Global Positioning System: A Comprehensive Assessment of Potential Options and Related Costs is Needed
Published: 2013-09-09T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: The GPS--a space-based satellite system that provides positioning, navigation, and timing data to users worldwide--has become an essential U.S. national security asset and component in daily life. The GPS program is being modernized to enhance its performance, accuracy and integrity. In 2013, the House Armed Services Committee directed the Air Force to report on lower-cost GPS solutions. The committee also mandated that GAO review the Air Force report. GAO (1) assessed the extent to which the Air Force GPS report met Committee requirements; and, (2) identified additional information that is important in guiding future GPS investments. GAO reviewed the Air Force report, interviewed officials responsible for preparing it, and consulted subject matter experts from the positioning, navigation, and timing advisory community.
section_title: What GAO Found
paragraphs: GAO found the Air Force, the military branch responsible for Global Positioning System (GPS) acquisition, in its report on Lower Cost Solutions for Providing Global Positioning System Capability, broadly addressed all four congressional requirements--system capability, implementation approaches, technical and programmatic risks, and estimated costs--for each option presented for the space segment. GPS consists of three segments--space, ground control, and user equipment--but the study only addressed the space segment, which accounts for the largest share of total GPS costs--more than half--in the Air Force's current budget. The Air Force identified and assessed nine options for future GPS space segments, ranging in cost from $13 billion to $25 billion from fiscal year 2013 through 2030. The report assessed each option based on a constellation or collection of 30 total satellites instead of 24, which is the Air Force's baseline GPS requirement for accuracy. This increase in total satellites raises an issue with the constellation size the Air Force intends to support in the future. Air Force officials stated that the cost analyses supporting the nine options were high-level cost estimates. Although this may be expected given the time constraints and other limitations of the study, these estimates are not at a level that would support future GPS investment decisions.
Although the Air Force report is a good starting point, more information on key cost drivers and cost estimates, and broader input from stakeholders would help guide future investment decisions. Specifically, the key cost drivers include dual launch capability (launching two satellites on a single launch vehicle), navigation satellites (smaller GPS-type satellites yet to be developed), and a nuclear detection capability. The cost estimates also excluded the ground control and user equipment segments and cost risk. Further, the Air Force did not obtain inputs from some key stakeholders such as those from the GPS positioning, navigation, and timing advisory community. Consequently, without conducting a more comprehensive assessment that addresses each of these concerns, the Air Force is not yet in a position to make sound future GPS investments.
section_title: What GAO Recommends
paragraphs: GAO recommends the Air Force: (1) affirm the future size of the GPS constellation it plans to support; (2) ensure future assessments are comprehensive and include cost risk and the impact of options on all three GPS segments; and (3) engage the broader stakeholder community in future assessments of options. DOD concurred with these recommendations.

section_title: Letter
paragraphs: The Global Positioning System (GPS)—a space-based satellite system  that provides positioning, navigation, and timing (PNT) data to users  worldwide—has become an essential U.S. national security asset and a  key component in economic growth; transportation safety; homeland  security; and critical national infrastructure, supporting power grids and  financial institutions, in the United States and abroad. In accordance with  national PNT policy, the Department of Defense (DOD) develops and  operates GPS, and an intergovernmental committee—co-chaired by DOD  and the Department of Transportation (DOT)—manages the U.S. space- based PNT infrastructure, which includes GPS. The Air Force, the military  service responsible for GPS acquisition, is in the process of modernizing  GPS to enhance its performance, accuracy, and integrity. This  modernization effort is divided into three separate programs: the GPS III  space segment, which comprises a constellation or collection of PNT  satellites orbiting the Earth; a new ground control segment; and a military  GPS user equipment segment. GPS III is an acquisition program to  develop and field a new generation of satellites to supplement and  eventually replace GPS satellites currently in use. The ground control  segment, which operates the GPS satellite constellation, is being  replaced for all existing and future GPS satellites. The user equipment  modernization effort will provide the military services with new GPS  receivers with enhanced capabilities to receive GPS signals in hostile  jamming or otherwise availability-challenged environments (such as  urban areas or mountainous terrain). The user equipment segment is  managed by each of the military services for the weapon systems they  own and operate.
In its report accompanying the 2013 national defense authorization bill  (H.R. 4310), the House Armed Services Committee directed that the Air  Force report to the congressional defense committees on lower-cost  solutions for providing GPS capability following the procurement of GPS  III satellites. The committee noted that since its inception in the 1970s,  the GPS space segment has remained generally the same, and that the  evolution of satellite and user equipment technology, combined with  today’s constrained budget environment, make this the right time to  evaluate alternatives for the system. The committee provided that the Air  Force report should identify (1) the system capability, (2) possible  implementation approaches, (3) technical and programmatic risks, and (4)  estimated costs of any recommended solutions. The Air Force submitted  its report, Lower Cost Solutions for Providing Global Positioning System  Capability, to the congressional defense committees on April 19, 2013.
