2009–2010 Technical Seminar Series

Technical Seminar Series booklet coverMembers of the technical staff at MIT Lincoln Laboratory are pleased to present these technical seminars to interested college and university groups. Costs related to the staff members' visits for these seminars will be assumed by the Laboratory.

To arrange a technical seminar, please contact:

College Recruiting Program Administrator
Human Resources Department
MIT Lincoln Laboratory
244 Wood Street
Lexington, Massachusetts 02420-9108
781-981-2465
email: collegerecr@ll.mit.edu

and provide the following information:

  • A rank-ordered list of requested seminars
  • Preferred date/time options
  • A description of the target audience

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Index of 2009–2010 Seminars

Ballistic Missile Defense

Air Traffic Control

Homeland Protection

Radar and Signal Processing

Optical Propagation and Technology

Solid State Devices, Materials, and Processes

Communications and Information Systems

Space Control Technology

Data Mining, Decision Support, and Data Fusion

Seminar Abstracts

Ballistic Missile Defense

A Comparison of Two Methods for Computing
Track-to-Track Assignment Probabilities

Dr. Matthew A. Horsley1
MIT Lincoln Laboratory

In an integrated Ballistic Missile Defense System (BMDS), a network of spatially and spectrally diverse sensors may be used to detect, track, and discriminate objects within a threat complex. Potential benefits of sharing data among sensors—such as improved tracking, discrimination, and interceptor performance—will be fully realized only if sensor tracks are correctly correlated. To ensure the robust and reliable handover of information from one sensor to another, confidence values for each assignment must be estimated. This is equivalent to computing the posterior probability of each assignment given the observed data by each sensor, which is a computationally challenging problem due to the large number of feasible assignments.

This seminar considers two algorithms for estimating confidence values. The first method uses Murty’s algorithm to generate an estimate of the posterior distribution using the k most likely solutions. The second method employs a Markov Chain Monte Carlo (MCMC) technique to efficiently sample assignments from the entire problem space in proportion to their posterior probabilities. This seminar demonstrates that the MCMC approach outperforms the first method in terms of the accuracy of the probability estimate, with far fewer computational resources required to perform the calculation. Moreover, its performance is characterized through analytically derived error bounds on the estimated probabilities. The seminar also introduces novel extensions of the MCMC technique and examines the performance of all the resulting methods when applied to track-to-track correlation problems encountered in certain ballistic missile defense applications.

1PhD, Physics, Yale University

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Air Traffic Control

Aircraft Separation Standards and Radar Performance
in the National Airspace System

Dr. Steven D. Thompson1
MIT Lincoln Laboratory

To maintain safety in the Air Traffic Control system, the Federal Aviation Administration (FAA) establishes the minimum distances between which air traffic controllers must separate aircraft. These distances directly impact the capacity and overall system delay of the Air Traffic Control system and are based, in part, on the performance of the surveillance systems used in tracking aircraft. Today's modern air traffic control radar systems rely on both "primary" reflections from the aircraft itself and onboard devices designed to electronically reply to a radar sensor's "interrogation" signal. Aircraft tracking based on the replies from an aircraft's transponder is known as "secondary" surveillance and is the dominant form of tracking and providing separation in the air traffic control system today.

The minimum separation between aircraft using radar surveillance has been three nautical miles for any sensor and required that both aircraft being separated be tracked by the same sensor and be within 40 nautical miles of that sensor. If these requirements are not met, the aircraft must be separated by five nautical miles or more with a corresponding impact on airspace capacity.

This presentation reviews the separation standards and their origins and discusses the different surveillance environments in use today in the National Airspace System. The error sources and characteristics of the sensors currently used to track aircraft are reviewed and discussed, and a metric is derived to facilitate comparison of the performance of various sensor designs used in different surveillance environments. It was found that modern "monopulse" radar sensors offer a significant performance advantage over older designs and the potential for expanded use of three-mile separation, both in the single-sensor environment and in mosaic environments involving the use of multiple sensors. As a result of this analysis, the FAA has recently extended the use of three-mile separation for aircraft within 60 nautical miles of monopulse sensors. A practical application of the results of this analysis is presented in a case study for three-mile separation within Boston's Air Route Traffic Control Center.

1PhD, Nuclear Engineering, Georgia Institute of Technology

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Integrating Unmanned Aerial Vehicles Safely
into the National Airspace System

Dr. Mykel J. Kochenderfer1
MIT Lincoln Laboratory

Unmanned aerial vehicles (UAVs) such as the Air Force's Global Hawk and Predator are increasingly employed by the military in roles that require sharing airspace with civilian aircraft. Many civil applications of UAVs have also been proposed for tasks that include border patrols, highway and agricultural observation, and cargo transport. Because of the pressure for widespread access for UAVs and the risk of collision with passenger aircraft, the United States is rapidly facing serious safety concerns.

This seminar provides an overview of the safety issues of UAVs sharing airspace with passenger airplanes, including methods for evaluating and mitigating collision risk. The presentation will describe an initiative at MIT Lincoln Laboratory to assess the safety of one particular application, the Traffic Alert and Collision Avoidance System (TCAS), on the Global Hawk UAV. TCAS is in use on all large passenger-carrying aircraft as an independent, last-resort collision-avoidance system. TCAS uses a set of sensors and algorithms to detect potential mid-air collisions, alert the flight crew, and provide guidance so that they can avoid a collision. Adapting TCAS to Global Hawk, which has unconventional flight characteristics and a pilot who may be thousands of miles away, creates challenges that require a thorough safety analysis before TCAS might be accepted by domestic and international communities.

This seminar describes the overall approach to safety analysis, including the use of fast-time simulation of UAVs and conventional air traffic. Finally, extensions to future applications, such as onboard infrared, visual, or radar detection systems designed to "see and avoid" other aircraft, will be discussed.

1PhD, Informatics, University of Edinburgh

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Multifunction Phased-Array Radar for U.S.
Civil-Sector Surveillance Needs

Dr. Mark E. Weber1 
MIT Lincoln Laboratory

This seminar describes a concept study for possible future utilization of active electronically scanned (AES) radars to provide weather and aircraft surveillance functions in the U.S. airspace. If transmit-receive element costs decrease sufficiently, multifunction AES radars might prove to be a cost-effective alternative to current surveillance radars (WSR-88D, TDWR, ASR, ARSR) since the number of required radars would be reduced and maintenance and logistics infrastructure would be consolidated. A radar configuration that provides terminal-area and long-range aircraft surveillance and weather measurement capability is described, and a radar network design that replicates or exceeds current airspace coverage is presented. Key technology issues are examined, including transmit-receive elements, overlapped subarrays, the digital beamformer, and weather and aircraft postprocessing algorithms. The presentation concludes with a discussion of how such a radar network might integrate with next-generation weather and aircraft surveillance architectures.

1PhD, Physics, Rice University

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Runway Status Lights

Dr. James R. Eggert1 
MIT Lincoln Laboratory

Aviation's single deadliest accident was the result of a runway incursion at Tenerife, Canary Islands, in 1977. Runway incursion accidents and incidents continue to occur, and their reduction has been identified by the National Transportation Safety Board and the Federal Aviation Administration as one of the most important aviation safety challenges.

There are many initiatives underway to prevent or mitigate runway incursions. MIT Lincoln Laboratory has been on the forefront of one of the most promising technological approaches to addressing the runway incursion problem through a system called Runway Status Lights. These lights are located on runways and on taxiway entrances to runways, and indicate to pilots whether the runway is safe to enter or cross, or for departure. The lights are driven automatically by computer processing of surveillance derived from multiple surveillance systems. The Runway Status Lights system is, therefore, the result of the careful integration of surveillance fusion, aircraft behavior identification and prediction, operational safety algorithms, and human-factors analysis needed to create an operational prototype suitable for testing at a major airport.

This seminar will introduce the need for runway incursion prevention, discuss the runway status lights concept, and describe the success of ongoing operational testing at Dallas/Fort Worth International Airport. The seminar will conclude with a description of future initiatives, including deployment to Los Angeles and additional types of lights under development for use at complex airports such as Boston's Logan International and Chicago O'Hare.

