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2 Space Network Program Element Assessment INTRODUCTION generation (F1 and F3-F7) and three second-generation (F8- F10) satellites, with three of the nine satellites being stored The Space Network is a major element of the Space on orbit. The first-generation spacecraft support three cat- Operations Mission Directorate’s (SOMD’s) space commu- egories of service: single access, multiple access, and track- nications program. It consists of a constellation of Tracking ing at the S and Ku bands. The second-generation spacecraft and Data Relay Satellite System (TDRSS) communications added Ka-band forward and return services in addition to the satellites and a series of ground tracking and relay stations to S- and Ku-band capabilities. Figure 2.3 depicts the current provide services to NASA, other government agencies, and TDRSS constellation orbital placement, Table 2.1 gives the commercial and international customers 24 hours per day, 7 launch dates, and Figure 2.4 indicates the overall health of days per week (Figure 2.1). the TDRSS constellation. Figure 2.5 shows projected The Space Network’s mission is to “provide global cov- TDRSS constellation capacity based on failures experienced erage tracking and data acquisition services during launch, to date and long-term reliability models. The lower portion early orbit, and operations in low Earth orbit, and satellite of Figure 2.5 shows anticipated user demand for service anomaly investigation via a constellation of geosynchronous (hours per day), representing in excess of 60 different mis- satellites, and associated ground systems located in New sions through 2017. The on-orbit health issues reflected in Mexico and Guam.”1 Figure 2.4 have had limited impact on tracking and data re- Since the 1980s, NASA has operated the TDRSS to lay services at this time due to built-in redundancy and op- provide communications links between Earth and low- erational rescheduling. Specific failure trends are closely Earth-orbiting satellites at S-, Ku-, and Ka-band frequen- monitored and used in individual satellite as well as constel- cies. The TDRSS satellites are located in geosynchronous lation end-of-useful life projections. Earth orbit and are positioned in orbital locations that are in The TDRSS satellites are controlled through the WSC constant view either of the White Sands Complex (WSC) at and the GRGT. The WSC consists of two functionally NASA’s White Sands Test Facility in New Mexico, or of equivalent ground terminals that provide network schedul- NASA’s Guam remote ground terminal (GRGT). The as- ing and command and control of the TDRSS satellites, as signed orbital locations provide continuous or full-period well as serving as the relay points for customer data to the telemetry, tracking, and command coverage for near-Earth- necessary control and data collection centers. The GRGT is orbiting satellites. used to support the TDRSS satellite located at 085 degrees The original TDRSS constellation was intended to pro- East longitude (275 degrees West) and the customer satel- vide three fully operational satellites, one in the East (or At- lites serviced through that relay. Major ground system up- lantic region) at 041 degrees West longitude, one in the West grades were completed in 1994 (second TDRSS ground ter- (or Pacific region) at 171 degrees West longitude, and a fully minal) and 1996 (White Sands ground terminal upgrade). functional spare at 079 degrees West longitude. The baseline The GRGT became operational in 1998, expanding system configuration is depicted in Figure 2.2. Over the years the capability to global coverage for near-Earth missions. A robust performance of the TDRSS satellites, as well as addi- Space Network expansion project is under way to add up to tional loading requirements, resulted in NASA’s expansion two additional ground terminals to increase available TDRSS of the system and the use of more spacecraft. capacity. For more than 20 years, the Space Network has The current TDRSS constellation consists of six first- supported a wide variety of near-Earth missions, including 15
