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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
Assessment of Operational Networks
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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
2
Space Network Program Element Assessment
INTRODUCTION
The Space Network is a major element of the Space Operations Mission Directorate’s (SOMD’s) space communications program. It consists of a constellation of Tracking and Data Relay Satellite System (TDRSS) communications satellites and a series of ground tracking and relay stations to provide services to NASA, other government agencies, and commercial and international customers 24 hours per day, 7 days per week (Figure 2.1).
The Space Network’s mission is to “provide global coverage tracking and data acquisition services during launch, early orbit, and operations in low Earth orbit, and satellite anomaly investigation via a constellation of geosynchronous satellites, and associated ground systems located in New Mexico and Guam.”1
Since the 1980s, NASA has operated the TDRSS to provide communications links between Earth and low-Earth-orbiting satellites at S-, Ku-, and Ka-band frequencies. The TDRSS satellites are located in geosynchronous Earth orbit and are positioned in orbital locations that are in constant view either of the White Sands Complex (WSC) at NASA’s White Sands Test Facility in New Mexico, or of NASA’s Guam remote ground terminal (GRGT). The assigned orbital locations provide continuous or full-period telemetry, tracking, and command coverage for near-Earth-orbiting satellites.
The original TDRSS constellation was intended to provide three fully operational satellites, one in the East (or Atlantic region) at 041 degrees West longitude, one in the West (or Pacific region) at 171 degrees West longitude, and a fully functional spare at 079 degrees West longitude. The baseline configuration is depicted in Figure 2.2. Over the years the robust performance of the TDRSS satellites, as well as additional loading requirements, resulted in NASA’s expansion of the system and the use of more spacecraft.
The current TDRSS constellation consists of six first-generation (F1 and F3-F7) and three second-generation (F8-F10) satellites, with three of the nine satellites being stored on orbit. The first-generation spacecraft support three categories of service: single access, multiple access, and tracking at the S and Ku bands. The second-generation spacecraft added Ka-band forward and return services in addition to the S- and Ku-band capabilities. Figure 2.3 depicts the current TDRSS constellation orbital placement, Table 2.1 gives the launch dates, and Figure 2.4 indicates the overall health of the TDRSS constellation. Figure 2.5 shows projected TDRSS constellation capacity based on failures experienced to date and long-term reliability models. The lower portion of Figure 2.5 shows anticipated user demand for service (hours per day), representing in excess of 60 different missions through 2017. The on-orbit health issues reflected in Figure 2.4 have had limited impact on tracking and data relay services at this time due to built-in redundancy and operational rescheduling. Specific failure trends are closely monitored and used in individual satellite as well as constellation end-of-useful life projections.
The TDRSS satellites are controlled through the WSC and the GRGT. The WSC consists of two functionally equivalent ground terminals that provide network scheduling and command and control of the TDRSS satellites, as well as serving as the relay points for customer data to the necessary control and data collection centers. The GRGT is used to support the TDRSS satellite located at 085 degrees East longitude (275 degrees West) and the customer satellites serviced through that relay. Major ground system upgrades were completed in 1994 (second TDRSS ground terminal) and 1996 (White Sands ground terminal upgrade). The GRGT became operational in 1998, expanding system capability to global coverage for near-Earth missions. A Space Network expansion project is under way to add up to two additional ground terminals to increase available TDRSS capacity. For more than 20 years, the Space Network has supported a wide variety of near-Earth missions, including
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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
FIGURE 2.1 NASA’s Space Network, comprising the TDRSS space segment and a ground segment. SOURCE: Ken Ford, NASA, “Space Network,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006, p. 6.
scientific, environmental, and human spaceflight missions, as well as launch vehicles and other non-NASA efforts. This capacity for global coverage and connectivity is expected to continue and expand as NASA defines future science and exploration missions. Planning for Space Network continuation apparently has started, but no details were available for assessment by this committee.
ASSESSMENT
Formulation of the Project Plan
Project Objectives
The Space Network’s objectives are clearly articulated in the mission statement; they are aligned with the NASA Strategic Plan2 and are traceable to the NASA Vision for Space Exploration.3,4 The principal focus of the Space Network is day-to-day operation of the space and ground segments of the TDRSS to provide global tracking and data relay services. Continuity of these services represents a significant technical and budgetary challenge to the Space Network as the existing architecture ages and new demands for service are identified.
The agency-wide Space Communications Architecture Working Group (SCAWG) addresses the communications and navigation architecture needed to support future (25 years) NASA science and exploration missions. At this writing, specific details are pending on both the architectural roadmap and a realignment of management responsibility for space communications.
