Lincoln Laboratory is a federally funded research and development center (FFRDC) laboratory operated by MIT for the Department of Defense (DoD). Lincoln Laboratory carries out research and development in advanced electronics for sensors, signal processing, and communications. During the past year, the services and agencies of the DoD supplied approximately 91 percent of the laboratory's budgetary support. Non-DoD activity includes work for the Federal Aviation Administration (FAA), the National Aeronautics and Space Administration (NASA), and the National Oceanographic and Atmospheric Agency (NOAA). Lincoln Laboratory also carries out noncompetitive research with industry under approved cooperative research and development agreements. For the federal fiscal year 2003, Lincoln Laboratory received $522 million that supported the efforts of 1,300 professional technical staff and 1,100 support personnel.
The following administrative changes occurred at the Laboratory Steering Committee level. Andrew Gerber was named head of the Sensor Systems Division, formerly the Sensor Technology Division. Anthony Sharon became the executive officer and secretary of the Steering Committee, replacing Roger W. Sudbury who joined the director's office staff. Buckner Creel stepped down from the Steering Committee to become the laboratory's special projects officer.
Activity at the laboratory focuses on DoD tasks in air defense, missile defense, tactical systems technology, space control, biological-chemical defense, communications and information technology, and advanced electronic technology. Non-DoD tasks are predominately related to air traffic control technology for the FAA. Unclassified summaries of several accomplishments during the past year are presented below.
Advanced Air Defense Technologies
Multiple air defense applications demand large aperture radars and advanced missile systems to counter threats. Large aperture radars stress technology by requiring large dynamic range, multiple electronic beams formed by using high performance digital signal processors, and on-board jamming resistance. We are working with the Navy to demonstrate a digital array radar that samples the radio frequency (RF) signals close to the antenna phase. Once we have the capability to digitize signals, we will implement an open system architecture to easily transfer algorithms to new systems as computing technology evolves. We designed and fabricated a 16-channel digital beam forming test bed in support of risk reduction for an S-band solid-state phased array radar development.
A global positioning system (GPS) is vulnerable to jamming because the long ranges between satellite GPS transmitters allows jamming to deny reception to airborne systems. Lincoln Laboratory is working with industry to demonstrate an airborne phased array to serve as a relay of GPS coordinates. This approach would permit suppression of jamming interference while maintaining enough signal strength. Last year we demonstrated a seven-element phased array in an anechoic chamber and then demonstrated the array's capabilities in a field test at the White Sands Missile Range Facility near Socorro, New Mexico. We are working on a number of experiments scheduled for the spring of 2004.
Sensor Array Technology
Accurate and efficient utilization of resources to perform surface surveillance, to improve the identification of air vehicles and to utilize multiple resources simultaneously is a major challenge. Lincoln Laboratory has started the design of a prototype to demonstrate space and air radar transformational array technologies. The prototype should improve the surface surveillance capabilities over current systems by a factor of ten.
Ground-Based Midcourse Defense Program
The National Missile Defense program has been renamed the Ground-Based Midcourse Defense (GMD) program. The goal of the program is to develop and to deploy a ground-based interceptor system that will engage during the midcourse phase of flight. The intent is to defend the United States against a limited ballistic missile attack. Lincoln Laboratory is supporting the GMD program at both the system and element levels. System work focuses on evaluating discrimination architectures against postulated and potential threats. Element support emphasizes characterization and assessment by early warning radars, prototype ground-based radars, and exoatmospheric seeker performance.
Over the past several years Lincoln Laboratory has supported the Aegis Program Office in developing a ballistic missile defense capability. The program focuses in part on the challenges associated with detection, discrimination, and handover of track data. The laboratory has developed a midcourse discrimination architecture that includes algorithms for synthetic wideband radar measurements and algorithms to improve two color infrared focal-plane performances.
Airborne Seeker Test Bed
The capabilities of modern air defense missile systems have been severely challenged by the advent of low-flying vehicles and modern electronic countermeasures. The Airborne Seeker Test Bed (ASTB) is an instrumentation platform developed by Lincoln Laboratory to investigate these challenges and to identify appropriate seeker architectures and signal processing algorithms. The ASTB, which operates in a Gulfstream II aircraft, provides high fidelity RF and IR reference instrumentation sensors. These sensors are used in parallel with special-purpose wing-pod payloads carrying seekers or sensors being tested. In 2003, ASTB activities include four test campaigns, sensor development, and infrastructure upgrades.
