The space shuttle
orbiter communication system transfers telemetry information about
orbiter operating conditions and configurations, systems and payloads;
commands to the orbiter systems to make them perform some function
or configuration change; documentation from the ground that is printed
out on the orbiter's teleprinter or text and graphics system; and
voice communications among the flight crew members and between the
fight crew and ground.
is transferred through hardline and radio frequency links. Hardline
refers to wires that connect communicating devices, and RF refers
to radio signals. RF communication takes place directly with the
ground or through the TDRS.
takes place through Air Force Satellite Control Facility remote
tracking station sites, also known as space-ground link system ground
stations, for military missions or through STDN ground stations
for NASA missions. Direct signals from the ground to the orbiter
are referred to as uplinks, and signals from the orbiter to the
ground are called downlinks.
takes place through the White Sands Ground Terminal. These indirect
signals from the TDRS to the orbiter are referred to as forward
links, and the signal from the orbiter to the TDRS is called the
return link. Communication with a detached payload from the orbiter
is also referred to as FL, and RL is the signal from the payload
to the orbiter.
communication system is divided into several smaller systems to
facilitate information transfer: S-band frequency modulation, S-band
phase modulation, Ku-band ultrahigh frequency, payload communications,
audio and closed-circuit television.
FM, S-band PM, Ku-band and UHF systems are used to transfer information
between the orbiter and the ground on RF signals in their frequency
bands. The payload communication system is used to transfer information
between the orbiter and its payloads either through hardline or
RF links. The audio systems transfer voice communications throughout
the orbiter, and the CCTV system is used for visually monitoring
and recording activities. Communication security equipment aboard
the orbiters provides the capability for encryption and decryption
of operational data.