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Air Traffic Management (ATM) Technology Demonstration - 1 (ATD-1):
Interval Management - Terminal Area Precision Scheduling and Spacing (IM-TAPSS)

Today’s National Airspace System

At any given moment, up to 5,000 aircraft crowd U.S. skies. In 2010, the National Airspace System (NAS) managed the progress of nearly 10 million flights. Such high air traffic demand, operating with procedures that were largely in place from the earliest days of commercial aviation, does not always result in the most efficient or coordinated operations. As a result, the air transportation system often experiences significant delays and lost productivity, and produces greater amounts of noise pollution, carbon dioxide, and other greenhouse gas emissions than if operations were more efficient. As air traffic demand is projected to double in the next 20 years, our current air traffic control system will be further strained and the environment adversely affected.

Improving the efficiency of the terminal area, which is the volume of airspace surrounding airports to a radius of about 50 miles, is an especially complex task due to operating characteristics that are quite distinct from the en route environment. Terminal area controllers manage both ascending and descending aircraft, more frequent turns, a wider range of separation standards, as well as terrain and increased traffic density within shorter time horizons.

In today’s terminal area arrival operations, as an aircraft transitions for landing, controllers track and guide the aircraft from cruise altitude to the runway using simple visual aids as well as their skills and judgment. They issue turn-by-turn instructions (a process known as vectoring) via radio communications. As aircraft approach the runways, controllers manually merge aircraft and sequence them for arrival. Busy terminal area conditions often force the aircraft to fly inefficient arrival paths involving frequent changes in direction, altitude, and speed to maintain safe separation from other aircraft. Frequently, controllers must employ longer routes (known as path stretching) or holding patterns to tactically accommodate larger amounts of delay. The tactical nature of this manual approach leads to increased fuel burn and noise pollution, contributes to high controller workload, and exacerbates traffic congestion. Moreover, the imprecision of this current system creates greater uncertainty, and forces controllers to add buffers to the separation required between aircraft, which decreases airspace capacity, leading to further delays.

While more efficient arrival paths are achievable today, current technology limits their feasibility to only during light traffic conditions, such as during the middle of the night. During periods of high-density traffic, maintaining safe separation and throughput take precedence over achieving efficient operations. The technical challenge facing the aviation community is to make efficient arrival procedures common practice during heavy traffic when they are needed most, while still ensuring safety and throughput.

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NextGen: The Airspace System of the Future

NASA is collaborating with the FAA and other industry partners to develop several advanced automation tools that provide air traffic controllers, pilots, and other airspace users with more accurate real-time information about the nation’s traffic flow, weather, and routing. The greater precision of this information is a key enabler of the Next Generation Air Transportation System (referred to as NextGen). NextGen is a comprehensive transformation of the NAS, which will be safer, more reliable and more efficient, and will reduce the impact of aviation on the environment. The transition to NextGen is vital to improving system performance, meeting continued growth in air traffic, and increasing the Nation’s mobility to support economic progress.

ATM Technology Demonstration-1 (ATD-1) will showcase an integrated set of NextGen technologies that provide an efficient arrival solution for managing aircraft beginning from just prior to top-of-descent and continuing down to the runway.
    These technologies are:
  • Automatic Dependent Surveillance – Broadcast (ADS-B)
  • Area Navigation (RNAV) Arrival Routes
  • Optimized Profile Descent (OPD) Procedures
  • Terminal Metering
  • Flight Deck Interval Management (FIM)
  • Controller Managed Spacing (CMS) tools
These ATM technologies have thus far been tested separately and each has demonstrated throughput, delay, and/or fuel-efficiency benefits. Together, the technologies will demonstrate the feasibility of high throughput of efficient arrival operations during peak traffic conditions in the terminal area. Simply put, the integration of these terminal arrival tools will allow arrival aircraft to safely fly closer together on more fuel-efficient routes to increase capacity, reduce delay, and minimize fuel burn, noise, and greenhouse gas emissions.

