Cobra Dane and other radar systems can provide capabilities that contribute to a range of missions, such as ballistic missile defense, space surveillance, and intelligence-gathering missions. DOD uses Cobra Dane and other radar systems to provide information over a short period of time to ground-based interceptors so they can hit their targets. Such radar systems contribute to ballistic missile defense by tracking incoming missile threats, classifying the missile threat, and determining if a threat was intercepted successfully. In addition, some radar systems can provide discrimination capabilities, which allow for that radar to identify a warhead when a missile threat deploys decoys at the same time. Radar systems can also have the capability to contribute to a space surveillance mission, which provides an awareness of space objects within or near the Earth’s orbit and their movements, capabilities, and intent. Finally, radars can also contribute intelligence-gathering capabilities. Each radar system’s ability to contribute to various missions can be dependent on that radar’s inherent capabilities and physical location. See table 1 for a description of selected radar systems that can provide some or all of these capabilities. Various offices within the Air Force, in coordination with MDA, are responsible for the operation and sustainment of the Cobra Dane radar. Since 2013, Air Force Space Command has overseen the operation of Cobra Dane, and contributes to the sustainment of Cobra Dane’s site at Shemya Island. The Air Force Life Cycle Management Center has overall responsibility of the sustainment of the Cobra Dane radar. In addition, MDA works in coordination with the Air Force and combatant commands to develop, test, and field ballistic missile defense assets. MDA also shares funding with the Air Force to operate and sustain Cobra Dane. U.S. Northern Command and U.S. Strategic Command define priorities for the overall radar infrastructure and establish the various missions that those radar systems are intended to meet. U.S. Northern Command oversees the homeland ballistic missile defense mission, and establishes operational objectives for radar systems operating in its region. U.S. Northern Command officials told us that they are the end user for Cobra Dane. U.S. Strategic Command has established a ballistic missile defense and a space surveillance mission, both of which are supported by Cobra Dane. Further, U.S. Strategic Command’s components coordinate global missile defense and space operations planning. In its January 2018 report to Congress, the Air Force described how Cobra Dane and LRDR can meet mission requirements through their shared and unique capabilities, as well as how their locations affect their ability to provide those capabilities for DOD’s ballistic missile defense mission. MDA studies we reviewed found that locating LRDR at Clear Air Force Station allows for operational advantages and cost savings. The Air Force included information in its report to Congress on the ballistic missile defense capabilities of Cobra Dane and LRDR, and the effects of each radar’s location on those capabilities. Specifically, the Air Force report stated that both radars have the capabilities to track and classify missile threats. However, the report incorrectly stated that both radar systems have the inherent capability to determine if a missile threat is successfully intercepted. MDA documentation that we reviewed shows that Cobra Dane does not yet have this capability. When we shared our finding with Air Force and MDA officials, they agreed that this reported capability was incorrectly identified in the Air Force report to Congress. MDA officials also told us that Cobra Dane could provide this capability in the future if it implements software changes, but they are unlikely to do this until calendar year 2025. The Air Force report also noted that LRDR would have a unique capability, once it is operational, to discriminate missile threats from any deployed decoys. See table 2 for a summary of what the Air Force reported for the ballistic missile defense capabilities of Cobra Dane and LRDR. In addition to identifying ballistic missile defense capabilities of each radar, the Air Force report noted that both Cobra Dane and LRDR will have the inherent capabilities to support space surveillance and intelligence-gathering missions. DOD officials we spoke to confirmed that they have plans to use those inherent capabilities to support these other missions. For example, U.S. Strategic Command identified that DOD needs Cobra Dane to support its space surveillance mission. Further, Air Force and MDA officials told us that they use Cobra Dane to track small objects that no other radar system can track. MDA officials told us that LRDR could be used for space surveillance. However, Air Force and U.S. Strategic Command officials stated that there are no plans to use LRDR’s space surveillance capabilities as a replacement for Cobra Dane. Additionally, Air Force officials told us that neither Cobra Dane nor LRDR is required to support an intelligence-gathering mission. The Air Force also included information in its report on how the locations of Cobra Dane and LRDR affect their abilities to contribute to the ballistic missile defense mission. For example, the Air Force reported that Cobra Dane’s location at Shemya Island, Alaska, allows it to track missile threats from North Korea earlier in their trajectories than LRDR would be able to track at Clear Air Force Station, Alaska. This is consistent with an MDA analysis that we reviewed that outlined additional advantages