Project Deliverables
Current Space Network activities are well structured to provide documented services to a broad range of users.5 The Space Network interacts daily with the user community, providing services within the network’s established capacity and capability. Formal project service-level agreements or memoranda of agreement with both the NASA and non-NASA user communities document the specific Space Network services to be provided. The project service-level agreement is a formal agreement between the project office and the customer for services, at a specific cost, within a
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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
FIGURE 2.2 Tracking and Data Relay Satellite System baseline configuration. SOURCE: Ken Ford, NASA, “Space Network,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006, p. 5.
specified time frame. Committee discussions with a cross section of the customers indicated general satisfaction with the level and timeliness of the services provided. A number of metrics have been developed and are closely monitored to ensure satisfactory overall Space Network performance.
The day-to-day customer mission requirements are addressed through a formal customer commitment process and the Customer Commitment Office. This office provides tracking and data acquisition options, assistance with mission-unique communications needs, and assistance in defining those needs.
The total Space Network 2006 budget of $90 million represents approximately 50 percent of the budget that is actually appropriated for the SOMD space communications program.6 That appropriated budget is currently augmented by reimbursable revenue from non-NASA users for Space Network services provided to them. However, as of January 2006 it was projected that the portion of the 2006 Space Network budget derived from these reimbursable sources would drop below the $70 million minimum level needed for operations and maintenance of the network. Such losses will be exacerbated as the constellation capacity for support to non-NASA missions degrades, as discussed in later sections.
Expected Services
The Space Network has a capacity/capabilities-driven architecture, rather than a requirements-driven architecture. There are continuing initiatives by the Space Network program element to interact with potential new users during the design phase of their missions. Documentation describing the Space Network’s capability, capacity, and services is widely distributed and available for users considering use of the Space Network to satisfy their mission needs. As a result, there is not a formal process for reviewing and validat-
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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
FIGURE 2.3 Space Network overview and current TDRSS constellation orbital placement. SOURCE: Ken Ford, “Space Network,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006, p. 9.
TABLE 2.1 Current TDRSS Constellation
S/C
Launched
Geosynchronous Orbit
In-Orbit Checkout Complete
Utilization
TDRS-1
April 4, 1983
STS-6 (Challenger)
June 29, 1983
December 28, 1983
Acceptance April 1985
One Satellite System
Operating at 49°W, providing South Pole Support
TDRS-3
September 29, 1988
STS-26 (Discovery)
September 30, 1988
January 15, 1989
Two Satellite System Acceptance
July 1989
Operating at 275°W
TDRS-4
March 13, 1989
STS-29 (Discovery)
March 14, 1989
June 9, 1989
Operating at 46°W
TDRS-5
August 2, 1991
STS-43 (Atlantis)
August 3, 1991
October 7, 1991
Operating at 171°W
TDRS-6
January 13, 1993
STS-54 (Endeavor)
January 14, 1993
March 4, 1993
In storage 174°W
TDRS-7
July 13, 1995
STS-70 (Discovery)
July 14, 1995
August 22, 1995
In storage 150°W
TDRS-8
June 30, 2000
Atlas IIA
July 1, 2000
April 23, 2002
Operating at 174°W
TDRS-9
March 8, 2002
Atlas IIA
September 30, 2002
February 14, 2003
In storage 62°W
TDRS-10
December 5, 2002
Atlas IIA
December 6, 2002
May 9, 2003
Operating at 41°W
NOTE: TDRS-2 lost January 28, 1986, aboard STS-51-L (Challenger).
SOURCE: Ken Ford, NASA, “Space Network,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006, p. 31.
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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
FIGURE 2.4 Health of the TDRSS constellation as of September 1, 2005. SOURCE: Ken Ford, NASA, “Space Network,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006, p. 32.
ing the totality of Space Network customer community requirements to establish a minimum acceptable, or threshold, level of Space Network capacity. The current process has worked well to date, but the need for infrastructure replenishment, upgrade, and transition to meet emerging exploration needs will demand an earlier and more formal interaction between the communications provider and the mission definition efforts.
Finding: The Space Network has a capacity/capabilities-driven architecture, rather than a requirements-driven architecture. Current Space Network activities are well structured to provide documented services to a broad range of users.
Long-Term Project Goals and Objectives
There is some indication of planning for near-term continuation of Space Network support for NASA missions, specifically TDRSS satellite replenishment,7 but no commitment of resources as of this writing. There is no indication of planning for an orderly transition to the out-year architecture. TDRSS constellation reliability has been identified as the number-one Space Network risk, with the potential for a significant impact on NASA missions starting in the 2015 time frame.8 See Figure 2.5. Moreover, a projection of capacity to support non-NASA missions shows a gap starting in the 2010 time frame. The committee noted that it is in NASA’s best interest to continue to participate with the other organizations addressing this issue. Unless specific programmatic actions are taken to reverse the shortfall in capacity, significant competition for limited resources will require decisions about prioritization and/or degraded mission support. Space communications program management has stated that a TDRSS satellite replenishment initiative, to support only NASA mission needs, will be submitted for inclusion in the FY 2008 budget. The committee agrees with this approach and strongly supports the need for an FY 2008 acquisition start.
