Satellite Communications Glossary

Telemetry.  Telemetry is a term used to refer to data gathered by sensors on board the satellite to monitor pressure, temperature, voltage and current, and so on, in the various subsystems.

Telstar.  On 10 July 1962, AT&T launched Telstar I, which was the first satellite to provide repeated transmission without delay. Telstar was launched into an orbit between 956 km and 5 633 km with 44.8º inclination.

Thermal Control Subsystem.  The Thermal Control Subsystem is essential to maintain the platform within its operating temperature limits for the type of equipment on board. Maintenance of a spacecraft’s thermal equilibrium requires rigorous consideration of the allowable operating temperature range, the energy absorbed by the platform, internal heat generation, and external heat radiation.

Thrust Subsystem.  The Thrust Subsystem contains the apogee boost (or apogee kick) motor used to circularise the final orbit. The subsystem also contains gas jets or small rocket motors that are used to reposition the satellite to compensate for orbital variations (called station keeping), or to move the satellite to a new slot. These movements are different from the attitudinal corrections.

Thuraya.  Thuraya is a geostationary satellite providing mobile phone coverage of Europe and northern Africa.

Thuraya phones.  Thuraya phones are dual-mode phones that can use the Thuraya satellite as well as terrestrial mobile phone services.

Thuraya SMS.  Thuraya SMS uses the Thuraya satellite phone system to provide SMS messages.

Time-division multiple access (TDMA).  Time-division multiple access in satellite communications is a mechanism for sharing a channel, whereby a number of satellite communications users have access to the whole channel bandwidth for a small period of time (a time slot).

Tracking Telemetry and Command Subsystem (TT&C).  The Tracking, Telemetry, and Command (TT&C) Subsystem comprises three elements: tracking to determine the position of the spacecraft and follow its travel using angle, range and velocity information; telemetry to collect, encode and transmit health information for the other subsystems; and a command element that receives and executes remote control commands to effect changes to the platforms functions, configuration, position and velocity.

Transponder.  The fundamental function of the communications satellite is to provide the communications subsystem, which comprises a number of clusters of receivers, frequency translators and transmitters called transponders.

Travelling-wave Tube Amplifier (TWTA).  In a satellite communications transponder, power amplification is carried out with a travelling-wave tube amplifier (TWTA).

Tunnel-diode amplifier.  A tunnel diode amplifier is a form of low-noise amplifier (LNA).

Two-way satellite Internet.  Topics in the Satellite Communications Glossary related to Two-way satellite Internet are: Mobile satellite Internet, Broadband Internet satellite, Satellite Internet Providers, Satellite wireless Internet, Satellite Internet Services, Satellite Internet, Satellite Internet Connection, Satellite Internet Access.

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