U.S.-NAS (United States - National Airspace System)
The Federal Aviation Act of 1958 established the FAA (Federal Aviation Agency) and made it responsible for the control and use of navigable airspace within the United States. The FAA created the NAS (National Airspace System) to protect persons and property on the ground, and to establish a safe and efficient airspace environment for civil, commercial, and military aviation. The NAS is made up of a network of air navigation facilities, ATC (Air Traffic Control) facilities, airports, technology, and appropriate rules and regulations that are needed to operate the system. In addition, this appendix details the various components of the NAS, and then describes how these components interact to facilitate safe and efficient air travel. 1)
As of 2020, the FAA provides every day air traffic service to more than 45,000 flights and 2.9 million airline passengers traveling across the more than 29 million square miles that make up the U.S. National Airspace System (NAS). 2) 3)
The NAS is a network of both controlled and uncontrolled airspace, both domestic and oceanic. It also includes air navigation facilities, equipment and services; airports and landing areas; aeronautical charts, information and services; rules and regulations; procedures and technical information; and manpower and material.
There are around 7,000 aircraft in the sky above America at once, according to the Federal Aviation Administration (FAA). This number is expected to only increase over the next 15 years, and it continues to get more difficult to fit all these aircraft into our current airspace structure. The FAA’s Next Generation Air Transportation System (NextGen) promises to transform the current airspace system to optimize the use of airspace, reduce emissions, save fuel and decrease flight delays. Until NextGen is fully implemented, though, our current airspace system will have to suffice.
Air Traffic Control Centers
The NAS involves more than just the control tower at your local airport. On a typical flight, a pilot will communicate with controllers at each of the following places:
• ARTCC (Air Route Traffic Control Center): The airspace over the United States is divided into 22 regional sectors, each controlled by an ARTCC. As a flight crosses the boundary from one ARTCC region to another, the air traffic controller transfers the communication responsibility for that flight to the ARTCC controller in the next region.
• TRACON (Terminal Radar Approach Control) is known simply as “approach” to pilots. When an aircraft gets close to an airport, the ARTCC controllers will transfer the communications to a TRACON controller, who will assist the aircraft for the arrival portion of its flight.
• ATCT (Controllers in the local air Traffic Control Tower) are responsible for aircraft in the associated airport's traffic pattern. Once the aircraft enters the local airport traffic pattern area, it is handed off to the ATCT, where the controllers will oversee its final approach and landing. Ground controllers are also a part of the ATCT, supervising taxi and gate operations.
• FSS (Flight Service Stations). There are currently sixFSS in operation. Flight service specialists assist pilots with preflight planning, weather briefings, and other information pertinent to a pilot’s route of flight.
The United States National Airspace System (NAS) is a complex collection of systems, procedures, facilities, aircraft, and people. These components work together as one system to ensure safe and efficient services are provided to the flying public, airlines, the US military, general aviation, and airports. The NAS includes: the US airspace, air navigation facilities, equipment, services, airports, aeronautical charts, information/services, rules, regulations, procedures, technical information, manpower, and material. Many of these components are shared jointly with the military. FAA airspace management is different from many other nations because the FAA manages both military and civil aircraft in the US airspace. 4)
All control towers, control centers, radios, radars and many airports are interconnected to form the NAS operational communications network, This network supports the transfer of voice and data among pilots, controllers and airline operation centers. Nearly all network components are capable of providing status information in (near) real time to monitoring facilities.
Figure 1: National Airspace System Major Components. The figure shows conceptually how the system currently works and what equipment is used to provide the service (image credit: FAA)
SDI - The Space Data Integrator
2016 timeframe: In response to the predicted increase in frequency and complexity of commercial launch and reentry operations, the FAA must continue its effort to develop integrated capabilities to meet the Administration's objectives to realize the anticipated operational benefits of the integration of these operations into the National Airspace System (NAS). The SDI (Space Data Integrator) platform is such a capability that automates the FAA's current manual, time consuming and resource-intensive procedures to support commercial launch and reentry operations. 5)
The objectives of the SDI are to allow for extending the operation's planning to include filing a plan, to provide situational awareness to the JSpOG (Joint Space Operations Group) at the FAA Air Traffic Control System Command Center (ATCSCC) on the launch and reentry vehicle position and mission parameters during the full operations, and to support the detection and response to abnormal events. The SDI is the result of a non-traditional approach for the FAA that is flexible, with high-implementation readiness, directly tailored to the end-user needs, and both low-cost/low impact on existing NASA automation structures. The SDI can be used as a shadow system while continuing to mature, a training tool for the JSpOG personnel, and a familiarization tool for commercial space vehicle operators, spaceport representatives and air traffic personnel.