The committee’s report also mandated that we review the Air Force’s  GPS report and provide our recommendations to congressional defense  committees. To respond to this mandate, we reviewed the extent to which  the Air Force GPS report met the Committee’s stated areas for reporting  and also identified additional information that is important to guide the Air  Force’s future investment decisions for GPS. To address the extent to  which the Air Force met the Committee’s reporting requirements, we  reviewed the approach, assumptions, and criteria the Air Force used to  conduct its study. We also assessed the completeness of the information  collected by reviewing the data collected and the reports that supported  the Air Force’s report, and discussed the report with GPS program and  Aerospace Corporation officials. The Aerospace Corporation is a federally  funded research and development center that provides technical and  scientific research, development, and advisory services to national  security space programs. According to program officials, Aerospace  Corporation officials participated extensively in the development of the  report, most notably conducting the cost analyses. We did not  independently verify the data the Air Force used in conducting its study.  To identify additional or clarifying information that is important to guide  future investment decisions, we reviewed the Air Force report and  discussed it with subject matter experts from the PNT advisory  community to obtain their insights on the GPS options identified, and  information that could provide additional insights. We also assessed the  process used to develop the cost estimates in the study to determine the  extent to which they followed GAO’s 12-Step Reliable Process for  Developing Cost Estimates assessment tool.
We conducted this performance audit from April 2013 to September 2013  in accordance with generally accepted government auditing standards.  Those standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives. See appendix I for more  information on our scope and methodology.
subsections: section_title: Background
paragraphs: Every satellite has a bus and payload. The bus is the body of the satellite  and is managed by the satellite control operations to maintain a desired  location. It carries the payload and is composed of a number of  subsystems, such as the power supply, antennas, and mechanical and  thermal control equipment. The bus also provides electrical power,  stability, and propulsion for the entire satellite. The payload includes the  devices the satellite needs to perform its mission. This configuration  differs for every type of satellite. For example, the payload for a weather  satellite could include cameras to take pictures of cloud formations, while  the payload for a GPS satellite would include equipment to pass  navigation information from the satellites to receivers on Earth. Monitoring  and operating of the satellite payload is done to collect data or provide a  capability to the warfighter or civilian user.
GPS is a global PNT network consisting of space, ground control, and  user equipment segments that support the broadcasts of military and  civilian GPS signals. Each of these signals includes positioning and  timing information, which enables users with GPS receivers to determine  their position, velocity, and time 24 hours a day, in all weather, worldwide.  GPS has changed the way the world operates, and underpins military  operations as well as major sections of the economy, including  telecommunications; electrical power distribution; banking and finance;  transportation; environmental and natural resource management;  agriculture; search and rescue; and other emergency services. GPS is  used by all branches of the military to guide troop movements, integrate  logistics support, and synchronize communications networks. In addition,  many U.S. and allied precision-guided munitions are directed to their  targets by GPS signals.
subsections: section_title: GPS System Description
paragraphs: The space, ground control, and user equipment segments are needed to  take full advantage of GPS capabilities. The GPS space segment, which  accounts for more than half of the total GPS costs in the Air Force’s  current budget is a constellation of satellites that orbit approximately  12,500 miles above the earth. According to Air Force officials, current  GPS requirements do not specify a number of satellites that are to be in  orbit, but rather an accuracy threshold for the system. Based upon the  threshold requirement for positioning and timing accuracy, the Air Force  derived a constellation size of 24 satellites available 95 percent of the  time. Due to the unanticipated longevity of some of the previously  launched satellites, the constellation has at times exceeded the derived  number of satellites. See figure 1 below for a depiction of the GPS  segments.
GPS satellites broadcast encrypted military signals and unencrypted  civilian signals that can be processed by GPS receivers to identify their  location worldwide. Since the constellation became fully operational in  1995, it has consisted of satellites from various generations of  development and production, each introducing improved capabilities and  additional signals. The latest generation of satellites in orbit—the GPS  IIF—broadcasts two military and three civilian signals. Additionally, the  GPS constellation currently hosts a nuclear detonation detection system  payload to monitor nuclear events on Earth.
The GPS ground control segment comprises the Master Control Station  at Schriever Air Force Base, Colorado; the Alternate Master Control  Station at Vandenberg Air Force Base, California; and various monitoring  stations and ground antennas. Information from the monitoring stations is  processed at the Master Control Station to determine the accuracy of the  satellites’ clocks (for signal timing) and the precision of their orbits. The  Master Control Station operates the satellites and regularly updates their  navigation messages, transmitting information to the satellites via the  ground antennas. The U.S. Naval Observatory Master Clock monitors the  GPS constellation and provides timing data for the individual satellites.
The GPS user equipment segment includes military and commercial GPS  receivers. A receiver determines a user’s position by calculating the  distance from four or more satellites based on the time it takes each of  the signals to reach the receiver. Military GPS receivers are designed to  utilize the encrypted military GPS signals that are only accessible to  authorized users; commercial receivers use the civilian GPS signal, which  is publicly available worldwide.
section_title: Current Modernization Efforts
paragraphs: The Air Force is in the process of modernizing the space segment under  the GPS III program, which will incorporate advances over the GPS IIF  satellites it is replacing, including a higher power military navigation signal  to improve jamming resistance and a new civilian signal to allow users to  receive GPS signals in combination with foreign satellite navigation  systems. The acquisition strategy is to purchase up to 34 satellites  following an incremental approach to replenish the current satellites in the  constellation as they reach the end of their operational life. The original  strategy was to purchase up to eight satellites in each of the first two  increments and up to 18 satellites in the last increment. However, the  GPS program is drafting a modified acquisition strategy to streamline the  last two increments into one to allow larger buying quantities to take  advantage of economies of scale, making this an appropriate time to  examine future GPS options. The Air Force has purchased four GPS III  satellites to date, the first of which is expected to launch in 2015. The Air  Force plans to incrementally increase the capabilities of the GPS III  satellites as technology maturation occurs and funding allows.