Undersea Warfare Systems
Lincoln Laboratory continues to provide algorithms directly to the submarine fleet for surveillance tasks. The most recent successful algorithm automated the detection and classification of diesel-class submarines by using the Navy's passive sonar array.
Foliage Penetration Technologies
During the past year, Lincoln Laboratory has successfully demonstrated algorithms to fully exploit polarimetric information to dramatically improve the ability to see targets under trees. These techniques are based on change detection among synthetic aperture radar (SAR) images. These technologies have been transitioned to the Air Force as part of a Foliage Penetration Advanced Technology Demonstration.
Lincoln Laboratory Analysis of Columbia Fragment
In the days following the Columbia Shuttle disaster, a search by Air Force Space Command analysts and Space Surveillance Network (SSN) radar operators yielded data on an object that appeared to separate from the Columbia on day two (January 17) of its mission and reenter the atmosphere on day four (January 19). At the request of Professor Sheila Widnall of the Columbia Accident Investigation Board, Lincoln Laboratory initiated an effort to investigate the observed motion behavior of this unidentified object and help determine its identity. The laboratory generated a hypothesis of an end-to-end scenario for a candidate object that is consistent with the very limited metric and radar signature data collected on the object. Working in coordination with the DoD Columbia Investigation Support Team, Lincoln Laboratory provided new insight into the Columbia Flight Day Two object that was incorporated into the Accident Review Board's final report.
Lincoln Near-Earth Asteroid Research
The Lincoln Near-Earth Asteroid Research (LINEAR) project continues to operate a wide-area asteroid search program employing an advanced electro-optics search. The LINEAR system has generated over 10 million observations during the period of March 1998 and July 2003. These observations account for 55 percent of all observations in the Minor Planet Center (MPC) archives and 65 percent of all near-Earth asteroid discoveries since 1998. LINEAR has discovered 1,239 near-Earth asteroids (2,370 total known), 110 comets, and more than 180,000 main belt asteroids.
In September 2002, NASA formed a special Science Definition Team to perform a nine-month study to address the question of feasibility of searching for smaller asteroids. Dr. Grant Stokes from Lincoln Laboratory served as chair. The final report, in production, is expected to receive significant attention in the community and to be widely distributed by NASA.
Remote Real-Time Radar Imaging of Satellites
Lincoln Laboratory successfully demonstrated remote real-time inverse synthetic aperture radar imaging of satellites. The raw data were processed at Lincoln Laboratory to form focused range-Doppler images of the target satellite, which were displayed locally or at a remote location. The combination of processing, wide-band network communication, and data fusion algorithms demonstrated improved space situational awareness and will enable development of future networked sensor architectures with enhanced sensitivity, discrimination, and target identification capabilities.
First Demonstration of an Integrated Solid-State Laser Radar Detector Array in an Airborne Platform
Lincoln Laboratory has successfully integrated and tested novel single-photon-sensitive detector array technologies for three-dimensional (3-D) laser radars in two different airborne platforms. The detector technology incorporated arrays of avalanche photodiodes bonded to commensurate arrays of complementary metal oxide semiconductor (CMOS) timing circuitry. One of the laser radar systems was developed to image objects under trees or other obscurants and was flown on a helicopter. The other system was developed to collect 3-D ground maps over wide areas and was flown on a Sabreliner jet. The advantages of the integrated solid-state detector technology are that the extreme sensitivity of the devices enables the laser radars to operate with low-power lasers. The arrays also significantly reduce the scanning requirements for imaging large areas.
High Energy Laser Beam Control Technology
As a result of renewed interest in tactical high-energy lasers, Lincoln Laboratory is expanding its efforts in high-energy laser (HEL) beam control technology. Research programs are focusing on several technologies critical to the success of tactical HEL systems and will explore innovative techniques for adaptive-optics compensation and tracking. A beam-control laboratory has been developed to investigate the effects of thermal blooming, a phenomena resulting from laser heating of the atmosphere. Recent results from this laboratory have focused on techniques to reduce these effects by optimizing the focus of the HEL beam.
