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Multifunction Phased Array Radar (MPAR): achieving Next Generation Surveillance and Weather Radar Capability

September 1, 2013
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Journal Article
Author:
Mark E. Weber
…
Published in:
J. Air Traffic Control, Vol. 55, No. 3, Fall 2013, pp. 40-7.
Topic:
radar
R&D area:
R&D group:

Summary

Within DOT, the FAA has initiated an effort known as the NextGen Surveillance and Weather Radar Capability (NSWRC) to analyze the need for the next generation radar replacement and assess viable implementation alternatives. One concept under analysis is multifunction radar using phased-array technology -- Multifunction Phased Array Radar or MPAR.
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Summary

Within DOT, the FAA has initiated an effort known as the NextGen Surveillance and Weather Radar Capability (NSWRC) to analyze the need for the next generation radar replacement and assess viable implementation alternatives. One concept under analysis is multifunction radar using phased-array technology -- Multifunction Phased Array Radar or MPAR.

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Multifunction Phased Array Radar (MPAR): achieving Next Generation Surveillance and Weather Radar Capability

Pixel-processing imager development for directed energy applications

August 26, 2013
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Conference Paper
Author:
Jeffrey W. Little
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Published in:
Directed Energy Systems Symposium, 26-29 August 2013.
Topic:
lasers
R&D area:
R&D group:

Summary

Tactical high-energy laser (HEL) systems face a range of imaging-related challenges in wavefront sensing, acquiring and tracking targets, selecting the HEL aimpoint, and assessing lethality. Accomplishing these functions in a timely fashion may be limited by competing requirements on total field of regard, target resolution, signal to noise, and focal plane readout bandwidth. In this paper, we explore the applicability of an emerging pixel-processing imager (PPI) technology to these challenges. The on-focal-plane signal processing capabilities of the MIT Lincoln Laboratory PPI technology have recently been extended in support of directed energy applications. We describe this work as well as early results from a new PPI-based short-wave-infrared focal plane readout capable of supporting diverse applications such as low-latency Shack-Hartmann wavefront sensing, centroid computation, and Fitts correlation tracking.
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Summary

Tactical high-energy laser (HEL) systems face a range of imaging-related challenges in wavefront sensing, acquiring and tracking targets, selecting the HEL aimpoint, and assessing lethality. Accomplishing these functions in a timely fashion may be limited by competing requirements on total field of regard, target resolution, signal to noise, and focal...

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Pixel-processing imager development for directed energy applications

Very large graphs for information extraction (VLG) - summary of first-year proof-of-concept study

August 20, 2013
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Project Report
Author:
Benjamin A. Miller
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Published in:
MIT Lincoln Laboratory Report VLG-1
Topic:
signal processing
R&D area:
R&D group:

Summary

In numerous application domains relevant to the Department of Defense and the Intelligence Community, data of interest take the form of entities and the relationships between them, and these data are commonly represented as graphs. Under the Very Large Graphs for Information Extraction effort--a one-year proof-of-concept study--MIT LL developed novel techniques for anomalous subgraph detection, building on tools in the signal processing research literature. This report documents the technical results of this effort. Two datasets--a snapshot of Thompson Reuters? Web of Science database and a stream of web proxy logs--were parsed, and graphs were constructed from the raw data. From the phenomena in these datasets, several algorithms were developed to model the dynamic graph behavior, including a preferential attachment mechanism with memory, a streaming filter to model a graph as a weighted average of its past connections, and a generalized linear model for graphs where connection probabilities are determined by additional side information or metadata. A set of metrics was also constructed to facilitate comparison of techniques. The study culminated in a demonstration of the algorithms on the datasets of interest, in addition to simulated data. Performance in terms of detection, estimation, and computational burden was measured according to the metrics. Among the highlights of this demonstration were the detection of emerging coauthor clusters in the Web of Science data, detection of botnet activity in the web proxy data after 15 minutes (which took 10 days to detect using state-of-the-practice techniques), and demonstration of the core algorithm on a simulated 1-billion-vertex graph using a commodity computing cluster.
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Summary

In numerous application domains relevant to the Department of Defense and the Intelligence Community, data of interest take the form of entities and the relationships between them, and these data are commonly represented as graphs. Under the Very Large Graphs for Information Extraction effort--a one-year proof-of-concept study--MIT LL developed novel...