provided by Cobra Dane’s location at Shemya Island. According to that analysis, Cobra Dane can begin tracking missile threats approximately 210 seconds earlier than LRDR. Air Force officials told us that the additional time to track missile threats allows the warfighter an earlier opportunity to intercept a missile threat and deploy additional interceptors if the first attempt fails. Further, the MDA analysis described a tracking gap between the areas covered by LRDR—once it is operational at Clear Air Force Station—and the two sets of AN/TPY-2 radars that are currently located in Japan. Without Cobra Dane’s coverage of this gap, the analysis found that the warfighter would have a more limited opportunity to intercept a missile threat from North Korea. Figure 2 shows how Cobra Dane covers a gap between the LRDR (once operational) and the two AN/TPY-2 radars in Japan. The Air Force report also noted that LRDR’s geographic location has its own advantages in contributing to ballistic missile defense compared to Cobra Dane’s location. For example, the Air Force report noted that LRDR’s location would allow it to track missile threats later in their trajectories beyond Cobra Dane’s coverage as those threats make their way to the continental United States. We also found that MDA has determined LRDR will have other advantages due to its location. For example, an MDA analysis that we reviewed found that LRDR’s location will allow for the radar system to contribute to ballistic missile defense from North Korean and Iranian threats. Absent LRDR, this analysis determined that there are no other radar systems that are located in a position to provide the capability to discriminate missile threats and determine if a threat was successfully intercepted. In addition to what the Air Force reported, we found that DOD decided to locate LRDR at Clear Air Force Station in Alaska after considering the advantages and disadvantages of other locations. For example, MDA completed studies that examined how LRDR could perform at various locations in Alaska, and the cost-effectiveness of constructing and sustaining the radar at those sites. In a June 2015 analysis, MDA compared how LRDR could perform in discriminating missile threats when co-locating it with Cobra Dane at Shemya Island or placing it at Clear Air Force Station. MDA determined that LRDR could provide more real-time discrimination information for missile threats targeting Alaska and the continental United States if it constructed the radar at Clear Air Force Station versus Shemya Island. Additionally, MDA identified in an October 2016 study that the department could obtain operational advantages and cost savings by constructing LRDR at Clear Air Force Station, Alaska, when compared to constructing it at Shemya Island, Alaska. Specifically, MDA determined that Clear Air Force Station could provide better results for 11 of the 13 factors it reviewed compared to Shemya Island. For example, MDA determined that locating LRDR at Clear Air Force Station would result in lower costs and enhanced system performance. According to DOD officials and documents we reviewed, other radar investments may reduce the department’s reliance on Cobra Dane for ballistic missile defense and space surveillance, given that U.S. Northern Command identified it has a need for Cobra Dane after DOD begins operating LRDR in fiscal year 2021. Specifically, the Pacific Radar and Space Fence may reduce DOD’s reliance on Cobra Dane to support ballistic missile defense and space surveillance, respectively. Pacific Radar: According to DOD officials, the department may no longer need Cobra Dane to meet the ballistic missile defense mission after MDA fields a new radar in the Pacific region in fiscal year 2025. MDA began developing the Pacific Radar to provide additional missile threat tracking and discrimination capabilities. According to U.S. Northern Command and MDA officials, the Pacific Radar may fill the gap in tracking missile threats currently covered by Cobra Dane. Space Fence: The Air Force has also determined it will no longer have a requirement for Cobra Dane to provide space surveillance once the Space Fence is fully operational. The Air Force plans for the Space Fence to be operational in fiscal year 2019. According to a U.S. Strategic Command briefing, the Space Fence will provide the same capabilities as Cobra Dane. Air Force officials noted that they want to continue relying on Cobra Dane for space surveillance when the Space Fence is operational, as long as the radar is available and used to contribute to ballistic missile defense. In its January 2018 report to Congress, the Air Force noted that Cobra Dane met its requirement for operational availability—i.e., the percentage of time that the radar system is able to meet its ballistic missile defense and space surveillance missions. Specifically, the Air Force report noted that Cobra Dane had been available an average of 91 percent of the time over a 2-year period (January 2016 through December 2017), which exceeded the 90 percent requirement for operational availability. Information that we reviewed from a more recent 2-year period (August 2016 through July 2018) showed that Cobra Dane’s 2-year average for operational availability had declined to approximately 88 percent—below the 90 percent requirement. Air Force officials stated that the decline in the operational availability over the more recent two-year period was due to a few instances where they needed to take Cobra Dane off-line for extended periods of scheduled downtime (e.g., regular operations and maintenance, calibration of