Publications
Evaluation of Eta model forecasts as a backup weather source for CTAS
August 6, 2001
Conference Paper
Published in:
AIAA Guidance, Navigation and Control Conf.: a collection of Technical Papers, Vol. 3, 6-9 August 2001, pp. 1837-1842.
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Summary
Knowledge of present and future winds and temperature is important for air traffic operations in general, but is crucial for Decision Support Tools (DSTs) that rely heavily on accurately predicting trajectories of aircraft. One such tool is the Center-TRACON Automation System (CTAS) developed by NASA Ames Research Center. The Rapid Update Cycle (RUC) system is presently the principal source of weather information for CTAS. RUC provides weather updates on an hourly basis on a nationwide grid with horizontal resolution of 40 km and vertical resolution of 25 mb in pressure. However, a recent study of RUC data availability showed that the NWS and NOAA servers are subject to frequent service interruptions. Over a 210 day period (4/19/00-11/11/00), the availability of two NOAA and one NWS RUC server was monitored automatically. It was found that 60 days (29%) had periods of one hour or more where at least one server was out, with the longest outage lasting 13 hours on 9/21/00. In addition, there were 9 days (4%) for which all three servers were simultaneously unavailable, with the longest outage lasting 6 hours on 5/7/00. Moreover, even longer outages have been experienced with the RUC servers over the past several years. RUC forecasts are provided for up to 12 hours, but these are not currently used in CTAS as back up sources (except that the 1 or 2 hour forecasts are used for the current winds to compensate for transmission delays in obtaining the RUC data). Since RUC outages have been experienced for longer than 12 hours, it is therefore necessary to back RUC up with another weather source providing long-range forecasts. This paper examines the use of the Eta model forecasts as a back-up weather sources for CTAS. A specific output of the Eta km model, namely Grid 104, was selected for evaluation because its horizontal and vertical resolution, spatial extent and output parameters match most closely those of RUC. While RUC forecasts for a maximum of 12 hours into the future, Eta does so for up to 60 hours. In the event that a RUC outage would occur, Eta data could be substituted. If Eta data also became unavailable, the last issued forecasts could allow CTAS to continue to function properly for up to 60 hours. The approach used for evaluating the suitability of the Eta model and RUC forecasts was to compare them with the RUC analysis output or 0 hour forecast file, at the forecast time. Not surprisingly, it was found that the RUC model forecasts had lower wind magnitude errors out to 12 hours (the limit of the RUC forecasts) than the Eta model had. Hosever, the wind magnitude error for the Eta model grew only from 9 ft/s at 12 hours (comparable with RUC) to 11 ft/s at 48 hours. We therefore conclude that RUC forecasts should be used for outages up to 12 hours and Eta model forecasts should be used for outages up to 60 hours.
Summary
Knowledge of present and future winds and temperature is important for air traffic operations in general, but is crucial for Decision Support Tools (DSTs) that rely heavily on accurately predicting trajectories of aircraft. One such tool is the Center-TRACON Automation System (CTAS) developed by NASA Ames Research Center. The Rapid...
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The design and implementation of the new center/TRACON automation system (CTAS) weather distribution system
August 6, 2001
Conference Paper
Published in:
AIAA Guidance, Navigation and Control Conf.: a collection of Technical Papers, Vol. 3, 6-9 August 2001, pp. 1818-1836.
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Summary
The National Aeronautics and Space Administration (NASA), working with the Federal Aviation Administration (FAA), is developing a suite of decision support tools, called the Center/TRACON Automation System (CTAS). CTAS tools such as the Traffic Management Advisor (TMA) and Final Approach Spacing Tool (FAST) are designed to increase the efficiency of the air traffic flow into and through Terminal airspace. A core capability of CTAS is the Trajectory Synthesis (TS) software for accurately predicting an aircraft's trajectory. In order to compute these trajectories, TS needs an efficient access mechanism for obtaining the most up-to-date and accurate winds. The current CTAS weather access mechanism suffers from several major drawbacks. First, the mechanism can only handle a winds at a single resolution (presently 40-80 km). This prevents CTAS from taking advantage of high resolution wind from sources such as the Integrated Terminal Weather System (ITWS). Second, the present weather access mechanism is memory intensive and does not extend well to higher grid resolutions. This potentially limits CTAS in taking advantage of improvements in wind resolution from sources such as the Rapid Update Cycle (RUC). Third, the present method is processing intensive and limits the ability of CTAS to handle higher traffic loads. This potentially could impact the ability of new tools such as Direct-To and Multi-Center TMA (McTMA) to deal with increased traffic loads associated with adjacent Centers. In response to these challenges, M.I.T. Lincoln Laboratory has developed a new CTAS weather distribution (WxDist) system. There are two key elements to the new approach. First, the single wind grid is replaced with a set of nested grids for the TRACON, Center and Adjacent Center airspaces. Each and the grids are updated independently of each other. The second key element is replacement of the present interpolation scheme with a nearest-neighbor value approach. Previous studies have shown that this nearest-neighbor method does not degrade trajectory accuracy for the grid sizes under consideration. The new software design replaces the current implementation, known as the Weather Data Processing Daemon (WDPD), with a new approach. The Weather Server (WxServer) sends the weather grids to a Weather Client (WxClient) residing on each CTAS workstation running TS or PGUI (Planview Graphical User Interface) processes. The present point-to-point weather file distribution is replaced in the new scheme with a reliable multi-cast mechanism. This new distribution mechanism combined with data compression techniques greatly reduces network traffic compared to the present method. Other new processes combine RUC and ITWS data in a fail-soft manner to generate the multiple grids. The nearest-neighbor access method also substantially speeds up weather access. In combination with other improvements, the winds access speed is more than doubled over the original implementation.
