Publications
Method to characterize potential UAS encounters using open source data
November 1, 2020
Journal Article
Published in:
Aerospace, Vol. 7, No. 11, November 2020, art. no. 158.
Summary
As unmanned aerial systems (UASs) increasingly integrate into the US national airspace system, there is an increasing need to characterize how commercial and recreational UASs may encounter each other. To inform the development and evaluation of safety critical technologies, we demonstrate a methodology to analytically calculate all potential relative geometries between different UAS operations performing inspection missions. This method is based on a previously demonstrated technique that leverages open source geospatial information to generate representative unmanned aircraft trajectories. Using open source data and parallel processing techniques,we performed trillions of calculations to estimate the relative horizontal distance between geospatial points across sixteen locations.
Summary
As unmanned aerial systems (UASs) increasingly integrate into the US national airspace system, there is an increasing need to characterize how commercial and recreational UASs may encounter each other. To inform the development and evaluation of safety critical technologies, we demonstrate a methodology to analytically calculate all potential relative geometries...
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Geospatial QPE accuracy dependence on weather radar network configurations
October 27, 2020
Journal Article
Published in:
J. Appl. Meteor. Climatol., Vol. 59, No. 1, 2020, pp. 1773-92.
Summary
The relatively low density of weather radar networks can lead to low-altitude coverage gaps. As existing networks are evaluated for gap-fillers and new networks are designed, the benefits of low-altitude coverage must be assessed quantitatively. This study takes a regression approach to modeling quantitative precipitation estimation (QPE) differences based on network density, antenna aperture, and polarimetric bias. Thousands of cases from the warm-season months of May–August 2015–2017 are processed using both the specific attenuation [R(A)] and reflectivity-differential reflectivity [R(Z,ZDR)] QPE methods and are compared against Automated Surface Observing System (ASOS) rain gauge data. QPE errors are quantified based on beam height, cross-radial resolution, added polarimetric bias, and observed rainfall rate. The collected data are used to construct a support vector machine regression model that is applied to the current WSR-88D network for holistic error quantification. An analysis of the effects of polarimetric bias on flash-flood rainfall rates is presented. Rainfall rates based on 2-year/1-hr return rates are used for a CONUS-wide analysis of QPE errors in extreme rainfall situations. These errors are then re-quantified using previously proposed network design scenarios with additional radars that provide enhanced estimate capabilities. Finally, a gap-filling scenario utilizing the QPE error model, flash-flood rainfall rates, population density, and potential additional WSR-88D sites is presented, exposing the highest-benefit coverage holes in augmenting the WSR-88D network (or a future network) relative to QPE performance.
Summary
The relatively low density of weather radar networks can lead to low-altitude coverage gaps. As existing networks are evaluated for gap-fillers and new networks are designed, the benefits of low-altitude coverage must be assessed quantitatively. This study takes a regression approach to modeling quantitative precipitation estimation (QPE) differences based on...
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TCAS II and ACAS Xa traffic and resolution advisories during interval management paired approach operations
October 11, 2020
Conference Paper
Published in:
2020 AIAA/IEEE 39th Digital Avionics Systems Conf., DASC, 11-15 October 2020.
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Summary
Interval Management (IM) is an FAA Next-Gen Automatic Dependent Surveillance – Broadcast (ADS-B) In application designed to decrease the variability in spacing between aircraft, thereby increasing the efficiency of the National Airspace System (NAS). One application within IM is Paired Approach (PA). In a PA operation, the lead aircraft and trail aircraft are both established on final approach to dependent parallel runways with runway centerline spacing less than 2500 feet. The trail aircraft follows speed guidance from the IM Avionics to achieve and maintain a desired spacing behind the lead aircraft. PA operations are expected to require a new separation standard that allows the aircraft to be spaced more closely than current dependent parallel separation standards. The behavior of an airborne collision avoidance system, such as TCAS II or ACAS Xa, must be considered during a new operation such as PA, because the aircraft are so closely spaced. This analysis quantified TAs and RAs using TCAS II Change 7.1 and ACAS Xa software with simulated IM PA operations. The results show no RAs using either TCAS II Change 7.1 or ACAS Xa, negligible TAs using TCAS II Change 7.1, and acceptable numbers of TAs using ACAS Xa software during simulated PA operations.