instruments). Further, they noted that when Cobra Dane is not operationally available, the reason is usually due to scheduled downtime. Officials also told us there was one instance of unscheduled downtime (e.g., part or system failure) in that 2-year period which required emergency maintenance on the radar’s mission control hardware. We also reviewed Air Force data on the frequency of unscheduled downtime between August 2016 and July 2018, which show that Cobra Dane is able to contribute to its missions without unscheduled downtime 99.7 percent of the time. According to U.S. Northern Command and MDA officials, they can mitigate the effect on the ballistic missile defense mission if they know far enough in advance that Cobra Dane will not be operationally available— such as during scheduled downtime. Officials stated that they do this by moving a transportable radar, known as the Sea-Based X-band radar, to specific locations in the Pacific Ocean to provide additional tracking coverage of missile threats. A U.S. Northern Command analysis that we reviewed describes how DOD can deploy the Sea-Based X-band radar at particular locations in the Pacific Ocean to supplement Cobra Dane. This analysis found that U.S. Northern Command can lose the ability to track some missile threat trajectories if Cobra Dane is not available and the Sea-Based X-band radar is not deployed. We also reviewed Air Force data on space surveillance, which shows that the Air Force would face some limitations in its ability to complete its space surveillance mission when Cobra Dane is not operationally available. According to the data, Cobra Dane tracks 3,300 space objects each day that cannot be tracked by any other radar system. Air Force officials noted that when Cobra Dane is not operationally available for space surveillance for short periods (less than 24 hours), they can overcome that downtime without losing track of those unique objects. However, officials told us that it would take six months to reacquire all of the small space objects that Cobra Dane tracks, if they encounter any significant scheduled or unscheduled downtime. MDA officials told us there are no scheduled plans to take Cobra Dane down long enough to compromise DOD’s ability to conduct space surveillance. In its January 2018 report to Congress, the Air Force projected that the Air Force and MDA would contribute total funding of $278.6 million based on their fiscal year 2019 budget plans for the operation and sustainment of Cobra Dane. According to the report, the Air Force and MDA plan to share funding for the operation and maintenance of the Cobra Dane radar, and for three modernization projects that make up their sustainment plan for the radar. Table 3 outlines the plan for how the Air Force and MDA will share funding for the operation and maintenance of Cobra Dane. In addition, the Air Force included information in its report on how the Air Force and MDA plan to share funding to support Cobra Dane’s three modernization projects. Specifically, the Air Force and MDA plan to redesign parts for three sets of obsolete systems: (1) mission system replacement; (2) traveling wave tubes; and (3) transmitter groups. The Air Force has identified that it no longer has vendors that manufacture some critical parts, and failure of any of the three systems could result in Cobra Dane not being available to meet mission requirements. As such, the Air Force determined that it could sustain these three systems more effectively if they were redesigned. Table 4 summarizes the reported funding for the three projects that make up the Cobra Dane sustainment plan. In addition to what the Air Force reported, we identified that the Air Force developed a total cost estimate for its transmitter group replacement, but not for its other two projects. For the other two projects, Air Force officials stated that they plan to complete estimates for the total costs in conjunction with their fiscal year 2020 budget submission. In August 2016, the Air Force estimated that the transmitter group replacement would have a total cost of $91.2 million, but reported it would fund this project at $94.0 million through fiscal year 2023 (see table 4). Air Force officials plan to request the transfer of any unused funding to the other projects once it completes the transmitter group project. The Air Force also completed a partial cost estimate for the traveling wave tube redesign—covering the redesign of the parts and replacement of 1 of 12 groups of parts—estimating that the first phase would cost $16.0 million. Further, Air Force officials told us that they have not yet developed a total cost estimate for the mission system replacement. We also found that the Air Force and MDA expedited Cobra Dane’s mission system replacement project, but Air Force officials told us they face challenges in expediting the other two projects without compromising Cobra Dane’s operational availability. For the mission system replacement, MDA requested additional funding in fiscal year 2018. Air Force and MDA officials told us that the additional funding they received allowed them to prioritize the mission system replacement and advance its timeline earlier that year. Air Force officials stated that they explored ways to expedite the two other projects: the traveling wave tubes and transmitter groups. However, they stated that replacing too many parts at the same time will result in their having to take Cobra Dane off-line for longer periods of time. According to Air Force and MDA officials, they may look for opportunities to expedite timeframes for their other two projects as long