Summary
The National Aeronautics and Space Administration (NASA), working with the Federal Aviation Administration (FAA), is developing a suite of decision support tools, called the Center/TRACON Automation System (CTAS). CTAS tools such as the Traffic Management Advisor (TMA) and Final Approach Spacing Tool (FAST) are designed to increase the efficiency of...
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Evaluation of runway-assignment and aircraft-sequencing algorithms in terminal area automation
September 1, 1994
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 7, No. 2, Fall 1994, pp. 215-238.
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The Federal Aviation Administration has responded to the steady growth of air traffic and the ensuing increase in delays at airports by initiating new programs for increasing the efficiency of existing air traffic control facilities. The Terminal Air Traffic Control Automation (TATCA) program is intended to increase efficiency by providing controllers with planning aids and advisories to help them in vectoring, sequencing, and spacing traffic arriving at busy airports. Two important algorithms in this system allocate arrivals to multiple runways and set up the best sequences for landing aircraft. This article evaluates the potential for such algorithms to achieve higher throughput with less delay. The results show that, at airports with multiple active runways, the introduction of algorithms for systematic allocation of runways increases throughput considerably. These algorithms are in fact more effective than algorithms that aim at generating optimal landing sequences based on aircraft weight-class inputs. This result is fortuitous because algorithms for optimal sequencing are significantly more difficult to implement in practice than are algorithms for runway allocation. This study also provides a scientific basis for estimating future benefits of terminal automation by using traffic models patterned on actual recorded traffic-flow data, and by proposing a unified method for assessing performance.
Summary
The Federal Aviation Administration has responded to the steady growth of air traffic and the ensuing increase in delays at airports by initiating new programs for increasing the efficiency of existing air traffic control facilities. The Terminal Air Traffic Control Automation (TATCA) program is intended to increase efficiency by providing...
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Effects of metering precision and terminal controllability on runway throughput
July 1, 1993
Journal Article
Published in:
Air Traffic Control Q., Vol. 1, No. 3, July 1993, pp. 277-297.
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Summary
In order to efficiently use available runway capacity while avoiding undue congestion within terminal airspace, systems of flow control and en route metering have been implemented. Recent work in automation has attempted to extend traffic flow planning to provide precise scheduling of traffic flow within the terminal area itself (from the metering fixes to the runways). The goal of this more detailed terminal scheduling is more efficient runway utilization. This article addresses an important practical question regarding the degree of precision required from the en route portion of such systems in order to allow the terminal scheduler to achieve its throughput benefits. The answer to this question determines the sophistication and rigidity required of en route automation and addresses the question of whether the success of new terminal automation is contingent upon improvements in en route metering. The method of analysis is mathematical modeling and fast-time computer simulation. A crucial parameter is controllability, which expresses the largest flight delay that the terminal scheduling can impose within the airspace available to it. The analysis reveals that achievable run-way utilization depends upon the type of metering employed, the available controllability within the terminal, and the extent to which controllers can be expected to intervene to handle transient peaks in arrival rates that cannot be handled by the automation. The major conclusion of the study is that in order to fully utilize a runway, the standard deviation of the errors in arrival time at the metering fixes should be kept to about half the terminal controllability. For the airports studied, there seems to be sufficient controllability available to allow a terminal scheduler to operate the runways at essentially full capacity when a metering system, even with modest delivery precision, is operating in the en route area.
Summary
In order to efficiently use available runway capacity while avoiding undue congestion within terminal airspace, systems of flow control and en route metering have been implemented. Recent work in automation has attempted to extend traffic flow planning to provide precise scheduling of traffic flow within the terminal area itself (from...
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Planning horizon requirements for automated terminal scheduling
October 1, 1990
Conference Paper
Published in:
Proc. 35th Annual Air Traffic Control Association Mtg., 16-20 September 1990, pp. 438-451.
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This paper presents the results of an engineering analysis of the ability of an automated terminal scheduling process to achieve efficient use of runways. The motivation for the analysis is the need to understand possible architectures for an implementation of the proposed Terminal Air Traffic Automation (TATCA) system. The performance of TATCA is dependent upon metering precision and the controllability that TATCA can apply to aircraft entering the scheduling process. Controllability refers to the amount of time by which the flight time of an aircraft can be lengthened or shortened between the scheduling horizon and the chosen runway. The analysis concludes that when current en route metering mechanisms are used to deliver traffic to the terminal, the terminal scheduler meets a controllability window of 300 seconds or so in order to achieve full runway utilization. Because this amount of controllability is often achievable within the terminal area itself, a TATCA system can provide significant benefits prior to the implementation of further improvements in the en route metering process.
