Publications
Volume 12, Number 2
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Radar and MIT Lincoln Laboratory: A View from a Distance Radar Development at Lincoln Laboratory: An Overview of the First Fifty Years This article provides an overview of the first fifty years of radar development at Lincoln Laboratory. It begins by reviewing early Laboratory efforts in North American air defense, which quickly branched into efforts in missile defense and space surveillance as the Soviet Union developed missiles and launched satellites into space. In the 1970s, two other radar-intensive activities began at the Laboratory: a program in tactical surveillance arose out of the challenges of the Vietnam War, and a program in air traffic control responded to the need to modernize systems for control of civilian aircraft. Research in advanced air defense also returned to the Laboratory with the advent of the modern cruise missile. This article summarizes these major Laboratory radar programs in a synoptic fashion, which can serve the reader as a road map to the ensuing fourteen articles, each of which provides a more in-depth view of the Laboratory’s radar developments. Early Advances in Radar Technology for Aircraft Detection In its early years, Lincoln Laboratory developed critical components of an air-defense system to guard North America against the threat of intercontinental bombers carrying nuclear weapons. Lincoln Laboratory used digital computer technology to automate several functions of the air-defense system and improve the quality of digitized radar data processed by the air-defense system. This article describes some of the experimental and theoretical efforts that led to early advances in radar technology for aircraft detection. Distant Early Warning Line Radars: The Quest for Automatic Signal Detection In the early 1950s, the threat of manned bombers carrying nuclear weapons across the arctic region was of paramount concern in continental defense. The 1952 Summer Study at MIT recommended the development of an early-warning radar line across the northern reaches of Alaska and Canada, from Cape Lisburne on the northwest corner of Alaska to Cape Dyer on Baffin Island on the east coast of Canada. It was an ambitious undertaking, particularly since the radar system had not yet been developed or designed and a new detection process had yet to be invented. Among other innovations the radar net was proposed to use automatic-detection techniques to reduce drastically the heavy manpower requirements and unacceptable time delays characteristic of manual radar operations of the period. After the U.S. Air Force accepted the Summer Study recommendation in December 1952, Lincoln Laboratory was contracted to deliver ten radar sets by 30 April 1953, a period of less than five months. F. Robert Naka was assigned the task of developing the automated radar signal processing and alarm system. The article reviews the primary author’s experiences with this challenging radar project. While the technical problems sound primitive in view of today’s radar capabilities, they were met and solved at a pace that was easily ten times faster than today’s Department of Defense developments. Long-Range UHF Radars for Ground Control of Airborne Interceptors The standard Air Force radars available in the early 1950s had major shortcomings for air-battle management in the face of plausible threats. At that time Lincoln Laboratory was achieving impressive success in developing UHF radars for airborne early warning with moving-target indication by changing from shorter to longer operating wavelengths. It appeared that similar innovations would also yield major performance improvements for radars devoted to the ground control of airborne interceptors. Lincoln Laboratory developed and fielded two different UHF radars that showed that this promise could be fulfilled. Both had quite large antennas rotating in azimuth. A narrowband radar operating near 425 MHz was built on Jug Handle Hill near West Bath, Maine; it became a primary sensor for the Cape Cod System and the Experimental SAGE Subsector. A broadband radar operating across the 400-to-450-MHz band was built atop Boston Hill near North Andover, Massachusetts. This radar was designed as a test bed for the development of techniques to combat active electronic jamming and passive countermeasures such as chaff dispensed by hostile aircraft. These radars paved the way for subsequent Air Force efforts to achieve frequency diversity in its air-defense network. Radars for the Detection and Tracking of Ballistic Missiles, Satellites, and Planets This article is an overview of the forty-plus years in which Lincoln Laboratory has been developing and applying radar techniques for the long-range detection and tracking of ballistic missiles, satellites, and planets. This effort has included the development and use of several large radar systems: the AN/FPS-17 radar in Turkey, the Millstone and Haystack radars in Massachusetts, and the Ballistic Missile Early Warning System (BMEWS). The Millstone and Haystack radars have been used to make significant contributions to space science and deep-space satellite tracking. The availability of high-power radars has spurred their application in ionospheric and radar-astronomy studies. The processing techniques developed in support of the astronomical mapping of the Moon and planets provided the foundation for subsequent radar imaging of objects in space. We highlight the radar technology involved and discuss the use of these systems and their legacy. Radars for Ballistic Missile Defense Research Lincoln Laboratory’s involvement in ballistic missile defense began over forty years ago at the time of the first launches of ICBMs and satellites by the Soviet Union and the formation of the Advanced Research Projects Agency (ARPA). The Reentry Physics