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Evaluation of the Multifunction Phased Array Radar Planning Process 6 The MPAR Planning Process The report Weather Radar Technology Beyond NEXRAD (NRC, 2002) specifically recommended the exploration of radar systems with agile-beam scanning capabilities. A 2004 report (Aerospace Corporation, 2004) provided a preliminary look at possible PAR implementation for weather surveillance. In 2005, the National Science and Technology Council (NSTC) identified phased array radar as a technology that could potentially be developed and deployed to “increase the quantity, quality, and timeliness of weather information during extreme weather events.” They also noted that “the greatest set of unmet observational requirements is for systematic, widespread coverage.” This assessment was provided by the NSTC Committee on Environmental and Natural Resources’ US Group on Earth Observations in their “Strategic Plan for the U.S. Integrated Earth Observation System” (NSTC, 2005). Based on this direction, the Federal Committee for Meteorological Services and Supporting Research (FCMSSR) charged the Office of the Federal Coordinator for Meteorology (OFCM) with exploring phased array radar technology for addressing gaps in weather observing and forecasting capabilities. OFCM formed the Joint Action Group/Phased Array Radar Project (JAG/PARP) in response and assigned the following specific tasks: (a) determine the specific needs of Federal agencies that could be met by surveillance radar, (b) show the benefits of phased array radar capability in meeting these needs, and (c) explore opportunities for expanded participation in the Phased Array Weather Radar Project (FCMSSR Action Item 2002-4.1). The project chairpersons were experts from the U.S. Air Force (Col. Mark O. Weadon, USAF Weather Deputy for Federal Programs) and NOAA (Dr. James J. Kimpel, Director, National Severe Storms Laboratory). The other project members came from the National Weather Service (NWS), Federal Aviation Administration (FAA), Federal Highway Administration (FHWA), U.S. Navy, National Aeronautics and Space Administration (NASA), National Science Foundation (NSF), Department of Homeland Security (DHS), Department of Energy (DOE), National Park Service and U.S. Department of Agriculture. THE JAG/PARP REPORT Although many groups were represented in this inclusive project, NOAA and FAA participants provided the leadership and initiative that ultimately culminated in the JAG/PARP report. This may have been anticipated, as the expertise gathered by these agencies in prior years was particularly relevant, and their own future needs may be met by MPAR. In the case of NOAA, the National Severe Storms Laboratory (NSSL) was experimenting with a Navy SPY-1 phased array radar antenna at the National Weather Radar Testbed (NWRT), intended to serve as a working Phased Array Radar (PAR) system for proving various future surveillance concepts. In the case of FAA, research during the 1990s on the Terminal Area Surveillance System (TASS) showed that both
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Evaluation of the Multifunction Phased Array Radar Planning Process terminal weather and aircraft surveillance functions could be met by a single multifunction phased array radar system, though cost was then prohibitive. Taking a fresh look at this technology makes sense for them, as industry advancements over the last decade have enabled new radar designs and greatly reduced PAR costs. Finally, with existing radar assets 10 to 40 years old, both agencies will have to initiate large scale radar replacement activities in the next decade, with some early key decisions required in the next few years. Although NOAA, FAA, and some DOD current and future requirements for radar surveillance are fairly detailed (Chapter 3), the gathering of requirements from the other agencies appears to be more problematic. Briefly, FAA near-term requirements include sustaining current surveillance capabilities while reducing overall FAA cost of ownership (e.g., via consolidation of assets, reduced O&M costs, or agency cost sharing). Future FAA requirements include a decrease in weather volume coverage update intervals from ~5 minutes to 1 minute and detection of icing, turbulence, and volcanic ash. NWS near-term requirements also insist on sustaining current or soon-to-be implemented surveillance capabilities (including hydrometeor identification). Emerging requirements include increased volume refresh rates and spatial resolution, decreased data latency, and mobile radar operations for improved hazardous weather detection and warning lead time. However, it is not clear that any agency is seriously addressing any requirement for systematic widespread coverage of non-cooperative aircraft targets or of low-altitude storm intensity that correlates well with quantitative precipitation measurements. Also, the JAG/PARP report notes other surveillance functions performable by radar but not currently articulated as federal requirements, such as fire weather, airborne toxic releases, or spaceflight weather support. The central core of the JAG/PARP report (Chapters 3-5) solidly reflects the planning of NOAA and FAA primary stakeholders. These chapters include comparison of alternatives for future civilian radar functions, technical aspects of meeting surveillance radar needs, and cost considerations. These chapters were presented in the spirit of providing some specificity, while neither expecting nor intending them to be taken as more than preliminary point examples of the types of analyses that a properly conducted MPAR research and development (R&D) program would tackle. Chapter 6 outlines an R&D plan to support technical risk reduction studies for the various surveillance capabilities, to document the basis for cost/benefit tradeoffs of various surveillance systems, and to lay out the required R&D program if an MPAR does appear feasible (Appendix D provides time lines and cost estimates for this plan). Chapter 7 then rolls up the key findings and recommendations of the JAG/PARP. More thorough discussion of these chapters can be found elsewhere in our report. The JAG/PARP report was issued in June 2006 and MPAR planning and R&D activities have continued since that time. As recommended by the JAG/PARP report, the Interdepartmental Committee for Meteorological Services and Supporting Research established a Working Group for the Multifunction Phased Array Radar (WG/MPAR) under the OFCM standing Committee on Integrated Observing Systems to develop an implementation plan for MPAR research and development. Current membership is defined as “stakeholders”, the loosely-defined membership of this committee is charged with oversight of the MPAR research program until a joint program office is established.