Summary
This paper presents the results of an engineering analysis of the ability of an automated terminal scheduling process to achieve efficient use of runways. The motivation for the analysis is the need to understand possible architectures for an implementation of the proposed Terminal Air Traffic Automation (TATCA) system. The performance...
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Alternate waveforms for a low-cost civil GPS receiver
April 14, 1980
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-86
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This report examines the technical feasibility of alternate waveforms to perform the GPS functions and to result in less complex receivers than is possible with the GPS C/A waveform. The approach taken to accomplish this objective is (a) to identify, after a quick broad overview, a few promising waveforms, (b) to complete the architectural synthesis of a GPS system based on the new waveforms, (c) to analyze the performance of these systems in providing ranging and communication capability and (d) to assess the impact on receiver hardware and software. One conclusion is that the class of pulsed waveform, when combined with emerging matched filter technology, permits the use of a greatly simplified receiver design. Although very specific, the design was intended as a vehicle for performance analysis only and many refinements and alternatives within the same class are possible. Other classes of waveforms such as tome ranging and chirped FM waveforms, although adequate, do not seem superior to the present PN encoded CW waveform for GPS. Finally, if the "alternate" waveform is simply the present C/A waveform but with substantially increased power level, it is shown that with the present designs the performance will be greatly increased or, alternatively, performance margin can be traded for a simplified receiver implementation.
Summary
This report examines the technical feasibility of alternate waveforms to perform the GPS functions and to result in less complex receivers than is possible with the GPS C/A waveform. The approach taken to accomplish this objective is (a) to identify, after a quick broad overview, a few promising waveforms, (b)...
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DABS sensor interactions with ATC facilities
April 22, 1976
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-51
Summary
This document presents, on a functional level, the interactions that occur between a DABS sensor and an ATC facility (terminal or enroute) in order to make full use of the capabilities provided by the addition of DABS sensors to the ATC system. There are three functions of the interactions: (1) handle surveillance reports from the DABS site, (2) handle the two-way digital communications messages between pilots and controllers, and (3) handle a variety of control data messages between the two sites. For each kind of interaction, the actions taken by the DABS sensor are summerized, the messages involved in the transaction are defined, and suggestions are made concerning possible appropriate actions by the ATC facility. The latter include message generation and display, data processing, and controller and system manager activities.
Summary
This document presents, on a functional level, the interactions that occur between a DABS sensor and an ATC facility (terminal or enroute) in order to make full use of the capabilities provided by the addition of DABS sensors to the ATC system. There are three functions of the interactions: (1)...
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Design validation of the network management function
February 2, 1976
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-54
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This document presents the results of a major design validation effort of the Network Management function described in the DABS Engineering Requirements document. The design validation is based on simulation of a DABS network of three sensors interacting with airborne traffic of approximately 800 aircraft
Summary
This document presents the results of a major design validation effort of the Network Management function described in the DABS Engineering Requirements document. The design validation is based on simulation of a DABS network of three sensors interacting with airborne traffic of approximately 800 aircraft
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Network management
May 16, 1975
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-45
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This report provides a discussion of the design of the DABS network management function. Network management is responsible for the interaction between the local sensor and the adjacent connected sensors. Based on a dynamic interpretation of the coverage map and the status of the network, network management determines (a) the coverage responsibility of the local sensor, (b) which other sensors are covering the same area, and (c) which of the sensors has principal data link responsibility. Interaction is effected through message exchange over ground communication links connecting the DABS sensors.
Summary
This report provides a discussion of the design of the DABS network management function. Network management is responsible for the interaction between the local sensor and the adjacent connected sensors. Based on a dynamic interpretation of the coverage map and the status of the network, network management determines (a) the...
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Provisional message formats for the DABS/NAS interface, revision 1
October 10, 1974
Project Report
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MIT Lincoln Laboratory Report ATC-33,I
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This document defines formats for messages which are to be transmitted between DABS and NAS facilities (en route or terminal). These messages include one-way Surveillance Reports to NAS and two-way Communications Messages. The latter support data link functions between NAS and DABS equipped aircraft, as well as aiding in the monitoring and control of DABS sensors. These message formats will be used in the design and construction of interface equipment and ground data links for prototype system test and evaluation at NAFEC during Phase II of the DABS Development Program; and, with modifications resulting from this test and evaluation effort, will form the basis for the operational implementation of DABS. This document supersedes FAA-RD-74-63, dated 25 April 1974.
Summary
This document defines formats for messages which are to be transmitted between DABS and NAS facilities (en route or terminal). These messages include one-way Surveillance Reports to NAS and two-way Communications Messages. The latter support data link functions between NAS and DABS equipped aircraft, as well as aiding in the...
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