1PhD, Physics, Harvard University

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Homeland Protection

Defending Against Biological Terrorism

Dr. Timothy J. Dasey1
MIT Lincoln Laboratory

The intentional use of disease as a weapon has been recorded throughout human history. With modern technology, the potential impact of biological attacks is exceeded by only nuclear weapons. The dramatic advances in the biological sciences in the last few decades, and the expertise accumulated in large state-funded offensive biological weapons programs, have made the process simpler for those who are inclined to pursue such weapons.

The United States is in the midst of an aggressive research and development program to prevent, detect, and mitigate the effects of biological attacks. Research thrusts include rapid detection and characterization of biological agents for surveillance, response, or forensic purposes. Strategies for organizing and deploying medical resources following an attack are being developed and tested. Improved medicines are needed for prophylactic and therapeutic purposes. Information fusion and data mining techniques are needed to intelligently process diverse data sets for detection and response to an attack. Modeling and simulation of attacks and remedies are used to develop system requirements and designs and to test defensive implementations. Extensive environmental and clinical measurements are needed to understand the performance of technologies and for proper parameterization of simulations.

This presentation will frame the problem by describing the important characteristics of biological weapons, discussing the technical challenges in defending against these weapons, and providing examples of the technologies and systems being developed at MIT Lincoln Laboratory to address the problem of biological weapons. The wide breadth of research disciplines in this field will be highlighted.

1PhD, Biomedical Engineering, Rutgers University

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Disease Modeling to Assess Outbreak Detection and Response

Dr. Diane C. Jamrog1 
MIT Lincoln Laboratory

Bioterrorism is a serious threat that has become widely recognized since the anthrax mailings of 2001. In response, one national research activity has been the development of biosensors and networks thereof. A driving factor behind biosensor development is the potential to provide early detection of a biological attack, thereby enabling timely treatment. This presentation introduces a disease progression and treatment model to quantify the potential benefit of early detection. To date, the model has been used to assess responses to inhalation anthrax and smallpox outbreaks.

1PhD, Computation and Applied Mathematics, Rice University

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Disaster Management Innovation Testbed

Dr. Andy Vidan1
MIT Lincoln Laboratory

The Disaster Management Innovation Testbed (DMIT) program at MIT Lincoln Laboratory aims to develop technical solutions to assist federal, state, and local government agencies to respond to and manage large-scale disasters. As an example, firefighters are typically hampered by a lack of real-time situational awareness when making critical decisions in response to rapidly changing conditions and life-threatening situations. The frequency of wildfires in California allows ample opportunity to test and evaluate new technical solutions for wildfire suppression. In collaboration with the California Department of Forestry and Fire Protection (CAL FIRE) and the Riverside County Fire Department, the program began with a reconstruction and analysis of the 2007 Harris Fire. The Harris Fire was one of four major fires in San Diego County that started on the same day, burning 400,000 acres, destroying over 1400 homes and commercial structures, and causing the evacuation of more than 500,000 people—the largest evacuation in California's history. Based on the situational awareness capability gaps that were identified through the Harris Fire analysis, a net-centric service-oriented architecture is being developed, in conjunction with sensors, communications, and visualization and collaboration technologies, to collect and distribute information to responders and decision makers. The system will be available as a testbed for technology and operation assessments and will also be used in upcoming wildfire management efforts.

1PhD, Physics, Harvard University

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Radar and Signal Processing

Synthetic Aperture Radar

Dr. Gerald R. Benitz1 
MIT Lincoln Laboratory

MIT Lincoln Laboratory is investigating the application of phased-array technology to improve the state of the art in radar surveillance. Synthetic aperture radar (SAR) imaging is one mode that can benefit from a multiple-phase-center antenna. The potential benefits are protection against interference, improved area rate and resolution, and multiple simultaneous modes of operation.

This presentation begins with an overview of SAR, giving the basics of resolution, collection modes, and image formation. Several imaging examples are provided. Results from the Lincoln Multimission ISR Testbed (LiMIT) X-band airborne radar are presented. LiMIT employs an 8-channel phased-array antenna and records 180 MHz bandwidth from each channel simultaneously. One result employs adaptive processing to reject wideband interference, demonstrating recovery of a corrupted SAR image. Another result employs multiple simultaneous beams to increase the area of the image beyond the conventional limitation due to the pulse repetition frequency. Areas that are Doppler ambiguous can be disambiguated by using the phased-array antenna.

1PhD, Electrical Engineering, University of Wisconsin–Madison

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GPS Space-Time Adaptive Array Processor Test Results

Dr. Gary F. Hatke1 
MIT Lincoln Laboratory

Global Positioning System (GPS) jamming has been acknowledged as a severe threat to military GPS usage during combat, with the number of systems linked to GPS growing daily. It is clear that an effective system for mitigating GPS interference (intentional or unintentional) is needed on some high-value assets. Spatial nulling has been proposed as an effective method for combating GPS jamming, and, in fact, there are available GPS processing units that can provide spatial nulling capabilities when coupled with a 7-element antenna array. For stressing interference environments, however, these spatial-only techniques will have difficulty providing adequate antijam (A/J) protection for GPS operations. For this reason, space-time adaptive (STAP) beamforming processors have been proposed for GPS A/J.

This talk will introduce the techniques involved in developing an effective STAP beamformer for GPS. Specifically, the design and test performance of one such STAP beamformer, the Multipath Adaptive Multi-Beam Array (MAMBA) processor, will be examined. The design of the processor will be reviewed, and then laboratory test results indicating the expected levels of performance achievable with the MAMBA will be presented. These tests include illuminating the antenna array with multiple broadband jamming signals (along with a GPS signal) to determine the increase in signal-to-interference plus noise (SINR) obtained on the GPS signal by MAMBA processing.

1PhD, Electrical Engineering, Princeton University

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Polynomial Rooting Techniques for Adaptive Array Direction Finding

Dr. Gary F. Hatke1 
MIT Lincoln Laboratory

Array processing has many applications in modern communications, radar, and sonar systems. Array processing is used when a signal in space, be it electromagnetic or acoustic, has some spatial coherence properties that can be exploited (such as far-field plane wave properties). The array can be used to sense the orientation of the plane wave, and thus deduce the angular direction to the source. Adaptive array processing is used when there exists an environment of many signals from unknown directions as well as noise with unknown spatial distribution. Under these circumstances, classical Fourier analysis of the spatial correlations from an array data snapshot (the data seen at one instance in time) is insufficient to localize the signal sources.

In estimating the signal directions, most adaptive algorithms require computing an optimization metric over all possible source directions and searching for a maximum. When the array is multidimensional (e.g., planar), this search can become computationally expensive, as the source direction parameters are now also multidimensional. In the special case of one-dimensional (line) arrays, this search procedure can be replaced by solving a polynomial equation, where the roots of the polynomial correspond to estimates of the signal directions. This technique had not been extended to multidimensional arrays because these arrays naturally generated a polynomial in multiple variables, which does not have discrete roots.

This talk introduces a method for generalizing the rooting technique to multidimensional arrays by generating multiple optimization polynomials corresponding to the source estimation problem and finding a set of simultaneous solutions to these equations, which contain source location information. It is shown that the variance of this new class of estimators is equal to that of the search techniques they supplant. In addition, for sources spaced closer than a Rayleigh beamwidth, the resolution properties of the new polynomial algorithms are shown to be better than those of the search technique algorithms.

1PhD, Electrical Engineering, Princeton University

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Multicore Programming in pMatlab® Using Distributed Arrays

Dr. Jeremy Kepner1
MIT Lincoln Laboratory

MATLAB is one of the most commonly used languages for scientific computing, with approximately one million users worldwide. Many of the programs written in MATLAB can benefit from the increased performance offered by multicore processors and parallel computing clusters. The MIT Lincoln Laboratory pMatlab library (http://www.ll.mit.edu/pMatlab) allows high-performance parallel programs to be written quickly by using the distributed arrays programming paradigm. This talk provides an introduction to distributed arrays programming and will describe the best programming practices for using distributed arrays to produce programs that perform well on multicore processors and parallel computing clusters. These practices include understanding the concepts of parallel concurrency vs. parallel data locality, using Amdahl's Law, and using a well-defined design-code-debug-test process for parallel codes.