The ground control segment is being modernized under the Air Force’s  Global Positioning System Next Generation Operational Ground Control  System (GPS OCX) program. GPS OCX is also being developed in three  increments and will eventually allow DOD to take full advantage of the  capabilities offered by the various satellites. The first increment is to  deliver a capability to launch and initiate on-orbit testing of GPS III  satellites; the next increment is to deliver a capability to command and  control GPS II and GPS III satellites; and the final increment is to deliver a  capability to make military and international signals operational.  Software challenges have delayed availability of the command and  control capability, which was previously planned for 2015 and is currently  expected to be operational in late 2016 (final block is planned for 2017).
Each of the military services is managing modernization of its user  equipment through the joint Military GPS User Equipment program, which  is to develop modernized military GPS receivers that deliver improved  capabilities for accurate, reliable, and available PNT service where  current receiver performance might be compromised (e.g., jammed) or  unavailable.
section_title: Broader Coordinating Structure
paragraphs: The 2004 U.S. Space-based PNT policy established a coordinating  structure to integrate input from, and delineate the respective roles of the  military and civilian departments and agencies for program planning  (including identification of system requirements), resource allocation,  system development, and operations. As part of the coordinating  structure, an executive committee advises and coordinates among U.S.  government agencies on maintaining and improving U.S. space-based  PNT infrastructures, including GPS and related systems. The executive  committee is co-chaired by the deputy secretaries of the DOD and the  DOT, and includes members at the equivalent level from the Departments  of State, Commerce, Homeland Security, the Interior, and Agriculture; the  Joint Chiefs of Staff; and the National Aeronautics and Space  Administration (NASA). The National Coordination Office for Space-based  PNT provides day-to-day support for the executive committee.
section_title: Committee Requirements Broadly Addressed but Constellation Size Remains a Key Issue
paragraphs: The Air Force broadly addressed all committee reporting requirements in  its assessment of future GPS options for the space segment. These  requirements include evaluation of system capabilities, implementation  approaches, technical and programmatic risks, and estimated costs.  However, each of the options presented and evaluated is based on a  GPS constellation of 30 satellites, whereas the Air Force’s requirement is  for a 24-satellite constellation. The 30-satellite constellation assumption  has a significant effect on the cost of the options studied. It also raises  questions about what constellation size the Air Force is committed to  fielding and maintaining in the future.
subsections: section_title: Air Force GPS Report Met Committee Requirements for the Space Segment
paragraphs: The Air Force GPS report identified and assessed nine options for the  space segment of a future GPS which were developed as part of a six- step process the Air Force used to conduct the study, to include:
Define the purpose, scope, and decision criteria.
Assess the user requirement or capability in operational context.
Develop a broad trade space of all available options.
Review the trade space with GPS Senior Advisory Group to select a  small set of promising options and to develop criteria for assessing  the down-selected options.
Analyze the options and assess them against the criteria using  modeling and analysis tools, and conduct a risk assessment for each  option.  Integrate all the findings and develop recommendations.
According to program officials, they focused the report on options for the  space segment because it is the most costly part of the GPS. The space  segment accounts for more than half of all GPS program costs in the  current budget. For the space segment, we found that the Air Force’s  report addressed all four Committee requirements for each of these nine  options. Specifically, the report identified system capability,  implementation approaches, technical and programmatic risks, and  estimated costs, as provided for by the Committee. Each of the options  for the space segment is assessed to determine how quickly it could be  fielded, implementation approaches, technical and programmatic risks,  and space segment costs (to include the cost of launch). GPS program  officials stated that the cost analyses that support the nine space  segment options were not high fidelity estimates but instead estimated at  a high level. Although this may be expected given the limited time  provided to complete the study and prepare the report, the high-level cost  estimates are not at a level that would support programmatic decisions.  Table 1 below identifies our evaluation relating to the Committee  requirements as well as our observations.
Of the nine options the Air Force identified for the space segment, several  relied on a core constellation of 18 to 24 GPS III satellites that would be  augmented with other satellites to reach a total of 30. The last two options  do not rely on a core GPS III constellation but would also consist of 30  satellites. See table 2 for a description of each option as well as  information on the results of the Air Force’s risk and cost assessments.  Technical risk, for some of the options, includes the incorporation of  technologies that are new to GPS. Programmatic risk includes areas such  as establishing requirements, budgeting for funds, and obtaining approval  of the acquisition strategy. The options are not presented in any particular  order of significance.
