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Development and performance of a CW coherent laser radar for detecting wake vortices

July 23, 1995
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Journal Article
Author:
Richard M. Heinrichs
…
Published in:
Optical Society of America, Coherent Laser Radar Topical Mtg., 1995 Technical Digest Series, Vol. 19, 23-27 July 1995, pp. 186-189
Topic:
ladar
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Summary

A CW-coherent laser radar using a 20-Watt CO2 laser has been constructed and deployed for the measurement of wake-vortext turbulence. This is part of a larger effort to understand the motion and decay of wake vortices as a function of the local atmospheric conditions. The construction and operation of the lidar and the initial fielding at Memphis International Airport are described.
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Summary

A CW-coherent laser radar using a 20-Watt CO2 laser has been constructed and deployed for the measurement of wake-vortext turbulence. This is part of a larger effort to understand the motion and decay of wake vortices as a function of the local atmospheric conditions. The construction and operation of the...

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Development and performance of a CW coherent laser radar for detecting wake vortices

A comparison of signal processing front ends for automatic word recognition

July 1, 1995
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Journal Article
Author:
Charles R. Jankowski Jr
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Published in:
IEEE Trans. Speech Audio Process., Vol. 3, No. 4, July 1995, pp. 286-293.
Topic:
speech recognition
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Summary

This paper compares the word error rate of a speech recognizer using several signal processing front ends based on auditory properties. Front ends were compared with a control mel filter banks (MFB) based cepstral front end in clean speech and with speech degraded by noise and spectral variability, using the TI-105 isolated word database. MFB recognition error rates ranged from 0.5 to 3.1%,, and the reduction in error rates provided by auditory models was less than 0.5 percentage points. Some earlier studies that demonstrated considerably more improvement with auditory models used linear predictive coding (LPC) based control front ends. This paper shows that MFB cepstra significantly outperform LPC cepstra under noisy conditions. Techniques using an optimal linear combination of features for data reduction were also evaluated.
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Summary

This paper compares the word error rate of a speech recognizer using several signal processing front ends based on auditory properties. Front ends were compared with a control mel filter banks (MFB) based cepstral front end in clean speech and with speech degraded by noise and spectral variability, using the...

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A comparison of signal processing front ends for automatic word recognition

Phased array calibrations using measured element patterns

June 18, 1995
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Conference Paper
Author:
Herbert M. Aumann
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Published in:
1995 IEEE Int. Symp. Digest, Antennas and Propagation, Vol. 2, 18-23 June 1995, pp. 918-921.
Topic:
antennas
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Summary

A technique to compensate for differences in phased array element patterns is presented. Each measured element pattern is approximated by a virtual array whose excitation function is determined by the Woodward-Lawson synthesis technique. By extending the virtual array beyond the physical array dimensions, mutual coupling and edge diffraction effects can be separated. An example is given where calibration by coupling matrix inversion resulted in significantly reduced array pattern sidelobes.
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Summary

A technique to compensate for differences in phased array element patterns is presented. Each measured element pattern is approximated by a virtual array whose excitation function is determined by the Woodward-Lawson synthesis technique. By extending the virtual array beyond the physical array dimensions, mutual coupling and edge diffraction effects can...

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Phased array calibrations using measured element patterns

Controller-human interface design for the final approach spacing tool

June 17, 1995
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Conference Paper
Author:
Maria Picardi Kuffner
Published in:
Proc. IFAC Man-Machine Systems Conf., 27-29 June 1995, pp. 559-564.
Topic:
air traffic control
R&D area:
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Summary

The Federal Aviation Administration is developing a set of software tools, known as the Center-TRACON Automation System (CTAS) to assist air traffic controllers in their management and control tasks. CTAS originated at National Aeronautics and Space Administration (NASA) Ames Research Center, where prototypes continue to evolve. In parallel, Massachusetts Institute of Technology/Lincoln Laboratory (MIT/LL) is refining and testing the software, including the Computer-Human Interface (CHI). This paper focuses on the CHI designed by MIT/LL for the Final Approach Spacing Tool (FAST) part of CTAS. The FAST design approach, CHI development and operational concept is presented.
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Summary

The Federal Aviation Administration is developing a set of software tools, known as the Center-TRACON Automation System (CTAS) to assist air traffic controllers in their management and control tasks. CTAS originated at National Aeronautics and Space Administration (NASA) Ames Research Center, where prototypes continue to evolve. In parallel, Massachusetts Institute...

