Publications
Finding focus in the blur of moving-target techniques
April 1, 2014
Journal Article
Published in:
IEEE Security and Privacy, Vol. 12, No. 2, March/April 2014, pp. 16-26.
Topic:
R&D area:
R&D group:
Summary
Moving-target (MT) techniques seek to randomize system components to reduce the likelihood of a successful attack, add dynamics to a system to reduce the lifetime of an attack, and diversify otherwise homogeneous collections of systems to limit the damage of a large-scale attack. In this article, we review the five dominant domains of MT techniques, consider the advantages and weaknesses of each, and make recommendations for future research.
Summary
Moving-target (MT) techniques seek to randomize system components to reduce the likelihood of a successful attack, add dynamics to a system to reduce the lifetime of an attack, and diversify otherwise homogeneous collections of systems to limit the damage of a large-scale attack. In this article, we review the five...
READ MORE
Effective parallel computation of eigenpairs to detect anomalies in very large graphs
February 14, 2014
Presentation
Published in:
SIAM Conference on Parallel Processing for Scientific Computing
Topic:
R&D area:
R&D group:
Summary
The computational driver for an important class of graph analysis algorithms is the computation of leading eigenvectors of matrix representations of the graph. In this presentation, we discuss the challenges of calculating eigenvectors of modularity matrices derived from very large graphs (upwards of a billion vertices) and demonstrate the scaling properties of parallel eigensolvers when applied to these matrices.
Summary
The computational driver for an important class of graph analysis algorithms is the computation of leading eigenvectors of matrix representations of the graph. In this presentation, we discuss the challenges of calculating eigenvectors of modularity matrices derived from very large graphs (upwards of a billion vertices) and demonstrate the scaling...
READ MORE
Secondary Surveillance Phased Array Radar (SSPAR): initial feasibility study
February 6, 2014
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-416
Summary
The U.S. Federal Aviation Administration is deploying Automatic Dependent Surveillance-Broadcast (ADS-B) to provide next-generation surveillance derived through down- and cross-link of global positioning satellite (GPS) navigation data. While ADS-B will be the primary future surveillance system, FAA recognizes that backup surveillance capabilities must be provided to assure that air traffic control (ATC) services can continue to be provided when individual aircraft transponders fail and during localized, short-duration GPS outages. This report describes a potential ADS-B backup capability, Secondary Surveillance Phased Array Radar or SSPAR. SSPAR will interrogate aircraft transponders and receive replies using a sparse, non-rotating array of approximately 17 omnidirectional (in azimuth) antennae. Each array element will transmit and receive independently so as to form directional transmit beams for transponder interrogation, and support high-resolution direction finding for received signals. Because each SSPAR element is independently digitized, transponder returns from all azimuths can be equipped with Traffic Alert and Collision Avoidance System (TCAS) and ADS-B avionics to reduce spectrum usage and maintain the high surveillance update rate (~1 per second) achieved by ADS-B. Recurring costs for SSPAR will be low since it involves no moving parts and the number of array channels is small. This report describes an SSPAR configuration supporting terminal operations. We consider interrogation and receive approaches, antenna array configuration, signal processing and preliminary performance analysis. An analysis of SSPAR's impact on spectrum congestion in the beacon radar band is presented, as are concepts for integrating SSPAR and next generation primary radar to improve the efficiency and accuracy of aircraft and weather surveillance.
Summary
The U.S. Federal Aviation Administration is deploying Automatic Dependent Surveillance-Broadcast (ADS-B) to provide next-generation surveillance derived through down- and cross-link of global positioning satellite (GPS) navigation data. While ADS-B will be the primary future surveillance system, FAA recognizes that backup surveillance capabilities must be provided to assure that air traffic...
READ MORE
Forecast confidence measures for deterministic storm-scale aviation forecasts
February 5, 2014
Conference Paper
Published in:
4th Aviation, Range, and Aerospace Meteorology Special Symp., 2-6 February 2014.
Topic:
R&D area:
R&D group:
Summary
Deterministic storm-scale weather forecasts, such as those generated from the FAA's 0-8 hour CoSPA system, are highly valuable to aviation traffic managers. They provide forecasted characteristics of storm structure, strength, orientation, and coverage that are very helpful for strategic planning purposes in the National Airspace System (NAS). However, these deterministic weather forecasts contain inherent uncertainty that varies with the general weather scenario at the forecast issue time, the predicted storm type, and the forecast time horizon. This uncertainty can cause large changes in the forecast from update to update, thereby eroding user confidence and ultimately reducing the forecast's effectiveness in the decision-making process. Deterministic forecasts generally lack objective measures of this uncertainty, making it very difficult for users of the forecast to know how much confidence to have in the forecast during their decision-making process. This presentation will describe a methodology to provide measures of confidence for deterministic storm-scale forecasts. The method inputs several characteristics of the current and historical weather forecasts, such as spatial scale, intensity, weather type, orientation, permeability, and run-to-run variability of the forecasts, into a statistical model to provide a measure of confidence in a forecasted quantity. In this work, the forecasted quantity is aircraft blockage associated with key high-impact Flow Constrained Areas (FCAs) in the NAS. The results from the method, which will also be presented, provide the user with a measure of forecast confidence in several blockage categories (none, low, medium, and high) associated with the FCAs. This measure of forecast confidence is geared toward helping en-route strategic planners in the NAS make better use of deterministic storm-scale weather forecasts for air traffic management.