Biological Defense Systems
Lincoln Laboratory is engaged in several activities that focus on the design, development, and implementation of systems to protect against biological-agent attack. We have been specifically addressing how facilities can use existing and emerging technologies to provide timely response in the event of an attack. These efforts will lead directly to recommendations for systems and, in some cases, to implementation of prototype protective systems.
The accurate detection of biological warfare agents is challenging on two fronts: rapid detection is required to warn and protect civilian populations and military units, screen food and water, and diagnose severe acute medical conditions; and the high background of benign biological particles in the environment can compromise detection accuracy. Accurate, rapid detection requires a fast identifier. For the identifier, Lincoln Laboratory researchers have developed several so-called sensors that use genetically engineered mouse B cells, or white blood cells, that rapidly bind to and then emit photons in less than a second after the binding event occurs. A number of assays have been developed using this technology for the rapid screening of fruits and vegetables for most of the top biowarfare agents as well as the rapid diagnosis of Chlamydia in urine and inhalation anthrax in nasal secretions. Most recently, a combined alarm/identify bio-aerosol prototype sensor has been constructed. Efforts are continuing to expand and refine the food and medical assays, and field tests of the prototype sensor will begin soon.
Optical Communications Technology
Lincoln Laboratory is pioneering the development of high speed, interplanetary laser communications links. Recently, a joint NASA-JPL-MIT Lincoln Laboratory Mars-to-Earth laser communications study investigated the technologies that would enable a data link with an order of magnitude improvement over existing interplanetary radio frequency links. The link would employ the ingenious use of photon-counting detector arrays and high-alphabet, signal encoding. While modern fiber optical communications systems may require from 10 to 100 photons-per-bit at a conventional photodetector, the Mars link theoretically would operate at multiple bits-per-photon at a photon counting detector. The receiver would use Lincoln Laboratory-developed, photon-counting detector arrays to overcome atmospheric turbulence limitations and provide data rates from 10 to 100 megabits per second. Currently, a plan is being developed for the laboratory to build a laser communications payload aboard a NASA Mars 2009 mission spacecraft.
Military Satellite Communications
The laboratory has made contributions to DoD's Transformational Communications (TC) initiative to remove bandwidth and capacity as operational constraints. Lincoln Laboratory's advanced optical networking technologies and protected satellite-communications technologies have been incorporated into a concept that includes a high data rate optically-based space backbone complemented by 'edge' service protected wideband satellites. This system filters out sensor information in the gigabits-per-second class while extending protected (anti-jam and low-probability-of-detection) services to wideband (Ethernet-class) users and permitting small mobile terminals to be accommodated. The alternative communications paths provided by the space backbone significantly increase the survivability of the nation's critical information infrastructure. Architectural options have been identified and performance assessments have been conducted. Higher capacity, more bandwidth efficient waveforms have been investigated and system-level proof-of-concept test beds (optical, networking, and RF) have been initiated.
There is a growing acceptance of the importance of information at all military echelons to ensure the success of any operation. To provide this information, an integrated global communication system is required to provide connectivity between the sustaining base and the deployed forces. Satellites are expected to provide range- and terrain-independent communications, particularly when force elements are beyond the range of line-of-sight limited radios. A particularly challenging problem is to provide satellite communications to vehicles on the move. The problem arises from vehicle motion, which results in expensive antenna pointing solutions, and passing objects such as trees or buildings, which block the signal. This year, Lincoln Laboratory continued its communications on the move (COTM) effort by developing a relatively low-cost, full-sky capable, accurate, motion-canceling antenna positioner. The effort included a compact multi-band, multi-polarization antenna feed. Lincoln is currently developing an advanced waveform that will allow many small COTM terminals to communicate.