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Controller-human interface design for the final approach spacing tool

Measuring fine structure in speech: application to speaker identification

May 9, 1995
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Conference Paper
Author:
Charles R. Jankowski Jr
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Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, ICASSP, Vol. 1, 9-12 May 1995, pp. 325-328.
Topic:
speaker recognition
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Summary

The performance of systems for speaker identification (SID) can be quite good with clean speech, though much lower with degraded speech. Thus it is useful to search for new features for SID, particularly features that are robust over a degraded channel. This paper investigates features that are based on amplitude and frequency modulations of speech formants, high resolution measurement of fundamental frequency and location of "secondary pulses," measured using a high-resolution energy operator. When these features are added to traditional features using an existing SID system with a 168 speaker telephone speech database, SID performance improved by as much as 4% for male speakers and 8.2% for female speakers.
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Summary

The performance of systems for speaker identification (SID) can be quite good with clean speech, though much lower with degraded speech. Thus it is useful to search for new features for SID, particularly features that are robust over a degraded channel. This paper investigates features that are based on amplitude...

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Measuring fine structure in speech: application to speaker identification

Language identification using phoneme recognition and phonotactic language modeling

May 9, 1995
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Conference Paper
Author:
Marc A. Zissman
Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, Vol. 5, ICASSP, 9-12 May 1995, pp. 3503-3506.
Topic:
language recognition
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Summary

A language identification technique using multiple single-language phoneme recognizers followed by n-gram language models yielded to performance at the March 1994 NIST language identification evaluation. Since the NIST evaluation, work has been aimed at further improving performance by using the acoustic likelihoods emitted from gender-dependent phoneme recognizers to weight the phonotactic likelihoods output from gender-dependent language models. We have investigated the effect of restricting processing to the most highly discriminating n-grams, and we have also added explicit duration modeling at the phonotactic level. On the OGI Multi-language Telephone Speech Corpus, accuracy on an 11-language identification task has risen to 89% on 45-s utterances and 79% on 10-s utterances. Two-language classification accuracy is 98% and 95% for the 45-s and 10-s utterance, respectively. Finally, we have started to apply these same techniques to the problem of dialect identification.
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Summary

A language identification technique using multiple single-language phoneme recognizers followed by n-gram language models yielded to performance at the March 1994 NIST language identification evaluation. Since the NIST evaluation, work has been aimed at further improving performance by using the acoustic likelihoods emitted from gender-dependent phoneme recognizers to weight the...

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Language identification using phoneme recognition and phonotactic language modeling

The effects of telephone transmission degradations on speaker recognition performance

May 9, 1995
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Conference Paper
Author:
Douglas A. Reynolds
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Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, ICASSP, Vol. 1, Speech, 9-12 May 1995, pp. 329-332.
Topic:
speaker recognition
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Summary

The two largest factors affecting automatic speaker identification performance are the size of the population an the degradations introduced by noisy communication, channels (e.g., telephone transmission). To examine experimentally these two factors, this paper presents text-independent speaker identification results for varying speaker population sizes up to 630 speakers for both clean, wideband speech and telephone speech. A system based on Gaussian mixture speaker identification and experiments are conducted on the TIMIT and NTIMIT databases. This is believed to be the first speaker identification experiments on the complete 630 speaker TIMIT and NTIMIT databases and the largest text-independent speaker identification task reported to date. Identification accuracies of 99.5% and 60.7% are achieved on the TIMIT and NTIMIT databases, respectively. This paper also presents experiments which examine and attempt to quantify the performance loss associated with various telephone degradations by systematically degrading the TIMIT speech in a manner consistent with measured NTIMIT degradations and measuring the performance loss at each step. It is found that the standard degradations of filtering and additive noise do not account for all of the performance gap between the TIMIT and NTIMIT data. Measurements of nonlinear microphone distortions are also...
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Summary

The two largest factors affecting automatic speaker identification performance are the size of the population an the degradations introduced by noisy communication, channels (e.g., telephone transmission). To examine experimentally these two factors, this paper presents text-independent speaker identification results for varying speaker population sizes up to 630 speakers for both...