GPS program officials noted that none of the options presented in the  report represent a radical departure from the GPS III program, which they  characterized as an essential investment for the health of the  constellation. The GPS III program plans to eventually replace the  existing constellation with upgraded satellites that carry the nuclear  detonation detection system payload. The first seven options presented in  the Air Force report involve GPS III or some modification of it.  Specifically, five options (numbers 3, 4, 5, 6, and 7) involve launching two  GPS III satellites on a single launch vehicle (referred to as dual launch),  and according to the Air Force report, are expected to substantially  reduce costs by eliminating the need to buy launch vehicles for each  satellite, as is currently practiced. Further, four options (numbers 4, 5, 8,  and 9) entail fielding smaller, lower-cost PNT satellites—referred to as  navigation satellites (NavSats)—yet to be developed satellites that would  complement the core constellation of GPS III satellites in various  configurations, or to replace GPS III satellites entirely. The NavSat  concept is comparable to GPS III except that it is comprised of dedicated  PNT satellites (without the secondary nuclear detonation detection  system); and according the Air Force report, is expected to be  significantly less costly than GPS III satellites due to the development and  use of mass-reducing technologies.
section_title: Future Supported Constellation Size is Unclear
paragraphs: According to Air Force officials, the baseline GPS requirement for  accuracy drives a requirement for a 24 satellite constellation at 95 percent  availability. However, each of the GPS space segment options the Air  Force assessed is based on a constellation of 30 satellites. Therefore, it  is unclear whether investment costs for these options will in fact be lower  than the baseline cost of the current GPS III program. Moreover, based  on the estimated costs presented in the report, basing all options on a 30- satellite constellation may actually increase the overall GPS investment  because the limited differences between the options assessed narrows  the range of costs across the seven options that rely on a core of GPS III  satellites.
Program officials noted that although the requirement is for 24 satellites,  for the last seven years the Air Force has operated at least 27 satellites in  the GPS constellation and, more recently, as many as 31 satellites due to  the existing satellites outlasting the useful life originally estimated. We  reported in 2010 that DOD predicted many of the older satellites in the  constellation will reach the end of their operational life faster than they will  be replenished over the next several years, decreasing the size of the  constellation from its current level. Since the magnitude of error  calculated by GPS receivers dramatically decreases as the constellation  reaches 30 satellites, and program officials stated that users have come  to rely on this increased accuracy over the last several years, the Air  Force determined it was appropriate to assess options for providing this  same level of service into the future. As a result, the report establishes a  constellation of 30 satellites—an increase over the Air Force’s  requirement for accuracy—as a baseline for each of the GPS options  assessed. Program officials, however, acknowledged that there is  reluctance to formally require the GPS constellation to be larger than the  24-satellite requirement supported by the Air Force without the certainty  of a corresponding growth in program funding. While a 30-satellite  constellation may be justifiable, using that as a baseline in the study may  have eliminated some lower cost options that may exist with 24 satellites.  Additionally, given the uncertainty regarding the magnitude of future GPS  investments, the DOD and civilian agency community would benefit from  knowing which constellation size the Air Force is committed to supporting.
section_title: More Information on Key Cost Drivers and Cost Estimates, and Broader Input from Stakeholders are Important for Future Investment Decisions
paragraphs: The Air Force GPS report identifies key drivers of cost and capability  across the assessed options, but more information on each of these  drivers is needed to fully assess their potential effect on the future GPS  program. Similarly, additional information is needed on inputs for the cost  estimates presented. This information includes analysis of costs and  other potential options associated with the ground and user equipment  segments, which were excluded from the study, as well as costs  associated with the various technical and programmatic risks identified in  the report. Assurance that best practices are followed for subsequent cost  estimates would also benefit future investment decisions. Additionally, the  Air Force was not required by the Committee to consult representatives  from the broader PNT advisory community, but several of these  individuals provided us with useful information relating to the options  assessed. Future investment decisions would benefit from a broader  outreach to gain the input and perspectives of other GPS stakeholders.
subsections: section_title: Information on Key Cost Drivers is Incomplete
paragraphs: Development of dual launch capability for GPS III satellites, development  of the NavSat concept, and the inclusion or exclusion of the nuclear  detonation detection system payload, are key drivers of cost and  capability between the GPS options assessed by the Air Force. For  example, both the dual launch capability and the NavSat concept require  use of technologies new to GPS with associated developmental risks, and  as key drivers of cost, they are factors that differ significantly enough to  have a material impact on the analysis and the resulting findings,  including estimated costs. Additionally, two of the NavSat options are  based on the possibility that the nuclear detonation detection mission  could eventually be transferred to another space-based system, but the  effect of such a change on overall system capability was not fully  considered in the report. To assess the options as a basis for making  future GPS investment decisions, more information on each of these  drivers is important to understand the full impact they could have on the  future integrity, capability, and cost of the system.