Summary
Deterministic storm-scale weather forecasts, such as those generated from the FAA's 0-8 hour CoSPA system, are highly valuable to aviation traffic managers. They provide forecasted characteristics of storm structure, strength, orientation, and coverage that are very helpful for strategic planning purposes in the National Airspace System (NAS). However, these deterministic...
READ MORE
Velocity estimation improvements for the ASR-9 Weather Systems Processor
February 2, 2014
Conference Paper
Published in:
American Meteorological Society Annual Meeting, 2-6 February 2014.
Summary
The Airport Surveillance Radar (ASR-9) is a rapid-scanning terminal aircraft detection system deployed at airports around the United States. To provide cost-effective wind shear detection capability at medium-density airports, the Weather Systems Processor (WSP) was developed and added on to the ASR-9 at 35 sites. The WSP on the ASR-9 is capable of utilizing dual fan-beam estimates of reflectivity and velocity in order to detect low-level features such as gust fronts, wind shear, and microbursts, which would normally be best detectable by a low-scanning pencil beam radar. An upgrade to the ASR-9 WSP, which is currently ongoing, allows for additional computational complexity in the front-end digital signal processing algorithms compared to previous iterations of the system. This paper will explore ideas for improving velocity estimates, including low-level dual beam weight estimation, de-aliasing, and noise reduction. A discussion of the unique challenges afforded by the ASR-9's block-stagger pulse repetition time is presented, along with thoughts on how to overcome limitations which arise from rapid-scanning and the inherent lack of pulses available for coherent averaging.
Summary
The Airport Surveillance Radar (ASR-9) is a rapid-scanning terminal aircraft detection system deployed at airports around the United States. To provide cost-effective wind shear detection capability at medium-density airports, the Weather Systems Processor (WSP) was developed and added on to the ASR-9 at 35 sites. The WSP on the ASR-9...
READ MORE
High-sensitivity detection of trace gases using dynamic photoacoustic spectroscopy
February 1, 2014
Journal Article
Published in:
Opt. Eng., Vol. 53 No. 2, February 2014, 021103.
Topic:
R&D area:
R&D group:
Summary
Lincoln Laboratory of Massachusetts Institute of Technology has developed a technique known as dynamic photoacoustic spectroscopy (DPAS) that could enable remote detection of trace gases via a field-portable laser-based system. A fielded DPAS system has the potential to enable rapid, early warning of airborne chemical threats. DPAS is a new form of photoacoustic spectroscopy that relies on a laser beam swept at the speed of sound to amplify an otherwise weak photoacoustic signal. We experimentally determine the sensitivity of this technique using trace quantities of SF6 gas. A clutter-limited sensitivity of ~100 ppt is estimated for an integration path of 0.43 m. Additionally, detection at ranges over 5 m using two different detection modalities is demonstrated: a parabolic microphone and a laser vibrometer. Its utility in detecting ammonia emanating from solid samples in an ambient environment is also demonstrated.
Summary
Lincoln Laboratory of Massachusetts Institute of Technology has developed a technique known as dynamic photoacoustic spectroscopy (DPAS) that could enable remote detection of trace gases via a field-portable laser-based system. A fielded DPAS system has the potential to enable rapid, early warning of airborne chemical threats. DPAS is a new...
READ MORE
Authenticated broadcast with a partially compromised public-key infrastructure
February 1, 2014
Journal Article
Published in:
Info. and Comput., Vol. 234, February 2014, pp. 17-25.
Topic:
R&D area:
R&D group:
Summary
Given a public-key infrastructure (PKI) and digital signatures, it is possible to construct broadcast protocols tolerating any number of corrupted parties. Existing protocols, however, do not distinguish between corrupted parties who do not follow the protocol, and honest parties whose secret (signing) keys have been compromised but continue to behave honestly. We explore conditions under which it is possible to construct broadcast protocols that still provide the usual guarantees (i.e., validity/agreement) to the latter. Consider a network of n parties, where an adversary has compromised the secret keys of up to tc honest parties, where an adversary has compromised the secret keys of up to tc honest parties and, in addition, fully controls the behavior of up to ta other parties. We show that for any fixed tc>0 and any fixed ta, there exists an efficient protocol for broadcast if and only if 2 ta + min (ta, tc) < n. (When tc = 0, standard results imply feasibility for all ta < n.) We also show that if tc, ta are not fixed, but are only guaranteed to satisfy the above bound, then broadcast is impossible to achieve except for a few specific values of n; for these "exceptional" values of n, we demonstrate broadcast protocols. Taken together, our results give a complete characterization of this problem.