Summary
Interval Management (IM) is an FAA Next-Gen Automatic Dependent Surveillance – Broadcast (ADS-B) In application designed to decrease the variability in spacing between aircraft, thereby increasing the efficiency of the National Airspace System (NAS). One application within IM is Paired Approach (PA). In a PA operation, the lead aircraft and...
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Weather radar network benefit model for nontornadic thunderstorm wind casualty cost reduction
September 28, 2020
Journal Article
Published in:
Wea. Climate Soc., Vol. 12, No. 4, October 2020, pp. 789-804.
Summary
An econometric geospatial benefit model for nontornadic thunderstorm wind casualty reduction is developed for meteorological radar network planning. Regression analyses on 22 years (1998–2019) of storm event and warning data show, likely for the first time, a clear dependence of nontornadic severe thunderstorm warning performance on radar coverage. Furthermore, nontornadic thunderstorm wind casualty rates are observed to be negatively correlated with better warning performance. In combination, these statistical relationships form the basis of a cost model that can be differenced between radar network configurations to generate geospatial benefit density maps. This model, applied to the current contiguous U.S. weather radar network, yields a benefit estimate of $207 million (M) yr^-1 relative to no radar coverage at all. The remaining benefit pool with respect to enhanced radar coverage and scan update rate is about $36M yr^-1. Aggregating these nontornadic thunderstorm wind results with estimates from earlier tornado and flash flood cost reduction models yields a total benefit of $1.12 billion yr^-1 for the present-day radars and a remaining radar-based benefit pool of $778M yr^-1.
Summary
An econometric geospatial benefit model for nontornadic thunderstorm wind casualty reduction is developed for meteorological radar network planning. Regression analyses on 22 years (1998–2019) of storm event and warning data show, likely for the first time, a clear dependence of nontornadic severe thunderstorm warning performance on radar coverage. Furthermore, nontornadic...
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Enhanced parallel simulation for ACAS X development
September 22, 2020
Conference Paper
Published in:
2020 IEEE High Performance Extreme Computing Conf., HPEC, 22-24 September 2020.
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Summary
ACAS X is the next generation airborne collision avoidance system intended to meet the demands of the rapidly evolving U.S. National Airspace System (NAS). The collision avoidance safety and operational suitability of the system are optimized and continuously evaluated by simulating billions of characteristic aircraft encounters in a fast-time Monte Carlo environment. There is therefore an inherent computational cost associated with each ACAS X design iteration and parallelization of the simulations is necessary to keep up with rapid design cycles. This work describes an effort to profile and enhance the parallel computing infrastructure deployed on the computing resources offered by the Lincoln Laboratory Supercomputing Center. The approach to large-scale parallelization of our fast-time airspace encounter simulation tool is presented along with corresponding parallel profile data collected on different kinds of compute nodes. A simple stochastic model for distributed simulation is also presented to inform optimal work batching for improved simulation efficiency. The paper concludes with a discussion on how this high-performance parallel simulation method enables the rapid safety-critical design of ACAS X in a fast-paced iterative design process.
Summary
ACAS X is the next generation airborne collision avoidance system intended to meet the demands of the rapidly evolving U.S. National Airspace System (NAS). The collision avoidance safety and operational suitability of the system are optimized and continuously evaluated by simulating billions of characteristic aircraft encounters in a fast-time Monte...
