice and data systems worked. Retired NASA JSC employee James L. Gibbons enriched the introductory text by gratefully sharing some of his experiences as test engineer and data manager with the Apollo Spacecraft Program Office. Joe Nastasi whose knowledge of the inner workings of the Mercury spacecraft helped clarify how the vehicle’s onboard voice and data systems worked. Steve Schindler, whose understanding on the history of Quindar tones helped fill an audible gap in this narrative. A special note of thanks to NASA JSC PAO contractors Greg Wiseman and John Stoll who steadfastly worked for nearly a year in transferring the remaining air-to-ground mission tapes to their current format. Their skill and patience in coaxing the last original MCC Soundscriber to remain functional long enough to complete their task is nothing short of a miracle. Special thanks to Ivan Blejec and Michael Ciancone for helping fill gaps in our transcript collection by lending us copies from their own collections. Thanks also to Kent Carter, Meg Hacker, and Michael Bainbridge of the National Archives and Records Administration’s Southwest Regional Facility for helping to track down several of the more difficult to find Gemini transcripts.

In the NASA History Office at Headquarters, thanks go to Colin Fries, Mark Kahn, Jane Odom, and Amanda Mellies who worked closely with Glen Swanson to track down and scan many of these transcripts. Louise Alstork performed her usual expert editorial duties and Nadine Andreassen assisted with the production.

In the Headquarters Printing and Design Office, John Edison Betts, Jr. patiently handled the layout of the CD booklet and the files on the CD-ROM set. Bryan Elrod, Jonathan Friedman, Warren Owens, and Stanley Artis saw this job through the final editing and production phases. Thanks are due to all these professional people who worked hard to produce what we hope will be a useful reference work.

Stephen Garber and Roger Launius
NASA History Office


Apollo 17: The Blue Marble   -   Overview   -   Timeline   -   Geometry   -   Image Catalog   -   Cameras and Photos   -   Transcripts
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This article was scrounged from the web in January 2006 from what appears to be an anonymous, uploaded version of "The Mission Transcript Collection" CDs at An extended version this article with references was published in Spaceflight Vol 43 February 2001 pp. 74-80 and a PDF of this is available from Ninfinger Productions's superb Scale models web site at http://www.ninfinger.org/~sven/models/vault/spaceflight.pdf