Finding: A NASA TDRSS satellite replenishment decision is needed not later than the FY 2008 budget cycle in order to ensure continuity of communications support for NASA missions.
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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
FIGURE 2.5 TDRSS capacity to support NASA missions, 2006 to 2017. Single access (SA) means provision of service to only one user at a given time. SOURCE: Ken Ford, NASA, “Space Network,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006, p. 28.
Recommendation: NASA should develop a compelling case for a TDRSS satellite replenishment acquisition start for the FY 2008 budget cycle.
Connections to the Broader Community
Department of Defense
Various elements of the Department of Defense (DOD) are represented in the user base of TDRSS services. This relationship is expected to continue; however, NASA’s planning for the sizing and the schedule for replenishment of the TDRSS space segment is proceeding independently of these external user considerations.
There is no substantive interaction between SOMD’s space communications program and the ongoing DOD MilSatCom efforts.9 NASA was involved with DOD in the original definition of the federal government’s Transformational Communications Architecture (TCA); however, there is little interaction at this time as elements of the TCA move into development and acquisition. NASA space communications are no longer an integral element of the TCA. At a minimum, some degree of interoperability between NASA’s Space Network as it evolves, and DOD MilSatCom would seem to be a worthwhile goal, but there is no indication of real movement in that direction.
Finding: The original objective of an appropriate level of interoperability between NASA/TDRSS and MilSatCom/TCA is still a worthwhile goal.
Recommendation: NASA should reestablish executive-level discussions with DOD MilSatCom to examine options for systems interoperability.
National Science Foundation
Since 1997 the oldest TDRSS satellite (F1, launched in 1983) has provided the bulk of the high-bandwidth data support for the National Science Foundation’s (NSF’s) advanced astronomy and astrophysics programs at South Pole Station.10 Projected increases in needs for data transfer, and the apparent absence of cost-effective long-term alternatives for continuation of service, present a significant dilemma for the NSF. While informal discussions on future NSF needs have taken place between NASA and NSF personnel, the NSF has not been a formal participant or consideration in NASA’s planning for future communications architectures,
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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
and future support for the NSF astronomy program’s increasing data communications needs is uncertain.
Finding: There appears to be a “caveat emptor” mind-set when it comes to consideration of communications service continuity (TDRSS satellite replenishment and longer-term continuity of service) for the non-NASA user community.
Recommendation: If in fact TDRSS, plus its follow-on, is truly a national asset, NASA should take the lead in identifying the appropriate policy, the required resources, and the planning, implementation, and requirements validation process necessary to serve all TDRSS user communities’ needs for communication services.
Utilization of Commercial Space Systems
NASA conducted a comprehensive assessment of alternatives to TDRSS and in 2000 published a report that evaluated the technical feasibility as well as the business risk of using a commercial satellite system to support NASA low-Earth-orbit (LEO) missions.11 The technical areas evaluated included the coverage and throughput available to NASA LEO users and the requirements that could be imposed on NASA LEO users to receive these necessary services. The business risk assessment identified characteristics of the commercial environment that affect the feasibility of relying on commercial satellite systems to support NASA LEO missions.
The assessment’s principal conclusions included the following: commercial systems are designed for commercial users; NASA’s high-volume traffic might be poorly supported; no commercial systems have the flexibility or the capacity of TDRSS; no commercial system can support NASA’s real-time communications requirements for manned spaceflight or launch missions; coverage decreases with increased user altitude due to the conic shape of the antenna beams of commercial satellites; coverage is usually not available for polar regions at LEO altitudes, reducing coverage for missions with highly inclined orbits, such as Earth Observing System satellites and LandSat; and coverage is not continuous for most LEO missions, and typically is not guaranteed owing to business imperatives.
The committee noted that many of the assumptions about baseline availability and performance characteristics of the eight representative systems made in the NASA report have changed, and an update addressing those changes would be appropriate.
In addition, although the NASA report did a commendable job in assessing a total system alternative to TDRSS, it did not look at moving specific mission communications services to commercial providers. It might be prudent to consider such an approach, in order to partially offset the predicted shortfall in capacity mentioned above, as NASA looks at TDRSS satellite replenishment and transition to a new architecture.
Finding: Commercial satellite communications systems may have limited ability to meet some of the mission needs currently being supported by the Space Network.
Recommendation: NASA should update its 2000 study using information on the current state of commercial communications systems and focus on offloading mission support needs as appropriate.
Methodology
Project Plan Completeness
NASA has developed a draft Space Network Operations Project Plan that focuses primarily on customer interactions and the day-to-day operations of the Space Network.12
There is no SOMD Space Network element plan, nor is there an integrating program plan for the various elements of SOMD’s space communications program.