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Processing of crowdsourced observations of aircraft in a high performance computing environment
September 22, 2020
Conference Paper
Published in:
2020 IEEE High Performance Extreme Computing Conf., HPEC, 22-24 September 2020.
Summary
As unmanned aircraft systems (UASs) continue to integrate into the U.S. National Airspace System (NAS), there is a need to quantify the risk of airborne collisions between unmanned and manned aircraft to support regulation and standards development. Both regulators and standards developing organizations have made extensive use of Monte Carlo collision risk analysis simulations using probabilistic models of aircraft flight. We've previously determined that the observations of manned aircraft by the OpenSky Network, a community network of ground-based sensors, are appropriate to develop models of the low altitude environment. This works overviews the high performance computing workflow designed and deployed on the Lincoln Laboratory Supercomputing Center to process 3.9 billion observations of aircraft. We then trained the aircraft models using more than 250,000 flight hours at 5,000 feet above ground level or below. A key feature of the workflow is that all the aircraft observations and supporting datasets are available as open source technologies or been released to the public domain.
Summary
As unmanned aircraft systems (UASs) continue to integrate into the U.S. National Airspace System (NAS), there is a need to quantify the risk of airborne collisions between unmanned and manned aircraft to support regulation and standards development. Both regulators and standards developing organizations have made extensive use of Monte Carlo...
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Detect-and-avoid closed-loop evaluation of noncooperative well clear definitions
July 12, 2020
Journal Article
Published in:
J. Air Transp., Vol. 28, No. 4, 12 July 2020, pp. 195-206.
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Four candidate detect-and-avoid well clear definitions for unmanned aircraft systems encountering noncooperative aircraft are evaluated using safety and operational suitability metrics. These candidates were proposed in previous research based on unmitigated collision risk, maneuver initiation ranges, and other considerations. Noncooperative aircraft refer to aircraft without a functioning transponder. One million encounters representative of the assumed operational environment for the detect-and-avoid system are simulated using a benchmark alerting and guidance algorithm as well as a pilot response model. Results demonstrate sensitivity of the safety metrics to the unmanned aircraft’s speed and the detect-and-avoid system's surveillance volume. The only candidate without a horizontal time threshold, named modified tau, outperforms the other three candidates in avoiding losses of detect and avoid well clear. Furthermore, this candidate's alerting timeline lowers the required surveillance range. This can help reduce the barrier of enabling unmanned aircraft systems' operations with low size, weight, and power sensors.
Summary
Four candidate detect-and-avoid well clear definitions for unmanned aircraft systems encountering noncooperative aircraft are evaluated using safety and operational suitability metrics. These candidates were proposed in previous research based on unmitigated collision risk, maneuver initiation ranges, and other considerations. Noncooperative aircraft refer to aircraft without a functioning transponder. One million...
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The 2017 Buffalo Area Icing and Radar Study (BAIRS II)
May 14, 2020
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-447
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Summary
The second Buffalo Area Icing and Radar Study (BAIRS II) was conducted during the winter of 2017. The BAIRS II partnership between Massachusetts Institute of Technology (MIT) Lincoln Laboratory (LL), the National Research Council of Canada (NRC), and Environment and Climate Change Canada (ECCC) was sponsored by the Federal Aviation Administration (FAA). It is a follow-up to the similarly sponsored partnership of the original BAIRS conducted in the winter of 2013. The original BAIRS provided in situ verification and validation of icing and hydrometeors, respectively, within the radar domain in support of a hydrometeor-classification-based automated icing hazard algorithm. The BAIRS II motivation was to: --Collect additional in situ verification and validation data, --Probe further dual polarimetric radar features associated with icing hazard, --Provide foundations for additions to the icing hazard algorithm beyond hydrometeor classifications, and --Further characterize observable microphysical conditions in terms of S-band dual polarimetric radar data. With BAIRS II, the dual polarimetric capability is provided by multiple Next Generation Weather Radar (NEXRAD) S-band radars in New York State, and the verification of the icing hazard with microphysical and hydrometeor characterizations is provided by NRC's Convair-580 instrumented research plane during