MIT Reports to the President 1995-96


Lincoln Laboratory is operated by MIT as a Federally Funded Research and Development Center for performing research and development in advanced electronics. During the past year, agencies of the Department of Defense (DoD), namely, the Air Force, the Army, the Navy, the Defense Advanced Research Projects Agency (DARPA), and the Ballistic Missile Defense Office (BMDO) supplied approximately 81% of the Laboratory's budgetary support. The Federal Aviation Administration (FAA) provided most of the non-DoD support. Lincoln Laboratory is permitted to carry out precompetitive research with industry under approved Cooperative Research and Development Agreements. For the federal fiscal year 1995, Lincoln Laboratory received $337 million, supporting the efforts of 1082 professional technical staff, of whom 770 are principal members. (The Laboratory is now reporting total professional staff for consistency with DoD reporting requirements.)


The following administrative changes occurred at the Laboratory Steering Committee level during the year: Dr. Herbert Kottler became Assistant Director, Dr. Antonio F. Pensa became Head of the Aerospace Division, Mr. William M. Brown Jr. became Associate Head of the Aerospace Division, Mr. Raymond R. LaFrey became Associate Head of the Surveillance and Control Division, Dr. Jonathan F. Schonfeld became Assistant Head of the Surveillance and Control Division, Dr. Richard W. Ralston became Associate Head of the Solid State Division, and Mr. Frank D. Schimmoller became Associate Head of the Administration Division.


Activity at the Laboratory focuses on surveillance, identification, and communications technology development for the DoD, and on air traffic control technology for the FAA. Technical work areas include radar and optical sensors, measurements, and systems; communications; signal design and processing; lasers; solid state devices; digital technology, circuitry, and data systems; and tactical control systems. Unclassified highlights of several accomplishments during the past year are summarized below.



Lincoln Laboratory continues to support DARPA and the U.S. Air Force Wright Laboratory in their efforts to develop a Foliage-Penetration (FOPEN) Synthetic Aperture Radar (SAR) system for the detection of stationary ground targets that are obscured by foliage. In September 1995, an experiment was conducted by Lincoln Laboratory that utilized the Naval Air Warfare Center/Environmental Research Institute of Michigan P-3-aircraft-mounted ultrawideband SAR to collect polarimetric UHF SAR imagery. This experiment was the culmination of a series of FOPEN experiments performed in 1995 that collected over 2,500 square kilometers of clutter including target data. Lincoln Laboratory has found encouraging results from applying change detection algorithms to the FOPEN target-detection problem.


A program to develop and demonstrate an image exploitation ground station for present and future airborne SAR systems was initiated at Lincoln Laboratory in late 1994. The goal is to develop a semiautomatic system, requiring only a few operators to process and interpret very large quantities of SAR imagery. The task is to detect and recognize stationary ground vehicles with high confidence. Preliminary real-time automatic detection experiments were carried out in New Mexico in May 1995 as part of the U.S. Government Roving Sands/Goldpan exercises. Currently, a large-scale processing system has been constructed and is now being tested. It will be ready for deployment to Edwards AFB in late fall of 1996 to participate in tests at the National Training Center.


Lincoln Laboratory is responsible for the design, development, and demonstration of the Advanced Land Imager (ALI) that will be launched on the National Aeronautics and Space Administration's (NASA) Earth Orbiter-1 mission in December 1998. ALI is a land imaging instrument that will demonstrate advanced technology that will meet NASA's Mission to Planet Earth science needs in the 21st century. The new technologies dramatically reduce the size, weight, and power of ALI versus the LANDSAT-7 Enhanced Thematic Mapper. The ALI multispectral and hyperspectral images will be compared with 100 to 200 images from LANDSAT-7 to validate the new technologies.


Lincoln Laboratory is collaborating with the MIT Civil and Environmental Engineering Department in an effort in remote monitoring of in-situ contamination using optical spectroscopy. This work uses miniature, fiber-coupled UV lasers to excite fluorescence in organic pollutants such as benzene, toluene, and xylene. The ultimate objective of the research is to develop a multiprobe system for long-term monitoring of contaminants in soils and ground water. This past year, laboratory measurements in soil samples were made with a prototype sensor.