For options 3 through 7, development of a dual launch capability for GPS  III satellites is necessary, but a lack of detail in the Air Force’s report on  the maturity of key technologies and cost considerations make it difficult  to conduct a fully informed assessment of the viability of these options.  Program officials indicated that this ongoing effort will require reductions  in the size, weight, and power of the GPS III satellites, as well as  development of equipment (adaptors) that will allow two satellites to fly on  a single launch vehicle. According to program officials, these adaptors are  nearing a high level of technology maturity. However, the report names  various other components and technologies under development for this  effort, such as lithium ion batteries and more efficient signal amplifiers,  but does not indicate where they stand in terms of technology maturity.  Instead, the report assumes that dual launch capability is fully developed  and that demonstration of the capability will be ready in time to launch the  seventh and eighth GPS III satellites (of potentially 32 production  satellites). Consequently, it is difficult to assess the near- to medium-term  feasibility and timeframes of all options that are based on dual launching  GPS III satellites.
Additionally, the Air Force did not fully consider the cost impact of its dual  launch approach. While cost savings may eventually be accrued from  dual launches, the report does not address the acquisition and operations  strategy—what is necessary to buy and conduct dual launches up front.  For example, one of the subject matter experts we consulted identified a  number of factors which would result in cost increases that offset some of  the expected savings from not procuring a second launch vehicle. These  include (1) taking the steps to ensure the constellation’s integrity would  remain intact in the event of a launch failure, as two satellites would be  lost in such an instance rather than one (e.g., Air Force officials would  have to decide whether to orbit more spares to overcome the effects of a  possible launch failure); (2) making changes at the manufacturing level to  accommodate two satellites, such as the additional storage costs to hold  the first satellite until the second satellite is ready to launch; (3) ensuring  launch site facilities are capable of processing two satellites essentially  simultaneously, noting that discovery of an anomaly during launch site  testing of one satellite could affect the other satellite; and (4) ensuring the  additional support equipment and personnel necessary to support  preparing two satellites for launch. This expert further acknowledged that  none of these factors were “showstoppers” but suggested that they  should be taken into consideration. Program officials noted that in  developing the notional launch schedule for the options, they factored in a  two percent probability of launch failure which is an industry standard for  mature launch vehicle designs. However, they acknowledged that  modifications needed on the launch vehicle to dual launch GPS satellites  have not been demonstrated.
Some of the identified technical risks for the notional NavSat options may  be understated given that they involve undertaking new acquisition  programs with technologies not previously used on GPS satellites. For  example, many of the initiatives to reduce satellite size, weight, and  power underway for developing dual launch capability are also being  explored for application on NavSats. We have found in our prior work  relating to best practices for weapon system acquisition that programs  employing technologies that are not fully mature tend to face challenges  staying on budget and on schedule, which increases risk to the overall  program. The Air Force report indicates that maturation of the NavSat  concept is a prerequisite for many options assessed, including  development of new satellite buses and payloads. These development  efforts are assigned medium and medium-high technical and  programmatic risk. While the report acknowledges that there are technical  risks involved with developing higher efficiency signal amplifiers and other  space, weight, and power reducing technologies, it concludes that none  of these technologies is high risk. However, officials from the Air Force  Research Laboratory, which is helping to develop some of these  technologies for potential application on NavSats, noted that some of the  new technologies are currently at a relatively low level of maturity (i.e.,  only tested in a laboratory environment), and will not likely be feasible for  the GPS program until at least 2018. Moreover, one of the subject matter  experts we consulted noted that there are other potential risks associated  with the NavSat options, such as not having a proven track record. This  expert noted problems in the NavSat programs could result in the loss of  user confidence in GPS that has been built up over decades of delivering  a reliable satellite navigation service.
Details regarding technology maturity are also needed to better  understand the cost impact of these options on the overall GPS program.  For example, program officials acknowledged that savings from dual  launching GPS III satellites could help offset some of the additional costs  associated with development of NavSats. However, they noted that there  would likely be significant initial development costs for the NavSats that  would result in the need for a net budget increase in the near-term.
Additionally, a key aspect of NavSat capability relevant to civilian GPS  users is not addressed in the Air Force report and without additional  clarification, it is difficult to determine the impacts to these users. The  report notes that one approach for reducing the size, weight, power, and  cost of proposed NavSats, would be to reduce the total number of  navigation signals they transmit. Specifically, under option 5 in the report,  NavSats would broadcast two of four civilian signals and two military  signals. Three of the subject matter experts we consulted noted concerns  in part because determining which civilian signals to exclude would likely  result in the prioritization of one user group over another, as the civilian  signals have different applications. Air Force officials indicated that,  option 5 is based on a larger core of GPS III satellites—which are  required to carry all civilian signals—and augmented by a smaller number  of NavSats. However, it is unclear how a core of GPS III satellites would  compare with a combined constellation of GPS III satellites and NavSats,  both required to broadcast all civilian signals.