1PhD, Physics, Princeton University

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Phased-Array Processing and Multiple-Input
Multiple-Output (MIMO) Radars

Dr. Vito F. Mecca1
MIT Lincoln Laboratory

Phased-array radar systems are a more flexible alternative to traditional single-element dish radar systems. Phased arrays operate by applying a different delay—or phase shift—to signals at each element of the array. This process effectively focuses or "steers" the radar's spatial beam response and can be performed on both signal transmission and reception. Continuing advances in computational capacity and hardware design have allowed for complete digital reception of multiple simultaneous beams and subsequent digital processing. However, radar systems capable of simultaneously transmitting multiple different coded waveforms from each transmit element have been unavailable in the past.

This talk introduces a class of multiple-input multiple-output (MIMO) radars that are capable of emitting different signals from each transmitter element. In this introductory-level talk, the fundamental concepts behind phased-array and MIMO radar techniques are explained in terms of real-world scenarios in which MIMO operation would be advantageous. The advanced MIMO techniques developed at MIT Lincoln Laboratory for joint transmit and receive array processing are presented in conjunction with data results.

1PhD, Electrical and Computer Engineering, Duke University

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Detection, Estimation, and Beamforming for Adaptive Sensor Arrays: Algorithms and Performance

Dr. Christ D. Richmond1 
MIT Lincoln Laboratory

A class of adaptive detection and estimation algorithms that exploit the spatial and temporal diversity available from sensor array systems in order to provide robust signal detection and parameter estimation under rather adverse/non-ideal conditions has emerged over the past thirty years. These arrays are often deployed in high multipath environments plagued by limiting interference with unknown statistics. A uniformly most powerful test does not exist for this class of problems. Consequently, optimal detection and estimation rely heavily upon maximum-likelihood (ML) estimates of unknown parameters, including use of data sample covariance matrix. Analyses embracing practicalities such as finite sample support, array response uncertainty/mismatch, nonstationarity, and nonlinear parameter estimation are quintessential for the design of systems requiring precision and robustness, e.g., adaptive radar/sonar systems.

This talk presents an overview analysis of this class of adaptive algorithms, addressing the aforementioned issues of practical interest via the use of random matrix theory. Specifically, the receiver operating characteristics are considered for the detector class that includes the adaptive matched filter, Kelly/Khatri’s generalized likelihood ratio test, Conte/Scharf’s adaptive coherence estimator, and the two-dimensional adaptive sidelobe blanker. The mean-squared error (MSE) performance of the signal parameter estimation class that includes the nonlinear ML estimator and the Capon-minimum variance distortionless response beamformer/estimator often used for frequency and/or angle estimation is considered. The MSE performance is considered below threshold where local error performance bounds, like the Cramér-Rao bound, are not useful. Lastly, some discussion of robust sample covariance-based adaptive beamforming is provided, and new results/insights on the statistical relationships between conventional and adaptive processing are presented.

1PhD, Electrical Engineering, Massachusetts Institute of Technology

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Covariance Matrix Estimation Bounds

Dr. Steven T. Smith1 
MIT Lincoln Laboratory

Algorithms and systems analysis for signal detection, location, and classification all rely on covariance-based methods. But how well understood is the important problem of covariance matrix estimation? What does "accuracy" mean in the context of covariance matrices? This talk addresses these questions at their deepest level, and provides powerful new tools and insights, as well as well as some startling surprises. The covariance matrix problem is framed as an intrinsic estimation problem on the space of positive definite (covariance) matrices, which has the structure of a homogeneous or quotient space, not a vector space—the necessary setting for classical Cramér-Rao bounds. Covariance matrix estimation accuracy bounds are derived from an intrinsic derivation of the Cramér-Rao bound on arbitrary Riemannian manifolds (another new development) and compared to the accuracy achieved by standard methods involving the sample covariance matrix (SCM). Estimator efficiency is discussed from different, novel viewpoints. Remarkably, it is shown that that from an intrinsic perspective, the SCM is a biased and inefficient estimator; the bias corresponds to the SCM's poor estimation quality at low sample support—this contradicts the well-known fact that E[SCM] = R because the linear expectation operator implicitly treats the covariance matrices as points in a real vector space, compared to the intrinsic treatment of positive-definite Hermitian matrices used in this talk. The accuracy bound on unbiased covariance matrix estimators is shown to be about (10/log10)*n/sqrt(K) decibels, where n is the matrix order and K is the sample support. Thus, a connection is established between estimation loss for covariance matrices and the well-known Reed-Mallett-Brennan detection loss in adaptive filtering problems. Simple, closed-form expressions for all results are presented and compared to numerical evidence based on Monte Carlo simulations. The analysis approach developed is directly applicable to many other estimation problems on manifolds encountered in signal processing and elsewhere, such as estimating rotation matrices in computer vision and estimating subspace basis vectors in blind source separation. Finally, several intriguing open questions pertaining to the possibility of improved covariance matrix estimation methods at low sample support are presented.

1 PhD, Mathematics, Harvard University

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Optical Propagation and Technology

Mechanical Systems Engineering of Optical Sensors

Dr. Steven E. Forman1 
MIT Lincoln Laboratory

During the past fifteen years, MIT Lincoln Laboratory has developed several different optical sensor experiments that have flown on airborne and space platforms. These include the Space-Based Visible, Airborne Infrared Imager, and Advanced Land Imager. Each represents a one-of-a-kind sensor fully engineered at MIT Lincoln Laboratory. This talk summarizes several of the mechanical systems engineering areas and issues that occurred throughout design, analysis, fabrication, integration, and testing of these systems. Included are discussions of optical, optomechanical, structural, and thermal engineering; electronic packaging; mechanism design; focal-plane packaging; control-system engineering; materials selection and testing; environmental testing; failure analysis; and computer-aided design and analysis tools.

1PhD, Mechanical Engineering, Harvard University

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Mechanical Design of Laser Communication Terminals
for Space Applications

Joseph J. Scozzafava1
MIT Lincoln Laboratory

Optical technology allows the transmission of high-data-rate communications without the large antenna and power requirements of RF-based communication systems. Optical-based transmission is already widespread using fiber-optic transmission lines, but free-space transmission is an attractive option for a number of applications. One potential application is for transmitting scientific data from space exploration payloads. These payloads would require compact, low-power terminals with the pointing accuracy necessary for maintaining good signal to noise over the long distances from the Moon, Mars, or other orbits back to Earth. MIT Lincoln Laboratory has pioneered the design and development of such terminals. This presentation describes an initial effort to design a terminal for communication from Mars and an ongoing follow-on effort for a lunar-orbiting system.

1BS, Mechanical Engineering, University of Bridgeport

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Solid State Devices, Materials, and Processes

Integrated Optics in Silicon

Dr. Steven J. Spector1, Dr. Michael W. Geis2, and Dr. Theodore M. Lyszczarz3
MIT Lincoln Laboratory

Silicon is an attractive platform for the integration of optical components because of the mature infrastructure dedicated to the fabrication of silicon microelectronic devices. Furthermore, the silicon optical components can be readily integrated with transistors to form complex signal processing systems. At the wavelengths most relevant for optical communication (near 1550 nm), silicon has a high index and low inherent loss, making it an ideal material for compact devices. However, such compact devices also have large scattering loss. In addition, the electro-optic effects are weak in silicon, making it difficult to realize active components. This talk will describe techniques for fabricating low-loss silicon waveguides, low-power silicon PIN diode optical modulators, and high-performance silicon photodiodes using a CMOS IC process. The photodiodes exploit ion implantation damage to create midgap states that enhance sensitivity at the 1550 nm wavelength. These components are being developed for a high-speed optical sampling system that will be used to implement an analog-to-digital converter.