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16 REVIEW OF THE SPACE COMMUNICATIONS PROGRAM The Space Segment—9 Satellites • 5 operational • 3 in storage • 1 residual (dedicated to the National Science Foundation) The Ground Segment • White Sands Complex White Sands White Sands Ground Terminal Ground Terminal — 2 Space-Ground Link Terminals Second TDRSS Ground Terminal — 3 Space-Ground Link Terminals Data Services Management Center — Scheduling — Monitor and control Second TDRSS • Guam Remote Ground Terminal Ground Terminal 1 Space-Ground Link Terminal Guam Remote Terminal 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, work as the existing architecture ages and new demands for as well as launch vehicles and other non-NASA efforts. This service are identified. capacity for global coverage and connectivity is expected to The agency-wide Space Communications Architecture continue and expand as NASA defines future science and Working Group (SCAWG) addresses the communications exploration missions. Planning for Space Network continua- and navigation architecture needed to support future (25 tion apparently has started, but no details were available for years) NASA science and exploration missions. At this writ- assessment by this committee. ing, specific details are pending on both the architectural roadmap and a realignment of management responsibility for space communications. ASSESSMENT Project Deliverables Formulation of the Project Plan Current Space Network activities are well structured to Project Objectives provide documented services to a broad range of users.5 The The Space Network’s objectives are clearly articulated Space Network interacts daily with the user community, pro- in the mission statement; they are aligned with the NASA viding services within the network’s established capacity and Strategic Plan2 and are traceable to the NASA Vision for capability. Formal project service-level agreements or Space Exploration.3,4 The principal focus of the Space Net- memoranda of agreement with both the NASA and non- work is day-to-day operation of the space and ground seg- NASA user communities document the specific Space Net- ments of the TDRSS to provide global tracking and data work services to be provided. The project service-level relay services. Continuity of these services represents a sig- agreement is a formal agreement between the project office nificant technical and budgetary challenge to the Space Net- and the customer for services, at a specific cost, within a
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17 SPACE NETWORK PROGRAM ELEMENT ASSESSMENT Spare Node (062W, 079W, 150W) East Node SGL (041W, 047W) Multiple Access West Node (171W, 174 W) SGL SGL Single Access K & S band S-band Single Access White Sands Complex SGL to South Pole GRGT (NSF) TDRS-1 TDZ (049W) (275 W) 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 Network budget derived from these reimbursable sources section of the customers indicated general satisfaction with would drop below the $70 million minimum level needed the level and timeliness of the services provided. A number for operations and maintenance of the network. Such losses of metrics have been developed and are closely monitored to will be exacerbated as the constellation capacity for support ensure satisfactory overall Space Network performance. to non-NASA missions degrades, as discussed in later The day-to-day customer mission requirements are ad- sections. dressed through a formal customer commitment process and the Customer Commitment Office. This office provides Expected Services tracking and data acquisition options, assistance with mis- sion-unique communications needs, and assistance in defin- The Space Network has a capacity/capabilities-driven ing those needs. architecture, rather than a requirements-driven architecture. The total Space Network 2006 budget of $90 million There are continuing initiatives by the Space Network pro- represents approximately 50 percent of the budget that is gram element to interact with potential new users during the actually appropriated for the SOMD space communications design phase of their missions. Documentation describing program.6 That appropriated budget is currently augmented the Space Network’s capability, capacity, and services is by reimbursable revenue from non-NASA users for Space widely distributed and available for users considering use of Network services provided to them. However, as of January the Space Network to satisfy their mission needs. As a re- 2006 it was projected that the portion of the 2006 Space sult, there is not a formal process for reviewing and validat-