Activities in space are typically divided into three sectors: civil, military and commercial. NASA represents the civil sector, while the DoD (Department of Defense) represents the military sector. For decades, the FAA has played a critical role in supporting NASA and DoD space launch and reentry operations by ensuring the safety of the NAS (National Airspace System). Using current procedures, volumes of airspace are temporarily closed during these operations, where the size, location, and duration correspond to the type of vehicle being operated, the location of the operation, and the duration of the operational window. In some cases, these closures can span hundreds of miles, cover the full height of the NAS, and last for several hours.
These airspace closures can have significant effects on NASA performance and capacity, imposing delays, excessive fuel burn due to route changes, or even diversions and cancellations on other NAS stakeholders. Nevertheless, the FAA's primary mission of ensuring NASA safety is never compromised, and the cost to other NASA operators has been deemed acceptable in view of the national importance attributed to NASA and DoD-sponsored launches. This critically important role is not expected to change in the near term or beyond.
For over 25 years, the FAA has also regulated the launches and reentries of commercial space transportation. Since 1988, the FAA has licenced or permitted over 250 commercial launch and reentry operations. Generally, the airspace management approach applied to these launches is the same as the approach applied to NASA and DoD launches. Since these operations have been conducted at a relatively low frequency and mostly from Federal ranges, they have, until recently, received little attention from the NAS stakeholders. This traditional role of the FAA is likely to change, although it may become more visible to both the legacy NAS stakeholders and to the public.
2021 timeframe: The Space Data Integrator (SDI) is the first of several new capabilities that the Federal Aviation Administration (FAA) is developing to further the safe integration of launch and reentry vehicles into the National Airspace System (NAS). SDI is an operational prototype that will receive and distribute launch and reentry data for initial use within the NAS to enable improved situational awareness and airspace management decision-making. 6)
While Launch and Reentry Operators (LROs) monitor their missions and vehicles in real-time, the FAA relied heavily on manual processes to retrieve and communicate space data. To monitor a mission, the FAA Air Traffic Organization (ATO) Space Operations team, located at the David J. Hurley Air Traffic Control System Command Center (ATCSCC) in Warrenton, VA, would manually gather operational data and send the data using FAA communications tools to adapt airspace usage with launch and reentry operations. SDI will provide some much-needed automation to improve the current operation.
How Does SDI Work?
The SDI operational prototype is designed to accept launch and reentry vehicle state vector data gathered from operators such as vehicle position, altitude, and speed. SDI will then process the data, display it, and distribute it to Traffic Flow Management System (TFMS). SDI allows the FAA to track the actual versus planned trajectory of launch and reentry operations, the status of various mission events, and the display of Aircraft Hazard Areas (AHAs). SDI sends vehicle position and AHAs to the TFMS for display on the TFMS Traffic Situation Display at the Command Center.
Launching the SDI, along with time-based procedural improvements, the FAA will begin to more dynamically manage the airspace, resulting in reduced duration of closed airspace to other NAS users as the mission progresses. The FAA will also respond more effectively to contingencies and release airspace back to the NAS more quickly.
SDI is one of many collaborative efforts in which the FAA has worked closely with industry stakeholders to identify opportunities to improve situational awareness to safely reduce the duration of closed airspace necessary for a launch or reentry operation, improve response effectiveness and timeliness for contingencies during launch or reentry operations, and release closed airspace back to day-to-day flight operations quickly.
Today, the ATO Space Operations team at the Command Center has the SDI operational prototype they can use, as a decision support tool, to make operational decisions while the FAA continues to refine and validate requirements. SDI is the foundational component for integrating space operations into the NAS.
In the future, new concepts will follow that further mature space integration efforts with NAS automation systems. Additional capabilities in research include enhanced situational awareness on air traffic controller displays and improved monitoring and alerting for mission conformity. These capabilities will allow air traffic to better manage, route, and schedule aircraft during launch and reentry operations. This integration will ensure safety as the FAA keeps pace with the increasing frequency and complexity of launch and reentry operations.
The end goal is to ensure we can optimize the safety, efficiency, and integration of space operations using our advanced automation tools and procedural improvements. This will allow the FAA to use the data to make more efficient airspace management decisions and improve situational awareness.