1PhD, Physics, State University of New York–Stony Brook
2PhD, Physics, Rice University
3PhD, Electrical Engineering, Massachusetts Institute of Technology

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Optical Sampling for High-Speed, High-Resolution
Analog-to-Digital Conversion

Dr. Jonathan C. Twichell1 and Dr. Paul W. Juodawlkis2
MIT Lincoln Laboratory

The performance of digital receivers used in modern radar, communication, and surveillance systems is often limited by the performance of the analog-to-digital converter (ADC) used to digitize the received signal. Optically sampled ADCs, which combine optical sampling with electronic quantization, have been demonstrated to extend the performance of electronic ADCs. The primary advantages of using optics to perform the sampling function include (1) the timing jitter of modern mode-locked lasers is more than an order of magnitude smaller than that of electronic sampling circuitry, (2) the low dispersion of optical components allows picosecond sampling pulses to be used to attain wide analog bandwidth, and (3) demultiplexing to arrays of time-interleaved electronic converters can be performed in the optical domain rather than in the electrical domain with no signal bandwidth, nonlinearity, or memory effect constraints.

MIT Lincoln Laboratory's work in this area has focused on the development of a linear sampling technique referred to as phase-encoded optical sampling. The technique uses a dual-output Mach-Zehnder electro-optic modulator as a sampling transducer to achieve both high linearity and 60 dB suppression of laser amplitude noise. Two-tone tests have been used to demonstrate an intermodulation-free dynamic range of 90 dB. We have also used optical sampling to directly downsample frequency-modulated chirp signals having 1 GHz bandwidth on an X-band (10 GHz) microwave carrier. The bandwidth of the technique is extended by optically distributing the post-sampling pulses to an array of time-interleaved electronic quantizers. Using high-extinction 1-to-8 LiNbO3 optical time-division demultiplexers to perform the optical distribution, we have demonstrated a 500 MS/s ADC having 10 effective bits of resolution and a spur-free dynamic range in excess of 70 dB.

1PhD, Nuclear Engineering, University of Wisconsin–Madison
2PhD, Electrical Engineering, Georgia Institute of Technology

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Photon-Counting Receiver Using InP Avalanche Photodiodes

Dr. Simon Verghese1
MIT Lincoln Laboratory

The Mars Laser Communications Demonstration (MLCD) was planned as a NASA-sponsored optical communications experiment from Mars to Earth. Although the satellite will no longer fly in 2009, the required technologies for both the space segment and the ground segment were developed at MIT Lincoln Laboratory and the Jet Propulsion Laboratory. One of the Earth-based receivers was to have four 0.8 m telescopes, each of which could collect light on its own 8 × 8 array of InP-based avalanche photodiodes (APDs). This talk describes the APDs and the associated read-out integrated circuit (IC) that can collect signal photons from Mars. The read-out IC was a full-custom design with shared heritage from LADAR focal-plane arrays. It includes high-speed timing circuits as well as control circuits that operate autonomously behind each pixel.

1PhD, Physics, University of California–Berkeley

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CANARY B-Cell Sensor for Rapid, Sensitive Identification of Pathogens

Dr. James D. Harper1, Dr. Frances E. Nargi2, Dr. Martha S. Petrovick3,
Dr. Todd H. Rider4, and Dr. Eric D. Schwoebel5
MIT Lincoln Laboratory

A novel type of biosensor for rapid pathogen identification is being developed that uses B cells, or white blood cells, as the sensing elements. B cells, which function within the body to detect pathogens, respond in a fashion that is much more rapid, sensitive, and specific than currently available man-made sensors. MIT Lincoln Laboratory's sensor cells are genetically engineered to selectively bind to specific pathogens and then emit photons starting in less than a second after the pathogen is bound. A biochemical signal-amplification mechanism inside the cells provides an enhanced response that enables detection and identification of even a few pathogenic particles. The rapid identification of pathogens that this technology enables should be particularly important for biological-warfare agent detection, medical diagnostics, food safety assurance, environmental monitoring, and other applications.

1PhD, Biochemistry, Massachusetts Institute of Technology
2PhD, Pathobiology, University of Connecticut
3PhD, Cell & Developmental Biology, Harvard Medical School
4PhD, Electrical Engineering, Massachusetts Institute of Technology
5PhD, Molecular & Cell Biology, Baylor College of Medicine

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Three-Dimensional Imaging Using Avalanche Photodiode Arrays

Dr. Brian F. Aull1
MIT Lincoln Laboratory

This presentation discusses the development of arrays of silicon avalanche photodiodes integrated with CMOS timing circuits and the application of these arrays to systems that capture three-dimensional images using laser radar techniques. The avalanche photodiodes are operated in Geiger mode; they are biased above the avalanche breakdown voltage so that the detection of a single photon leads to a discharge that can directly trigger a digital circuit. The CMOS circuits to which the photodiodes are connected contain high-speed counters that measure the times at which the detection events occur. Examples are presented of three-dimensional images from a laser radar system that uses a Geiger-mode avalanche photodiode array.

1PhD, Electrical Engineering, Massachusetts Institute of Technology

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Novel Detector Technology for Challenging
Time-Dependent Imaging Applications

Dr. Bernard B. Kosicki1, Dr. Robert K Reich2, and Dr. James A. Gregory3
MIT Lincoln Laboratory

For most imaging applications, movement in the image is a concern after some exposure time threshold. The Advanced Imaging Technology Group at MIT Lincoln Laboratory has developed three novel imaging devices to handle image motion in different ways. The orthogonal-transfer charge-coupled device (CCD) is designed to image on scenes with continuous translational motions, such as those caused by camera vibration or first-order atmospheric distortions. This device allows exposure times much longer than those allowed by a typical CCD imager, which, to avoid blur, must allow short exposure times. An electronic shutter has been developed for scientific CCDs. MIT Lincoln Laboratory has used this shutter to create an imager that captures, and stores in the pixel, several consecutive frames at 500 ns frame intervals while still having high quantum efficiency and low read noise. As a final example, an imager has been developed to record the time of arrival of the first photon to each pixel with time resolution of 250 ps. This imager utilizes a single-photon-sensitive Geiger-mode avalanche-photodiode (APD) array as the light sensing layer. Each APD is connected to a high-speed digital timing circuit located directly below it. This imager has enabled construction of a flash LADAR system capable of creating three-dimensional images with 5 cm depth resolution.

1PhD, Physics, Harvard University
2PhD, Electrical Engineering, Colorado State University
3PhD, Materials Science/Metallurgy, Massachusetts Institute of Technology

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Three-Dimensional Integration Technology for
Advanced Focal Planes and Integrated Circuits

Dr. Craig L Keast1
MIT Lincoln Laboratory

Over the last five years, MIT Lincoln Laboratory has developed a three-dimensional circuit integration technology that exploits the advantages of silicon-on-insulator technology to enable wafer-level stacking and micrometer-scale electrical interconnection of fully fabricated circuit wafers [1].

Advanced focal-plane arrays have been the first applications to exploit the benefits of this three-dimensional integration technology because the massively parallel information flow present in two-dimensional imaging arrays maps very nicely into a three-dimensional computational structure as information flows from circuit tier to circuit tier in the z-direction. To date, the Laboratory's three-dimensional integration technology has been used to fabricate four different focal planes, including a two-tier 64 × 64 imager with fully parallel per-pixel analog-to-digital (A/D) conversion [2]; a three-tier 640 × 480 imager consisting of an imaging tier, an A/D conversion tier, and a digital signal processing tier; two-tier 1024 × 1024 pixel, four-side-abuttable imaging modules for tiling large mosaic focal planes [3, 4]; and a three-tier Geiger-mode avalanche photodiode (APD) three-dimensional LIDAR array, using a 30-volt avalanche-photodiode tier, a 3.3-volt CMOS tier, and a 1.5-volt CMOS tier [5].

Recently, the three-dimensional integration technology has been made available to the circuit-design research community through Multiproject fabrication runs sponsored by the Defense Advanced Research Projects Agency. Two different Multiproject runs have been completed and included over 60 different circuit designs from 30 different research groups. Three-dimensional circuit concepts explored in these runs included stacked memories, field-programmable gate arrays, and mixed-signal and RF circuits. A third Multiproject run is currently in fabrication.