Speaker and Language Recognition
Lincoln Laboratory has made significant progress in improving the accuracy of automatic speaker and language recognition systems. Conventional speaker recognition systems operate by examining short-term spectral information from the speech signal. New laboratory research exploits higher levels of information in the speech signal that characterize a speaker's style. These new levels of information include prosodics (pitch, energy and pauses), idiosyncratic pronunciations, particular word usage (idiolect) and conversational dialog patterns (taciturn or dominating). Applications can range from assisting in indexing and searching audio archives, such as recorded meeting or news broadcasts, to aiding in voice comparisons for forensic applications. By combining these new levels of information with short-term spectral features, Lincoln Laboratory has produced outstanding performance in annual evaluations conducted by the National Institute of Standards and Technology. Over the past two years Lincoln Laboratory has reduced equal error rates (where probability of miss equals probability of false alarm) from 2.2 percent in 2002 to a new low of 1.0 percent in 2003.
CCD Imagers for Los Alamos National Laboratory
A high-speed imager has been developed for Dual Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory (LANL). The imager will be used on the second axis of DARHT in experiments to collect data for the Nuclear Stockpile Stewardship Project. The second axis is unique in that it will provide up to four X-ray pulses in approximately two microseconds. Previous radiographic systems were able to produce at most two pulses. Sensitive, high-speed detection of the light signal is enabled by the scintillator and custom optics developed at LANL in combination with the electronically shuttered, back-illuminated imager from Lincoln Laboratory. The multiple X-ray pulses and consequent scintillation patterns will be used to image density fluctuations of imploding or exploding objects. The custom charge-coupled-device (CCD) imager developed by Lincoln Laboratory can capture and locally store up to four sequential images with the time between images being less than 650 nanoseconds. Five CCD imagers that make up one camera system along with a prototype CCD imager were provided to LANL in December 2002, meeting a critical milestone for the DARHT project. Lincoln Laboratory participated in a dedication ceremony of the DARHT facility on 22 April 2003.
Laser-Induced Breakdown Spectroscopy (LIBS) for Bio-Aerosol Discrimination
Laser-induced fluorescence techniques are currently utilized in bio-aerosol detectors, such as the Bio-Aerosol Warning Sensor (BAWS) that was developed at Lincoln Laboratory and recently transferred to industry for production. LIBS uses focused laser beams on a target specimen to create a plasma; the elemental composition of the target material can be determined from the atomic spectrum of the emitted radiation. Lincoln Laboratory has recently performed LIBS measurements on a variety of biological and non-biological samples and shown that LIBS can differentiate among classes of biological materials such as bacterial spores, mold spores, pollens, and growth media. These signatures can be measured down to targets as small as single particles. Additionally, it has been shown that relatively few elements are needed in order to provide adequate information for this discrimination among classes. This work is currently being extended to a test bed to characterize the performance of a bio-aerosol detector that simultaneously utilizes LIBS and fluorescence.
Near Infrared Geiger-Mode Avalanche Photodiodes
Avalanche photodiodes (APDs), operating in the Geiger mode, have been developed for efficient detection of single photons in the near infrared. These solid-state photomultipliers produce large signals capable of directly switching a logic gate upon detection of single photon. These devices are extremely fast, providing time resolution for the incident photon to about 100 picoseconds. Because the devices are fabricated with standard integrated circuit techniques, large arrays have been built. This technology rests on the ability to grow low defect density epitaxial indium gallium arsenide phosphide/indium phosphide (InGaAsP/InP) alloys with tightly controlled composition and doping profiles. This material system allows selection of the operating wavelength to be optimized around 106-nm, a wavelength at which efficient short-pulse neodymium:yttrium aluminum garnet (Nd:AG) lasers are readily available. Single-photon detection probabilities of 60 percent have been achieved at 106-nm in structures engineered to reduce undesired dark counts. These arrays have been bump bonded to fast complementary metal oxide semiconductor (CMOS) chips, which are silicon integrated circuits that put a timing circuit behind every APD pixel in order to generate a 3-D image from a single short-pulse laser illuminator.