Screenshot of the Traffic Management Advisor (TMA) timelines
The Traffic Management Advisor (TMA) will determine an arrival schedule along advanced RNAV arrival routes for safe, orderly, and expeditious flow of traffic in the terminal area.

Using the ATD-1 technologies, both pilots and controllers will have more accurate and timely information and advisories, thus reducing the need for extensive coordination and negotiation between them to achieve more efficient operations. Terminal Metering (based on precision scheduling enhancements to the Traffic Management Advisor [TMA]) will determine an arrival schedule based on airport conditions, airport capacity, required spacing, and weather conditions and utilize new, more direct RNAV routes that extend from en route airspace and continue through terminal airspace to the runway. The schedule, determined well in advance of when it is executed, will be communicated to both controllers and flight crews. Flight crews will know their intended flight path, which aircraft they ought to be following, and the desired spacing interval at certain points along their designated RNAV route to reach the destination airport safely and on schedule. Controllers will no longer have to make tactical, last second decisions concerning merges and arrival slots, and will not likely need to provide as many interventions as they do in today’s busy traffic conditions.

Image of Flight Deck Interval Management (FIM) tools
Flight Deck Interval Management (FIM) tools aboard the aircraft will enable flight crews to precisely space their aircraft relative to others to achieve ideal spacing.

To achieve the precise schedule set by TMA, some flight decks will be equipped with sophisticated onboard avionics. Flight Deck Interval Management (FIM) tools will provide guidance to pilots on whether to speed up or slow down to precisely merge and space their aircraft relative to others. The FIM tools will calculate speed advisories using information provided by ADS-B technology aboard the aircraft that is more accurate than traditional radar. Flight crews will be able to make finer adjustments to their speed and react more quickly to achieve ideal spacing. The tighter control enabled by FIM will reduce excess spacing buffers and result in higher terminal throughput.

NextGen will leverage the ADS-B infrastructure currently being implemented by the FAA. ADS-B uses a Global Positioning Satellite (GPS) System receiver aboard the aircraft to determine that aircraft’s exact position. The ADS-B system combines the position data with the aircraft’s identifier, course, speed, and altitude, then continuously broadcasts the information to other ADS-B equipped aircraft flying in the area. The information is also broadcast to a network of ADS-B ground stations, which in turn feed controller displays and other air traffic control technologies. ADS-B information provides greater situational awareness to flight crews and allows spacing responsibility to be shifted from the ground to the air, alleviating controller workload.

Screenshot of Controller Managed Spacing (CMS) tool
Controller Managed Spacing (CMS) tools will provide controllers with the information needed to properly space all aircraft (including those not equipped with FIM) to meet terminal metering schedules.

For aircraft not equipped with FIM and ADS-B technologies in the mid-term, new Controller Managed Spacing (CMS) decision support tools will provide controllers with the information needed to properly space aircraft to meet terminal metering schedules created by TMA. CMS display enhancements will indicate to the controller where an aircraft is scheduled to be along its RNAV route, and will calculate the speed advisories needed to maintain this schedule.

Optimized Profile Descent (OPD) Procedures allow aircraft to fly a continuous, gliding descent at low engine power. Contrary to today’s typical “dive and drive” procedures in which aircraft fly powered constant-altitude segments in a step-down fashion, OPDs are considered “green descents” because they reduce fuel consumption, environmental emissions, and noise pollution. Decision support tools will synchronize the descents of all arrival aircraft and advise controllers of the RNAV route and speed profile needed so that each can maintain an efficient descent and remain properly separated from preceding and following aircraft. OPD enhancements will make green descents possible during more traffic conditions, even heavy congestion, all while satisfying terminal metering schedules and achieving precise in-trail spacing to maximize terminal throughput.

This image shows two aircraft descending for landing, one behind the other with some distance between them identified as excess spacing.
The higher precision achieved by ATD-1 technologies will reduce the size of excess spacing buffers, resulting in higher terminal throughput and capacity.

