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P G Smith (ed P G Smith), 1999, "Concept of Operations in the National Airspace System in 2005", FAA.
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Commercial Space Transportation
Concept of Operations in the National Airspace System in 2005
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This document provides a conceptual overview of commercial space transportation operations in the National Airspace System (NAS) in 2005 and beyond. This document is intended to support evolution of a fully integrated , modernized NAS inclusive of commercial space transportation. Further, this overview concept will be coordinated in a collaborative manner with industry stakeholders to ensure the viability of the concepts represented.
Patricia G. Smith

Associate Administrator for Commercial Space Transportation

The Commercial Space Transportation organization thanks the many professionals within the Federal Aviation Administration, support organizations, and academia for their assistance in developing this Concept of Operations. We particularly appreciate the support provided by Air Traffic Services, and Research and Acquisitions in helping to develop this important product.

Space and Air Traffic Working Council
  • Kelvin Coleman, AST-100
  • Col. Roger Rapier, USAF
  • Clarence Jones, ATO-410
  • Alton Scott, ATO-130
  • Reginald Matthews, ATA-400
  • Lorelei Peter, AGC-230
  • Laura Montgomery, AGC-250
  • Thomas VanMeter, ATCSCC
FAA Office of System Architecture & Investment Analyses
  • Greg Burke, ASD-110
  • Betty Falato, ASD-110
  • Mary Stevens-Loggins, ASD-130
Crown Communications, Inc.
  • Michele Merkle
  • Harry Eberlin
  • Stormy Thornhill
  • Brian Legan
National Center of Excellence for Aviation Operations Research
  • James Kuchar, MIT
  • Antonio Trani, VPI
Table Of Contents
Nomenclature Page References
Document References


Intended Use


Space Vehicles
Technologies & Automation Support
CDM Functions
Regulation of Commercial Space Transportation


Mission Planning
Ascent Through the NAS
Positive ATC From The Surface To A High-Altitude STC
Ascent Through An STC From The Surface
Descent Through the NAS & Landing
Positive ATC From A High-Altitude STC To The Surface
Descent Through An STC From The Upper Limit Of The NAS To The Surface
Hypersonic Point-to-Point

AAF FAA/Airway Facilities Service
AAT FAA/Air Traffic Service
ADIZ Air Defense Identification Zone
AFS FAA/Flight Standards Service
AIR FAA/Aircraft Certification Service
ALTRV Altitude Reservation
AOC Airline Operations Center
ARS FAA/Air Traffic Requirements Service
ARTCC Air Route Traffic Control Center
ASD FAA/Office for System Architecture and Investment Analysis
AST FAA/Commercial Space Transportation
ATA FAA/Air Traffic Airspace Management Program
ATC Air Traffic Control
ATCSCC Air Traffic Control System Command Center
ATO FAA/Air Traffic Operations Program
ATS FAA/Air Traffic Services
CDM Collaborative Decision Making
CDTI Cockpit Display of Traffic Information
CNS Communications/Navigation/Surveillance
DoD Department of Defense
DSS Decision Support System
EELV Evolved Expendable Launch Vehicle
ELV Expendable Launch Vehicle
FAA Federal Aviation Administration
FAS FAA Flight Advisory Services
FIP Flight Information Posting
GEO Geostationary Earth Orbit
GPS Global Positioning System
ICAO International Civil Aviation Organization
IFR Instrument Flight Rules
IIP Instantaneous Impact Point
ISFO International Space Flight Organization
LEO Low Earth Orbit
LSO Launch Safety Operations
MARSA Military Assumes Responsibility for Separation of Aircraft
MC Mission-Control
MEO Medium Earth Orbit
MIP Mission Information Posting
MM Mission Manager
MOC Mission Operations Center
MP Mission Planning
MPS Mission Planning Specialist
NAS National Airspace System
NAS-WIS NAS-Wide Information System
NOTAM Notice To Airmen
RLV Reusable Launch Vehicle
SpOC Space Operations Center
STC Space Transition Corridor
SUA Special Use Airspace
TM Traffic Management
VFR Visual Flight Rules
Nomenclature Page References

