South Pole TDRSS Relay (SPTR) and TDRSS Operations

Mr. Dave Israel, NASA Network Services and Mission Projects Office, led the presentation and discussion of South Pole TDRSS Relay (SPTR) and TDRSS Operations. The SPTR consists of South Pole TDRSS Relay (File Server, Ku-Band Return Link and S Band Forward & Return Link) <-> TDRS-1 Spacecraft <—> White Sands Complex (File Server and Ku-band TDRS SGL) <—> Internet connection. The SPTR web page (http://nmsp.gsfc.nasa.gov/SPTR) has a summary of bandwidth usage of TDRSS suggesting that of the 1 MBytes/day available, that only 40 kBytes/day is used (bandwidth underutilized). An MPEG-facilitated video was demonstrated successfully for CBS during the 1998-99 season, using SPTR. This system exercised the SPTR Ku-Band link at a transmission rate of approximately 6 Mb/s. Engineering tests performed during initial installation of the present SPTR earth station indicated that the SPTR system has sufficient capability to permit a 50 Mb/s link without difficulty. This would more than meet South Pole's bulk data transfer requirements. Modest engineering changes are required to enable the link to operate at speeds of 6-10 Mb/s, with limitations mainly due to the computer systems that transmit and receive data over the link (and not the RF link). The Ku-Band component of a standard TDRSS satellite can operate at speeds up to 300 Mb/s, as has been documented by NASA at McMurdo Station.

In February 1999, NASA made the decision to keep TDRS F1 operational to support the communications requirements of South Pole Station. However new resources are needed at the NASA White Sands Complex to accomplish this. Hence the White Sands Alternate Relay Terminal (WART) project begun. WART will provide these services:

  1. SSAF: 1.024 Mb/s IP (expandable to 2 Mb/s)
  2. SSAR: 1.024 Mb/s IP (expandable to 2 Mb/s)
  3. KSAR: 2 Mb/s (expandable to 50 Mb/s)

is expected to be operational 6 months after start-up (target date is Sept. 1999), and have costs of $500K (non recurring) and $550K/year (recurring). There is still a need to develop a data store/forward center in the U.S., which will improve the operational efficiency of links at South Pole Station.

Present Internet networking architecture problems experienced by the interconnection of the University of Miami and NASA Integrated Services Network (NISN) Internet service to South Pole will remain until structural changes are made to the network. These should be performed in conjunction with the implementation of WART. The interconnection of the SPTR White Sands data terminal and SPTR IP router with IP routers at the University of Miami have been recommended by NASA NISN to solve IP network instabilities and performance problems. In order for NSF to fully capitalize on the 2 Mb/s expansion capability of the present SPTR SSAF/R Internet link when WART is completed, a different network connection to NISN would be required, also. The 2 Mb/s capability for the SSAF/R Internet link will come automatically and at no cost due to the transition of SPTR White Sands operations to WART. At present, NASA NISN is funding a T1 line to connect the SPTR service at White Sands to the NISN Internet backbone. Any changes would most likely require NSF funding.

Bill Decker is the NASA Program Director for Advanced Network Infrastructure. The vBNS and Abilene backbones will yield aggregate speeds of OC48 — 2.4 GB/s. All of these projects are part of the Next Generation Internet (NGI), which other agencies can tie into. Discussion focused on how NSF could more effectively use the increase bandwidth made possible by SPTR enhancements (and future TDRS service by other satellites) so that the Internet as a data distribution system does not be come a bottleneck. Jeff Peterson of CMU inquired about the potential for interconnection of the SPTR links with the NGI backbones, noting that observatories in southern New Mexico are becoming connected (Sun Spot). It was thought that New Mexico State in Las Cruces may be a vBNS award recipient. Synergisms for a data center management, vBNS connectivity, and satellite operations support were briefly discussed regarding support for South Pole as a means to provide needed service and keep total operating expense down.

Opportunities from Industry: Possibilities for a Dedicated Satellite

Mr. Jim Adams, NASA Rapid Spacecraft Development Office (RSDO), led the presentation and discussion of possibilities for a dedicated satellite to support South Pole Station communications.

The communications issues raised by scientists at South Pole are not different than those raised by space scientists. Scientists are concerned about the latency of the data ranging from hours and minutes to seconds. The goal at South Pole Station is for direct transmission to/from PIs at institutions worldwide.

The cost of a communications satellite currently is $60-80 million in today’s market for purchase, launch, operations and maintenance for five years. International partnering is possible to reduce cost. There is a possibility of bolting science payloads (transponders) on the sides of planned commercial satellites, which might serve South Pole Station communications. A constellation of two to three satellites may be required to serve South Pole Station (Molniya highly inclined, highly elliptical orbit). Soon there will be a GSA-type catalogue of "almost-off-the-shelf" satellites. Bandwidth of 5-10 TB/d will also be possible. Regardless of the satellite selected, significant systems engineering is required.

NSF should pattern its pursuit of communications for South Pole Station like NASA’s capability to develop dedicated space missions. South Pole Station is an excellent space station analogue. It is a world class science facility operating in an extremely hostile polar environment. One of the requirements to accomplish the science mission at South Pole Station as in outer space is reliable, high bandwidth communications.

Several investment options are available to NSF/OPP to provide a dedicated, high latitude, communications constellation to South Pole Station. The NASA/GSFC Integrated Mission Design Center (IMDC) is recommended to be used for systems engineering and an MOA exists between NSF and NASA for use of IMDC when needed. NSF/OPP should not rule out commercial service as they have many great possibilities, including hybrid satellites (with multiple payloads aboard). Commercial satellite development time is presently at 18 months and dropping to 12 months, which is good news. The top cost of satellite systems is the cost of the launch vehicles, not the satellites. LEO and GEO satellite downlinks could serve NOAA customers at South Pole Station. In the future a satellite might be parked over South Pole using solar sail technology. Options could be pursued with IMDC that would benefit both Antarctic and arctic communications, which would be appealing from the standpoint of sharing costs among countries and between hemispheres.

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