Program, started in 1958 and sponsored by ARPA, set out to understand the behavior of hypervelocity objects reentering the atmosphere, with the expectation that this research would lead to a means of discriminating between warheads and decoys. The program, which combined theoretical analysis, laboratory experiments, and field measurements, provided a foundation that soon led to other similar programs. The U.S. Air Force, interested in the performance of its own ICBMs against enemy defense systems, also initiated a program of radar development and measurements similar to that of ARPA. As a consequence, the Laboratory became heavily involved in ARPA’s Project PRESS (Pacific Range Electromagnetic Signature Studies) and ARPAT (ARPA Terminal) programs and the Air Force Penetration Aids program. By 1963, these three large programs, combined with related efforts in the development of radar technology, occupied approximately half of Lincoln Laboratory’s staff. Fifteen large sensitive radars designed for signature measurements were built as a result, and Lincoln Laboratory had some role in the development of each. This article traces the history of the measurement radars and the technology programs that supported them. It concentrates on the four major radars at the Kwajalein Missile Range. These radars continue to play a major role in the development of ballistic missile defense systems and discrimination techniques. Wideband Radar for Ballistic Missile Defense and Range-Doppler Imaging of Satellites Lincoln Laboratory led the nation in the development of high-power wideband radar with a unique capability for resolving target scattering centers and producing three-dimensional images of individual targets. The Laboratory fielded the first wideband radar, called ALCOR, in 1970 at Kwajalein Atoll. Since 1970, the Laboratory has developed and fielded several other wideband radars for use in ballistic-missile-defense research and space-object identification. In parallel with these radar systems, the Laboratory has developed high-capacity, high-speed signal and data processing techniques and algorithms that permit generation of target images and derivation of other target features in near real time. It has also pioneered new ways to realize improved resolution and scatterer-feature identification in wideband radars by the development and application of advanced signal processing techniques. Through the analysis of dynamic target images and other wideband observables, we can acquire knowledge of target form, structure, materials, motion, mass distribution, identifying features, and function. Such capability is of great benefit in ballistic missile decoy discrimination and in space-object identification. Displaced-Phase-Center Antenna Technique This article describes Lincoln Laboratory contributions to the development of the displaced-phase-center antenna (DPCA) technique, which was used to improve the detection performance of airborne or space-borne MTI radars that are subject to clutter. In the 1950s the DPCA technique was applied to airborne early warning (AEW) radars for defense of North America against long-range bombers carrying nuclear weapons. Lincoln Laboratory built the first UHF AEW radar, which became the prototype for both Air Force and Navy operational radars. In the 1970s, experience during the Vietnam War showed the possible usefulness of a wide-area surveillance radar to monitor moving ground vehicles. DPCA radar theory and the emergence of medium-scale digital signal processing showed the feasibility of such an airborne radar. Lincoln Laboratory proceeded to design and test a Multiple-Antenna Surveillance Radar (MASR). The Air Force then built a developmental DPCA radar called Pave Mover, which was followed by the currently operational Joint Surveillance and Target Attack Radar System (Joint STARS). In the 1980s, space-based radar showed potential for a variety of applications, including early detection of aircraft raids against Navy battle groups and the detection of moving ground targets such as mobile missile launchers. The DPCA technique allowed the use of smaller, cheaper satellites at lower altitudes than the conventional high-altitude, pulse-Doppler radar. Antennas were designed and their clutter-cancellation capabilities measured and compared with theory. A new technique for calibrating remote phased-array antennas, called the mutual-coupling technique, was discovered. Radar Signal Processing This article recounts the development of radar signal processing at Lincoln Laboratory. The Laboratory’s significant efforts in this field were initially driven by the need to provide detected and processed signals for air and ballistic missile defense systems. The first processing work was on the Semi-Automatic Ground Environment (SAGE) air-defense system, which led to algorithms and techniques for detection of aircraft in the presence of clutter. This work was quickly followed by processing efforts in ballistic missile defense, first in surface-acoustic-wave technology, in concurrence with the initiation of radar measurements at the Kwajalein Missile Range, and then by exploitation of the newly evolving technology of digital signal processing, which led to important contributions for ballistic missile defense and Federal Aviation Administration applications. More recently, the Laboratory has pursued the computationally challenging application of adaptive processing for the suppression of jamming and clutter signals. This article discusses several important programs in these areas. The Development of Phased-Array Radar Technology Lincoln Laboratory has been involved in the development of phased-array radar technology since the late 1950s. Radar research activities have included theoretical analysis, application studies, hardware design, device fabrication, and system testing. Early phased-array