Receiving Space Shuttle Astronaut Voice Communications

KSC Contact: George Diller

KSC Release No. 40-00

Space Shuttle air-to-ground communication is transmitted on one of two
designated S-band frequencies. Because the S-Band voice is digitized, it is
unintelligible. When the orbiter is above the horizon, air-to-ground voice on the
UHF band can be heard either on 259.7 mhz or 296.8 mhz. However these
frequencies are primarily used only during launch and landing. It will, of course,
be necessary to know if and when the Space Shuttle will be above the horizon at
your location. Unless you are near a NASA tracking station, you will hear only
the “downlink,” or one side of the conversation, which will be the astronauts
talking to ground controllers.

On some missions, the Space Shuttleís orbital inclination is 28.45
degrees, meaning the orbiter travels no farther north in the U.S. than the latitude
of Cape Canaveral, the Canary Islands in the Atlantic Ocean region or Midway
Island in the Pacific, which limits geographical voice coverage. However, flights
which rendezvous with the International Space Station and many scientific Space
Shuttle missions have higher inclinations, ranging between 39 degrees and 57
degrees. At these inclinations, voice may be heard as far north as the Gulf of
Alaska, Hudson Bay in Canada, and the Hebrides in Scotland.

During all Space Shuttle flights, air-to-ground voice (both uplink and
downlink) and video from the orbiter are transmitted on NASA Television which
is a C-band satellite transmission on GE-2, Transponder 9C, (3880.0 mhz).
This is a geostationary satellite with an orbital location of 85 degrees West.
Audio only is also available on 6.8 mhz. GE-2 can be received in all 50 states
and much of Canada, Mexico and the Caribbean. While the Space Shuttle is in
orbit, this system is always broadcasting. The signal is not encoded, or
scrambled, and may be picked up with a home satellite receiver. Some cable
television companies carry it, at least on a limited basis. NASA Television
is also available on a continuous basis on two direct satellite-to-home broadcast
systems, Dish Network and DirectTV.

The Space Shuttle on-orbit communications through the Tracking and
Data Relay Satellite (TDRS) system uses S-band and K-band. This is encoded
and also transmitted digitally, so it is not possible for a home satellite system to
receive air-to-ground voice or television from TDRS.

The Amateur Radio Club at the Goddard Space Flight Center in
Greenbelt, Maryland, WA3NAN, retransmits the air-to-ground Space Shuttle
communications on shortwave frequencies. The best reception on each
frequency will vary based on the time of day. The frequencies are:

• 3.860 mhz
• 7.185 mhz
• 14.295 mhz
• 21.395 mhz
• 28.650 mhz

Some amateur radio organizations retransmit NASA Television or mission
audio. As an example, an amateur radio FM transmitter, located on Merritt
Island near Gate 2 at the Kennedy Space Center, retransmits Space Shuttle air-
to-ground communications on 146.94 mhz. Mission Audio is also transmitted by
the amateur radio club at the Goddard Space Flight Center on frequency 147.45
mhz, and by the club at the Johnson Space Center in Houston on 146.64 mhz.
The signals can be received for about 25 miles. An amateur television
transmitter (ATV) in Cocoa, Fla., retransmits NASA Television on 421.25 mhz.
This can be received with a normal cable-ready television set on Channel 57 by
using an external antenna. The signal can be received for at least 20 miles.

Transmitters of various power on other frequencies are provided by local
amateur radio organizations in cities around the country. A list of amateur
retransmissions of audio or video/audio from NASA TV is available on the
World Wide Web at http://amsat.org/amsat/sarex/shutfreq.html

Some Space Shuttle missions also carry amateur radio transmitters called
SAREX (Shuttle Amateur Radio Experiment). As the schedule permits, amateur
radio operators can have their call sign confirmed directly by an astronaut.
When the flight crew is busy, a “computer packet module” will automatically
transmit a computer message. For further information on the SAREX program
frequencies, contact the American Radio Relay League, 225 Main Street,
Newington, CT 06111, (860) 594-0200. A SAREX Worldwide Web Page from
the NASA Goddard Space Flight Center may be found at
http://www.nasa.gov/sarex/sarex_mainpage.html