Two of the NavSat options included in the Air Force report would require  the eventual elimination of the nuclear detonation detection system  payload from GPS satellites, and the report notes that as long as this  mission is a priority and is planned to be hosted on GPS satellites, these  options—and the low relative costs—would therefore not be viable.  Elimination of the nuclear detonation detection system could have other  effects on the overall capability of the GPS system not recognized or  addressed in the Air Force report. For example, one of the subject matter  experts we consulted mentioned that the GPS search and rescue  function, a requirement for GPS III satellites, shares an antenna with the  nuclear detonation detection system payload. Thus, the two options  (numbers 8 and 9) that drop the nuclear detonation detection system  completely would potentially forgo the search and rescue function as well.  However, program officials said the search and rescue payload is  relatively small and could be adapted to the NavSats without the nuclear  detonation detection system, and also noted that in a mixed constellation  of GPS III satellites and NavSats, there would likely be sufficient  coverage for the search and rescue mission even if the search and  rescue sensors were only on the GPS III satellites. Given the differing  views of these officials and subject matter experts, this issue will need to  be resolved as the Air Force pursues future assessments of GPS options.
section_title: Cost Estimates are Not Comprehensive
paragraphs: The Air Force’s high-level cost estimates appear consistent across the  options for the space segment, but the estimates do not include the other  two key GPS segments. For its study, the Air Force defined affordability  as the reduction in total ownership cost of sustaining GPS throughout its  life cycle. However, without inclusion of the other two key segments of the  system, the methodology used does not reflect true life cycle costs.  Additionally, Air Force officials noted that the cost estimates developed  for the report do not include cost risk. This leaves some question as to the  ultimate usefulness of the cost estimates, risk rankings, or both. In  addition, the Air Force did not apply all aspects of best practices in  developing its cost estimates, which further reduces the usefulness of  these estimates in decisionmaking. Finally, the Air Force did not obtain  input from the PNT advisory community which may have helped inform its  assessment.
For a defense acquisition program, DOD defines life cycle costs as the  total cost to the government of acquisition and ownership for a program  over its full life. This includes the cost of development, acquisition,  operations, and support (to include personnel), and where applicable,  disposal. While the Air Force report indicates that the estimates are  based upon life cycle costs, it does not include key elements necessary to  meet the definition of life cycle cost, thereby underestimating the total  costs of the options and limiting their usefulness. The Air Force’s cost  estimates for each option only included the space segment—satellite and  launch vehicles—which it determined to be the only segment to have  significant impact on overall costs. As mentioned previously, the space  segment accounts for the largest share—more than half—of total GPS  costs in the Air Force’s current budget. Under this methodology, program  officials said options dealing with the ground control system were not  included in the cost estimates because costs associated with adding  capability to control new satellites were estimated to be a small  percentage of the total GPS system cost, and would not provide a  significant distinction between the options. However, this estimation,  without the ground control segment, may not be valid given that there  could be unknown cost and schedule risks for the ground control segment  associated with modifications to accommodate new and different satellite  vehicles. More specifically, while changes to the ground segment may not  be a major cost differentiator between the options, they have presented  significant challenges. For example, program officials said the costs of  adding ground control capability for a new generation of satellites are  known, but this is based on updates to the current ground control system.  However, in our prior work, we also reported that modernization of the  current ground control segment has been challenging, and has only  enabled limited capability to control the new satellites, rather than  facilitating full access to their new capabilities. Additionally, the ground  control segment is being completely replaced as part of the GPS OCX  program, which according to Air Force officials, will eventually enable  users to take full advantage of the capability offered by the GPS  constellation, and is expected to cost nearly $3.7 billion through fiscal  year 2017. This cost is significantly higher than initial planning estimates  due to software and other challenges experienced thus far, and the extent  and cost of this effort were not recognized in the Air Force report.
Additionally, two of the subject matter experts we consulted indicated that  inclusion of user equipment could have benefited the study. The Air Force  report did not assess any options that would require hardware changes to  user equipment beyond what is already planned for user equipment  modernization because of the large number of civilian receivers currently  in use. One subject matter expert noted that although the report cites this  as the primary reason user equipment was not examined; civilian user  equipment will continue to evolve by integrating GPS signals with signals  from other global navigation systems, as well as with non-space-based  PNT capabilities such as inertial navigation sensors, chip scale atomic  clocks, and terrestrial radiolocation technologies. The expert noted that  this could reduce some of the capability that the space segment needs to  provide in the future. Based on our discussions with officials from the Air  Force Research Laboratory, this could in turn potentially reduce the size  and power requirements for the space vehicle and thereby the overall  cost.
According to Air Force officials involved in the study, the overall cost  estimates do not include cost risk, which is defined as the risk  associated with the ability of the program to achieve its acquisition  strategy cost objectives. Similarly, identified technical and programmatic  risks and their relative rankings do not generally appear to have a basis in  cost. The options involving a constellation of all NavSats or at least a core  of NavSats (numbers 8 and 9 respectively) both reflect high technical and  programmatic risks. At the same time, the cost estimates for these  options reflect the lowest development and procurement costs (excluding  operations and sustainment costs) over the fiscal year 2013 to fiscal year  2030 timeframe. We have found in our prior work relating to key practices  for weapon system acquisition that programs employing technologies that  are not fully mature tend to require more time in development or  production and more funding than is initially anticipated. Without  additional details as to how cost factors into the risk determination, it is  difficult to know the relative utility of the Air Force’s cost estimates for  making further GPS decisions.
Best practices in cost estimating result in accurate and credible cost  estimates that management can use for making informed decisions. The  methodology consists of 12 steps that we present in figure 2.
