1
Introduction

In the mid 1990s, the Department of Defense (DoD), Federal Aviation Administration (FAA) and National Oceanic and Atmospheric Administration’s (NOAA) National Weather Service (NWS) completed the installation of a network of approximately 150 ground-based, mechanically rotating Doppler weather radars, known commonly as the Next Generation Radar (NEXRAD) network and formally as the Weather Surveillance Radar 1988-Doppler (WSR-88D) network. The installation of this network marked a paradigm shift in NWS’s capability to observe the atmosphere and provide accurate warnings to the public for severe thunderstorms, tornadoes, and flash floods.

NOAA/NWS and its partners in industry, government, and academia have continually improved the performance and capability of these radars through a variety of research and development efforts. Significant software advances have improved the real-time processing and display of the data. Perhaps most significantly, the network will be retrofitted with dual-polarization capability in the near future. This technology will provide a significant advance in the operational observation of the types and concentrations of hydrometeors in clouds and precipitation-producing systems, as well as an improvement in overall data quality. This will allow significant improvements in such things as rainfall estimation and detection of cloud icing conditions, with the benefits to water managers and the aviation industry such observations afford.

The Federal Aviation Administration (FAA) makes use of the weather observations from this network, and also operates a number of Terminal Doppler Weather Radars (TDWR) at major airports. The TDWRs were designed specifically for detection of wind shear hazards in airport approach and departure zones, but they also provide some more general surveillance of weather in the terminal area. In addition, the FAA operates Airport Surveillance Radars (ASR) at many terminals as well as a network of longer-range Air Route Surveillance Radars (ARSR) across the country. The ASR and ARSR systems are of varying vintage, some being more than forty years old and others just installed in the 21st century. Some of the newer systems provide supplementary weather surveillance capability in addition to their aircraft observations, and others are being retrofitted with such a capability.

Even the newest of these radar systems are based mainly on technology a decade or more old. Research and development efforts continue to advance radar technology and its many applications, including weather surveillance, civil aviation, military, and homeland security. As the existing radar networks age and the nation considers the next steps for its entire civilian radar infrastructure, a variety of advanced technologies have emerged as the basis for possible upgrades or replacement. An overarching issue in these considerations is whether the various existing (“legacy”) systems designed for separate



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1 Introduction In the mid 1990s, the Department of Defense (DoD), Federal Aviation Administration (FAA) and National Oceanic and Atmospheric Administration’s (NOAA) National Weather Service (NWS) completed the installation of a network of approximately 150 ground-based, mechanically rotating Doppler weather radars, known commonly as the Next Generation Radar (NEXRAD) network and formally as the Weather Surveillance Radar 1988-Doppler (WSR-88D) network. The installation of this network marked a paradigm shift in NWS’s capability to observe the atmosphere and provide accurate warnings to the public for severe thunderstorms, tornadoes, and flash floods. NOAA/NWS and its partners in industry, government, and academia have continually improved the performance and capability of these radars through a variety of research and development efforts. Significant software advances have improved the real- time processing and display of the data. Perhaps most significantly, the network will be retrofitted with dual-polarization capability in the near future. This technology will provide a significant advance in the operational observation of the types and concentrations of hydrometeors in clouds and precipitation-producing systems, as well as an improvement in overall data quality. This will allow significant improvements in such things as rainfall estimation and detection of cloud icing conditions, with the benefits to water managers and the aviation industry such observations afford. The Federal Aviation Administration (FAA) makes use of the weather observations from this network, and also operates a number of Terminal Doppler Weather Radars (TDWR) at major airports. The TDWRs were designed specifically for detection of wind shear hazards in airport approach and departure zones, but they also provide some more general surveillance of weather in the terminal area. In addition, the FAA operates Airport Surveillance Radars (ASR) at many terminals as well as a network of longer-range Air Route Surveillance Radars (ARSR) across the country. The ASR and ARSR systems are of varying vintage, some being more than forty years old and others just installed in the 21st century. Some of the newer systems provide supplementary weather surveillance capability in addition to their aircraft observations, and others are being retrofitted with such a capability. Even the newest of these radar systems are based mainly on technology a decade or more old. Research and development efforts continue to advance radar technology and its many applications, including weather surveillance, civil aviation, military, and homeland security. As the existing radar networks age and the nation considers the next steps for its entire civilian radar infrastructure, a variety of advanced technologies have emerged as the basis for possible upgrades or replacement. An overarching issue in these considerations is whether the various existing (“legacy”) systems designed for separate 7

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8 EVALUATION OF THE MPAR PLANNING PROCESS applications can be replaced with one or more consolidated systems that could serve multiple functions and multiple agencies. One such candidate under consideration by the federal government is a Multifunction Phased Array Radar (MPAR) network, which is envisioned as a network of radar installations with electronically (as opposed to mechanically) steered antennas. This candidate is but one of many discussed in Weather Radar Technology Beyond NEXRAD (NRC, 2002)1, which specifically recommended the exploration of radar systems with agile-beam scanning capabilities. In 2000, the United States Navy supplied NOAA’s National Severe Storms Laboratory (NSSL) in Norman, Oklahoma, with a phased array antenna. Several agencies contributed funds to construct the National Weather Radar Testbed (NWRT) using this antenna; the NWRT has been collecting data since 2004. It serves as the facility where phased array technology is being tested as part of the federal government’s research and development (R&D) for a possible future MPAR network. However, the MPAR R&D effort includes multiple activities within many additional agencies, including the FAA, the Department of Homeland Security (DHS) and the Department of Defense (DOD). In June 2006, these and other agencies, under the auspices of the Joint Action Group for Phased Array Radar Project (JAG/PARP), Office of the Federal Coordinator for Meteorology (OFCM) and the Federal Committee for Meteorological Services and Supporting Research (FCMSSR), issued a report titled Federal Research and Development Needs and Priorities for Phased Array Radar (OFCM, 2006; hereafter “JAG/PARP report”). The JAG/PARP report summarized federal planning for the MPAR R&D effort, including estimates of costs and benefits of a future MPAR network. The purpose of the present report is to evaluate the MPAR R&D plans. The JAG/PARP report provides a starting point for this evaluation, but it also incorporates information from a variety of additional sources (see Preface for more details on the evaluation process). In Chapter 2, the evaluation begins with an overview of the existing U.S. civilian radar infrastructure. Chapter 3 outlines the needs for a next generation system of civilian radars. Chapters 4 and 5 describe the capabilities of phased array radar and discuss why and how those capabilities render MPAR a possible candidate for a next generation system. Chapters 6 and 7 summarize and assess the MPAR planning process, as described in more detail in the JAG/PARP report and additional sources of information. Chapter 8 places a potential MPAR network in the context of a broader family of sensing systems. Chapter 9 concludes the report by providing a principal finding and overarching recommendation. 1 This report provides a concise summary of various technical options for a future ground-based system of radars for weather surveillance. These options include phased array technology, polarization diversity, mobile radars, short-range radars, and space-based radars. The reader is referred to various technical documents cited through the present report that provide more detailed technical specifications for each of these options.