The Haystack Long Range Imaging Radar (LRIR) has collected data on man-made orbital debris for more than 4 years. Recently, the Haystack Auxiliary (HAX) radar has joined this effort to increase the data collection capability. The data thus far collected represent the largest data base available to help researchers characterize the space debris environment. The LRIR and HAX radars operate in a "stare" mode pointing at a fixed point in space. They detect debris objects passing through the beam and record data for later analysis. Debris size, altitude, and orbital inclination have been determined. A new "stare and chase" mode will allow acquisition and tracking of debris objects to characterize their orbits.



The Theater High-Altitude Area Defense (THAAD) system is currently in development to provide large-area defense against theater ballistic missiles. This past year, Lincoln Laboratory supported several key elements of this development for the THAAD radar, which is the surveillance and fire control sensor for the system and which came on line early in the year. Laboratory support included testing and analysis of the THAAD radar baseline discrimination architecture, characterization of the radar performance, and analysis of the radar performance during THAAD flight tests at White Sands Missile Range for government evaluators.


Development of the Lexington Discrimination System (LDS) has continued in an effort to incorporate a broader set of missile defense critical functions. The LDS is the key facility for assessing the performance of algorithms to be used in the various elements of missile defense. With its extensive field measurement data base it provides the ballistic missile defense community with the highest-fidelity phenomenology inputs available to exercise the key algorithms.


The Kwajalein Missile Range (KMR), for which Lincoln Laboratory serves as Scientific Director, is preparing to support testing of theater missile defense (TMD) components and several other test programs aimed at acquiring data to support advanced development of such components. The Laboratory is aiding in preparations for these tests with test-planning activities and a program of improvements and modifications to various optical and radar sensors. Two new telescopes designed to collect metric and signature data in the mid-wave infrared (MWIR) band have been built, and one will be installed at KMR for use on Theater Missile Defense Critical Measurements Program missions. These systems, in conjunction with bandwidth and pulse repetition frequency upgrades at the Millimeter Wave radar, are expected to provide the extremely accurate miss-distance/impact-point measurements needed by the TMD community during planned intercept tests. A major addition to KMR's capability to support TMD testing is the recently completed KMR Mobile Range Safety System, which will be used to support the launch of target vehicles from Wake or other Micronesian sites. Lincoln Laboratory participated in the system design and provided computers, telemetry and command destruct antennas, and the stabilization system sensors for this shipboard system.


Lincoln Laboratory is developing the prototype COBRA GEMINI radar system, which will be used to acquire data in rest-of-world (ROW) ballistic missile launches. Since the end of the Cold War and dissolution of the Soviet Union, the missile data collection effort has been focused on ROW countries rather than on Soviet systems. A key and consistent recommendation of studies addressing ROW missile data collection has been to develop a number of low-cost, air and ground transportable, mechanical scanning dish radars. The COBRA GEMINI system will be dual frequency and have a high-resolution, wideband imaging capability. The design and development information from this operational prototype radar will be transferred to industry for use in their manufacture of at least two additional radar systems.


The Theater Missile Defense (TMD) Critical Measurements Program (TCMP) provides IR and radar measurements to address critical issues for TMD elements through a sequence of flight tests executed at KMR. The objective of the current flight test campaign (TCMP-2) is twofold: first, to collect sensor data (IR and radar) to support resolution of TMD element critical issues and, second, to provide measurements to characterize and mitigate plausible countermeasures. TCMP-2 consists of three medium-range theater ballistic missile flights from Wake Island to Kwajalein Atoll, one scheduled for July 1996 and two for March 1997. Lincoln Laboratory is supporting TCMP-2 in four task areas during the current fiscal year: (1) mission planning and integration, (2) payload development, (3) fly-away IR sensor development, and (4) data analysis. The planning for the next campaign (TCMP-3) has begun. There will be two medium-range theater ballistic missile flights scheduled for FY98 and two longer range flights for FY99.