five icing missions covering about 21 mission hours. The ability to reliably interpret the NEXRAD dual polarization radar-sensed thermodynamic phase of the hydrometeors (solid, liquid, mix) in the context of cloud microphysics and precipitation physics makes it possible to assess the icing hazard potential to aviation. The challenges faced are the undetectable nature of supercooled cloud droplets (for Sband) and the isotropic nature of Supercooled Large Drops (SLD). The BAIRS II mission strategy pursued was to study and probe radar-identifiable, strongly anisotropic crystal targets (dendrites and needles) with which supercooled water (and water saturated conditions) are physically linked as a means for dual polarimetric detection of icing hazard. BAIRS II employed superior optical array probes along with state and microphysical instrumentation; and, using again NEXRAD-feature-guided flight paths, was able to make advances from the original BAIRS helpful to the icing algorithm development. The key findings that are given thorough treatment in this report are: --Identification of the radar-detectable "crystal sandwich" structure from two anisotropic crystal types stratified by in situ air temperature in association with varying levels of supercooled water --with layer thicknesses observed to 2 km, --over hundred-kilometer scales matched with the mesoscale surveillance of the NEXRAD radars, --Development and application of a multi-sensor cloud phase algorithm to distinguish between liquid phase, mixed phase, and glaciated (no icing) conditions for purposes of a "truth" database and improved analysis in BAIRS II, --Development of concatenated hydrometeor size distributions to examine the in situ growth of both liquid and solid hydrometeors over a broad size spectrum; used, in part, to demonstrate differences between maritime and continental conditions, and --The Icing Hazard Levels (IHL) algorithm’s verification in icing conditions is consistent with previous work and, new, is documented to perform well when indicating "glaciated" (no icing) conditions.
Summary
The second Buffalo Area Icing and Radar Study (BAIRS II) was conducted during the winter of 2017. The BAIRS II partnership between Massachusetts Institute of Technology (MIT) Lincoln Laboratory (LL), the National Research Council of Canada (NRC), and Environment and Climate Change Canada (ECCC) was sponsored by the Federal Aviation...
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Weather radar network benefit model for flash flood casualty reduction
April 1, 2020
Journal Article
Published in:
J. Appl. Meteor. Climatol., Vol. 59, No. 4, April 2020, pp. 589-604.
Summary
A monetized flash flood casualty reduction benefit model is constructed for application to meteorological radar networks. Geospatial regression analyses show that better radar coverage of the causative rainfall improves flash flood warning performance. Enhanced flash flood warning performance is shown to decrease casualty rates. Consequently, these two effects in combination allow a model to be formed that links radar coverage to flash flood casualty rates. When this model is applied to the present-day contiguous U.S. weather radar network, results yield a flash-flood-based benefit of $316 million (M) yr-1. The remaining benefit pools are more modest ($13M yr-1 for coverage improvement and $69M yr-1 maximum for all areas of radar quantitative precipitation estimation improvements), indicative of the existing weather radar network's effectiveness in supporting the flash flood warning decision process.
Summary
A monetized flash flood casualty reduction benefit model is constructed for application to meteorological radar networks. Geospatial regression analyses show that better radar coverage of the causative rainfall improves flash flood warning performance. Enhanced flash flood warning performance is shown to decrease casualty rates. Consequently, these two effects in combination...
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Wind information requirements for NextGen applications phase 7 report
February 12, 2020
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-444
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This report details the Required Time of Arrival (RTA) performance of B757 aircraft arriving at various meter fixes across a range of altitudes from 33,000' down to 3,000' above ground level (AGL). The system tested demonstrated less than ±10 second arrival error in at least 95% of flights at meter fixes down to 7,000' AGL regardless of the forecast quality provided. Below 7,000' AGL, RTA performance significantly degraded demonstrating around 80% compliance under the best forecast and operating conditions. This report also provides a comprehensive lexicon of aviation and air traffic control related "wind" terms.
Summary
This report details the Required Time of Arrival (RTA) performance of B757 aircraft arriving at various meter fixes across a range of altitudes from 33,000' down to 3,000' above ground level (AGL). The system tested demonstrated less than ±10 second arrival error in at least 95% of flights at meter...
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