Spacecraft Classification

Communications & Navigation Spacecraft
TDRSS Spacecraft
TDRSS
Communications and navigation spacecraft are abundant in Earth orbit, but they are largely incidental to JPL's missions. The Deep Space Network's Ground Communications Facility does make use of Earth-orbiting communications spacecraft to transfer data among its sites in Spain, Australia, California, and JPL. The Deep Space Network uses Earth-orbiting Global Positioning System navigation spacecraft to maintain an accurate time reference throughout the network.
In the future, communications and navigation spacecraft may be deployed at Mars, Venus, or other planets, dedicated to communications with orbiters, rovers, penetrators, and atmospheric spacecraft operating in their vicinity. This task is currently carried out to some extent by various orbiter spacecraft that are also equipped for limited communications relay. The purpose of dedicated Mars communications orbiters would be to augment the Deep Space Network's capabilities to communicate with the resident spacecraft. None have been funded or developed as of early 2013. This concept is revisited in Chapter 18.

The communications spacecraft example offered here is NASA's Tracking and Data Relay Satellite System, TDRSS. NASA missions supported by the system include the Hubble Telescope, the Space Shuttle, GRO, Landsat, TOPEX, JASON, and EUVE and the International Space Station. Click the TDRSS image for details of this communications spacecraft. Other examples of communications and navigation spacecraft include:

Milstar
GPS System
Global Positioning System (GPS)
DirecTV
Globalstar