The Ground-Based Radar (GBR) is being developed as a surveillance and fire control sensor for the National Missile Defense (NMD) system, which is currently in its design phase. A prototype GBR is to be built and tested at KMR. This past year, Lincoln Laboratory supported several key elements of this development. GBR NMD discrimination architectures were developed and tested to check the performance of the baseline algorithms that will be used during the upcoming prototype demonstrations in FY98. Additional research was conducted on the more sophisticated algorithms and architectures that will be required to meet future requirements for NMD.


Over the past several years, Lincoln Laboratory and the Advanced Electronic Guidance and Instrumentation System (AEGIS) PMS-400 office have been supporting the development of the Navy Area (or lower tier) Theater Ballistic Missile Defense (TBMD) System. Much of the early work covered an analysis of the AEGIS Weapon System performance in autonomous and cued search modes. The studies quantified the cueing accuracies of systems such as the Defense Support Program satellites, netted AN/SPY-1 and Patriot radars, and airborne Infra-Red Space Telescope/Laser Detection and Ranging sensors. The AN/SPY-1 firm-track ranges and SM-2/BLK-IVA flyout capability were then related to potential defended footprints against a wide class of TBMs.

More recent work has covered a TBM debris environment characterization based on the measurement data base. Data from Lincoln Laboratory supported sensors such as the Kwajalein radars, Cobra Judy, and the Airborne Surveillance Testbed were used to quantify the radar and IR characteristics of TBM debris. The results of the analysis have been used to define system requirements for Lockheed-Martin, Raytheon, and Hughes. Following the debris characterization the Laboratory worked to develop the discrimination algorithms and timelines for the Area TBMD System. The discrimination approach is based on radar cross section scintillation and atmospheric drag measurements and has been tested using data from the TBM debris data base. The results show that the Area TBMD System has a significant discrimination capability against incidental debris and some countermeasures.

This year the Laboratory has begun systems analysis work for the Navy Theater-Wide (or upper tier) TBMD and Anti-Air Warfare Programs. This work has included an assessment of potential radar and IR discrimination metrics in the exoatmosphere. Other work has covered an analysis of new sensors and techniques for area defense against low-altitude cruise missiles. The results have been used to plan an acquisition strategy for developing new Navy surveillance and fire control systems.



In 1994 the ARPA Mountaintop Program moved the Radar Surveillance Technology Experimental Radar (RSTER) to the Pacific Missile Range Facility's (PMRF) Makaha Ridge Site on the island of Kauai in order to continue the development of techniques and technology related to Space Time Adaptive Processing. The phenomenology measurements program at Makaha Ridge has concentrated on collecting and analyzing data related to bistatic scattering, low-flyer detection, noncooperative target recognition, and sea clutter. Technology development efforts have included testing several antennas which can be used in a phased-array system capable of placing adaptive nulls in the direction of active and passive sources of interference.

The Navy Mountaintop Program moved the RSTER system to the Kokee site on Kauai, where it functioned as the surveillance sensor in the Cruise Missile Defense Advanced Concept Technology Demonstration Phase I. RSTER acted in concert with the Cooperative Engagement Capability system to hand over target detections to an MK-74 fire control radar. Throughout the series of live fire tests, involving SM-2 missiles launched from AEGIS cruisers, the Mountaintop sensors successfully provided accurate directing information to the AEGIS cruisers, resulting in over-the-horizon intercepts of BQM-74 target drones that had been launched from Barking Sands at PMRF. Following the series of demonstrations, RSTER was moved back to Makaha Ridge where the ARPA Mountaintop Program is continuing.


The capabilities of modern air defense missile seekers have been severely challenged by the advent of low-observable vehicles and modern electronic countermeasures. The Airborne Seeker Test Bed (ASTB) is an instrumentation platform developed by Lincoln Laboratory to investigate these challenges and identify appropriate seeker architectures and signal processing algorithms for dealing with them.

The ASTB is based in a Gulfstream II aircraft which provides high-fidelity reference instrumentation sensors that are used in parallel with special purpose wing pod payloads carrying production seekers or sensors under test. The IR instrumentation provides high-resolution imagery of target and background environments.