as the amount of scheduled downtime is kept to acceptable levels. In its report to Congress, the Air Force identified that it plans to provide $140 million in funding for the sustainment and maintenance of operational access to Cobra Dane’s site at Shemya Island based on its fiscal year 2019 budget plans. According to the report, the Air Force is solely responsible for funding all work related to the operation and sustainment of Shemya Island, shared between two of its major commands: Air Force Space Command and Pacific Air Forces. Table 5 summarizes the information the Air Force included in its report on how funding will be shared for Shemya Island. We also reviewed a support agreement between Air Force Space Command and Pacific Air Forces that identifies how they will sustain the site and the calculation for sharing costs. The agreement describes the specific work to sustain the site, including maintaining the airfield, support facilities, and communication infrastructure. Air Force officials told us that they are constantly addressing challenges related to operational access to the site at Shemya Island, but Air Force Space Command and Pacific Air Forces work together to address those challenges. We provided a draft of this report to DOD for review and comment. DOD told us that it had no comments on the draft report. We are sending copies of this report to the Secretary of Defense; the Under Secretary of Defense for Acquisitions and Sustainment; the Secretary of the Air Force; the Director of the Missile Defense Agency; and the Commanders of U.S. Northern Command and U.S. Strategic Command. 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 Joe Kirschbaum at (202) 512-9971 or kirschbaumj@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. GAO staff who made contributions to the report are listed in Appendix I. In addition to the contact named above, Kevin O’Neill (Assistant Director), Scott Bruckner, Vincent Buquicchio, Martin De Alteriis, Amie Lesser, and Richard Powelson made key contributions to the report.

Summary: First fielded in 1976 on Shemya Island in Alaska, the Cobra Dane radar faces growing sustainment challenges that DOD plans to address through modernization projects. Anticipating future needs, DOD began investing in new radar systems that share capabilities with Cobra Dane to support ballistic missile defense and space surveillance, including the LRDR (Alaska), the Space Fence (Marshall Islands), and the Pacific Radar (location to be determined). The conference report accompanying a bill for the National Defense Authorization Act for Fiscal Year 2018 included a provision that GAO review the Air Force's report to Congress on the operation and sustainment of Cobra Dane. This report identifies information included in the Air Force's report and describes additional information that GAO reviewed on (1) the capabilities of the Cobra Dane radar and other planned radars to meet DOD's mission requirements, (2) Cobra Dane's operational availability and the plan to mitigate the effect on those missions when Cobra Dane is not available, and (3) DOD's funding plan and project cost estimates for the operation and sustainment of Cobra Dane and its site at Shemya Island. GAO reviewed the Air Force report and related documentation, and interviewed relevant officials. In its January 2018 report to Congress, the Air Force reported how the Cobra Dane radar and the Long Range Discrimination Radar (LRDR) have shared and unique capabilities to support ballistic missile defense and space surveillance missions. The report noted that the respective locations of both radar systems affect their ability to provide those capabilities. The Department of Defense (DOD) also has other radar investments—the Pacific Radar and the Space Fence, which, according to DOD officials, may reduce DOD's reliance on Cobra Dane to provide ballistic missile defense and space surveillance capabilities. The Air Force's report to Congress noted that Cobra Dane met its requirement for operational availability, which refers to the percentage of time that the radar is able to meet its missions. GAO found that the Air Force has developed procedures to mitigate risks when Cobra Dane is not available. For example, U.S. Northern Command and Missile Defense Agency (MDA) officials stated that they can mitigate risks when Cobra Dane is not available by using the Sea-Based X-band radar to provide support for ballistic missile defense. The Air Force would face some limitations in its ability to conduct space surveillance if Cobra Dane were not available, as Cobra Dane tracks objects no other radar can track. However, MDA officials noted there are no plans to take Cobra Dane offline long enough to compromise space surveillance. The Air Force and MDA plan to contribute total funding of $278.6 million for the operation and sustainment of Cobra Dane, according to their fiscal year 2019 budget plans. Specifically, the Air Force and MDA plan to share funding for the operation and maintenance of the Cobra Dane radar and for three modernization projects that make up their sustainment plan for the radar. Further, the Air Force report noted that the Air Force also plans to provide $140 million in funding for the sustainment and maintenance of operational access to Cobra Dane's site at Shemya Island. In addition, GAO found that the Air Force developed a total cost estimate for one project—known as the transmitter group replacement—but not for its other two projects. Air Force officials plan to complete cost estimates for those two projects in conjunction with their fiscal year 2020 budget submission.