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Very large graphs for information extraction (VLG) - summary of first-year proof-of-concept study

Due regard encounter model version 1.0

August 19, 2013
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Project Report
Author:
John Daniel Griffith
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Published in:
MIT Lincoln Laboratory Report ATC-397
Topic:
collision avoidance
R&D area:
R&D group:

Summary

Airspace encounter models describe encounter situations that may occur between aircraft in the airspace and are a critical component of safety assessment of sense and avoid (SAA) systems for Unmanned Aircraft Systems (UASs). Some UAS will fly in international airspace under due regard and may encounter other aircraft during these operations. In these types of encounters, the intruder aircraft is likely receiving air traffic control (ATC) services, but the UAS is not. Thus, there is a need for a due regard encounter model that can be used to generate these types of encounters. This report describes the development of a due regard encounter model. In order to build the model, Lincoln Laboratory collected data for aircraft flying in international airspace using the Enhanced Traffic Management System (ETMS) data feed that was provided by the Volpe Center. Lincoln processed these data, and extracted important features to construct the model. The model is based on Bayesian networks that represent the probabilistic relationship between variables that describe how aircraft behave. The model is used to construct random aircraft trajectories that are statistically similar to those observed in the airspace. A large collection of encounters generated from an airspace encounter model can be used to evaluate the performance of a SAA system against encounter situations representative of those expected to actually occur in the airspace. Lincoln Laboratory has previously developed several other encounter models. There is an uncorrelated encounter model that is used to generate encounters with an intruder that does not have a transponder, or between two aircraft using a Mode A code of 1200 (VFR). There is also a correlated encounter model that is used when both aircraft have a transponder and at least one aircraft is in contact with ATC. Both of these models were built from radar data collected from the National Airspace System (NAS). There is also an unconventional encounter model that is used to generate encounters with unconventional intruders such as gliders, balloons, and airships--these vehicles have different flight characteristics than conventional aircraft. The framework used to construct the due regard encounter model described in this paper is similar to the prior models. The primary difference is that a different data feed is used and the model covers encounters in international flight where the aircraft of interest is flying due regard, which were not within the scope of prior models. Separate electronic files are available from Lincoln Laboratory that contain the statistical data required to generate encounter trajectories.
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Summary

Airspace encounter models describe encounter situations that may occur between aircraft in the airspace and are a critical component of safety assessment of sense and avoid (SAA) systems for Unmanned Aircraft Systems (UASs). Some UAS will fly in international airspace under due regard and may encounter other aircraft during these...

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Due regard encounter model version 1.0

A language-independent approach to automatic text difficulty assessment for second-language learners

August 4, 2013
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Conference Paper
Author:
Wade Shen
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Published in:
Proc. 2nd Workshop on Predicting and Improving Text Readability for Target Reader Populations, 4-9 August 2013.
Topic:
artificial intelligence
R&D area:
R&D group:

Summary

In this paper we introduce a new baseline for language-independent text difficulty assessment applied to the Interagency Language Roundtable (ILR) proficiency scale. We demonstrate that reading level assessment is a discriminative problem that is best-suited for regression. Our baseline uses z-normalized shallow length features and TF-LOG weighted vectors on bag-of-words for Arabic, Dari, English, and Pashto. We compare Support Vector Machines and the Margin-Infused Relaxed Algorithm measured by mean squared error. We provide an analysis of which features are most predictive of a given level.
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Summary

In this paper we introduce a new baseline for language-independent text difficulty assessment applied to the Interagency Language Roundtable (ILR) proficiency scale. We demonstrate that reading level assessment is a discriminative problem that is best-suited for regression. Our baseline uses z-normalized shallow length features and TF-LOG weighted vectors on bag-of-words...

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A language-independent approach to automatic text difficulty assessment for second-language learners

Exploring the variable sky with LINEAR. II. Halo structure and substructure traces by RR Lyrae stars to 30 kpc

August 1, 2013
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Journal Article
Author:
Branimir Sesar
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Published in:
Astron. J., Vol. 146, No. 21, August 2013.
Topic:
LINEAR
R&D area:
R&D group:

Summary

We present a sample of ~5000 RR Lyrae stars selected from the recalibrated LINEAR data set and detected at heliocentric distances between 5 kpc and 30 kpc over ~8000 deg^2 of sky. The coordinates and light curve properties, such as period and Oosterhoff type, are made publicly available. We analyze in detail the light curve properties and Galactic distribution of the subset of ~4000 type ab RR Lyrae (RRab) stars, including a search for new halo substructures and the number density distribution as a function of Oosterhoff type. We find evidence for the Oosterhoff dichotomy among field RR Lyrae stars, with the ratio of the type II and I subsamples of about 1:4, but with a weaker separation than for globular cluster stars. The wide sky coverage and depth of this sample allow unique constraints for the number density distribution of halo RRab stars as a function of galactocentric distance: it can be described as an oblate ellipsoid with an axis ratio q = 0.63 and with either a single or a double power law with a power-law index in the range -2 to -3. Consistent with previous studies, we find that the Oosterhoff type II subsample has a steeper number density profile than the Oosterhoff type I subsample. Using the group-finding algorithm EnLink, we detected seven candidate halo groups, only one of which is statistically spurious. Three of these groups are near globular clusters (M53/NGC 5053, M3, M13), and one is near a known halo substructure (Virgo Stellar Stream); the remaining three groups do not seem to be near any known halo substructures or globular clusters and seem to have a higher ratio of Oosterhoff type II to Oosterhoff type I RRab stars than what is found in the halo. The extended morphology and the position (outside the tidal radius) of some of the groups near globular clusters are suggestive of tidal streams possibly originating from globular clusters. Spectroscopic follow-up of detected halo groups is encouraged.
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Summary

We present a sample of ~5000 RR Lyrae stars selected from the recalibrated LINEAR data set and detected at heliocentric distances between 5 kpc and 30 kpc over ~8000 deg^2 of sky. The coordinates and light curve properties, such as period and Oosterhoff type, are made publicly available. We analyze...