Under the Advanced Distributed Simulation Program, funded principally by DARPA and the Defense Modeling and Simulation Office, Lincoln Laboratory developed software implementing an initial prototype of a common run-time infrastructure (RTI) for linking together a broad variety of DoD models and simulations. This reusable RTI software is a critical element of the DoD High-Level Architecture for Modeling and Simulation, which is currently being evaluated for adoption as a DoD standard. The Laboratory completed a feasibility assessment and developed a straw man architecture for linking virtual simulations with instrumented combat vehicles in unprepared locations. Such ìinstant rangesî can be used for rehearsing planned operations and evaluating alternative courses of action, using the same command, control, communication, computing, and intelligence (C4I) equipment that would be used in actual combat.


With the explosion in global speech communication, the identification of the language of a speaker and the verification of his or her identity are important factors contributing to reliable information interchange. Over the past several years, Lincoln Laboratory and a number of other key research laboratories in the U.S. and Europe have been developing automatic algorithms for both language identification and speaker verification. During the first half of 1996, tests were conducted under the supervision of the National Institute of Standards and Technology, which compared both speaker and language identification systems of all the participating laboratories on a battery of test measures using standardized evaluation data. The Lincoln Laboratory systems outperformed all the others in both the speaker and language identification evaluations.


Lincoln Laboratory has developed a prototype system for automated two-way English/Korean text and speech translation of military messages, and has demonstrated this system successfully aboard the USS Coronado, command ship of the Third Fleet, in conjunction with the June 1996 Rim of the Pacific Coalition exercises. The system builds directly upon advances over the past decade at the MIT Laboratory for Computer Science in natural language understanding and generation, and extends this technology to a new language (Korean), a new application (translation), and a new domain (military messages). Natural language understanding is used to transform the input message into a military interlingua, referred to as a Common Coalition Language; this approach facilitates extensions to other languages. The system is implemented as a translatorís aid, running on either a workstation or a Pentium laptop, and is configured for robust operation, so that when the understanding system encounters new sentences which it cannot fully translate, a backup to a phrase-by-phrase or word-for-word translation is invoked. Currently, the system achieves fully correct sentence translation on 85% of the training/development sentences and on 65% of new sentences in a 2000-word vocabulary Naval Operations Report domain.


In collaboration with the Air Force Rome Laboratory, Lincoln Laboratory has developed a secure voice conferencing system that allows for a natural speaker interrupt capability in contrast to speaker selection techniques used in previous narrowband conferencing systems. A prototype system, including a compact vocoder built by Motorola on subcontract, which integrated the Lincoln multi-rate Sinusoidal Transform Coder algorithm with Motorolaís Secure Telephone Unit (STU-III), was demonstrated in September 1995 as part of the Joint Warrior Interoperability Demonstration. During the two-week demonstration, over 1000 persons, including high-level government communications officials, had the opportunity to hear and use the equipment from sites at Hanscom AFB, Massachusetts; Camp Pendleton, California; Ft. Gordon, Georgia; and aboard a KC01 Airborne Command Post aircraft.


Lincoln Laboratory is developing advanced night vision technology that has diverse military and civilian applications. The technology will provide a useful night vision capability at lower light levels than are now possible with image intensifier technology, will function under a wider range of ambient light and scene variability conditions, and will enhance the overall utility of night vision devices by the addition of a pseudo-color capability derived from the fusion of visible and thermal IR images. Highly sensitive charge-coupled device (CCD) imagers have been developed at Lincoln Laboratory to image in the visible through the near-infrared spectrum under starlight or darker conditions at video rates. Dual-band imagers are being developed using these low-light CCD imagers and thermal IR imagers (both cryogenic forward-looking IRs and uncooled thermal imagers). The dual-band imagery is processed, using neural models of biological color vision, to create a fused color rendition of the scene in real time.