These best practices represent an overall process of established,  repeatable methods that result in high-quality cost estimates that are  comprehensive and accurate, and that can be easily and clearly traced,  replicated, and updated. We found that the Air Force followed some  aspects of the 12-step process in developing its estimates for GPS  architecture options, but did not follow others. For example, the Air Force  defined the estimate’s purpose and identified some ground rules and  assumptions, but did not perform sensitivity analysis and conducted  minimal analysis of cost-related risks. This would be expected given the  time constraints and other limitations of the study; however, to further  assess its GPS options, more fully-developed cost estimates would be  important in facilitating more rigorous comparisons across the options.
section_title: Consultation with Key Stakeholders Could Provide Additional Insights
paragraphs: GPS has grown into a global utility whose multi-use services are integral  to U.S. national security and transportation safety, and are an essential  element of the worldwide economic infrastructure. As a result, any  decision regarding GPS has far reaching consequences for many beyond  DOD. This fact was clearly addressed in the national PNT policy which  formalized the membership of the PNT executive committee to include  other government departments and agencies that have a stake in the  stewardship of GPS. This committee ensures that the national security,  homeland security, and civil requirements receive full and appropriate  consideration in the PNT decision process and facilitates the integration  and reduction of conflicts of these requirements for PNT, as required.  However, the Air Force did not seek input from those departments and  agencies that are represented on the committee, including the  Department of Transportation, which co-chairs the committee with DOD.  These key stakeholders could have provided valuable insight on potential  impacts of the options presented, as well as future needs arising from any  changes to the GPS.
Several of the subject matter experts we consulted directly represent the  stakeholders identified in the PNT policy. While these individuals largely  believe the Air Force report is a good starting point for future GPS  decisions, they provided additional, meaningful insights relating to  potential risks and costs associated with the individual options as well as  with ground control and satellite launch; user equipment capabilities; and  the concerns and needs of various GPS users. According to Air Force  officials, they did receive input from individuals who advocated for the  needs of non-DOD users, but acknowledged that these individuals did not  directly represent those users or other stakeholders identified in PNT  policy. While not specifically required by the House Armed Services  Committee to seek input from others, obtaining input from key  stakeholders, such as was provided by the subject matter experts we  consulted, the Air Force may have been able to obtain additional insights  as it developed and weighed the various GPS options. This was a  sentiment shared by some of our subject matter experts who expressed  concern over the lack of input from the civilian community.
section_title: Conclusions
paragraphs: The Air Force’s GPS report met the committee’s reporting requirements  and serves as a good starting point from which to assess potential lower  cost GPS options. The study focused on the space segment and as such,  the options consist of various configurations of satellites and launch  options—whether to launch satellites individually or in multiples. The less  risky options appear to be relatively minor deviations from the  department’s current approach in fielding GPS III, with the key decision  being whether to launch one or two satellites at a time. Pursuing any  options would likely require a near term increase in the overall GPS  budget to achieve future savings—a challenge in the current fiscally  constrained environment. Yet, the study used a larger constellation size  than the Air Force’s current derived requirements and lacked the  comprehensiveness that would allow the study to be used for future  decision making. Based on acquisition best practices, there are actions  the Air Force could take to improve the study results to include: identifying  the constellation size to be supported; expanding the areas of  consideration to include ground control and user equipment; more  thoroughly defining and analyzing key capabilities and implementation  approaches; and using a higher fidelity approach in assessing risk and  estimating cost going forward. The Air Force could also benefit from  greater consultation from the broader PNT stakeholder and advisory  community, which could offer valuable perspectives relating to the overall  approach for investigating future GPS options, as well as the relative  merits and unknowns associated with each option analyzed. While there  are a number of limitations in the study, it is valuable as a basis for  substantive discussion of long-term GPS investments. Going forward, it is  important for the Air Force to take a more comprehensive approach in  assessing options for making sound future GPS investments.
section_title: Recommendations for Executive Action
paragraphs: To better position the DOD as it continues pursuing more affordable GPS  options, and to have the information necessary to make decisions on how  best to improve the GPS constellation, we recommend that the Secretary  of Defense direct the Secretary of the Air Force to take the following three  actions:  1.  Affirm the future GPS constellation size that the Air Force plans to  support, given the differences in the derived requirement of the 24- satellite constellation and the 30-satellite constellations called for in  each of the space segment options in the Air Force’s report.  2.  Ensure that future assessments of options include full consideration of  the space, ground control, and user equipment segments, and are  comprehensive with regard to their assessment of costs, technical  and programmatic risks, and schedule.  3.  Engage stakeholders from the broader civilian community identified in  PNT policy in future assessments of options. This input should include  civilian GPS signals, signal quality and integrity, which signals should  be included or excluded from options, as well as issues pertaining to  other technical and programmatic matters.
section_title: Agency Comments and Our Evaluation
paragraphs: In written comments on a draft of this report, DOD concurred with all three  of our recommendations to better position the DOD as it continues  pursuing more affordable GPS options, and to have the information  necessary to make decisions on how best to improve the GPS  constellation. DOD’s written comments are reprinted in appendix II.