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18 REVIEW OF THE SPACE COMMUNICATIONS PROGRAM WHITE SANDS COMPLEX GUAM REMOTE GROUND TERMINAL TDRS-6 TDRS-7 F-9 173.7°W 150°W 62.4 °W (stored) (stored) (stored) F-8 F-5 F-1 F-4 F-10 F-3 174.3°W 171.4°W 049°W 046°W 041°W 275°W TDW (SPTR) TDS TDE TDZ McMurdo Ground Station McMurdo TDRS Relay System original small map (McMurdo, Antarctica) 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 Operating at 49°W, providing TDRS-1 April 4, 1983 June 29, 1983 December 28, 1983 STS-6 (Challenger) One Satellite System South Pole Support Acceptance April 1985 TDRS-3 September 29, 1988 September 30, 1988 January 15, 1989 Operating at 275°W STS-26 (Discovery) Two Satellite System Acceptance July 1989 Operating at 46°W TDRS-4 March 13, 1989 March 14, 1989 June 9, 1989 STS-29 (Discovery) Operating at 171°W TDRS-5 August 2, 1991 August 3, 1991 October 7, 1991 STS-43 (Atlantis) In storage 174°W TDRS-6 January 13, 1993 January 14, 1993 March 4, 1993 STS-54 (Endeavor) In storage 150°W TDRS-7 July 13, 1995 July 14, 1995 August 22, 1995 STS-70 (Discovery) Operating at 174°W TDRS-8 June 30, 2000 July 1, 2000 April 23, 2002 Atlas IIA In storage 62°W TDRS-9 March 8, 2002 September 30, 2002 February 14, 2003 Atlas IIA Operating at 41°W TDRS-10 December 5, 2002 December 6, 2002 May 9, 2003 Atlas IIA 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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19 SPACE NETWORK PROGRAM ELEMENT ASSESSMENT Indicates fully operational Launch 09/88 Launch 04/83 Launch 03/89 F-1 F-3 F-4 East 49.0 ∞W ZOE 275.25∞W East 46∞W Indicates backup unit(s) in use Note 9 Note 11 Note 9 SA1 SA1 SA1 SA1 SA1 SA1 Indicates failed subsystem S S S S S S Note TT&C TT&C TT&C General Notes: BUS BUS 10 BUS MA MA 2 MA • One spare SGL TWTA on F-3 and F-4 • Ten-year design life for F-1 - F-7, 11 years Ku Ku Ku Ku Ku Ku for F-8 - F-10, and 4 years for on-orbit Note Note Note Note storage 13 1 7 Notes: Launch 01/93 • F-3 KSA2 polarization restricted to LCP, Launch 08/91 Launch 07/95 F-5 F-6 F-7 174.0°W Stored KSAR2 low performance; redundant Ku- West 171.0°W 150.5°W Stored band parametric amplifier selected to recover from switch anomaly SA1 SA1 SA1 SA1 SA1 SA1 • S-band TWTA failed on F-3 (SSAF2), F-5 (SSAF1) Note 6 Note 2 S S S S TT&C S S TT&C BUS • Both Ku-band TWTA units on F-5 failed TT&C BUS MA BUS MA (KSAF1); return available MA • F-8 MAR G/T shortfall Ku Ku Ku Ku Ku Ku • F-9 propulsion anomaly: failure of A-3 and W-2 thrusters Note 3 • SSAR2 parametric amplifier failure on F-5 • F-4 ESA and MFG LO failures Launch 06/00 Launch 03/02 Launch 12/02 • F-9 LO failure KSAR2 F-8 F-9 F-10 West 174.3°W 62.4 °W Stored East 40.9°W • KSA polarization services restricted on F-3 and F-4 SA1 SA2 SA1 SA2 SA1 • F-3 Primary coarse sun sensor failure S S S S S S • F-1 SA2 SSAR and SSAF, KuSAR2 TT&C TT&C operational using WART TT&C BUS BUS BUS MA MA Note 8 Ku Ku • F-9 primary central telemetry and MA Ka Ku Ka Ku Ku Ku Command Unit failure • F-4 KSA1F TWTA failure Note 12 Note 8 Note 5 Ka Ka Ka Ka Note **Indicates updates and changes 4 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 re- chitecture. TDRSS constellation reliability has been identi- quirements to establish a minimum acceptable, or threshold, fied as the number-one Space Network risk, with the poten- level of Space Network capacity. The current process has tial for a significant impact on NASA missions starting in the 2015 time frame.8 See Figure 2.5. Moreover, a projec- worked well to date, but the need for infrastructure replen- ishment, upgrade, and transition to meet emerging explora- tion of capacity to support non-NASA missions shows a gap tion needs will demand an earlier and more formal interac- starting in the 2010 time frame. The committee noted that it tion between the communications provider and the mission is in NASA’s best interest to continue to participate with the definition efforts. other organizations addressing this issue. Unless specific programmatic actions are taken to reverse the shortfall in Finding: The Space Network has a capacity/capabilities- capacity, significant competition for limited resources will driven architecture, rather than a requirements-driven ar- require decisions about prioritization and/or degraded mis- chitecture. Current Space Network activities are well struc- sion support. Space communications program management tured to provide documented services to a broad range of has stated that a TDRSS satellite replenishment initiative, to users. 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 Long-Term Project Goals and Objectives acquisition start. There is some indication of planning for near-term con- tinuation of Space Network support for NASA missions, Finding: A NASA TDRSS satellite replenishment decision is specifically TDRSS satellite replenishment,7 but no com- needed not later than the FY 2008 budget cycle in order to mitment of resources as of this writing. There is no indica- ensure continuity of communications support for NASA mis- tion of planning for an orderly transition to the out-year ar- sions.