[1] J.A. Burns, et al., "A Wafer-Scale 3-D Circuit Integration Technology," IEEE Transactions on Electron Devices, vol. 53, no. 10, pp. 2507–2516, October 2006.
[2] J.A. Burns, et al., "Three-dimensional Integrated Circuits for Low Power, High Bandwidth Systems on a Chip," 2001 ISSCC International Solid-State Circuits Conference, Digest of Technical Papers, vol. 44, pp. 268–269, February 2001.
[3] V. Suntharalingam, et al., "Megapixel CMOS Image Sensor Fabricated in Three-Dimensional Integrated Circuit Technology," 2005 ISSCC International Solid-State Circuits Conference, Digest of Technical Papers, vol. 48, pp. 356–357, February 2005.
[4] V. Suntharalingam, et al., "A 4-Side Tileable, Back Illuminated, 3D- Integrated Mpixel CMOS Image Sensor," IEEE 2009 ISSCC International Solid-State Circuits Conference, Digest of Technical Papers, pp. 38–39, February 2009.
[5] B. Aull, et al., "Laser Radar Imager Based on 3D Integration of Geiger-Mode Avalanche Photodiodes with Two SOI Timing Circuit Layers," 2006 ISSCC International Solid-State Circuits Conference, Digest of Technical Papers, vol. 49, pp. 304–305, February 2006.

1PhD, Electrical Engineering, Massachusetts Institute of Technology

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Wireless Sensor Node Design for Data Communications and Geolocation

Dr. Timothy M. Hancock1
MIT Lincoln Laboratory

This presentation discusses the development of the system architecture and component technology for a low-power, long-lifetime custom wireless sensor node system. The system comprises a base station that collects data from and determines the location of a large number of miniature battery-powered sensors. There are key system trade-offs associated with the wakeup techniques employed, which are essential for extending battery life, and the geolocation update rate. The choice of modulation protocol is also a key factor in overall system performance. Sensor miniaturization is enabled through the use of advanced custom RF integrated circuits (RFICs). Several examples of RFIC development will be described, including indirectly modulated fraction-N synthesizers for low-power generation of constant envelope modulated RF waveforms as well as a wakeup receiver design for initiating sensor node communication.

1PhD, Electrical Engineering, University of Michigan

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Laser-Based Remote Detection of Trace Explosives

Dr. Charles M. Wynn1, Dr. Roderick R. Kunz2, and Dr. Mordechai Rothschild3
MIT Lincoln Laboratory

The development of a technique with the ability to detect trace quantities of explosives at a distance is of great interest because the detection of such residues can be an indicator for attempts at concealed assembly or transport of explosive materials and devices. In order to be of practical use, the desired detection technique must be rapid and effective from a distance. A measure of effectiveness includes high sensitivity to traces of the target compounds and the ability to detect a broad range of explosive materials. It also includes low susceptibility to false alarms, a requirement that is often at odds with that of high sensitivity.

Several laser-based remote detection methods have been under investigation, including those relying on Raman scattering and laser-induced breakdown spectroscopy. In this talk, we will describe an alternative approach, which involves ultraviolet photodissociation of condensed-phase material, followed by laser-induced fluorescence of the photofragment nitric oxide. A significant fraction of the photofragment from the dissociation of organo-nitrate explosives is formed in vibrationally excited states. This circumstance is conducive to generating laser-induced fluorescence at wavelengths shorter than the excitation wavelength, thereby significantly reducing the probability of false alarms. Laboratory demonstrations with single laser pulses of several nanoseconds' duration indeed exhibit a high detection efficiency with low false-alarm rates. Further development of this method will require a combination of phenomenological surveys, photochemical studies, and laser engineering.

1PhD, Physics, Clark University
2PhD, Chemistry, University of North Carolina–Chapel Hill
3PhD, Optics, University of Rochester

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Slab-Coupled Optical Waveguide (SCOW) Devices and Their Applications

Dr. Joseph P. Donnelly1, Dr. Robin K. Huang2,
Dr. Paul W. Juodawlkis3, and Dr. George W. Turner4
MIT Lincoln Laboratory

For the past decade, MIT Lincoln Laboratory has been developing new classes of high-power semiconductor optoelectronic emitters and detectors based on the slab-coupled optical waveguide (SCOW) concept. The key characteristics of the SCOW design include (1) the use of a planar slab waveguide to filter the higher-order transverse modes from a large rib waveguide, (2) low overlap between the optical mode and the active layers, and (3) low excess optical loss. These characteristics enable waveguide devices having large (> 5 × 5 μm) symmetric fundamental-mode operation and long length (~1 cm). These large dimensions, relative to conventional waveguide devices, allow efficient coupling to optical fibers and external optical cavities, and provide reduced electrical and thermal resistances for improved heat dissipation. In this talk, we will review the SCOW operating principles and describe applications of the SCOW technology, including watt-class semiconductor SCOW lasers (SCOWLs) and amplifiers (SCOWAs), monolithic and ring-cavity mode-locked lasers, single-frequency external cavity lasers, and high-current waveguide photodiodes. The SCOW concept has been demonstrated in a variety of material systems at wavelengths including 915, 960–980, 1040, 1300, 1550, and 2100 nm. In addition to single emitters, higher brightness has been obtained by combining arrays of SCOWLs and SCOWAs using wavelength beam-combining and coherent combining techniques. These beam-combined SCOW architectures offer the potential of kilowatt-class, high-efficiency, electrically pumped optical sources.

1PhD, Electrical Engineering, Carnegie Mellon University
2PhD, Physics, Stanford University
3PhD, Electrical Engineering, Georgia Institute of Technology
4PhD, Electrical Engineering, Johns Hopkins University

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Interferometry, Cooling, and Amplitude Spectroscopy
with a Superconducting Artificial Atom

Dr. William D. Oliver1
MIT Lincoln Laboratory

Superconducting persistent-current qubits are quantum-coherent artificial atoms with multiple energy levels. In the presence of large-amplitude harmonic excitation, the qubit state can be driven through one or more of the energy-level avoided crossings. The resulting Landau-Zener transitions mediate a rich array of quantum-coherent phenomena as a function of the driving amplitude and frequency.

This talk presents three demonstrations of Landau-Zener–mediated quantum coherence in a strongly driven niobium persistent-current qubit. The first is Mach-Zehnder–type interferometry [1], with which colleagues and I observed quantum interference fringes in the transition rates for n-photon transitions, with n = 1…50. The second is microwave-induced cooling [2], by which we achieved effective qubit temperatures <3 mK, a factor 10 to 100 times lower than the dilution refrigerator ambient temperature. The third is amplitude spectroscopy [3], a spectroscopy approach that monitors the system response to amplitude rather than frequency. This allowed us to probe the energy spectra of our artificial atom from 0.01 to 120 GHz, while driving it at a fixed frequency 0.16 GHz.

These experiments exhibit a remarkable agreement with theory and are extensible to other solid-state qubit modalities. In addition to our interest in these techniques for fundamental studies of quantum coherence in strongly driven solid-state systems, we anticipate they will find application to nonadiabatic qubit control and state-preparation methods for quantum information science and technology.

[1] W.D. Oliver et al., "Mach-Zehnder Interferometry in a Strongly Driven Superconducting Qubit," Science, vol. 310, no. 5754, pp. 1653–1657, December 2005.
[2] S.O. Valenzuela et al., "Microwave-Induced Cooling of a Superconducting Qubit," Science, vol. 314, no. 5805, pp. 1589–1592, December 2006.
[3] D.M. Berns et al., "Amplitude Spectroscopy of a Solid-State Artificial Atom," Nature, vol. 455, pp. 51–57, September 2008.

1PhD, Electrical Engineering, Stanford University

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Submicrosecond to Subnanosecond Snapshot Imaging Technology

Dr. Dennis D. Rathman1
MIT Lincoln Laboratory

Research laboratories for both the Department of Defense and the Department of Energy have imaging applications that require very fast snapshot imagers to analyze a wide range of rapidly evolving phenomena. MIT Lincoln Laboratory has a long history of developing high-frame-rate imagers to meet those application needs. This seminar will discuss the most recent technology development of three imagers: a charge-coupled device (CCD)–based 4-exposure device and a CCD-based 50-exposure device that both have burst rates greater than one million frames per second, and a CMOS-based X-ray imager capable of taking 100 ps snapshot exposures.