FAA Activates the SDI to Track Space Launch, Reentry Vehicles
• July 8, 2021: The U.S. FAA can now track a space launch or reentry vehicle in near-real time as it travels through the National Airspace System. This new capability increases safety for all airspace users and assists the FAA in efficiently managing air traffic during space operations. 7)
The SDI (Space Data Integrator) prototype automates the delivery of vehicle-related telemetry data to the FAA Air Traffic Control System Command Center. This vastly improves the FAA’s situational awareness of where the vehicle is as it travels to space or as it returns to the Earth. In addition to existing tools, the FAA also can use SDI to manage air traffic more efficiently as a space operation progresses and address contingencies in the event of an anomaly during a mission.
The SDI capability recently became operational and was first used with the June 30 SpaceX Transponder-2 launch from Cape Canaveral Space Force Station in Florida. It will next be used with the upcoming reentry of the SpaceX CRS-22 Dragon vehicle carrying cargo on its return trip from the International Space Station.
“This is a critical tool as the number of users of our already busy airspace increases,” said FAA Administrator Steve Dickson. “With this capability, we will be able to safely reopen the airspace more quickly and reduce the number of aircraft and other airspace users affected by a launch or reentry.”
Currently, the FAA has to close airspace for extended periods of time when a launch or reentry vehicle travels through the National Airspace System. SDI will allow the FAA to more dynamically manage airspace and minimize the impact on other airspace users.
Telemetry data provided via SDI includes vehicle position, altitude, speed, and if it deviates from its expected flight path. It also displays tracking for the vehicle during its full flight and allows the FAA to monitor whether the vehicle is performing as planned. In addition, the SDI capability is able to display and share aircraft hazard areas that may potentially contain falling debris from a launch or reentry vehicle.
Space operators share the telemetry data on a voluntary basis. SpaceX is the first company to participate and has provided data to the FAA since 2016 in the early stages of the SDI concept research and development. Other partners include Blue Origin, Firefly, and the Alaska Aerospace Corporation.
The FAA also recently began using time-based procedures and dynamic windows as tools to more efficiently manage launch or reentry operations in the National Airspace System. Both offer great promise showing the FAA reduced the length of airspace closures from an average of more than four hours per launch to just more than two hours. As the SDI capability evolves, it will help the FAA reopen the airspace even more quickly.
In 2020, the FAA safely managed 45 space launches and reentries into the National Airspace System, the most in the agency’s history. For 2021, that number could exceed 70.
Airspace Integration 8)
The U.S. airspace is the busiest and most complex in the world, and FAA's core mission is safety. When a commercial space vehicle is scheduled to fly, FAA uses regulatory and operational means to segregate launch and reentry operations from other flights in the National Airspace System (NAS) to ensure safety. Relatively large volumes of airspace are closed for extended periods of time, causing other users to incur delays and other inefficiencies. As the frequency and complexity of commercial space activities continue to increase, the existing approach will become increasingly unsustainable.
The FAA and the Commercial Space Transportation (CST) industry are working together to minimize disruption by moving from accommodation to integration. We are working on new procedures and technologies to safely reduce the amount of airspace that must be closed in advance of the operation, quickly respond to contingencies and release airspace so that it can be used by other flights as soon as it is no longer needed. In the future, airspace will be managed dynamically, safely minimizing inefficiencies and paving the way for routine access to low Earth orbit and beyond through the NAS.
As part of the licensing and permitting process, a commercial launch or reentry vehicle operator or site operator must enter into a letter of agreement with FAA air traffic control to define procedures for notification, communication, and contingencies. Once an operator receives a license or permit, they continue to work with FAA as the day of operation approaches, providing operation-specific information according to the timelines in the agreement. As part of its preparation for the operation, FAA assesses the effect of the operation on the system. This includes identifying a potential hazard area and determining which regularly scheduled flights need to be rerouted, negotiates with the operator as needed based on the assessment and relevant constraints upon the NAS, develops an airspace management plan and distributes the plan to affected facilities and other stakeholders.
During the operation, the FAA and operator execute their plans, communicating readiness and mission status over hotlines and other means as specified in their agreement. The FAA implements the necessary airspace restrictions, based on pre-operation safety computations, and monitors the mission's progress. In the case of a vehicle malfunction, FAA works quickly to identify the affected airspace and take actions necessary to ensure safety. As the operation unfolds toward its completion, airspace restrictions are lifted as quickly as possible.