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20 REVIEW OF THE SPACE COMMUNICATIONS PROGRAM Hours of SA Demand per Day Number of Available SAs SA Demand (NASA Missions) = Full SA Capability 50% Confidence Level 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 seem to be a worthwhile goal, but there is no indication of for a TDRSS satellite replenishment acquisition start for the real movement in that direction. FY 2008 budget cycle. Finding: The original objective of an appropriate level of interoperability between NASA/TDRSS and MilSatCom/TCA Connections to the Broader Community is still a worthwhile goal. Department of Defense Recommendation: NASA should reestablish executive-level Various elements of the Department of Defense (DOD) discussions with DOD MilSatCom to examine options for are represented in the user base of TDRSS services. This systems interoperability. relationship is expected to continue; however, NASA’s plan- ning for the sizing and the schedule for replenishment of the National Science Foundation TDRSS space segment is proceeding independently of these external user considerations. Since 1997 the oldest TDRSS satellite (F1, launched in There is no substantive interaction between SOMD’s 1983) has provided the bulk of the high-bandwidth data sup- space communications program and the ongoing DOD port for the National Science Foundation’s (NSF’s) advanced MilSatCom efforts.9 NASA was involved with DOD in the astronomy and astrophysics programs at South Pole Sta- tion.10 Projected increases in needs for data transfer, and the original definition of the federal government’s Transforma- tional Communications Architecture (TCA); however, there apparent absence of cost-effective long-term alternatives for is little interaction at this time as elements of the TCA move continuation of service, present a significant dilemma for into development and acquisition. NASA space communica- the NSF. While informal discussions on future NSF needs tions are no longer an integral element of the TCA. At a have taken place between NASA and NSF personnel, the minimum, some degree of interoperability between NASA’s NSF has not been a formal participant or consideration in Space Network as it evolves, and DOD MilSatCom would NASA’s planning for future communications architectures,
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21 SPACE NETWORK PROGRAM ELEMENT ASSESSMENT and future support for the NSF astronomy program’s increas- at TDRSS satellite replenishment and transition to a new ing data communications needs is uncertain. architecture. Finding: There appears to be a “caveat emptor” mind-set Finding: Commercial satellite communications systems may when it comes to consideration of communications service have limited ability to meet some of the mission needs cur- continuity (TDRSS satellite replenishment and longer-term rently being supported by the Space Network. continuity of service) for the non-NASA user community. Recommendation: NASA should update its 2000 study using Recommendation: If in fact TDRSS, plus its follow-on, is information on the current state of commercial communica- truly a national asset, NASA should take the lead in identify- tions systems and focus on offloading mission support needs ing the appropriate policy, the required resources, and the as appropriate. planning, implementation, and requirements validation pro- cess necessary to serve all TDRSS user communities’ needs Methodology for communication services. Project Plan Completeness Utilization of Commercial Space Systems NASA has developed a draft Space Network Operations NASA conducted a comprehensive assessment of alter- Project Plan that focuses primarily on customer interactions and the day-to-day operations of the Space Network.12 natives to TDRSS and in 2000 published a report that evalu- ated the technical feasibility as well as the business risk of There is no SOMD Space Network element plan, nor is using a commercial satellite system to support NASA low- there an integrating program plan for the various elements of Earth-orbit (LEO) missions.11 The technical areas evaluated SOMD’s space communications program. included the coverage and throughput available to NASA The committee believes that program planning docu- LEO users and the requirements that could be imposed on mentation is essential in order for the Space Communica- NASA LEO users to receive these necessary services. The tions Office to address its split management responsibilities; business risk assessment identified characteristics of the negotiate cross-program-element requirements, resources, commercial environment that affect the feasibility of relying and scheduling issues; and provide a more unified NASA on commercial satellite systems to support NASA LEO mis- space communications interface if future collaborative ef- sions. forts are initiated with military and commercial communica- The assessment’s principal conclusions included the fol- tions systems. lowing: commercial systems are designed for commercial users; NASA’s high-volume traffic might be poorly sup- Finding: There is no SOMD Space Network element plan ported; no commercial systems have the flexibility or the that addresses requirements, a requirements validation pro- capacity of TDRSS; no commercial system can support cess, resources, and schedule, nor is there an integrating NASA’s real-time communications requirements for plan for all of the various elements of SOMD’s space com- manned spaceflight or launch missions; coverage decreases munications program. There is a draft Space Network Op- with increased user altitude due to the conic shape of the erations Project Plan; however, it is focused primarily on antenna beams of commercial satellites; coverage is usually customer interfaces and the day-to-day operation of the not available for polar regions at LEO altitudes, reducing Space Network. coverage for missions with highly inclined orbits, such as Earth Observing System satellites and LandSat; and cover- Recommendation: Given the opportunity offered by the im- age is not continuous for most LEO missions, and typically pending reorganization of space communications work is not guaranteed owing to business imperatives. across NASA, NASA should develop a Space Network ele- The committee noted that many of the assumptions ment plan as part of a space communications program plan- about baseline availability and performance characteristics ning documentation tree. of the eight representative systems made in the NASA report have changed, and an update addressing those changes would Risk Management be appropriate. In addition, although the NASA report did a commend- NASA has a formal risk identification and assessment able job in assessing a total system alternative to TDRSS, it process for the Space Network. Under this process, various did not look at moving specific mission communications risk scenarios are examined, and mitigation plans are identi- services to commercial providers. It might be prudent to con- fied. As of this writing, two high-risk items have been iden- tified by NASA:13 long-term TDRSS satellite reliability and sider such an approach, in order to partially offset the pre- dicted shortfall in capacity mentioned above, as NASA looks inadequate funding to perform required sustaining engineer- ing and upgrades.
