The South Pole TDRSS Relay (SPTR) is a satellite radio relay communication system that provides an Internet link for a station at the South Pole. As the name of the system suggests, the radio connection is made via the TDRSS. The northern end of the link is located at the TDRSS ground-terminal complex at White Sands Test Facility.

The concept of a radio link with the Internet is not new; what is new here is the use of the TDRSS for transmission and reception of data at high speed according to the Internet Protocol (IP).

The TDRSS Internet Link Terminal at the South Pole station is a set of equipment that transmits and receives IP traffic, using the TDRSS as a radio relay.

The visibility of Tracking and Data Relay Satellite 1 (TDRS-1) from the South Pole was a consideration in the choice of the TDRSS (instead of another satellite system) for the SPTR; the inclination (>9.5 °) of the orbit of TDRS-1 makes this satellite visible from the South Pole for more than 3.5 hours each day, and the period of visibility is expected to increase in the long term. In addition, the capabilities of the TDRSs are greater than those of other satellites visible from the South Pole.

The SPTR was designed to provide the following services:

  • K-band transmission of data from the South Pole to White Sands at a rate up to 50 Mb/s,
  • K-band file-transfer service from the South Pole to White Sands at a rate between 2 and 10 Mb/s, and
  • S-band bidirectional IP service at a rate of 1.024 Mb/s.

The SPTR was installed in December 1997. By the next month, it was fully operational, providing the services listed above. Both the South Pole and White Sands terminals were assembled from mostly commercially available equipment. The South Pole equipment (see figure) includes the following:

K-Band Subsystem

  • file-server computer
  • convolutional encoder
  • binary phase-shift keying (BPSK) modulator
  • 20-W traveling-wave-tube (TWT) amplifier
  • 4-ft (1.2-m) antenna.

S-Band Subsystem

  • router
  • satellite modem
  • up- and down-converters
  • 10-W power amplifier
  • 4-ft (1.2-m) antenna.

The SPTR additions to the White Sands ground terminal include the following:

  • new 1.024-Mb/s connection between the terminal and the Internet
  • file-server computer for K-band transfers and the Internet File Transfer Protocol (FTP)
  • router for connections among the Internet, the TDRSS, and a local-area network (LAN)
  • TDRSS interface that provides coding, scrambling, and descrambling.

The main advantage of the SPTR is that it provides high-level Internet service between the South Pole and other locations. Any IP software can be used, and it is possible to make full use of commercial standards and new developments consistent with the IP. The only major disadvantages are that satellite-communication delays affect the bidirectional IP service and that radio-communication noise could raise the bit-error rate beyond the maximum allowable level of 10-5. The basic SPTR concept could be applied to establish Internet links at field camps and aboard balloons and airplanes.

This work was done by David J. Israel of Goddard Space Flight Center. GSC-14037


NASA Tech Briefs Magazine

This article first appeared in the June, 1999 issue of NASA Tech Briefs Magazine.

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