Until now, much of this activity was executed manually, using non-integrated systems and operation-specific procedures. The FAA and the CST industry have been working collaboratively to develop time-based procedures and operator mission triggers to more effectively manage airspace and mitigate launch and re-entry effects on the NAS. Procedural changes will serve as a bridge in integration efforts as FAA pursues advanced automation that will be required as the industry continues to grow. The Space Data Integrator (SDI) is the first of several new capabilities that will more efficiently integrate commercial space operations into the NAS. The FAA plans to deploy an initial SDI capability in 2020 that will offer immediate improvements, including increased situational awareness and more timely airspace management decisions. Other technologies will follow, also developed in collaboration with the CST industry, to automate mission planning, to standardize and streamline data exchange, to more quickly identify the affected airspace in the case of an off-nominal event, and to provide air traffic controllers, pilots, and other stakeholders with the information they need to operate safely and at optimal efficiency.
NAS Operations 9)
Each day, the FAA's Air Traffic Organization (ATO) watches over a vast airspace of more than 29 million square miles, providing service to tens of thousands of flights and millions of airline passengers. Tasked with ensuring the safety and efficiency of the National Airspace System (NAS), the NAS Operations Directorate fulfills this mission by continuously monitoring and directing the daily flow of air traffic across the nation from the Air Traffic Control System Command Center (ATCSCC).
The NAS Operations Directorate is a large, multilayered, and geographically dispersed organization that ensures that the nation's airspace is operated efficiently. The ATCSCC resides within the Directorate and is responsible for planning, directing, implementing, and monitoring all national traffic management initiatives (TMIs). The Directorate is also responsible for other NAS functions including Space Operations, and Collaborative Decision Making (CDM).
Figure 2: How dedication keeps thousands of flights safe and efficient every day (video credit: FAA)
The largest component of the NAS Operations Directorate is the ATCSCC. The ATCSCC is the National Airspace System's central hub and ensures the entire network achieves optimum performance by balancing system demand and capacity. ATCSCC traffic managers provide strategic and tactical NAS oversight and regulate real-time air traffic when constraints such as weather, runway closures, equipment outages, security issues, or other impacting conditions affect the NAS. The ATCSCC provides a network-centric platform from which the FAA manages and recovers from large-scale disaster events and infrastructure outages.
The Director of NAS Operations leads a team of Deputy Directors of System Operations (DDSOs) who are strategically located around the country and are focused on improving system efficiency. They engage with the ATCSCC, NAS stakeholders, local FAA facilities, and other FAA lines of business to help mitigate system constraints such as airport construction and high-volume events like the Super Bowl. They also work to accomplish NAS-wide efforts such as the Air Traffic Organization's Efficiency Performance Initiatives (PDF).
Figure 3: As commercial space operators innovate, Space Operations keeps the NAS safe and efficient (video credit: FAA)
The Space Operations group is the Air Traffic Organization's (ATO) office of primary responsibility for launch and reentry of space operations and oversees the ATO effort to integrate space operations into the NAS. From the ATCSCC Challenger Room, ATO Space Operations coordinates launch and reentry missions with industry, the Office of Commercial Space Transportation, and Air Traffic facilities.
This group is leading the effort to improve safety and efficiency by deploying new capabilities and procedures while advances in technology and commercial enterprise increase the tempo of space operations.
NAS Operations continually strives to improve gate-to-gate strategic traffic management. The Director of NAS Operations provides leadership, direction, and guidance in the development of procedures and standards for air traffic control utilizing the Collaborative Decision Making (CDM) Process. Collaborative Decision Making is a joint government, industry, aviation associations, and academia initiative focused on strengthening Air Traffic Flow Management (ATFM) through information exchange.
SDI development status
• July 8, 2021: The Federal Aviation Administration (FAA) has started to use a new tool intended to better integrate commercial launches and reentries into the National Airspace System, reducing the disruptions those events have on aviation. 10)
- The FAA announced July 8 that it formally started use of the Space Data Integrator (SDI) with the June 30 launch of a SpaceX Falcon 9 from Cape Canaveral on the Transporter-2 rideshare mission. It will be used again when the CRS-22 cargo Dragon spacecraft splashes down off the Florida cost late July 9.
- SDI, under development by the FAA for several years, automates the transfer of data about launches and reentries to air traffic controllers so they have up-to-date information on the progress of those activities, including any anomalies that might create debris or other aviation hazards. That can allow controllers to more efficiently manage air traffic around those closures.
- “The overall impact and the benefit is reducing the amount of time it takes to close or reopen airspace,” Tim Arel, deputy chief operating officer of the FAA’s Air Traffic Organization, said of the SDI in a call with reporters.
- The intent is to allow quicker reopening of airspace once a launch or reentry has safely transited airspace. “We’re able to more dynamically adjust those closures,” he said. “What it means is that those flights moved out of the way to accommodate a safe operation of that space mission will be able to more quickly get back on to their normal flight path, or maybe even get some shortcuts.”