Slab-Coupled Optical Waveguide Laser Arrays
Efficiently generating high-power, single-mode laser light from diode laser sources has been a long-standing problem. In general, single-mode semiconductor lasers have been limited to tens of milliwatts, with heroic efforts achieving hundreds of milliwatts. As was reported last year, a new waveguide structure had been developed at Lincoln Laboratory that allows single transverse mode lasers with output powers of a few watts to be built. The slab-coupled optical waveguide laser (SCOWL) has demonstrated 1.8 watts continuous wave at 980 nm in single-mode. Butt coupling the fiber to the laser results in 86 percent coupling efficiency with routinely achieved micron alignment tolerances. Researchers have continued to advance the materials, design, and fabrication of these devices and are now able to build dense arrays of these single mode lasers. Recently, a laser array was operated with a combination of ~1 watt, 975-nm-wavelength lasers on 100-micrometer centers, producing a record linear power density of 9.8 watts/mm in an array of 10 devices. These laser arrays can subsequently be wavelength-beam combined to put all this power (except for parasitic optical losses) into an output beam that maintains the beam quality of the individual lasers. Scaling to multi-100-watt beams appears practical.
Lincoln Laboratory is working with the FAA and NASA to enhance air safety, reduce controller workload, and increase airport capacity by developing planning aids for air traffic controllers. A NASA-sponsored effort is underway to assess techniques for automating the basic separation functions now performed manually by air traffic controllers, thus freeing them to perform more efficient tactical and strategic airspace management.
The New York Port Authority, through a cooperative research and development agreement, has sponsored the development of a decision support tool to assist air traffic controllers with the management of traffic in the busy New York terminal airspace during convective weather events. The Route Availability Planning Tool (RAPT) uses the convective weather forecast of the Corridor Integrated Weather System and modeled aircraft trajectories to determine when specific departure routes will be blocked by severe weather. During its first year of operation, the prototype RAPT has permitted substantial delay reduction in the New York area.
Surveillance Technology Improvements
The FAA is sponsoring the laboratory to assist with the development of time-difference multilateration, an airport surface surveillance technique. This technique will form the basis for improved management of surface traffic and the prevent runway incursions. The FAA has adopted this technology for use at the nation's busiest airports.
The FAA is sponsoring the laboratory to assist with the design of modifications to the Airport Surveillance Radar (ASR-9) and Mode Select (Mode-S) Beacon Radar systems currently in use at the nation's busiest airports. The modifications provide a means for retaining the capabilities of these systems to at least 2025. In this effort, the laboratory is applying the principles of the Radar Open Systems Architecture (ROSA) that were developed for the modernization of instrumentation radars for the DoD. The end objective is to integrate the currently separate systems into a single system capable of both tracking aircraft and detecting hazardous weather. A proof of design of the integrated processing has been prototyped and is being demonstrated to the FAA. This year the proof of design system will be integrated with the front end of an FAA radar at the laboratory and used to support capability demonstrations to industry.
Aviation Weather Surveillance and Forecasting
The Laboratory is working in three broad areas to improve the capability of the US National Airspace System to cope with adverse weather: modernizing the processing systems utilized in FAA Doppler weather radar networks and enhancing their processing algorithms; developing automated forecast algorithms to reduce the impact of thunderstorms and visibility constraints at large US airports; and developing and demonstrating weather systems that integrate sensor data to provide operational guidance to air traffic controllers.
An enhancement to the Terminal Doppler Weather Radar will exploit contemporary digital processing technology to make the radar more easily supportable, and to extend the instrumented range. In addition the enhancement will improve ground clutter suppression and eliminate data quality degradations caused by range and/or Doppler ambiguous weather returns. The laboratory is developing new algorithms for the NEXRAD Open Radar Product Generator to enhance the utility of this radar's products for use by FAA systems. New products resulting from this work include high-resolution depictions of vertically integrated liquid water and echo tops.
The laboratory has made significant progress in automated thunderstorm forecasting and is demonstrating this operationally at key terminal and en route Air Traffic Control facilities. The time horizon for the forecasts has been extended to two hours and their accuracy improved through identification of storm type (e.g., line storm versus air mass) and through detection of growth and decay trends. The laboratory's automated forecast of ceiling and visibility changes at San Francisco is in its third year of operational demonstration and will be transferred this year to the National Weather Service for long-term operations.
More information about Lincoln Laboratory can be found online at http://www.ll.mit.edu/.