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22 REVIEW OF THE SPACE COMMUNICATIONS PROGRAM Overall Capabilities placed on the space communications enterprise that will re- quire significant management attention, particularly in the Quality of Work Performed areas of personnel qualifications, motivation, and retention. The current leadership has done a good job in these areas, The Space Network has performed admirably for more but the possible implementation of a new management struc- than 20 years, providing for a wide range of customers ser- ture with expanded responsibilities will impose even greater vices that are available from no other single source. In dis- demands. cussions with the committee, a variety of users indicated unanimous satisfaction with service provided by the Space NOTES Network in support of their missions. As the necessary back- bone for any future NASA communications initiative, the 1. Spearing, Robert, “Space Communications,” briefing to the Space Network not only must be provided sufficient re- NRC Committee to Review NASA’s Space Communications Pro- sources, but also must be an integral part of the planning gram, Washington, D.C., January 26-27, 2006. process. The current management structure of split responsi- 2. National Aeronautics and Space Administration (NASA), bilities for the overall NASA space communications pro- 2006 NASA Strategic Plan, NP-2006-02-423-HQ, available at gram is being reexamined in light of new exploration and http://www.nasa.gov/pdf/142302main_2006_NASA_ Strategic_Plan.pdf. science initiatives. The establishment of a SCAWG with 3. NASA, The Vision for Space Exploration, February 2004, widespread NASA representation to focus the development available at http://www.nasa.gov/pdf/55583main_vision_space_ of a communications and navigation architecture is a step in exploration2.pdf. the right direction, but additional management and budget- 4. Spearing, Robert, “Space Communications,” briefing to the ary alignments should be considered to implement a truly NRC Committee to Review NASA’s Space Communications Pro- integrated space communications program. gram, Washington, D.C., January 26-27, 2006. 5. NASA, Space Network Operations Project Plan, 452- Finding: The Space Network today sets a world-class stan- PLAN-0003, NASA, Washington, D.C., February 22, 2006. dard for global coverage, tracking, and data acquisition ser- 6. Spearing, Robert, “Space Communications,” briefing to the vices. NRC Committee to Review NASA’s Space Communications Pro- gram, Washington, D.C., January 26-27, 2006. 7. TDRSS replenishment as used in this report refers specifi- Adequacy of Resources cally to the next acquisition of replacement spacecraft needed to maintain some (currently unspecified) level of service to users as Space Network resources (people, facilities, and bud- the on-orbit spacecraft reach the end of their useful life. Neither the get) are adequate to execute the current project scope. How- planned capabilities/configuration of these replacement spacecraft, ever, since currently more than one-half of the $90 million nor possible alternative approaches to provide comparable service, annual Space Network budget derives from non-NASA us- have been developed as yet, and therefore were not assessed by the ers (reimbursable funds), alternative approaches should be committee. pursued by management to provide a more stable level of 8. Ford, Ken, “Space Network,” briefing to the NRC Com- support for the operations and maintenance of the Space mittee to Review NASA’s Space Communications Program, Wash- Network. ington, D.C., January 26-27, 2006. 9. Pawlikowski, Brigadier General Ellen M., MilSatCom SPD, personal communication, April 13, 2006. Finding: Reliance on reimbursable funds from non-NASA 10. Chiang, Erick, National Science Foundation Office of Po- users as the major component of the funding needed for the lar Programs, “Data Communications Supporting Astronomy/As- operations and maintenance of the Space Network is an un- trophysics at South Pole Station,” presentation to NASA-NSF As- healthy basis for long-term planning and stability. tronomy/Astrophysics Advisory Committee, Arlington, Virginia, May 11, 2006. Recommendation: NASA, in conjunction with the user com- 11. NASA, Assessment of Commercial Alternatives to TDRS munity, should examine alternatives for providing long-term, Services, GSA-118, December 2000. stable funding at the level required for operation and main- 12. NASA, Space Network Operations Project Plan, 452- tenance of the Space Network. PLAN-0003, February 22, 2006. 13. Ford, Ken, “Space Network,” briefing to the NRC Com- The committee notes that as NASA moves forward on mittee to Review NASA’s Space Communications Program, Wash- ington, D.C., January 26-27, 2006. the exploration path there will be expanded requirements