Research and development are under way at Lincoln Laboratory on techniques, mechanisms, and tools for detecting computer network intrusion attempts and computer misuse. A user-configurable filter architecture is being pursued, which monitors interfaces between a local area network and the Internet or other outside entities, and supports automated recognition of command/response sequences characteristic of exploitation of specific network security vulnerabilities. The system goals are to achieve low miss and false-alarm probabilities for catalogs of known security vulnerabilities, and for newly discovered intrusion indicators adaptively targeted through the programmability feature as they are discovered by network security operators in the field.



The most likely foreign military crises for the United States in the near future will be regional (likely Third World) conflicts that threaten our interests overseas. Since these conflicts can occur anywhere geographically, there is the need for a global defense communications network that can provide instant connectivity to surveillance/

reconnaissance assets, rapid deployment forces, and other military assets in a newly formed theater of operation as well as CONUS. This information infrastructure should have global reach and will comprise an interconnection of multiple, sometimes very disparate, communications systems or networks, some of which will be new and some will include heritage systems in existence or planned for deployment in the near future. These systems include (1) satellite communications systems for the relay and downlinking of very high data rate sensor data; (2) military and commercial satcom systems for voice, video, and data communications (such as Milstar, the Defense Satellite Communication System, the Global Broadcast System, the Tracking and Data Relay Satellite System, and the International Maritime Satellite); (3) mobile satcom terminals for aircraft, ground forces, and ships; (4) communications relay nodes on board unmanned air vehicles (UAVs) and other airborne platforms; and (5) a global reach ground network infrastructure that includes military and commercial networks.


In 1993 a DARPA-sponsored consortium made up to AT&T Bell Laboratories, Digital Equipment Corporation, and MIT was formed to develop architectures and technologies to exploit the unique properties of fiber optics for advanced broadband networking. Two promising technologies are being investigated for utilizing the large bandwidth of a fiber: wavelength-division multiplexing (WDM) and time-division multiplexing, the latter utilizing soliton pulses. Both approaches have merit and each will likely find applications in future civilian and DoD networking environments.

The Wideband All-Optical Networks WDM effort consists of developing architectures, technology components, and a test bed for the realization of scalable, high-speed (user data rates from 10 Mbps to 10 Gbps), high-capacity (~Tbps) transparent optical WDM networks. The architecture addresses all-optical transport over wide, metropolitan and local areas utilizing wavelength partitioning, wavelength routing, and active multiwavelength cross-connect switches to achieve a network that is scalable in the number of users, data rates, and geographic span. The network supports three optical services which can be point-to-multipoint, or multipoint-to-multipoint simplex or duplex connections. A 20-channel local and metropolitan area WDM test bed has been developed and deployed in the Boston metropolitan area based on these architectural principles using advanced components. Multiple rate and format connectors over a variety of optical services and over 130 Gbps of capacity through a metropolitan area hub have been demonstrated. A full all-optical network (AON) control and management system has also been developed and implemented.

In March 1996 the Advanced Technology Demonstration Network (ATDNet) was initiated to integrate AON technology into Washington, D.C. ATDNet is a DoD-sponsored networking initiative with six principal network nodes: the National Security Agency, Naval Research Laboratory, Defense Information Systems Agency, Defense Intelligence Agency, NASA, and DARPA. The interoperation of ATDNet with an advanced technology test bed will provide an early indication of the efficacy of AONs in a realistic DoD setting. Quantitative information concerning the utility and performance transparency and the major increase in capacity of the WDM network can be obtained. Flield evaluation of the two networking technologies will provide important qualitative and quantitative results for guiding future architecture, technology, application development, and procurement decisions.


The Satellite Communications Technology Program is responsive to evolving satellite communications service trends and challenges, including the need to lower costs (via smaller, lighter-weight implementations) and the performance-related goals of increased capacities (especially to small, mobile terminals), interoperable networking (where satellite communications extend national/international information networks to remote areas and/or mobile users), and robustness against co-user as well as intentional interference. Many of the concepts and technologies that are being developed are also applicable to augmentation of tactical communications via UAVs and to the emerging commercial wireless and mobile satcom services. One of the key accomplishments during this year has been the development of an architecture for efficient data services via satellites. Key elements are an on-board packet-switching processor and a satellite-compatible link layer protocol that can accommodate all of the standard data transfer techniques (e.g., asynchronous transfer mode, transmission control protocol/Internet protocol, and file transfer protocol).