The more orderly, precise, and direct traffic flow enabled by the ATD-1 technologies will make the National Airspace System more predictable overall. This will allow airspace users to better respond to unexpected delays caused by convective weather and other airspace constraints. Instead of tactically absorbing delay close to the airport, where it is traditionally handled using path stretching and holding patterns, subtle variations in speed will be applied from cruise altitude to landing to distribute small amounts of delay over a longer portion of the flight. Strategically absorbing delay in this way relieves congestion that would normally build up near the airport, further increasing the efficiency of terminal area traffic flows.

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Next Steps to Achieving NextGen

ADS-B will serve as the future surveillance source for the NAS. To further the widespread implementation of ADS-B, the Aviation Rulemaking Committee has recommended that demonstrations, such as ATD-1, should be used to help both the government and industry evaluate potential benefits and costs of such implementation, as well as to understand the necessary equipment standards, aircraft certification guidance, and operational approvals. NASA is teaming with the FAA and other industry partners to demonstrate the capabilities of integrated terminal area scheduling with an operational field trial in the 2014-2015 timeframe. The goals of the field demonstration will be to validate the benefits of the terminal area integrated arrival solution, system interoperability, and requirements for technology transfer.

The first phase of demonstration activities will involve development of prototype systems, integration of all of the technologies, and initial human-in-the-loop simulations in NASA laboratories. The next phase will involve development of the demonstration systems, follow-on simulations using FAA facilities and personnel, flight testing of avionics, and shadow testing of the integrated system. The last phase will finalize the demonstration plans and culminate in a field trial in a controlled, yet realistic operational environment at a major U.S. airport.

ATD-1 will be a truly collaborative endeavor between government and industry. It will involve the support, cooperation, and financial commitment of NASA and the FAA, as well as key industry and commercial aviation partners. NASA foundational research and technologies in terminal area scheduling, controller decision support tools, and flight deck automation will actively leverage the FAA's NextGen infrastructure. The participation of airspace users, avionics and aircraft manufacturers, and system integrators will enable these integrated terminal area ATM technologies to be evaluated in an operational environment. The demonstration is the next major step in NASA's NextGen research and development process, and it will bring us one step closer to realizing the air transportation system of the future.

Benefits of ATD-1's Integrated Terminal Area Scheduling Technologies

  • System Benefits
    • More efficient handling of delay
    • Reduced excess spacing buffers
    • Increased throughput
    • More orderly flow of terminal area traffic
    • Better predictability
    • Decreased controller workload
  • User Benefits
    • Fewer delays
    • Greater fuel-efficiency
    • Increased use of advanced RNAV arrival procedures
  • Environmental Benefits
    • Fewer greenhouse gas emissions
    • Less noise pollution
  • Economic Benefits
    • Increased mobility to support economic progress

