Proceedings of National Science FoundationUnited States Antarctic Program Communications Workshop
The goal of this workshop is to define South Pole Station communications requirements and to develop the short and long-term strategies to support those requirements based on our knowledge to date on available and planned systems. Discussion of various subjects included:
Summary Conclusions |
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Nine summary conclusions were developed among the participants to complement the NSF/OPP strategy to maintain and increase the communication capability at Amundsen-Scott South Pole station.
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Dr. Karl Erb, the Director, Office of Polar Programs (OPP), discussed the important relationship between the construction of the new South Pole Station and NSF/OPP’s planning support of communications for the new station. The goal of this workshop is to define communications requirements and options to support these requirements (short- and long-term) so that the capability exists to support the science through the completion of the new South Pole Station in 2005. |
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Mr. Patrick Smith, Technology Development Manager, OPP, led a presentation and discussion of current satellite communication capabilities at all of the USAP Antarctic stations. At McMurdo Station, commercial satellite communication service, a full period (24 hrs/day) T1 communications circuit (1.544 Mb/s), is provided by SPAWAR Systems Center, Charleston, SC, through a contract to AT&T/ALASCOM until Feb. 2000. Continuity of service is of prime concern and SPAWAR plans to re-compete the service contract, with award planned by 1 Oct. 1999. It is estimated that the bandwidth may be able to double without increase in cost. The time division multiplexed (TDM) fractional T1 service provided includes telephone, fax, Internet, and private data network links (Table 1). McMurdo Station-based scientists find the satellite communications provided comparable to any institution, although they are presently not moving large files (image or data) like South Pole astronomers and physicists. Scientists working on the Long Term Ecological Research (LTER) Project, based in the nearby McMurdo Dry Valleys, however, have increasing requirements for Internet access for e-mail and data file transfer, which has only recently been provided in a limited fashion. Table 1 McMurdo Station Satellite Communications
At Palmer Station, satellite communication service for part of the day is provided by three satellites presently (ATS-3, LES-9, and INMARSAT). Palmer Station has excellent visibility to many international satellites in the geosynchronous arc servicing North and South America and Europe. Future plans call for the installation of 24 hour a day coverage by one of the international satellite operators (e.g., Intelsat or Hughes/Panamsat) (Table 2). Table 2 Palmer Station Inventory of Present/Future Satellite Capability
At South Pole Station, approximately 13 hr/day of connectivity exist using four satellites, ATS-3, LES-9, GOES-3, and TDRS F1 (Table 3). South Pole has a theoretical daily total throughput of 5,180 MBytes/day with all existing satellite resources and 656 MB/d without any TDRS F1 service. This estimate does not include a realistic derating of throughput based on such factors as TCP/IP Internet protocol overhead, data transmission session overhead, link fade periods, link error rates, etc. This estimate must be considered an optimal upper bound of throughput. Any practical systems implemented will perform at lower levels of performance. Loss of TDRS F1 would have a catastrophic effect on scientific research being conducted at South Pole Station. An Iridium handset was successfully tested at South Pole Station for voice (only) during the 1998-99 season as a part of the Iridium Beta Test Program. Table 3 South Pole Station Inventory of Present Satellite Capability
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Dr. Dennis Peacock, Head of the NSF/OPP Antarctic Science Section, led a presentation and discussion of science communication requirements at South Pole Station for both the immediate future and over the next five years. NSF forecasts, based on active and approved future projects, indicate that science communication requirements should peak for FY2000 and then stabilize at a flat level for the period of FY2001-2003 + (Table 4). Table 4 NSF Forecasts of Science Communication Requirements at South Pole Station FY1999-2003
Good communications at South Pole are required by scientists for:
The Communication Working Group of the South Pole Users Committee had two recommendations for communications in 1997 and 1998. First, availability of communications (e.g. multiple satellites, total communication time, times spread throughout the day, etc.) and bandwidth (e.g. sufficient for data, voice, and video) are of primary importance to South Pole scientists. Second, performance of the communications (e.g. how is communications implemented) is of secondary importance. Two priority requirements for communications were summarized by participating scientists:
In contrast to the forecast presented in Table 4 (current active and known approved future projects), the projected data communications requirements forecast by evaluating proposal ideas from the community in the concept or review stage indicate a growth in demand in the years after 2005. Current and projected science requirements forecast by participating scientists were gathered (Table 5). The current bandwidth requirement is estimated at 14.63 GBytes/day and by 2005 is forecasted to be 558.6 GBytes/day as a result of this exercise. The near term forecast does not match the projection presented in Table 4 because Table 5 reflects the potential "pent-up demand" that exists that cannot be actualized due to the present limited resources. Table 5 South Pole Scientist Communication Requirements
Note: Not a comprehensive list of requirements. Figures are approximate estimates of workshop participants and selected scientists not participating, which reflect the majority of current South Pole Station science projects. |
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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:
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. |