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Evaluation of the Multifunction Phased Array Radar Planning Process MPAR SYMPOSIUM The OFCM held a Multifunction Phased Array Radar Symposium in Norman, Oklahoma, October 10-12, 2007. The theme was “Leveraging Technology to Build a Next Generation National Radar System,” and the purpose was to build consensus for an MPAR risk-reduction program. Over 180 people attended the conference, and the organizers have made the proceedings available to all via the World Wide Web (http://www.ofcm.gov/mpar-symposium/index.htm). The various special presentations and senior leader perspectives offered at the Symposium advanced the OFCM goals of supporting a comprehensive and inclusive planning process. There was excellent participation with agency programmatic leadership present to address the attendees. The six symposium panels discussed many of the common themes that were echoed within our committee. Below we list each of the six symposium topics and highlight several important themes, as excerpted from the MPAR Symposium Summary Report1 (see Appendix D). MPAR User Communities of Interest For both weather and aircraft surveillance, a national primary radar network is going to be needed into the foreseeable future. New systems such as MPAR must show both improvements in capability and reduction in overall life cycle costs to be viable candidates for acquisition. MPAR R&D efforts must be anchored to solid requirements from the user community. Current State of Military Investment in Phased Array Radar Military PAR systems are increasingly based on open architectures, drawing upon commercial off-the-shelf versus very high-priced military specification parts. The goal is to have a scalable system with reusable parts and modules; technical improvements should require little to no retro-engineering. A great deal of military PAR research has direct relevance to MPAR R&D efforts. Latest Innovations in PAR: An Industry Perspective A major issue to be determined is cost. While ultimate cost of a national MPAR system is yet to be determined, building an architecture around open systems and building in scalability will both serve to drive down future costs. 1 Available at www.ofcm.gov.
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Evaluation of the Multifunction Phased Array Radar Planning Process Many user “requirements” are not requirements at all, but simply the upper performance level of legacy systems; users must not confuse what they really need with what they have had to settle with in the past. Component Technology: What the Future Holds in Cost and Performance Sheer volume of a national MPAR acquisition of any configuration would tend to drive down cost of T/R modules through economies of scale. Integration of more functions onto the same chip lowers cost and increases reliability because fewer high-cost Radio Frequency (RF) interconnects are needed on surface-mounted chips. New semiconductor materials provide much higher efficiency, allowing low-cost air cooling for heat dissipation, rather than complex, high-cost liquid cooling. Component manufacturers look to exploit dual use (same components for military and civil applications) as key to affordability. MPAR Alternative Configurations Weather will be the principal radar resource driver in any multifunction phased array system of the future. If MPAR can meet weather requirements (in particular, for clear air reflectivity), it can almost certainly meet any aircraft surveillance requirements that will be levied against it. Gaps in low-level (boundary layer) coverage inherited from legacy radars need to be addressed by any follow-on radar system. Earth curvature and topographic blockage create blind spots in current radar coverage that are important from both meteorological and air defense perspectives. Blanket coverage may not be feasible; rather, coverage may be “grown” on the network over high-priority areas. The Way Ahead to Address MPAR Risk Reduction The overall conclusion was that the symposium demonstrated solid consensus on both the desirability and feasibility of MPAR to meet national surveillance requirements for both weather and aircraft, but that developing an effective interagency management structure for MPAR risk reduction will prove challenging. MPAR must engage the four principal agencies involved: NOAA, FAA, DOD, and DHS. The NEXRAD interagency management model may prove an effective precedent for MPAR. Engaging agency support for risk reduction will depend on building a compelling business case; the need for more robust DOD involvement was highlighted. The most urgent requirement is to develop a risk-reduction implementation strategy, which includes the building and field-testing of a prototype with modern active