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Exploring the variable sky with LINEAR. II. Halo structure and substructure traces by RR Lyrae stars to 30 kpc

The directivity of a Yagi-Uda antenna from an effective propagation constant

July 7, 2013
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Conference Paper
Author:
Herbert M. Aumann
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Published in:
IEEE Int. Symp. Antennas and Propagation (APSURSI), 7-13 July 2013.
Topic:
antennas
R&D area:
R&D group:

Summary

A technique is presented for determining the directivity of a long, uniform Yagi-Uda antenna. It is shown that the maximum directivity is limited by the propagation constant of the particular antenna structure. The propagation constant can be determined by means of a two-part antenna test fixture with M and M + 1 directors.
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Summary

A technique is presented for determining the directivity of a long, uniform Yagi-Uda antenna. It is shown that the maximum directivity is limited by the propagation constant of the particular antenna structure. The propagation constant can be determined by means of a two-part antenna test fixture with M and M...

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The directivity of a Yagi-Uda antenna from an effective propagation constant

Stepped notch antenna array used as a low thermal resistance heat sink

July 7, 2013
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Conference Paper
Author:
Sean M. Duffy
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Published in:
IEEE Antennas and Propagation Society Int. Symp. 2013, 7-13 July 2013.
Topic:
antennas
R&D area:
R&D group:

Summary

A stepped notch antenna at Ku-band is developed to provide a thermal heat sink for active arrays. The antenna with forced air cooling provides up to 0.4 degrees C/W of thermal resistance. The antenna integration with a printed circuit board allows for high volume surface mount assembly of active devices.
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Summary

A stepped notch antenna at Ku-band is developed to provide a thermal heat sink for active arrays. The antenna with forced air cooling provides up to 0.4 degrees C/W of thermal resistance. The antenna integration with a printed circuit board allows for high volume surface mount assembly of active devices.

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Stepped notch antenna array used as a low thermal resistance heat sink

Leading the charge - microgrids for domestic military installations

June 19, 2013
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Journal Article
Author:
Scott B. Van Broekhoven
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Published in:
IEEE Power & Energy Magazine, Vol. 11, No. 4, July/August 2013, pp. 40-5.
Topic:
energy systems
R&D area:
R&D group:

Summary

In today's interconnected battlefield, our war fighters are increasingly reliant on capabilities at domestic military installations to support critical missions, often in near real time. Many of the domestic installations of the U.S. Department of Defense (DoD) also support everything from sensitive research and development facilities such as microelectronics and biological laboratories to large industrial plants such as shipyards and aviation depots. These facilities depend on the electricity provided by the commercial electric grid. Extended-duration outages on the domestic electric grid will therefore both significantly affect the operational mission of the DoD and bring substantial economic consequences. The changing nature of electricity markets presents new opportunities for the DoD to reduce electricity costs while addressing its energy security needs. Demand response, ancillary service markets, and real-time pricing offer large consumers of electricity such as military installations a significant opportunity to use installation assets during grid-tied operation. Nevertheless, this is an opportunity the DoD can only exploit if it does so in a secure fashion, well protected from cyber threats.
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Summary

In today's interconnected battlefield, our war fighters are increasingly reliant on capabilities at domestic military installations to support critical missions, often in near real time. Many of the domestic installations of the U.S. Department of Defense (DoD) also support everything from sensitive research and development facilities such as microelectronics and...

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Leading the charge - microgrids for domestic military installations

Estimation of Causal Peer Influence Effects

June 17, 2013
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Conference Paper
Author:
Panos Toulis
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Published in:
International Conference on Machine Learning, 17-19 June 2013
Topic:
machine learning
R&D area:

Summary

The broad adoption of social media has generated interest in leveraging peer influence for inducing desired user behavior. Quantifying the causal effect of peer influence presents technical challenges, however, including how to deal with social interference, complex response functions and network uncertainty. In this paper, we extend potential outcomes to allow for interference, we introduce welldefined causal estimands of peer-influence, and we develop two estimation procedures: a frequentist procedure relying on a sequential randomization design that requires knowledge of the network but operates under complicated response functions, and a Bayesian procedure which accounts for network uncertainty but relies on a linear response assumption to increase estimation precision. Our results show the advantages and disadvantages of the proposed methods in a number of situations.
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Summary

The broad adoption of social media has generated interest in leveraging peer influence for inducing desired user behavior. Quantifying the causal effect of peer influence presents technical challenges, however, including how to deal with social interference, complex response functions and network uncertainty. In this paper, we extend potential outcomes to...

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Estimation of Causal Peer Influence Effects
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