1PhD, Physics, Lehigh University

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Communications and Information Systems

MIMO Wireless Communication

Dr. Daniel W. Bliss1
MIT Lincoln Laboratory

Wireless communication using multiple-input multiple-output (MIMO) systems enables increased achievable spectral efficiency and reliability for a given total transmit power. The increased capacity is achieved through the introduction of antenna arrays at both the transmitter and receiver. These arrays are used to take advantage of the multiple spatial modes provided by complicated multipath environments. Actual link performance is sensitive to a particular channel environment, receiver approach, and space-time code. Environmental characteristics include channel spatial correlation and external interference. Because of computational complexity, suboptimal receivers are often employed in real systems. Space-time coding describes the mapping from information bits to the transmitted waveforms employed by MIMO systems.

In this talk, a number of MIMO wireless communication topics are discussed. An introduction to MIMO communication is provided. The sensitivity of theoretical capacity to environmental factors is considered. These factors include channel complexity and external interference. Channel phenomenology and its effect on capacity is investigated by using parametric models, asymptotic calculations, and experimental data. A theoretical performance comparison of various receiver approaches is presented. Innovative space-time coding concepts are introduced. Experimental performance results for space-time turbo and low-density parity check coding techniques are presented as a function of channel characteristics and receiver design.

1PhD, Physics, University of California–San Diego

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Cooperative Communication in Heterogeneous Wireless Networks

Dr. Brooke E. Shrader1
MIT Lincoln Laboratory

Cooperative communication techniques, in which users relay for other users in order to improve performance, are typically explored in wireless networks consisting of homogeneous nodes, such as sensor networks or vehicular ad hoc networks. Future wireless networks will consist of a blend of different types of nodes, including satellite, airborne, and terrestrial nodes, with widely varying characteristics in terms of achievable data rate, loss rate, and propagation time. This seminar will include a tutorial and focus on recent research in cooperative capabilities and techniques, including the use of network coding, for heterogeneous wireless networks.

1PhD, Electrical Engineering, University of Maryland

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Waveform Design for Airborne Networks

Dr. Frederick J. Block1
MIT Lincoln Laboratory

Airborne networks are expected to play a significant role in future military communications. Successful deployment of these ad hoc networks requires overcoming many unique challenges. For example, nodes are often separated by great distances and can be highly mobile. In addition to multiple-access interference from other radios in the network, interference from jammers located over a wide geographic region may be able to reach a receiver because of its high altitude. The presentation gives an overview of channel models for airborne networks and examines the trade-offs that must be made when choosing the modulation, coding, and channel access protocol.

1PhD, Electrical Engineering, Clemson University

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Automated Topology Control for Wideband Directional
Links in Airborne Military Networks

Dr. Bow-Nan Cheng1
MIT Lincoln Laboratory

Future airborne and military operations will rely on merging wideband directional RF and optical links for machine-to-machine networking. Management and control for such directional wireless links on mobile platforms is a significant challenge that does not arise in fixed terrestrial networks. As a consequence, new protocols and approaches are needed. In this talk, an architectural framework for control of wideband directional links in airborne military networks is presented. Three distributed algorithms for automated topology management that have been devised and prototyped at MIT Lincoln Laboratory are compared. Results and experience from simulations, emulations, and field tests are presented.

1PhD, Computer Science, Rensselaer Polytechnic Institute

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New Approaches to Automatic Speaker Recognition

Dr. Joseph P. Campbell1 and Dr. Pedro A. Torres-Carrasquillo2
MIT Lincoln Laboratory

The area of automatic speaker recognition has been dominated by systems using only short-term, low-level acoustic information, such as cepstral features. While these systems have produced reasonably low error rates, they ignore other levels of information beyond low-level acoustics that convey speaker information. This seminar will include a tutorial and focus on late-breaking research that exploits high-level information, e.g., idiosyncratic word usage and pronunciation, in automatic speaker recognition systems to add robustness and improve accuracy.

1PhD, Electrical Engineering, Oklahoma State University
2PhD, Electrical Engineering, Michigan State University

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Implementation Considerations for Wideband Wireless Communications

Dr. Nancy B. List1
MIT Lincoln Laboratory

Unexpected technical challenges often arise in the process of transferring technology from theory into practical applications. It is well known that modulator distortion causes problems for the transmission of communications signals. Less obvious, however, is the effect of modulator distortion on signals used for time tracking in wireless systems requiring strict timing control. Narrowband tracking signals are often used to synchronize systems transmitting wideband communications signals. While narrowband tracking signals may be less sensitive than communications signals to many types of distortion, they are particularly sensitive to group delay variation. As a result, relatively small levels of group delay variation across the frequency band can cause unexpected overall system degradation. This presentation will describe the real-world challenges of time-tracking in frequency-hopped satellite communications systems transmitting signals at high data rates, as well as practical methods to analyze and overcome these challenges.

1PhD, Electrical Engineering, Georgia Institute of Technology

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Laser Communications Transceiver Design

Dr. David O. Caplan1
MIT Lincoln Laboratory

Optical communications has provided unprecedented capacity in modern networks and has fueled the rapid growth of the Internet. Until recently, the sensitivity and efficiency of optical transmitters and receivers have not been driving factors in the buildup of fiber-optical networks. But as the demand for bandwidth approaches the limitations of current communication systems, more sensitive receivers can provide a means for improving optical network performance in terms of both power and bandwidth efficiency. High-sensitivity receivers can also reduce mid-span amplifier requirements, can extend link distances, and are especially beneficial for free-space optical communications because improvements in receiver sensitivity directly reduce transmitted power requirements.

This talk will provide an overview of optical transmitter and receiver designs, from relatively simple direct detection systems used in short terrestrial fiber-optic links to sophisticated near quantum-limited systems suitable for deep-space-based optical links. The basic characteristics of optical sources, modulators, amplifiers, detectors, and associated noise sources will be discussed along with some of the unique properties that distinguish optical communication systems and components from their RF counterparts. Also presented will be practical trade-offs and implementation issues that arise from using various technologies, modulation formats, and coding in both free-space and fiber-optic links.

1PhD, Electrical Engineering, Northwestern University

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Free-Space Laser Communications

Dr. Frederick G. Walther1
MIT Lincoln Laboratory

Laser communications (lasercom) provides significant advantages, compared to RF communications, including a large, unregulated bandwidth and high beam directionality for free-space links. These advantages provide capabilities for high (multi Gb/s) data-transfer rates, reduced terminal size, weight, and power, and a degree of physical link security against out-of-beam interferers or detectors. This seminar addresses the key components of lasercom system design, including modeling and simulation of atmospheric effects, link budget development, employment of spatial and temporal diversity techniques to mitigate signal fading due to scintillation, and requirements for acquisition and tracking system performance.

1PhD, Physics, Massachusetts Institute of Technology

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Superconducting Nanowire Detectors for Photon-Counting Optical Communications at Gigabit/second Data Rates

Dr. Andrew J. Kerman1
MIT Lincoln Laboratory

Optical receivers capable of detecting single photons can be used to provide a dramatic increase in the efficiency of optical communications over conventional methods, opening the possibility of communication over extremely large distances. Already under way at MIT Lincoln Laboratory is a demonstration of photon-counting optical communications between a satellite in Mars orbit and an Earth-based receiver; even larger interplanetary distances can be envisioned. So far, the most sensitive single-photon detectors in the near-infrared region used for communications are InGaAs Geiger-mode avalanche photodiodes; however, these devices suffer from several important limitations, including a long reset time after a detection event, high dark count rates, and large timing jitter, the combination of which limits achievable data rates to ~tens of megabits/second.

In this presentation, a new optical detector technology based on nanowires lithographically patterned onto ultrathin, superconducting NbN films will be discussed. When biased with a DC current close to the critical current above which the material becomes resistive, these nanowires become highly sensitive to incident photons and exhibit sufficiently fast reset times, low dark count rates, and low timing jitter to support photon-counting optical communications at gigabit/s data rates. Their high speed and timing resolution may also be of interest for experiments in solid-state and biological physics. This seminar will present the physics of these devices, their fabrication, characterization, and integration into an optical receiver architecture, as well as future directions and potential improvements.