- Arel said that other measures it had been taking for airspace closures already reduced the average length from more than four hours to more than two hours. “We know SDI will help us open the airspace even quicker,” he said, but didn’t offer an estimate of how much of an improvement it will provide.
- The growing cadence of commercial launches in recent years — there have been 33 licensed launches so far in 2021, compared to 11 in all of 2016 — prompted pushback from the aviation industry given the conventional approach to closing large amounts of airspace for each launch. A breaking point was the first Falcon Heavy launch in February 2018 that closed airspace off the Florida coast for hours on a weekday afternoon, affecting hundreds of flights in a busy corridor.
- The aviation and commercial spaceflight industries have been working together more closely together since then, including pushing for tools like SDI that have the potential to reduce the size and duration of airspace closures. However, the long development cycle for SDI prompted congressional criticism at a June 16 hearing of the House Transportation Committee’s aviation subcommittee.
Figure 4: The June 30 Falcon 9 launch of the Transporter-2 mission was the first launch to use the FAA's Space Data Integrator, a tool intended to reduce the time airspace is closed for launches (image credit: SpaceX)
- At the hearing, Rep. Peter DeFazio (D-Ore.), chair of the full committee, pressed the FAA on the slow progress on SDI, stating he was opposed to delaying airline flights “because some millionaire or billionaire is going to experience 15 minutes of weightlessness.”
- At the hearing, Wayne Monteith, associate administrator for commercial space transportation at the FAA, said operational tests of SDI would begin soon, although there wasn’t a timeline for full integration of SDI. Work on it has accelerated, he said, since the project was handed over to Teri Bristol, chief operating officer of the FAA’s Air Traffic Organization (ATO).
- “We have seen tremendous, tremendous progress in just the last two years as Teri Bristol and the ATO has taken this responsibility on with our technical help,” he said in the call with reporters.
- Currently, participation in the SDI is voluntary. Besides SpaceX, which started cooperating with the FAA on the SDI in 2016, others include Blue Origin, Firefly Aerospace and Alaska Aerospace Corporation, which operates the launch site on Kodiak Island, Alaska. Monteith didn’t give a schedule for bringing other companies into the system, but emphasized the importance of having an automated system like SDI to improve safety.
- There are limits, though, to what tools like SDI can do to improve management of launches in the National Airspace System. On June 29, the first Transporter-2 launch attempt was scrubbed shortly after a helicopter entered restricted airspace near the pad, halting the countdown seconds before liftoff. “Unfortunately, launch is called off for today, as an aircraft entered the ‘keep out zone’, which is unreasonably gigantic,” Elon Musk, chief executive of SpaceX, tweeted shortly after the scrub. “There is simply no way that humanity can become a spacefaring civilization without major regulatory reform. The current regulatory system is broken.”
- Arel said that SDI did not play a factor in the Transporter-2 scrub, since the airspace violation took place before launch. “It was ready to be used for the first attempt and was not needed,” he said.
1) ”National Airspace System Overview, , FAA, ” URL: https://www.faa.gov/air_traffic/nas/nynjphl_redesign/documentation/
3) ”The National Airspace System Explained,” 4 March 2019, URL: https://www.thebalancecareers.com/the-national-airspace-system-explained-282584
4) James H. Williams, T. L. Signore, ”National Airspace System Security Cyber Architecture,” The Mitre Corporation, November 22, 2010, URL: https://www.mitre.org/sites/default/files/publications/10_4169.pdf
5) Laurence H. Mutuel, Daniel P. Murray, ”Space Data Integrator: FAA's Innovative Platform for Launch and Reentry Operations,” 54th AIAA Aerospace Sciences Meeting, San Diego, CA, USA, AIAA 2016-0218, Published online: 2 January 2016, https://doi.org/10.2514/6.2016-0218
6) Steve Kulm, ”Fact Sheet – The Space Data Integrator (SDI),” FAA News, 8 July 2021, URL: https://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=23476
7) ”FAA Activates System to Track Space Launch, Reentry Vehicles -Increases the safety and efficiency of the National Airspace System,” FAA Press Release, 8 July 2021, URL: https://www.faa.gov/news/press_releases/news_story.cfm?newsId=26301
9) ”NAS Operations,” FAA, 27 January 2021, URL: https://www.faa.gov/about/office_org/
10) Jeff Foust, ”FAA begins use of system to reduce impact of launches on airspace,” SpaceNews, 8 July 2021, URL: https://spacenews.com/faa-begins-use-of-system-to-reduce-impact-of-launches-on-airspace/
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).