Airborne radio telephone communication via a satellite is usually abbreviated to the term SATCOM.
Use of satellites for this purpose complements satellite-based navigation capability. Aircraft onboard equipment for SATCOM includes a satellite data unit, a high power amplifier and an antenna with a steerable beam.
A typical aircraft SATCOM installation can support data link channels for packet data services as well as voice channels. This makes it technically possible to extend ATM data link (CPDLC) beyond the airport and TMA environments currently served by VDL (VHF Data Link) Mode 2.
SATCOM data link is currently used for only a small proportion of en route ATM communications in contrast to the much more extensive use as an alternative to VHF and HF for non-ATC purposes. The Asia-Pacific Region has been a particular focus for many of the early developments in the use of SATCOM for ATM data link. SATCOM functionality, which primarily depends upon geostationary satellites, is poor in polar regions, where HFDL (HF Data Link) provides equivalent service for some uses.
There are currently nearly 5,000 satellites in orbit. Almost all of them got there the same way – a satellite launch vehicle (SLV) known as a carrier rocket.
An SLVis classed by NASA according to low Earth orbit payload capability:
- Small-lift launch vehicles are less than 4,400 pounds.
- Medium-lift launch vehicles are 4,400 to 44,100 pounds
- Heavy-lift launch vehicles are 44,000 to 110,000 pounds
- Super-heavy lift vehicles are more than 110,000 pounds
In every case, the orbital satellite is packed carefully onto the satellite launch vehicle. Then, powered by a rocket engine, the carrier rocket with its satellite payload must travel at speeds of at least 4.9 miles per second to overcome Earth’s gravitational forces and reach orbit altitude.
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