1PhD, Physics, Stanford University

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Directions in Military Wireless Communications

Dr. Wayne G. Phoel1
MIT Lincoln Laboratory

This talk discusses some of the recent work performed at MIT Lincoln Laboratory toward advancing wireless communications for military environments, with a focus on satellite communications and airborne networking. The talk first describes some of the special requirements of military communications, covers standard techniques, and presents future needs. Examples of practical implementation issues are then analyzed, along with potential solutions. The talk concludes with a discussion of technologies to provide the desired capabilities for the next generation of military wireless communications networks.

1PhD, Electrical Engineering, Northwestern University

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QoS and Cross-Layer Optimization for
Satellite Communications Networks

Dr. Jeffrey S. Wysocarski1
MIT Lincoln Laboratory

To efficiently utilize limited RF resources, future packet-switched satellite networks will dynamically allocate resources on the uplink and downlink. Designing the resource-allocation algorithms to maximize link-layer efficiency is insufficient. The resource-allocation algorithms must work cooperatively with the network layer and transport layer to optimize network layer performance and provide quality of service (QoS) to applications and users. Several mechanisms for facilitating this required cooperation between the layers are presented. The individual roles and actions of the layers as well as their interaction are defined. Router QoS schedulers that continue to provide service differentiation in the presence of link variations are illustrated, and downlink scheduling architectures that provide terminal QoS guarantees are demonstrated. Finally, the interaction between TCP and the dynamic resource-allocation algorithms is investigated, leading to suggested modifications of either the resource-allocation algorithms, the TCP protocol, or both.

1PhD, Electrical Engineering, Clemson University

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Dynamic Link Adaptation for Satellite Communications

Dr. Huan Yao1
MIT Lincoln Laboratory

Future protected military satellite communications will continue to use high transmission frequencies to capitalize on the large amounts of available bandwidth. However, the data flowing through these satellites will transition from the circuit-switched traffic of today's satellite systems to Internet-like packet traffic. One of the main differences in migrating to packet-switched communications is that the traffic will become bursty (i.e., the data rate from particular users will not be constant). The variation in data rate is only one of the potential system variations. At the frequencies of interest, rain and other weather phenomena can introduce significant path attenuation for relatively short time periods. However, the current systems are designed to always provide sufficient margin even when it is not raining. The focus of this seminar is the design of a future satellite system that autonomously reacts to changes in link conditions and offered traffic. This automatic adaptation drastically improves the overall system capacity and the service that can be provided to ground terminals.

1PhD, Electrical Engineering, Massachusetts Institute of Technology

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Managing Large-Scale Information Operations Tests

Tamara H. Yu1
MIT Lincoln Laboratory

The Lincoln Adaptable Real-time Information Assurance Testbed (LARIAT) allows researchers and government buyers to test the effectiveness of information operations (IO) technologies in a realistic, closed network environment. As IO tests scale up in size and complexity, it is increasingly difficult to set up and validate test bed networks and to monitor test progress. Recent efforts to improve the LARIAT software suite focus on the ease of use of the software, especially in large tests, by introducing a set of user interface and visualization tools that help users manage test bed resources, rapidly install and configure software, and control and monitor the test bed from a central location.

1MEng, Computer Science, Massachusetts Institute of Technology

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Improving Software Security and Robustness Using Automated Testing

Michael Zhivich1
MIT Lincoln Laboratory

The complexity of the software required to operate modern real-time embedded systems (used in satellites and critical infrastructure control) makes it prone to programming errors. Software developers perform rigorous functionality tests to reduce errors; nevertheless, serious problems such as memory corruption and resource leaks may remain in software operating critical systems. These errors in turn create vulnerabilities that, if exploited, can affect the availability, reliability, and integrity of operations and thus degrade the system's overall robustness.

This talk will discuss automated testing and analysis tools that can help developers discover and redress these kinds of vulnerabilities before software is put in operation. The focus of the talk will be on MIT Lincoln Laboratory's DEADBOLT tool that automatically discovers memory corruption problems, resulting not only in more robust and secure software, but in lowered development and maintenance costs for both software developers and users.

1MEng, Electrical Engineering, Massachusetts Institute of Technology

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Practical Attack Graph Generation for Network Defense

Kyle Ingols1
MIT Lincoln Laboratory

Attack graphs, a valuable tool for network defenders, illustrate paths an attacker can use to gain access to a targeted network. Defenders can then focus their efforts on patching the vulnerabilities and configuration errors that allow the attackers the greatest amount of access. MIT Lincoln Laboratory has created a new type of attack graph, the multiple-prerequisite graph, that scales nearly linearly as the size of a typical network increases. The Laboratory has built a prototype system using this graph type. The prototype uses readily available source data to automatically compute network reachability, classify vulnerabilities, build the graph, and recommend actions to improve network security. The prototype has been tested on an operational network with over 250 hosts, where it helped to discover a previously unknown configuration error. The prototype can evaluate large enterprise networks using commodity hardware in seconds and has processed complex simulated networks with over 50,000 hosts in under four minutes.

1MEng, Electrical Engineering & Computer Science, Massachusetts Institute of Technology

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Space Control Technology

Discovering Near-Earth Asteroids at MIT Lincoln Laboratory

Dr. J. Scott Stuart1
MIT Lincoln Laboratory

The Lincoln Near-Earth Asteroid Research (LINEAR) program has discovered more than half of all near-Earth asteroids (NEAs) ever discovered. Since beginning full-time operations in 1998, it has provided 60% of the worldwide discoveries of new NEAs from its site near Socorro, New Mexico. On top of its success in discovering NEAs, LINEAR has become the leading ground-based discoverer of comets, with more than 150 comets now named "LINEAR." LINEAR discovers many comets when they are far away from the Sun on their inbound trajectory, thus allowing observation of the heating process missed when comets are discovered closer to the Sun. LINEAR now operates two wide-area search telescopes with 1-meter apertures and has recently added a 31-inch aperture telescope dedicated to automated follow-up of possible NEAs detected by the search telescopes.

The LINEAR program originated as a new application of technology developed by MIT Lincoln Laboratory to provide the U.S. Air Force with enhanced capability to track spacecraft. This successful technology migration has resulted in an improved understanding of the NEAs with LINEAR data providing the basis for the best analyses of the asteroid impact risk to the Earth. This talk provides an overview of the LINEAR program, including recent enhancements to the LINEAR system, the productivity of the program, the scientific results gleaned from LINEAR data, and descriptions of some of the more interesting objects discovered.

1PhD, Earth, Atmospheric, & Planetary Sciences, Massachusetts Institute of Technology

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A System for Predicting Close Approaches and Potential
Collisions in Geosynchronous Orbits

Dr. Richard I. Abbot1 and Miquela C. Vigil2
MIT Lincoln Laboratory

The geosynchronous orbit is getting crowded with over 300 active, revenue-producing large satellites and over 500 inactive resident space objects that pose a physical collision threat to the active satellites. The in situ demise of a particular satellite, Telstar 401, followed by a similar demise of SOLIDARIDAD 1, initiated a research and development effort at MIT Lincoln Laboratory to address this threat. This work with commercial satellite operators is accomplished using the mechanism of Cooperative Research and Development Agreements. Initial work to detect and warn of close approaches with these two failed satellites led to more extensive research on the collision threat over the entire geosynchronous belt. It is apparent that
  1. There is a significant probability of collision
  2. The probability has increased considerably in the last decade or so
  3. The continuing failure of geosynchronous satellites and injection of rocket bodies into or near geosynchronous orbit will increase the threat
  4. Debris in or near geosynchronous orbit poses another problem that has to be addressed

This seminar surveys what has been achieved so far in predicting the threat and protecting satellites. An assessment of the probability of collision is presented as well as a description of the Geosynchronous Monitoring and Warning System (GMWS). The operations of the GMWS, as well as some of the results achieved so far, are described. Areas of current research are mentioned.