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The effects of telephone transmission degradations on speaker recognition performance

Data processing techniques for airport surveillance radar weather sensing

May 8, 1995
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Conference Paper
Author:
Mark E. Weber
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Published in:
Proc. IEEE 1995 Int. Radar Conf., 8-11 May 1995, pp. 521-528.
Topic:
aviation weather
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Summary

Discusses data processing techniques that can provide high quality, automated weather information using the FAA's existing Airport Surveillance Radars (ASR-9). The cost of modifying the ASR-9 is significantly less than that for deployment of the dedicated terminal Doppler weather radar. These techniques have been implemented on a prototype ASR-9 weather surveillance processor (WSP) and have been tested operationally at the Orlando, FL and Albuquerque, NM air traffic control towers. The key to the success of this system has been the development of innovative data processing techniques that accommodate the non-optimum parameters of the ASR as a weather sensor. The authors motivate the development of the ASR-9 WSP system and describe in detail the data processing techniques that have been employed to achieve an operationally useful capability. They provide an overview of the WSP and the ongoing system development and test program. They provide specifics on the data processing algorithms that have been key to successful implementation of this capability.
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Summary

Discusses data processing techniques that can provide high quality, automated weather information using the FAA's existing Airport Surveillance Radars (ASR-9). The cost of modifying the ASR-9 is significantly less than that for deployment of the dedicated terminal Doppler weather radar. These techniques have been implemented on a prototype ASR-9 weather...

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Data processing techniques for airport surveillance radar weather sensing

Comparative analysis of ground-based wind shear detection radars

May 8, 1995
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Conference Paper
Author:
Mark E. Weber
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Published in:
Proc. IEEE 1995 Int. Radar Conf., 8-11 May 1995, pp. 486-495.
Topic:
wind shear
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Summary

The UNISYS Corporation has developed a microburst prediction radar (MBPR) to provide detection and short-term predictions of the most hazardous form of low altitude wind shear in the vicinity of an airport. The MBPR is intended for deployment on- or near-airport so as to minimize range coverage (and associated radar power-aperture) requirements. Like the airport surveillance radar wind shear processor (ASR-WSP), the cost of the MBPR is significantly less than that of the terminal Doppler weather radar (TDWR) so that its deployment at smaller airports might be economically justified if the performance is operationally acceptable. Field tests of engineering prototypes of the MBPR have been conducted in conjunction with FAA-sponsored TDWR and WSP demonstration programs. We assess the capabilities and limitations of each of these systems using a consistent methodology that emphasizes the comparative analysis of the significant parameters of each radar in relation to wind shear phenomenology. An extensive database on wind shear event radar cross section, spatial structure and intensity distribution-derived through our FAA-sponsored testing of TDWR and ASR-WSP prototypes is an important asset in developing this comparison.
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Summary

The UNISYS Corporation has developed a microburst prediction radar (MBPR) to provide detection and short-term predictions of the most hazardous form of low altitude wind shear in the vicinity of an airport. The MBPR is intended for deployment on- or near-airport so as to minimize range coverage (and associated radar...

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Comparative analysis of ground-based wind shear detection radars

Terminal Weather Information for Pilots (TWIP) Test Report for 1994 Memphis and Orlando Demonstrations

April 28, 1995
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Project Report
Author:
Steven D. Campbell
Published in:
MIT Lincoln Laboratory Report ATC-227
Topic:
weather
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Summary

Demonstrations of delivering the Terminal Weather Information for Pilots (TWIP) products to air carrier pilots via the Aircraft Communications Addressing and Reporting System (ACARS) data link were carried out at Memphis and Orlando during the summer of 1994. Six airlines participated in the demonstrations at both airports. The Terminal Weather Text Message and the Terminal Weather Character Graphics Depiction were evaluated using request/reply and forced update approaches. In the first case, the pilot needed to make a request in order to obtain the TWIP products. In the second case, the TWIP message was sent to the aircraft automatically when certain criteria were met (e.g., the aircraft was within 20 minutes of landing and wind shear alerts began at the airport). Five of the airlines used the request/reply approach, and one airline used the forced update approach. Pilot and contoller response to the TWIP products were evaluated using questionnaires. Statistics on message traffic and content were analyzed, and some cases were analyzed in detail to compare the TWIP products with the existing Surface Aviation Observation (SAO) reports. Recorded radio traffic also was analyzed to determine if there was any effect on the number of requests for terminal weather information. Pilots rated the TWIP products favorably, with most indicating that the messages provided improved situational awareness of terminal weather hazards without substantially increased cockpit workload. Controller reaction to the TWIP demonstration was generally neutral, indicating that providing these messages to pilots caused no substantial increase in contoller workload. Further results of the demonstration are discussed in the report, along with recommendations for subsequent TWIP demonstrations.
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Summary

Demonstrations of delivering the Terminal Weather Information for Pilots (TWIP) products to air carrier pilots via the Aircraft Communications Addressing and Reporting System (ACARS) data link were carried out at Memphis and Orlando during the summer of 1994. Six airlines participated in the demonstrations at both airports. The Terminal Weather...

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Terminal Weather Information for Pilots (TWIP) Test Report for 1994 Memphis and Orlando Demonstrations
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