Summary
Given a public-key infrastructure (PKI) and digital signatures, it is possible to construct broadcast protocols tolerating any number of corrupted parties. Existing protocols, however, do not distinguish between corrupted parties who do not follow the protocol, and honest parties whose secret (signing) keys have been compromised but continue to behave...
READ MORE
Initial assessment of wind forecasts for Airport Acceptance Rate (AAR) and Ground Delay Program (GDP) planning
January 29, 2014
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-414
Summary
The planning and execution of the Airport Acceptance Rate (AAR) for major metroplex airports is a complex and critical function of traffic managers in the National Airspace System (NAS). Despite the importance of AAR planning, traffic managers currently have no widely available decision support to provide guidance for runway selection and the determination of a sustainable AAR. The AAR Decision Support Capability (AARDSC), currently under development as part of the Collaborative Air Traffic Management Technology Work Package 4 (CATMT WP4), will provide such guidance. This report provides an initial analysis of the impacts of surface winds and winds aloft on the key factors associated with the AAR (the selection of runway configuration and aircraft ground speed and spacing on final approach) and the capabilities of currently available weather forecasts to accurately predict those impacts. The report was limited in scope by the schedule and available resources, and is intended as a foundation for a comprehensive forecast assessment in follow-on work. Surface wind forecasts from the Terminal Aerodome Forecast (TAF) and numerical prediction models (the High Resolution Rapid Refresh [HRRR], Rapid Refresh [RAP] and Rapid Update Cycle [RUC], collectively described as "MODEL") were compared to observed winds gathered from METAR reports as Newark International Airport (EWR). TAF and METAR were compared for 639 days of operations from 2011-2013. MODEL forecasts and METAR were compared for 21 days of operation, 16 of which had Traffic Management Initiatives (TMI) in place to mitigate adverse weather impacts. Winds aloft were translated into several wind impact metrics. The impacts of winds aloft forecast errors were evaluated by comparing impact metrics calculated from MODEL forecasts with those calculated from analysis fields for the 21 case days. Forecasts were evaluated at horizons of 2, 4, 6, and 8 hours.
Summary
The planning and execution of the Airport Acceptance Rate (AAR) for major metroplex airports is a complex and critical function of traffic managers in the National Airspace System (NAS). Despite the importance of AAR planning, traffic managers currently have no widely available decision support to provide guidance for runway selection...
READ MORE
Adaptive RF canceller for transmit-receive isolation improvement
January 19, 2014
Conference Paper
Published in:
2014 IEEE Radio and Wireless Symposium (RWS), 19-23 January 2014.
Topic:
R&D area:
Summary
For effective operation, Simultaneous Transmit and Receive (STAR) systems require high isolation between the transmitted signals and the receiver input, the absence of which can lead to the saturation of a receiver's front end. This paper presents an adaptive RF canceller used to improve isolation. The canceller is configured as an RD tapped delay line with four taps, each with independent amplitude and phase weights that are tuned by a Dithered Linear Search algorithm. This canceller produces 30 dB of signal cancellation over a 20 MHz bandwidth centered at 2.45 GHz in an isolated environment. When combined with a high-isolation antenna, an overall STAR system isolation of 90 dB is achieved, while also maintaining omnidirectional transmit and receive antenna patterns.
Summary
For effective operation, Simultaneous Transmit and Receive (STAR) systems require high isolation between the transmitted signals and the receiver input, the absence of which can lead to the saturation of a receiver's front end. This paper presents an adaptive RF canceller used to improve isolation. The canceller is configured as...
READ MORE
Insensitivity of the rate of ion motional heating to trap-electrode material over a large temperature range
January 16, 2014
Journal Article
Published in:
Phys. Rev. A, At. Mol. Opt. Phys., Vol. 89, No. 1, 2014, 012318.
Summary
We present measurements of trapped-ion motional-state heating rates in niobium and gold surface-electrode ion traps over a range of trap-electrode temperatures from approximately 4 K to room temperature (295 K) in a single apparatus. Using the sideband-ratio technique after resolved-sideband cooling of single ions to the motional ground state, we find low-temperature heating rates more than two orders of magnitude below the room-temperature values and approximately equal to the lowest measured heating rates in similarly sized cryogenic traps. We find similar behavior in the two very different electrode materials, suggesting that the anomalous heating process is dominated by non-material-specific surface contaminants. Through precise control of the temperature of cryopumping surfaces, we also identify conditions under which elastic collisions with the background gas can lead to an apparent steady heating rate, despite rare collisions.
Summary
We present measurements of trapped-ion motional-state heating rates in niobium and gold surface-electrode ion traps over a range of trap-electrode temperatures from approximately 4 K to room temperature (295 K) in a single apparatus. Using the sideband-ratio technique after resolved-sideband cooling of single ions to the motional ground state, we...
READ MORE