1PhD, Physics/Meteorology, University of Texas–Austin
2MS, Earth, Atmospheric, & Planetary Sciences, Massachusetts Institute of Technology

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Retrieval of Atmospheric Temperature and Moisture Profiles from Hyperspectral Sounding Data Using a Projected Principal
Components Transform and a Neural Network

Dr. William J. Blackwell1
MIT Lincoln Laboratory

A novel statistical method for the retrieval of atmospheric temperature and moisture (relative humidity) profiles has been developed and evaluated with simulated clear-air hyperspectral sounding data. The accuracies of the estimates produced by the algorithm meet or exceed (in some cases by a factor of two) the accuracies of the estimates from traditional iterated minimum variance retrieval techniques while requiring less computation. The algorithm is implemented in two stages. First, a projected principal components (PPC) transform is used to reduce the dimensionality of and optimally extract geophysical profile information from the spectral radiance data. Second, an artificial feedforward neural network (NN) is used to estimate the desired geophysical parameters from the projected principal components.

The performance of this method (henceforth referred to as the PPC/NN method) was evaluated using simulated clear-air observations from the 2378-channel Atmospheric Infrared Sounder. Separate training and validation profile data were selected from the NOAA88b radiosonde set of approximately 7500 profiles. Surface, solar, and instrument effects were modeled.

It was found that the PPC/NN method has a number of advantages over traditional statistical and physical/iterative hyperspectral profile retrieval techniques. Neural-network estimates based on the PPC transform were significantly more accurate than neural-network estimates obtained with conventional principal components techniques, including the Karhunen-Loeve transform and the noise-adjusted principal components transform. The retrieval accuracy of PPC/NN was also superior to that of a principal components regression technique.

One particularly noteworthy result of the current work is a comparative study between the PPC/NN method and an iterated minimum-variance (IMV) method. The temperature profile retrieval accuracy of both methods is similar, but the relative humidity profile retrieval accuracy of PPC/NN was greater than that of the IMV method at all altitudes and substantially better near the surface.

1PhD, Electrical Engineering, Massachusetts Institute of Technology

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Space Surveillance with the Space-Based Visible Sensor

Dr. Jayant Sharma1
MIT Lincoln Laboratory

The Midcourse Space Experiment satellite was launched in 1996. A principal sensor on board the satellite is the Space-Based Visible (SBV) sensor, a visible-band, electro-optical camera designed at MIT Lincoln Laboratory to perform the first technical and functional demonstration of space-based space surveillance. The principal task of the SBV sensor is to gather tracking data on satellites. In 1997, after the successful technology-demonstration phase of the mission, the SBV sensor was transitioned from an experimental sensor to a dedicated sensor in the Space Surveillance Network. The Space-Based Space Surveillance Operations is now providing the Space Surveillance Network with the first operational space-based space surveillance sensor. With its orbital location, wide field of view, and high metric accuracy, the SBV sensor has made significant contributions to the Space Surveillance Network. The performance of the SBV sensor and the application of its observations to satellite tracking will be demonstrated. This talk will introduce the topic of satellite tracking and the development and evolution of satellite tracking from a space-based sensor.

1PhD, Aerospace Engineering, University of Texas–Austin

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Advances in Precision Orbit Determination

Dr. Steven M. Hunt1
MIT Lincoln Laboratory

The U.S. military puts significant resources into tracking U.S. spacecraft, foreign space systems, and orbital debris. Knowing the location and orbital motion of space objects is a key component of space situational awareness (SSA), coupled with measures to ascertain the purpose and function of these objects. The ability to incorporate sensor measurements into precision orbits is critical to a robust SSA capability; reliably propagating orbits into the future is necessary to enable timely warning of potential threats to U.S. space systems. This talk provides an overview of the physics and the state of the art in precision orbit determination, including recent advances accomplished at MIT Lincoln Laboratory. Several measurement examples are given of the potential accuracies that can be achieved in both orbit determination and propagation.

1PhD, Electrical Engineering, Boston University

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Integrated Optomechanical System Design of Terrestrial,
Airborne, and Spaceborne Sensors

Dr. Keith B. Doyle1
MIT Lincoln Laboratory

MIT Lincoln Laboratory has developed a wide range of sensors, ranging from radar antennas, free-space laser communication terminals, missile and countermeasure platforms, and infrared airborne systems, to satellite space sensors. These high-performance sensors must perform and survive in harsh environments while meeting strict pointing and imaging requirements subject to temperature, inertial, vibrations, and shock loads. Sensor designs are optimized within a complex array of typically competing design parameters by utilizing multidisciplinary design and analysis techniques that couple CAD, thermal, structures, controls, and optical design tools. The integration of design tools allows system performance to be evaluated as a function of environmental disturbances and mechanical design variables.

This talk provides an overview of the integrated mechanical system design process that turns conceptual designs into operationally functional sensors out in the field. Examples discussed include ground-based imaging sensors that operate subject to the effects of gravity, diurnal temperature variations, and wind loads; open-cavity airborne sensors that operate subject to acoustic, aerodynamic, and aircraft vibrations; and spaceborne systems that must survive launch and operate subject to thermal orbital variations and spacecraft dynamic disturbances.

1PhD, Mechanical Engineering, University of Arizona

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Data Mining, Decision Support, and Data Fusion

Bayesian Inference Approach to Learning Coordinated
Traffic Behavior for Non-tracking Sensors

Lawrence A. Bush1
MIT Lincoln Laboratory

MIT Lincoln Laboratory has developed a method for learning and detecting coordinated traffic behavior for situations in which tracking is infeasible. For example, tracking in large areas with dense traffic is very demanding of sensor resources, and maintaining track of interacting objects is extremely difficult. Therefore, non-tracking methods for interpreting intentional traffic coordination have been explored.

The approach is to statistically model different traffic behavior classes, at a particular location, in order to detect the activity of interest and then combine the results from multiple locations by using a reasoning structure. The seminar will present a method for learning this reasoning structure from the data by using a Bayesian Network structure search, then using the Bayesian Network to infer the overall situation across multiple sites. This approach emphasizes evidence accumulation and continuous learning, which lend strong support to the proposed multi-input computational framework.

MIT Lincoln Laboratory's research is applied to wide-area persistent surveillance using moving-target indication (MTI) radar data. MTI is a radar data processing technique for detecting moving vehicles. The MIT Lincoln Laboratory approach was tested by collecting MTI data while running multiple experimental military ground scenarios, each involving coordinated activity over multiple sites. By using this approach, the overall behavior classes were reliably identified.

This talk will include a tutorial of the related statistical modeling process and Bayesian inference technique. This will be followed by an evaluation of the Laboratory's results, which demonstrate the ability of this technique to identify military activity.

1MS, Computer Science, Rensselaer Polytechnic Institute

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Feature Extraction for Classification: Class-Independent
Statistics vs. Class-Dependent Statistics

Virginia K. Hafer1
MIT Lincoln Laboratory

There currently exist a large number of algorithms aimed at reducing the dimensionality of a feature set used for classification by relying on the statistical properties of the underlying distribution of data. Three common examples of this type of technique are Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA), and Singular Value Decomposition (SVD). Each technique has its own operating conditions and a priori assumptions about the statistical nature of the data. For instance, of the techniques mentioned, only the LDA algorithm explicitly uses class information. Recently, there has been interest in comparing PCA against LDA. It is generally felt that the projected feature subset produced by LDA is better for classification purposes since the LDA algorithm finds a linear transformation that maximizes a measure of class separation.

In this presentation, we will empirically compare and contrast the performance of the PCA, LDA, and SVD techniques on a variety of standard data sets. In addition, we introduce two additional algorithms called Classwise Principal Component Analysis (C-PCA) and Classwise Singular Value Decomposition (C-SVD), based on PCA and SVD, respectively, that incorporate class-specific information into their constructions. We will demonstrate empirically that these new algorithms classify data better than their standard PCA and SVD counterparts. In addition to classification, each of the algorithms we present has a natural method for dimensionality reduction via eigenspace truncation. As such, we will also present results examining how classification performance degrades as the number of implicit algorithm-specific degrees of freedom are decreased. Our results demonstrate that the C-PCA and C-SVD techniques allow one to potentially do significant dimensionality reduction with negligible impact in classification accuracy.

1BA, Physics, Wellesley College


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