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Evaluation of the Multifunction Phased Array Radar Planning Process phased array radar technology that will actually demonstrate simultaneous multifunction capability. Attendees of the Symposium agreed that evaluation of MPAR needs to begin, and a series of near-term actions to ensure this were identified. When the OFCM MPAR planning exhibits consisting of the JAG/PARP report and the MPAR Symposium are examined together, the process may appear more inclusive than it actually was. The apparent agency consensus for funding significant advancements in our nation’s surveillance may actually be more muted. The NOAA and FAA stakeholders have been clear leaders in the MPAR planning effort. Industry is clearly energized and moving out on innovative MPAR radar designs. DEVELOPMENTS TO DATE: ACTIVITIES IN THE NWRT Significant time and effort were originally necessary to retrofit the SPY-1A antenna for weather observations using a WSR-88D transmitter. Since then, the maintenance and operation of the system have required a large investment in personnel and funding, with the bulk of this effort being led by the NSSL. In addition, NSSL is working closely with engineers from both Lockheed Martin Corporation and Basic Commerce & Industries, Inc. Several research projects are also ongoing in collaboration with scientists and engineers from the University of Oklahoma (OU). The NWRT has been collecting data since 2004. With the impetus of experimentally testing the MPAR concept, data from the NWRT have been used for numerous R&D activities. The following list provides a brief summary of this work; more complete discussion can be found in a series of American Meteorological Society (AMS) conference presentations by Forsyth et al. (latest in 2008). Severe Weather Observations/Validation Data from numerous high-impact weather events have been collected with the NWRT. Ongoing scientific studies emphasize validating the advantages of high-temporal-resolution observations against more conventional measurements from the WSR-88D network (Heinselman et al., 2008). (The spatial resolution of the NWRT is poorer than that of the WSR-88D; however, the manually controlled adaptive scanning can produce higher temporal resolution.) Hardware Upgrades To implement true adaptive scanning, upgrade to the Real-Time Controller of the NWRT is necessary. This modification is currently being pursued, along with the required software enhancements. At present, emphasis has been placed on adaptive beam pointing rather than waveform agility. An OU grant from the NSF Major Research Instrumentation Program has allowed the development of an eight-channel receiver for
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Evaluation of the Multifunction Phased Array Radar Planning Process the NWRT, which will allow implementation of numerous techniques not possible before. Data Quality Several methods of enhancing data quality in various stages of study (research, development, operational) for the WSR-88D radar are also being investigated for the NWRT. Examples include staggered pulse repetition intervals, phase coding, range oversampling/whitening, and conventional clutter filtering. With the new eight-channel receiver, spatial clutter filtering will also be possible. New Products and Techniques Research has been conducted on new techniques made possible with phased array radar, with the goal of operational implementation on the NWRT. The Beam Multiplexing (BMX) technique is now a standard scanning mode, with a detailed analysis of its limitations currently underway. Real-time refractivity (moisture) fields are now available on the NWRT with the advantages of eliminated beam smearing and rapid update of this new product (Cheong et al., 2008). The Spaced Antenna Interferometer (SAI) method is now being implemented on the NWRT with the recent availability of the monopulse channels and the new eight-channel receiver. Aircraft Detection/Tracking Although the NWRT system has been used for aircraft detection, tracking has not been pursued due to the lack of the monopulse channels. With the successful completion of the new eight-channel digital receiver, advanced tracking will soon be possible using either power- or phase-comparison methods. DEVELOPMENTS TO DATE: 2007 ANNUAL MPAR STATEMENT AND 2008 PLANS Agencies including NOAA, the FAA and DOD have initiated or continued several activities that were in their nascent stages when the JAG/PARP report was released. Several of these activities were completed in 2007 or are scheduled for completion during 2008. Box 6.1 provides a brief summary of those activities, which are discussed in more detail in the Annual Statement of MPAR Research Priorities and Previous Year Accomplishments 2007-2008,2 (This summary includes only those activities that were identified as scheduled for completion in 2007 or 2008.). The Statement also covers 2 Available at www.ofcm.gov.
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Evaluation of the Multifunction Phased Array Radar Planning Process activities and accomplishments related to the NWRT, which are outlined above. The reader is referred to the Statement for further details. BOX 6.1 Summary of CY2007 Research Accomplishments MPAR Concept of Operations (CONOPS): Description of a multifunction system supporting multiple agencies and agency missions. Legacy Radar Life Cycle Cost Study: Collection and analysis of legacy radar (ground-based rotating radar systems) operations and maintenance (O&M) life cycle costs, in preparation for an MPAR business case. ADS-B Backup Requirements: Description of a network of radars to provide surveillance in the event of a regional loss of GPS signal. MPAR Impact on Safety- and Efficiency-Enhancing Weather Services: A study to explore MPAR’s impact on aviation weather algorithms. Risk Reduction Program: Completed initial risk-reduction effort begun during FY06, including proposed phased array architecture, and design and component cost for a transmit/receive module.