The committee believes that program planning documentation is essential in order for the Space Communications Office to address its split management responsibilities; negotiate cross-program-element requirements, resources, and scheduling issues; and provide a more unified NASA space communications interface if future collaborative efforts are initiated with military and commercial communications systems.
Finding: There is no SOMD Space Network element plan that addresses requirements, a requirements validation process, resources, and schedule, nor is there an integrating plan for all of the various elements of SOMD’s space communications program. There is a draft Space Network Operations Project Plan; however, it is focused primarily on customer interfaces and the day-to-day operation of the Space Network.
Recommendation: Given the opportunity offered by the impending reorganization of space communications work across NASA, NASA should develop a Space Network element plan as part of a space communications program planning documentation tree.
Risk Management
NASA has a formal risk identification and assessment process for the Space Network. Under this process, various risk scenarios are examined, and mitigation plans are identified. As of this writing, two high-risk items have been identified by NASA:13 long-term TDRSS satellite reliability and inadequate funding to perform required sustaining engineering and upgrades.
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Review of the Space Communications Program of Nasas Space Operations Mission Directorate
Overall Capabilities
Quality of Work Performed
The Space Network has performed admirably for more than 20 years, providing for a wide range of customers services that are available from no other single source. In discussions with the committee, a variety of users indicated unanimous satisfaction with service provided by the Space Network in support of their missions. As the necessary backbone for any future NASA communications initiative, the Space Network not only must be provided sufficient resources, but also must be an integral part of the planning process. The current management structure of split responsibilities for the overall NASA space communications program is being reexamined in light of new exploration and science initiatives. The establishment of a SCAWG with widespread NASA representation to focus the development of a communications and navigation architecture is a step in the right direction, but additional management and budgetary alignments should be considered to implement a truly integrated space communications program.
Finding: The Space Network today sets a world-class standard for global coverage, tracking, and data acquisition services.
Adequacy of Resources
Space Network resources (people, facilities, and budget) are adequate to execute the current project scope. However, since currently more than one-half of the $90 million annual Space Network budget derives from non-NASA users (reimbursable funds), alternative approaches should be pursued by management to provide a more stable level of support for the operations and maintenance of the Space Network.
Finding: Reliance on reimbursable funds from non-NASA users as the major component of the funding needed for the operations and maintenance of the Space Network is an unhealthy basis for long-term planning and stability.
Recommendation: NASA, in conjunction with the user community, should examine alternatives for providing long-term, stable funding at the level required for operation and maintenance of the Space Network.
The committee notes that as NASA moves forward on the exploration path there will be expanded requirements placed on the space communications enterprise that will require significant management attention, particularly in the areas of personnel qualifications, motivation, and retention. The current leadership has done a good job in these areas, but the possible implementation of a new management structure with expanded responsibilities will impose even greater demands.
NOTES
1. Spearing, Robert, “Space Communications,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006.
2. National Aeronautics and Space Administration (NASA), 2006 NASA Strategic Plan, NP-2006-02-423-HQ, available at http://www.nasa.gov/pdf/142302main_2006_NASA_ Strategic_Plan.pdf.
3. NASA, The Vision for Space Exploration, February 2004, available at http://www.nasa.gov/pdf/55583main_vision_space_ exploration2.pdf.
4. Spearing, Robert, “Space Communications,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006.
5. NASA, Space Network Operations Project Plan, 452-PLAN-0003, NASA, Washington, D.C., February 22, 2006.
6. Spearing, Robert, “Space Communications,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006.
7. TDRSS replenishment as used in this report refers specifically to the next acquisition of replacement spacecraft needed to maintain some (currently unspecified) level of service to users as the on-orbit spacecraft reach the end of their useful life. Neither the planned capabilities/configuration of these replacement spacecraft, nor possible alternative approaches to provide comparable service, have been developed as yet, and therefore were not assessed by the committee.
8. Ford, Ken, “Space Network,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006.
9. Pawlikowski, Brigadier General Ellen M., MilSatCom SPD, personal communication, April 13, 2006.
10. Chiang, Erick, National Science Foundation Office of Polar Programs, “Data Communications Supporting Astronomy/Astrophysics at South Pole Station,” presentation to NASA-NSF Astronomy/Astrophysics Advisory Committee, Arlington, Virginia, May 11, 2006.
11. NASA, Assessment of Commercial Alternatives to TDRS Services, GSA-118, December 2000.
12. NASA, Space Network Operations Project Plan, 452-PLAN-0003, February 22, 2006.
13. Ford, Ken, “Space Network,” briefing to the NRC Committee to Review NASA’s Space Communications Program, Washington, D.C., January 26-27, 2006.
Representative terms from entire chapter:
space communications