DOD concurred with our first recommendation that the Secretary of the  Air Force affirm the future GPS constellation size the Air Force plans to  support. In its response, the department stated the numbers of satellites  are affirmed annually in the President’s Budget request. However, the  budget shows satellite procurements over time and does not specify the  target constellation size to meet current or future accuracy requirements,  which has a direct impact on annual procurement costs. Additionally, as  our report indicates, the Air Force report based all options on a 30- satellite constellation while reporting a GPS requirement for accuracy of a  24 satellite constellation at 95 percent availability. Therefore, the need  remains for the department to more clearly and transparently identify the  target GPS constellation size the department intends to pursue.
DOD also concurred with our second recommendation to ensure future  assessments of options include full consideration of the space, ground  control, and user equipment segments, and are comprehensive with  regard to their assessment of costs, technical and programmatic risks,  and schedule. In its response, the department stated that while  consideration of the space and ground control segments should be  comprehensive in these areas, the user equipment segment should be  included in future assessments when those assessments include the  fielding of new user equipment capability. As one of the subject matter  experts we consulted noted, user equipment continues to evolve and  could potentially embrace PNT technologies and capabilities that would  reduce required capabilities for GPS satellites. As our report indicates, a  comprehensive look at user equipment is warranted, especially given that  the user equipment modernization program is in a pre-development  phase.
Finally, DOD concurred with our third recommendation to engage  stakeholders from the broader civilian community identified in PNT policy  in future assessments of options. In its response, the department said  stakeholders from the broader civilian community identified in PNT policy  should be engaged in future assessment of options that include changes  to the Standard Positioning System performance standard or to  agreements or commitments the DOD has already made with civil  stakeholders. However, as we noted in our report, considering the  unknown effect on the civilian user community of some of the options  presented, as well as potential future application of new technology for  user equipment, comprehensive assessment of future GPS options  should involve the broader PNT community, particularly those  stakeholders identified in PNT policy.
We are sending copies of this report to the appropriate congressional  committees, the Secretary of Defense, and the Secretary of the Air Force.  In addition, the report is available at no charge on the GAO website at  http://www.gao.gov.
If you or your staff have any questions about this report, please contact  me at (202) 512-2527 or makm@gao.gov. Contact points for our Offices  of Congressional Relations and Public Affairs may be found on the last  page of this report. Key contributors to this report are listed in appendix  III.
section_title: Appendix I: Scope and Methodology
paragraphs: House Report No. 112-479 accompanying H.R. 4310, the National  Defense Authorization Act for Fiscal Year 2013 directed the Commander  of the Space and Missile Systems Center, U.S. Air Force, to provide a  report to the congressional defense committees on lower-cost solutions  for providing GPS capability following the procurement of the GPS III  satellites. The Committee provided that the report should identify the  system capability, possible implementation approaches, technical and  programmatic risks, and the estimated costs of any solutions it  recommends. The committee also mandated GAO to review the report  provided by the Commander of the Space and Missile Systems Center,  and to provide its recommendations to the congressional defense  committees within 90 days after the Air Force report is received.
To determine the extent to which the Air Force’s report, Lower Cost  Solutions for Providing Global Positioning System (GPS) Capability, met  the requirements, and to identify additional information that could guide  future investment decisions, we assessed the report and the approach,  assumptions, and criteria the Air Force used to conduct the study. To  accomplish this, we obtained and reviewed documents that supported the  Air Force’s report. We then discussed the report and our preliminary  analysis of the report with GPS program and Aerospace Corporation  officials responsible for the report to obtain their perspectives and clarify  aspects of the report. We also reviewed other relevant high-level space  strategic documents including the National Space Policy and the 2008  Biennial GPS Report to Congress. To identify the technological  advances available to the Air Force and the readiness of those  technologies, we interviewed officials from Defense Advanced Research  Projects Agency and the Air Force Research Laboratory. To identify  additional or clarifying information that could help guide future investment  decisions, we sent data collection instruments to ten subject matter  experts from the Positioning, Navigation and Timing stakeholder and  advisory community to obtain their insights on GPS options the Air Force  identified, as well as information that could provide additional insights,  and received responses from seven of them. These subject matter  experts were advisors to the National Space-Based Positioning,  Navigation, and Timing Executive Committee or were identified by the  National Coordination Office for Space-Based Positioning, Navigation,  and Timing as experts in the field, and who were also government  officials. To assess the completeness of cost estimates cited in the report,  we assessed the process used to develop the cost estimates in the study  to determine the extent to which they followed GAO’s 12-Step Reliable  Process for Developing Cost Estimates assessment tool.
We conducted this performance audit from April 2013 to September 2013  in accordance with generally accepted government auditing standards.  Those standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives.
section_title: Appendix II: Comments from the Department of Defense
section_title: Appendix III: GAO Contact and Staff Acknowledgments
subsections: section_title: GAO Contact
paragraphs: Marie A. Mak, (202) 512-2527 or makm@gao.gov.
section_title: Staff Acknowledgments
paragraphs: In addition to the contact named above, Art Gallegos, Assistant Director;  Andrew Redd; Emile Ettedgui; Jean Lee; Marie Ahearn; Karen Richey;  Roxanna Sun; and Robert Swierczek made key contributions to this  report.