Page One of "The Gazette",
Cedar Rapids, Iowa on June 16, 1959
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The Collins Radio Company provided the radio communications for all US astronauts from the Mercury, Gemini, Apollo and Space
Shuttle missions. Neil Armstrong's famous words on the first moon landing, as well as the images, were sent via Collins Radio equipment.
Project Mercury (1959-1963) was the first US human spaceflight program, consisting of 20 unmanned flights and 6 manned flights. The first
two manned flights were suborbital and Alan Sheppard was the first American in space on May 5, 1961. John Glenn was the first American to
orbit the earth on February 20, 1962.
The Collins radios used in the Mercury program were installed in the capsules and the ground stations around the world. The ground
station radios included the AN/FRW-2 radio set, first developed by Collins Radio in 1956 for use with guided missiles and unmanned flights.
These flights were required to have secure communications to prevent the Russians or other countries from gathering intelligence on the progress
or specifics of the mission. Another security requirement was to prevent any attempts to jam the signal or send false commands to the aircraft
or missile. The radio set included the T-560B transmitter, paired with a KY-171 Audio Frequency Coder. The R-669A Receiver was paired
with the KY-172 Audio Frequency Decoder. The coder and decoder were connected to a C-1669 Coder Control.
The receiver and transmitter can operate on 144 channels at one megahertz increments between 406 and 549 megahertz. The 500 watt transmitter
could be switched between continuous carrier and keyed carrier operation. The coder and decoder both support 20 audio frequency channels,
supporting tones between 7.5 and 75 kilohertz, of which up to 6 could be active at one time. The type of telemetry used for Project Mercury
was the combination of time and frequency division multiplex telemetry, using PAM/FM/FM. This was state of the art at the time but also a
well-proven technology. PAM (pulse-amplitude modulation) is a time division multiplex signal which was used to modulate an FM/FM frequency
division modulated subcarrier.
Listen to the telemetry data from Sputnik I as it passed overhead on
October 4, 1957, the first day of its 3 month mission.
The receiver and transmitter also supported voice calls between the capsule and ground stations, but a different UHF radio set was primarily used
for that purpose. The FRW-2 radio set was HF and used as an emergency backup for voice calls, in which case it would bypass the KY-171/KY-172.
John Glenn's Mercury capsule (Friendship 7)
because of their small size they were worn, not ridden
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The KY-171 Audio Frequency Coder pictured below is a rare device, this one has a serial number of "8". The "KY" designation later became
the identifier for voice encryption devices. While the KY-171 does not perform voice encryption, it does perform audio frequency encryption
of telemetry data in combination with the decoder and coder control devices. The FRW-2 radio set was the same as used for
previous ballistic missile projects, except for the C-1669 Coding Control. The coding controller was reprogrammed with updated features and
software to handle the new needs of the Mercury project. They also had to be compatible with the specific coding technique employed in
the Mercury spacecraft and the need to provide fast switching between stations as the capsule proceeded through its orbit. The coding
controllers could be activated remotely and were also able to rapidly change to several available coding schemes.
The data plate on the front of the KY-171 also shows it was made for contract number NAS-1-430. This contract was
issued by NASA on July 30, 1959 in the amount of $33 million to the Western Electric Company. The contract was for the construction and
engineering of the Mercury communications network and was completed by July 1961 when the final report was issued.
Radio equipment was installed around the world in a total of 18 ground stations, plus the Mercury Control Center at Cape Canaveral, and the
Computing and Communication Center at Goddard Space Flight Center in Greenbelt Maryland. These ground stations tracked the capsule and
provided voice and instrumentation communications. They were also interconnected via a ground network to the Goddard Space Flight Center.
The Mercury communications network included 102,000 miles of teletype lines, 60,000 miles of telephone lines, and 15,000 miles of high-speed
data lines.
Much of the communication technology used in the Mercury Project developed from research that originated in WW2. The type of time and
frequency division multiplexing used for telemetry data, the coding and decoding of the signal, encryption techniques and other protocols were
improved upon with the advances made in ballistic missile testing just after the war. Because of the time pressure to compete with the Russians,
the choice was made to use existing, proven technology in the communication systems. This was in the days before digital electronics, integrated
circuits, memory, etc. The technology used was all analog, with mechanical gauges and vacuum tubes, making the achievements of the Mercury
Project all the more impressive.
See the Entire Collection of Cipher Machines
See detailed pictures of the KY-171 Audio Frequency Coder
This is the KY-171 Audio Frequency Coder used for the NASA Mercury Project (1958-1963) to encode radio traffic between ground stations, and
ground stations and the space capsule. It is used with the T-560B Radio Transmitter to send encoded telemetry data. The transmitter bypassed
the coder when used for emergency voice backup. The R-669A Radio Receiver is paired with a KY-172 Audio Frequency Decoder and the C-1669 Coder
Control to decipher the messages. All of these devices are part of the AN/FRW-2 Radio Set.