research was centered on improving the national capability in phased-array radars. The Laboratory has developed several test-bed phased arrays, which have been used to demonstrate and evaluate components, beamforming techniques, calibration, and testing methodologies. The Laboratory has also contributed significantly in the area of phased-array antenna radiating elements, phase-shifter technology, solid-state transmit-and-receive modules, and monolithic microwave integrated circuit (MMIC) technology. A number of developmental phased-array radar systems have resulted from this research, as discussed in other articles in this issue. A wide variety of processing techniques and system components have also been developed. This article provides an overview of more than forty years of this phased-array radar research activity. Tactical Radars for Ground Surveillance Battlefield awareness is the key to battlefield dominance. The field commander who knows the enemy’s location and the types of forces being deployed enjoys a great tactical advantage. The problem of detecting and classifying ground targets presents substantial technical challenges, which Lincoln Laboratory has addressed for nearly three decades in its Tactical Technology program. Substantial progress has been made in many aspects of ground surveillance since the mid-1960s, but many challenges remain. These challenges include sensor development, signal processing, and target-recognition technology. Among its successes, the Laboratory has provided the foundation for operational national assets such as the Joint Surveillance Target Attack Radar System (Joint STARS) airborne surveillance system. This article describes in chronological order several important Laboratory tactical-radar programs and the technologies that were developed for both airborne and ground-based surface surveillance. Radars for the Detection and Tracking of Cruise Missiles The advent of the modern cruise missile, with reduced radar observables and the capability to fly at low altitudes with accurate navigation, placed an enormous burden on all defense weapon systems. Every element of the engagement process, referred to as the kill chain, from detection to target kill assessment, was affected. While the United States held the low-observable-technology advantage in the late 1970s, that early lead was quickly challenged by advancements in foreign technology and proliferation of cruise missiles to unfriendly nations. Lincoln Laboratory’s response to the various offense/defense trade-offs has taken the form of two programs, the Air Vehicle Survivability Evaluation program and the Radar Surveillance Technology program. The radar developments produced by these two programs, which became national assets with many notable firsts, is the subject of this article. Weather Radar Development and Application Programs Weather phenomena such as microburst wind shear and severe thunderstorms are major concerns to the aviation industry. A number of significant airplane accidents have resulted from wind-shear encounters during takeoff and landing, and thunderstorms are a major contributor to airplane delay. Providing fully automated and timely warnings of these phenomena by radar is challenging because it requires rapid and accurate analysis of the three-dimensional storm structure in the presence of intense ground-clutter returns. For the last two decades, Lincoln Laboratory has been tackling this challenge by applying advanced radar signal- and image-processing techniques to weather radar data. The resulting technology is being deployed in radar-based weather information systems at major airports throughout the United States. We first discuss the salient meteorological factors that contribute to the formation of microburst wind shear, then we provide some general background on the use of pulse-Doppler radar for weather detection. We describe two specific Lincoln Laboratory programs that have generated deployed systems: the Terminal Doppler Weather Radar (TDWR) and the ASR-9 Weather Systems Processor (WSP). The article concludes with a discussion of future detection strategies that emphasizes the fusion of weather radar data by the Integrated Terminal Weather System (ITWS). Development of Coherent Laser Radar at Lincoln Laboratory The invention of the laser in 1960 created the possibility of using a source of coherent light as a transmitter for a laser radar. Coherent laser radars share many of the basic features of more common microwave radars. However, it is the extremely short operating wavelength of lasers that introduces new military applications, especially in the area of target identification and missile guidance. This article traces laser-radar development at Lincoln Laboratory from 1967 to 1994. This development involved the construction, testing, and demonstration of two laser-radar systems—the high-power, long-range Firepond laser-radar system and the compact short-range Infrared Airborne Radar (IRAR) system. Firepond addressed strategic military applications such as space-object surveillance and ballistic missile defense, while IRAR was used as a test bed for airborne detection and identification of tactical targets. Widgets and Wonders: Lincoln Laboratory’s Unique Radar Hardware Legacy One of the more distinguishing characteristics of Lincoln Laboratory is its insistence on analyzing real-world data from the advanced electronic systems the Laboratory develops and operates. As a result of this commitment, the Laboratory must often build and field hardware with capabilities exceeding those available commercially. Over the past five decades, the Laboratory’s profound devotion to data-based radar performance analysis has resulted in the production of many hundreds of small or specialized radar systems and supporting hardware items. |
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