Under the Advanced Distributed Simulation Program-funded by DARPA, the Defense Modeling and Simulation Office, and the Simulation, Training, and Instrumentation Command-the Laboratory developed a set of network communication control algorithms that achieved a tenfold reduction in total backbone traffic for ARPA's Synthetic Theater of War Exercises, conducted in September 1994. The lessons learned from this highly successful effort are being incorporated in the development of the "Next Generation" Distributed Interactive Simulation architecture for the DoD. Also, the feasibility of linking virtual simulations with instrumented combat vehicles to create a range environment that can be quickly established at an unprepared location was studied. Such an "instant range" could be used to great advantage in rehearsing planned operations and evaluating alternative courses of action, using the same command, control, communication, and intelligence equipment that will be used in actual combat. Key instrumentation, data link transmission, and distributed network issues have been identified.



By developing planning aids for the air traffic controllers responsible for landing aircraft, Lincoln Laboratory is helping the FAA to enhance air safety, reduce controller workload, and increase airport capacity. The Center/Terminal Automation System (CTAS) helps coordinate activities between arrival controllers located at en route centers and final approach controllers located at airport radar control facilities.

In January 1996, a Lincoln Laboratory CTAS field prototype became operational linking the new Denver Airport with the Denver En route Center in Longmont, Colorado. In addition to providing a well-structured and fully tested and documented software system, Lincoln Laboratory developed a complete suite of interfaces to existing FAA equipment to extract the necessary surveillance, flight plan, and weather data and to enable the automation software to access existing radar display terminals. Lincoln Laboratory also designed and built a comprehensive test environment for the automation logic. This realistic test equipment allowed FAA controllers to evaluate the automation logic under simulated operational conditions and supported rigorous operational testing.

The system at Denver has been enthusiastically received by controllers because it provides them greater awareness of traffic flows, giving them advance warnings of situations that may cause problems and allowing them to develop more efficient traffic management plans to reduce delays and increase safety.


The Mode S radar beacon system was developed, prototyped, and tested at Lincoln Laboratory for the FAA and is now being deployed at 144 sites nationwide. Mode S has an integral air-ground digital data link, and Lincoln Laboratory has developed data link applications for use by air transport and general aviation aircraft. The Traffic Information Service provides pilots with the location of nearby aircraft by uplinking surveillance information gathered by the Mode S radar. The Text Weather Service and Graphical Weather Service provide pilots with weather text and graphics uplinked via Mode S from ground-based weather sources, including weather radars. These data link applications have been implemented in an operational Mode S radar at Dulles International Airport for a field evaluation in preparation for a national implementation. General aviation groups such as the Aircraft Owners and Pilots Association have equipped their aircraft with data link avionics built by industry in collaboration with Lincoln Laboratory and are participating in a 1-year field evaluation. Several airlines are participating in a demonstration of text data link products derived from the Terminal Doppler Weather Radar and transmitted on the airlinesí own VHF data link, the Aircraft Communication Addressing and Reporting System.


A new Laboratory-developed technology for surveillance of airborne and surface aircraft is the broadcast of Global Positioning System (GPS) determined position, and other key flight data, via the Mode S data link to all listeners. This technique, termed GPS-Squitter, was first demonstrated for surface surveillance at Logan Airport in Boston in February 1994. A successful evaluation was then conducted for air surveillance in December 1994 in the Gulf of Mexico for helicopters servicing oil platforms. In 1996, GPS-Squitter was demonstrated for the air-to-air Cockpit Display of Traffic Information. It has been adopted for use by the Traffic Alert and Collision Avoidance System now carried by all airliners in U.S. airspace. GPS-Squitter is expected to become the accepted technology for improved cooperative surveillance in U.S. airspace.