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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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Dr. Jay April, Assistant Project Director, Management Systems, and Mr. Chris Rhone, Director, Information Systems, Antarctic Support Associates (ASA), led a presentation and discussion of ASA’s integration and implementation of USAP requirements. ASA has been intimately involved with NSF/OPP in strategic planning for Information Technology (IT). USAP IT planning issues have focused on standardization of systems, configuration management, technology changes, and communications capabilities. ASA has addressed these issues during the IT strategic planning process, which consists of:
Through its interactions with the Communications Working Group of the SPUC and planning support from review of requirements in grant proposals and Support Information Packages (SIPs), ASA has defined communications goals to better support scientific research at South Pole, including:
The current communication systems and their capabilities at South Pole are summarized in Table 6. Table 6 Current South Pole Station Communication Systems and Capabilities
ASA’s has reviewed with NSF/OPP the recommendations from the SPUC from the May 1998 Meeting and implemented the following changes during the 1998-99 season:
ASA’s planned future activities in communications support at South Pole Station are:
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Mr. Jim Pettit, AlliedSignal Technical Services Corporation (ATSC), led a presentation and discussion of sustainable future options. Based on ATSC’s review, the following are South Pole Station’s communications needs:
A review of communication support at South Pole Station tells the present science story. Only 5 GB/d bandwidth is being used currently by scientists at South Pole, versus T1 providing approximately 15 GB/d. The conclusion is that the present communications model adequately provides for science support requirements at South Pole Station. A heuristic formulation by ATSC for proposed communication requirements at South Pole Station, summarized in Table 7, was presented to stimulate discussion. Table 7 Future Proposed South Pole Station Communication Requirements
The challenge of providing the projected communications at South Pole Station is based on:
ATSC considered these challenges and ranked potential solutions as shown in Table 8. Table 8 Potential Satellite Communication Solutions for South Pole Station Ranked by Cost
There are three types of solutions, which have tradeoffs:
One new possibility would be for NSF to acquire a Molniya satellite for the southern hemisphere. The advantage of a Molniya satellite would be that a large portion of the Southern Hemisphere is covered within the visibility limit of a satellite global antenna beam. Most of Antarctica would be covered within the visibility limit of a typical high gain spot beam. ATSC assessed issues of partnering and cutting deals with others to cut and share communications costs at South Pole Station. Advantages are:
The chief disadvantage is that NSF is working in a region where partners are scarce and resources (satellites) are limited. ATSC recommended this follow on work:
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Mr. Phil Sobolewski, SPAWAR Charleston, presented and led a discussion on potential U.S./foreign military and other U.S. government satellite resources to meet South Pole Station communication requirements. Over forty satellites were examined by SPAWAR for present and future capabilities and are summarized in Table 9. Table 9 U.S./Foreign Military and Other U.S. Government Satellite Resources for Potential Communication Use at South Pole Station
Satellite bandwidth capability varied from Milstar and EHF Polar (0.000075 MHz) to DSCS (85 MHz). Geo orbit satellite inclinations ranged from UFO-7 (4 degrees) to FLTSAT-1 (13.8 degrees). South Pole daily visibility was a minimum with FLTSAT-4 (6.5 hrs) to a maximum with GPS 2A-13 (9.5 hrs). South Pole/CONUS Mutual Daily Visibility varied from GPS 2A-13 (3 hrs) to FLTSAT-4 (5.5 hrs). Daily theoretical data transfer capability ranged from a minimum with FLTSAT-4 (9.9 GB/d) to a maximum with GPS 2A-13 (12 GB/d). SPAWAR concluded that the current possibilities are the FLTSAT F1 and F4, GPS NAVSTAR 2A-13, and NRO satellites, and future possibilities are, Advanced EHF Polar Follow-On System, and DSCS-3 F1 and NATO III-D following replacement (see Table 9 for details). SPAWAR recommends that NSF/OPP consider taking these next steps:
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Mr. Erick Chiang, NSF/OPP Section Head, Polar Research Support Section, led the participants in a review discussion of possible options and detailing summary recommendations. NSF/OPP is transitioning from an ad hoc process to a systematic approach to addressing communications, which is learning a different mode of doing business at South Pole. The following questions were presented for clarification by the participants of the workshop:
The recommended availability, reliability, and bandwidth for communication systems at South Pole Station were defined (Table 10). Table 10 Recommended Availability, Reliability, and Bandwidth for Communication Systems at South Pole Station
A 99% availability translates into an annual acceptable total outage of 87.6 hours per year (based on continuous 24 hour/day coverage), or equivalently 7.3 hours per month or 14.4 minutes/day. In the case of the Internet, outage would have to be defined as the service not being available due to whatever causes, to include performance degrading below some pre-defined acceptable level (a present issue with the service provided via LES-9 - the link is highly available when the satellite is visible, but link quality is often marginal, meaning that many kinds of applications cannot be performed over the Internet link). Short-term (FY02)/long-term (beyond FY02) options were identified and three categories of capability recommended: minimum, acceptable, and wish list. To meet short-term communication requirements, while the long-term options are being identified, the following primary satellites are recommended to be maintained with backup satellites:
Last, it was recommended that NSF/OPP consider installation of a flexible ground station to take advantage of the various satellite systems presently available and potentially available in the future. The workshop concluded with nine summary conclusions being made to NSF/OPP for review and action (see Executive Summary and Summary Conclusions). |
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