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Operational Integration Assessment (OIA) of NASA's Terminal Sequencing and Spacing (TSS) Completed
May 28, 2015
The Operational Integration Assessment (OIA) was a joint FAA/NASA operational assessment of the FAA's Ground-based Interval Management for Spacing (GIM-S) integrated with NASA's Terminal Sequencing and Spacing (TSS) ground automation technology in an operational-like environment at the FAA's William J. Hughes Technical Center (WJHTC).
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FAA Approves Deployment of NASA's Terminal Sequencing and Spacing (TSS)
May 1, 2015
The Federal Aviation Administration (FAA) successfully passed its final investment decision for full-scale implementation of the latest NASA-developed air traffic management (ATM) tools that allow air traffic controllers to maximize the benefits of Performance Based Navigation (PBN) procedures on approach to the runway.
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Completion of Operational Integration Assessment (OIA) Shakedown #2
May 1, 2015
The Operational Integration Assessment (OIA) is an FAA/NASA demonstration of the FAA's Ground-based Interval Management for Spacing (GIM-S) integrated with NASA's Terminal Sequencing and Spacing (TSS) ground automation technology. The second OIA shakedown was completed April 28-30, 2015.
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FIAT-5 Data Collection Completed
December 12, 2014
Twenty participants, comprised of eleven pseudo-pilots and nine controller subjects, took part in the second and last human-in-the-loop (HITL) simulation and data collection for the Fully-Integrated ATD-1 Test (FIAT)-5 during December 2-9th, 2014.
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FIAT-5 Shakedown Completed
October 3, 2014
The Fully-Integrated ATD-1 Test (FIAT) simulation #5 shakedown was conducted the week of September 29-October 3, 2014 and met all simulation objectives.
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Shakedown Simulation for Fully-Integrated ATD-1 Test (FIAT) #5 Completed
September 19, 2014
About 20 subjects participated in a series of shakedown runs of the Fully-Integrated ATD-1 Test (FIAT) #5 experiment, over three days during the week of September 8.
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Method to Enhance Scheduled Arrival Robustness (MESAR) Pilot Training and Data Collection Completed
September 19, 2014
The Method to Enhance Scheduled Arrival Robustness (MESAR) team completed two weeks of pseudo-pilot training with Subject Matter Experts (SMEs) and data collection with two different groups of participants from August 11-29.
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Tackling Optimized Profile Descent Procedures
September 8, 2014
Article by John Croft Washington. A version of this article appears in the September 8 issue of Aviation Week & Space Technology (page 36).
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Operational Integration Assessment (OIA) Progress Continues
September 4, 2014
Successful initial integration of the Terminal Sequencing and Spacing (TSS)-enhanced Standard Terminal Automation Replacement System (STARS) prototype into the FAA's William J. Hughes Technical Center (WJHTC) lab was achieved in August.
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NASA and FAA Operational Integration Assessment for Terminal Sequencing and Spacing Kickoff Meeting
August 22, 2014
NASA and the Federal Aviation Administration (FAA) are planning an Operational Integration Assessment (OIA) of the Terminal Sequencing and Spacing (TSS) technology.
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Fully-Integrated ATD-1 Test (FIAT) Shakedown Simulation #5 Completed
August 8, 2014
The second shakedown simulation of FIAT-5 was conducted from July 28-31 and focused on Albuquerque Center (ZAB) airspace.
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NASA Turns Over Next-Generation Air Traffic Management Tool to FAA
July 15, 2014
NASA press release on the technology transfer of the Terminal Sequencing and Spacing technologies from NASA to the FAA.
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Delivery of STARS Version of ATD-1 Ground Tool Software
May 29, 2014
On May 22, 2014, NASA accepted the Raytheon delivery and demonstration of the "SCOUT" version of the Air traffic management Technology Demonstration-1 (ATD-1) ground tools software.
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Fully Integrated ATD-1 Test (FIAT) 4 Completes Shakedown Simulations
November 1, 2013
Human-in-the-loop simulations were completed the week of October 28 to evaluate the performance of the ATD-1 system, specifically assessing the new airborne spacing algorithm (ASTAR12) in a variety of wind conditions and traffic scenarios.
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Terminal Sequencing and Spacing-2 (TSS-2) Simulation
April 18, 2012
In April 2013, the Division hosted the successful completion of a two-week, high-fidelity Air Traffic Control (ATC) simulation of the Air traffic management Technology Demonstration-1 (ATD-1) technologies, focusing on the ATD-1 ground scheduling and control tool which the Federal Aviation Administration (FAA) has adopted, and is calling Terminal Sequencing and Spacing (TSS).