The last FAA airport surveillance radar, ASR-9, uses computer processing technology dating to the early 1980s. Its obsolete hardware and software limitations prohibit the installation of needed improvements and upgrades. In 1993, Lincoln Laboratory initiated a program to design and program a single plug-in card (the ASR-9 Processor Augmentation Card, or 9-PAC) to replace the radarís data processor. This card offers ten times the processing power and improved software maintainability and upgradability. In addition, the new 9-PAC data processing algorithms improve aircraft tracking over roads and through heavy radar clutter and reject false beacon targets. The software automatically adapts its processing parameters to the radar environment, eliminating the need for intensive manual site adaptation procedures. Following intensive FAA testing in 1995, prototype 9-PAC boards are now operating in commissioned FAA air traffic control radars located at airports in Los Angeles, Dallas-Fort Worth, Oakland, and Honolulu.


A continuing multi-year program to improve the FAAís capability to detect and predict weather conditions impacting aviation utilizes test bed radars and advanced signal and data processing. The system provides wind shear information automatically to air traffic controllers, pilots, and air traffic control automation systems. Lincoln Laboratory is supporting the refinement of the wind shear detection and storm motion algorithms utilized in the Laboratory-designed Terminal Doppler Weather Radar now deployed at major airports. When combined with suitable signal processing techniques to estimate low-altitude Doppler velocity, these algorithms enable the FAAís Airport Surveillance Radar to be equipped with a Weather Systems Processor, providing similar wind shear warning and storm motion capability at the nationís medium-density airports.

A Laboratory-developed Integrated Terminal Weather System (ITWS) is under test to determine its ability to delineate hazardous airspace conditions and to provide short-term forecasts of significance to aviation. The Laboratory is developing the ITWS algorithms that will utilize data from FAA and National Weather Service systems such as terminal sensors, lightning mappers, and numerical forecast models. The Laboratory is continuing to operate ITWS test beds in Memphis, Orlando, and Dallas-Fort Worth to increase the ITWS data base and test enhanced products as they become available. An additional experimental site in San Francisco supports the development of ceiling and visibility products.



Lincoln Laboratory has been developing high-performance semiconductor lasers emitting in the mid-infrared spectrum between 2 and 5 um. Such lasers are potentially important for detecting trace gas concentrations (as low as 1 part per billion) and for IR countermeasures to protect aircraft against heat-seeking missiles. The lasers are fabricated from heterostructures and quantum wells containing antimony-based III-V compounds grown by molecular beam epitaxy on either GaSb or InAs substrates. Lincoln Laboratory was the first to demonstrate high-power diode lasers emitting approximately 1 W at 2 um in continuous-wave (cw) operation at room temperature. (Previously, the maximum cw power had been approximately 1 mW.) At longer wavelengths reduced operating temperatures are required because of Auger recombination, a parasitic loss mechanism. At 3.5 um, quantum-well diode lasers have operated cw up to -98deg.C, with cw power of 430 mW at -193deg.C (liquid nitrogen temperature). At 4 um, double-heterostructure lasers, pumped optically using 0.94-um high-power diode lasers as pump sources, have operated with a peak power of 2.7 W and average power of 350 mW at -193deg.C. Work is continuing in an attempt to increase the operating temperature by optimizing the laser structures and epitaxial growth conditions. In parallel with the laser development, compact prototype subsystems have been built for field demonstrations.


Significant milestones have been reached in the Laboratory's 193 nm lithography program. In a major effort to refine and commercialize the 193-nm technology pioneered at Lincoln Laboratory, the U.S. semiconductor industry has adopted the goal of using 193 nm for volume production of 0.18-um feature-size integrated circuits in the 2001 time frame. The Laboratory's unique large-field 193-nm lithography tool, capable of patterning features below 0.2 um, was used for all 11 masking levels in a low-power, high-performance, silicon-on-insulator CMOS process. First-pass success was achieved on both test devices and simple circuits, with 0.2-um-gate-length inverter delays of 29 ps at 3 V and 57 ps at 1 V. The latter represents a ten times reduction in power consumption and a simultaneous two times improvement in speed when compared with conventional 0.5-um technology.

W. E. Morrow, Jr.

MIT Reports to the President 1995-96