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Forecast confidence measures for deterministic storm-scale aviation forecasts

February 5, 2014
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Conference Paper
Author:
Mark S. Veillette
…
Published in:
4th Aviation, Range, and Aerospace Meteorology Special Symp., 2-6 February 2014.
Topic:
aviation weather
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.
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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...

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Forecast confidence measures for deterministic storm-scale aviation forecasts

Velocity estimation improvements for the ASR-9 Weather Systems Processor

February 2, 2014
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Conference Paper
Author:
James M. Kurdzo
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Published in:
American Meteorological Society Annual Meeting, 2-6 February 2014.
Topic:
algorithms
R&D area:
R&D group:

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.
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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...

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Velocity estimation improvements for the ASR-9 Weather Systems Processor

High-sensitivity detection of trace gases using dynamic photoacoustic spectroscopy

February 1, 2014
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Journal Article
Author:
Charles M. Wynn
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Published in:
Opt. Eng., Vol. 53 No. 2, February 2014, 021103.
Topic:
detection systems
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.
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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...

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High-sensitivity detection of trace gases using dynamic photoacoustic spectroscopy

Authenticated broadcast with a partially compromised public-key infrastructure

February 1, 2014
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Journal Article
Author:
S. Dov Gordon
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Published in:
Info. and Comput., Vol. 234, February 2014, pp. 17-25.
Topic:
cryptography
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.
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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...

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Authenticated broadcast with a partially compromised public-key infrastructure

Initial assessment of wind forecasts for Airport Acceptance Rate (AAR) and Ground Delay Program (GDP) planning

January 29, 2014
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Project Report
Author:
Richard A. DeLaura
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Published in:
MIT Lincoln Laboratory Report ATC-414
Topic:
weather
R&D area:
R&D group:

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.
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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...

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Initial assessment of wind forecasts for Airport Acceptance Rate (AAR) and Ground Delay Program (GDP) planning

Adaptive RF canceller for transmit-receive isolation improvement

January 19, 2014
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Conference Paper
Author:
Kenneth E. Kolodziej
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Published in:
2014 IEEE Radio and Wireless Symposium (RWS), 19-23 January 2014.
Topic:
antennas
R&D area:
R&D group:

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.
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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...

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Adaptive RF canceller for transmit-receive isolation improvement

Insensitivity of the rate of ion motional heating to trap-electrode material over a large temperature range

January 16, 2014
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Journal Article
Author:
John Chiaverini
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Published in:
Phys. Rev. A, At. Mol. Opt. Phys., Vol. 89, No. 1, 2014, 012318.
Topic:
advanced materials
R&D area:
R&D group:

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.
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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...

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Insensitivity of the rate of ion motional heating to trap-electrode material over a large temperature range

A frequency selective atom interferometer magnetometer

January 13, 2014
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Journal Article
Author:
Danielle A. Braje
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Published in:
J. Mod. Opt., Vol. 61, No. 1, 2014, pp. 61-71.
Topic:
optics
R&D area:
R&D group:

Summary

In this article, we discuss the magnetic-field frequency selectivity of a time-domain interferometer based on the number and timing of intermediate pi pulses. We theoretically show that by adjusting the number of pi pulses and the pi-pulse timing, we can control the frequency selectivity of the interferometer to time varying and DC magnetic fields. We present experimental data demonstrating increased coherence time due to bandwidth filtering with the inclusion of a pi pulse between the initial and final pi/2 pulses, which mitigates sensitivity to low frequency magnetic fields.
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Summary

In this article, we discuss the magnetic-field frequency selectivity of a time-domain interferometer based on the number and timing of intermediate pi pulses. We theoretically show that by adjusting the number of pi pulses and the pi-pulse timing, we can control the frequency selectivity of the interferometer to time varying...

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A frequency selective atom interferometer magnetometer

Characterizing phonetic transformations and acoustic differences across English dialects

January 1, 2014
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Journal Article
Author:
Nancy Chen
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Published in:
IEEE Trans. Audio, Speech, and Lang. Process., Vol. 22, No. 1, January 2014, pp. 110-24.
Topic:
language recognition
R&D area:
R&D group:

Summary

In this work, we propose a framework that automatically discovers dialect-specific phonetic rules. These rules characterize when certain phonetic or acoustic transformations occur across dialects. To explicitly characterize these dialect-specific rules, we adapt the conventional hidden Markov model to handle insertion and deletion transformations. The proposed framework is able to convert pronunciation of one dialect to another using learned rules, recognize dialects using learned rules, retrieve dialect-specific regions, and refine linguistic rules. Potential applications of our proposed framework include computer-assisted language learning, sociolinguistics, and diagnosis tools for phonological disorders.
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Summary

In this work, we propose a framework that automatically discovers dialect-specific phonetic rules. These rules characterize when certain phonetic or acoustic transformations occur across dialects. To explicitly characterize these dialect-specific rules, we adapt the conventional hidden Markov model to handle insertion and deletion transformations. The proposed framework is able to...

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Characterizing phonetic transformations and acoustic differences across English dialects

Transactional array reconciliation tomography for precision indoor location

January 1, 2014
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Journal Article
Author:
Vincent T. Amendolare
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Published in:
IEEE T. Aero. Elec. Sys. Vol. 50, No. 1 January 2014, pp. 17-32.
Topic:
antennas
R&D area:
R&D group:

Summary

A novel system is described for precision indoor location and tracking of personnel inside a building using RF signals exchanged with reference units deployed outside the building without benefit of infrastructure or site survey. Localization in high multipath without multilateration by fusion of unidirectional signals using singular array reconciliation tomography is reviewed. The bidirectional signal fusion approach is introduced with transactional array reconciliation tomography. Underlying theory is developed, and performance evaluated with simulated and experimental data.
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Summary

A novel system is described for precision indoor location and tracking of personnel inside a building using RF signals exchanged with reference units deployed outside the building without benefit of infrastructure or site survey. Localization in high multipath without multilateration by fusion of unidirectional signals using singular array reconciliation tomography...

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Transactional array reconciliation tomography for precision indoor location
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