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Air Traffic Management Technology Demonstration-1 (ATD-1) Research Transition Team Kickoff
November 15, 2012
The ATD-1 team participated in a kickoff meeting of the NASA-FAA Research Transition Team on November 6-7 in Washington, DC.
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Fully Integrated ATD-1 Test (FIAT) Simulation Achieves Major Milestone
October 19, 2012
The Terminal Area Precision Scheduling and Spacing (TAPSS) research group has made major strides in the past four months, extending the TAPSS system to include the flight deck interval management capabilities for human-in-the-loop (HITL) evaluation.
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Validation of Air traffic management Technology Demonstration-1 (ATD-1) ground-based scheduling and controller advisory tools
October 19, 2012
From September 10-14, 2012, Aviation Systems Division researchers completed a simulation to validate the Federal Aviation Administration's (FAA's) interest in ATD-1 tools to enhance the FAA's current NextGen investment in Performance Based Navigation (PBN) procedures throughout the National Airspace System.
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Completion of ATD-1/STARS Feasibility Study
October 19, 2012
In September 2012, a Raytheon Corporation team under contract to NASA successfully completed a demonstration of an Air traffic management Technology Demonstration-1 (ATD-1) feasibility study that will significantly reduce the risk of technology transfer of the ATD-1 ground tools to the Federal Aviation Administration (FAA).
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FY2012 Highlights
ATD-1 highlights for fiscal year 2012
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ATD-1 Tech Transfer Documents
Version 2, February 2014
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"NASA's ATM Technology Demonstration-1: Moving NextGen Arrival Concepts from the Laboratory to the Operational NAS"
Swenson, H.N., Robinson, J.E., and Winter, S., Journal of Air Traffic Control, Summer 2013, Volume 55, No. 2, pp. 27-37.
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"Air Traffic Management Technology Demonstration-1 Concept of Operations (ATD-1 ConOps)"
Baxley, B., Johnson, W.C., Swenson, H.N., Robinson, J.E., Prevot, T., Callantine, T.J., Scardina, J., Greene, M., NASA TM-2012-217585, July 2012.
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"Air Traffic Management Technology Demonstration-1 Concept of Operations (ATD-1 ConOps), Version 2.0"
Baxley, B., Johnson, W.C., Swenson, H.N., Robinson, J.E., Prevot, T., Callantine, T.J., Scardina, J., Greene, M., NASA TM-2013-218040, Sep. 2013.
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"NASA's ATM Technology Demonstration-1: Integrated Concept of Arrival Operations"
Baxley, B., Swenson, H., Prevot, T., Callantine, T., 31st Digital Avionics Systems Conference (DASC), Williamsburg, VA, 14-18 Oct. 2012.
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"Design and Evaluation of the Terminal Area Precision Scheduling and Spacing System," Swenson, H.N., Thipphavong, J., Sadovsky, A., Chen, L., Sullivan, C., and Martin, L., 9th USA/Europe ATM R&D Seminar (ATM2011), Berlin, Germany, 14-17 June 2011.
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"Efficiency Benefits Using the Terminal Area Precision Scheduling and Spacing System," Thipphavong, J., Swenson, H., Lin, P., Seo, A.Y., and Bagasol, L.N., AIAA-2011-6971, 11th American Institute of Aeronautics and Astronautics (AIAA) Aviation Technology, Integration, and Operations (ATIO) Conference, Virgina Beach, VA, 20-22 Sep. 2011.
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"Effects of Scheduling and Spacing Tools on Controllers' Performance and Perceptions of Their Workload," Martin, L., Swenson, H., Sadovsky, A., Thipphavong, J., Chen, L., and Seo, A. Y., 30th Digital Avionics Systems Conference (DASC), Seattle, WA, 16-20 Oct. 2011.
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"A Concept for Robust, High Density Terminal Air Traffic Operations," Isaacson, D. R., Robinson III, J. E., Swenson, H., and Denery, D.,10th AIAA Aviation Technology, Integration, and Operations (ATIO) Conference, Fort Worth, TX, 13-15 Sep. 2010.
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2011 DASC Best in Session Award
“Effects of Scheduling and Spacing Tools on Controller's Performance and Perceptions of their Workload” authored by Lynne Martin (code TH), Harry Swenson, Alex Sadovsky, Jane Thipphavong, Liang Chen and Anthony Seo (all of code AF) was awarded best paper in session. The paper documented recent Terminal Area Precision Spacing and Scheduling (TAPSS) system human-in-the-loop simulation experiments and the positive system performance and workload benefits.
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2011 NASA Honor Award
The TAPSS Team received a Group Achievement Award “for groundbreaking research, development and real-time simulation of a state-of-the-art area scheduling system for NextGen terminal area air traffic operations.” The team included representatives from NASA Ames, Optimal Synthesis Inc., San Jose State University, and UC Santa Cruz/UARC.
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NASA Fact Sheet
Download the NASA Fact Sheet on ATD-1.
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