Air Traffic Control 8
Airspace 5
Ascent Through an STC from the Surface 14
Ascent Through the NAS 13
Ballistic Return to Base 4
CDM Functions 8
CDM Tools 7
Commercial Space Operations 11
Conflict Prediction & Resolution 6
Decision Support Tools 7
Descent Through an STC from the Upper Limit of the NAS to the Surface16
Descent Through the NAS & Landing 15
Dynamic Airspace Configuration 5
Enhanced CNS Capabilities 7
Enhanced Weather Information 7
Flexible Spaceway 6
Horizontal Takeoff 4
Hypersonic Point-To-Point 16
Infrastructure Management Tools 8
International Space Flight Organization (ISFO) 9
Launch & Re-entry Concepts 4
Launch Safety Operations 8
Launch/Takeoff 13
Mission Information Posting (MIP) 11
Mission Management 8
Mission Operations Center (MOC) 8
Mission Planning Specialist (MPS) 8
Mission Planning Tools 6
Mission Planning 11
Mission-Control (MC) 8
NAS Upper Limit 5
NAS-Wide Information System (NAS-WIS) 6
Positive ATC from a High Altitude STC to the Surface 15
Positive ATC From the Surface to a High Altitude STC 13
Powered Flight to Base 4
Re-Entry 14
Regulation of Commercial Space Transportation 9
Space Operations Control Center (SpOC) 9
Space Transition Corridor (STC) 6
Spaceports 5
System Performance Analysis Tools 7
Traffic Management 9
Trajectory Modeling/Simulation Tools 6
Trajectory Predictability 5
Unpowered Flight to Base 4
Vehicle Equipage 5
Vehicle Performance 5
Vehicle Pilotage 5
Vehicle Responsiveness to ATC Clearances 4
Vertical Launch 4
Workload/Traffic-Load Management Capabilities 7
Document References
  1. Air Traffic Control Handbook 7110.65L. Federal Aviation Administration.
  2. Air Traffic Services Plan 1997 - 2002 (Draft). Federal Aviation Administration.
  3. An Evolutionary Operational Concept for Users of the National Airspace System. Draft v3.0. RTCA Select Committee on Free Flight Implementation.
  4. ATS Concept of Operations for the National Airspace System in 2005-Narrative. Federal Aviation Administration, September 30, 1997.
  5. Commercial Aerospace Transport-Aerospace Traffic Control. Draft White Paper. Vela Technology Development, Inc. July 21, 1997.
  6. Impact Analysis of Commercial Space Launches: Potential User Costs to Civil Aviation. MITRE Center for Advanced Aviation Systems Development (CAASD), September 1997.
  7. Integration of Reusable Launch Vehicles (RLVs) into the Air Traffic Management System. Virginia Polytechnic Institute and State University, April 13, 1998.
  8. Integration Of Reusable Launch Vehicles Into Air Traffic Management-Phase I Final Report. NEXTOR Research Report (RR-97-7), Massachusetts Institute of Technology & Virginia Polytechnic Institute and State University, November 30, 1997.
  9. Integration of Reusable Launch Vehicles Into Air Traffic Management-Phase II Progress Report. Virginia Polytechnic Institute and State University.
  10. Integration of RLVs into Air Traffic Management-Phase II Mid-Term Briefing. Massachusetts Institute of Technology, April 13, 1998.
  11. The Views of a Space Futurist. Presented at the 1st FAA Commercial Space Transportation Forecast Conference: 'Commercial Space Transportation in the 21st Century: Technology and Environment, 2001 - 2025'. February 1998.

The demand for access and use of national airspace is projected to rise sharply in the 21st century. This rise in demand can be attributed, in part, to growth of the commercial space transportation industry. Growth of the space transportation industry, coupled with significant increases in conventional air travel forecasted for the coming years, dictates re-examination of the current technology and methodology used for managing the National Airspace System (NAS). With this in mind, technological advances in the areas of communication, navigation, surveillance (CNS) and decision support must be leveraged to evolve a modernized NAS. From a NAS service provider perspective, space and aviation operations in 2005 must be seamless and fully integrated in order to continue to provide efficient service to all NAS users.

Therefore, this Concept of Operations has been developed by the FAA Associate Administrator for Commercial Space Transportation (AST) in anticipation of the evolution of a seamless, fully integrated NAS operational environment in the 21st century. This document is intended to support the expansion of the NAS to include commercial space operations as an integral component. Additionally, it is intended to support achievement of the Nation's goals in space, as well as the FAA's strategic goals for maximizing system efficiency. This document underscores the importance of providing equitable access to all users of the NAS in a safe and efficient manner. Moreover, it provides a resource to establish a framework for collaboration among stakeholders in developing a cost-effective strategy to meet projected demand increases for NAS services.

1.1 Background

The U.S. commercial space transportation industry is becoming a flourishing business. In 1987 the Department of Transportation issued the first commercial launch operator's license, and the first U.S. commercial launch occurred in 1989. Since then, over 100 licensed commercial launches have taken place. A large majority of these launches have occurred at federal sites utilizing expendable launch vehicles (ELVs). Traditionally, these operations have had minimal impact on NAS efficiency due to the infrequency with which they have occurred. However, consumer demand for services - such as mobile telephony, data communications, remote sensing imagery, etc. - have led to the emergence of new commercial space markets in low earth orbit ( LEO), medium earth orbit (MEO), and geostationary earth orbit ( GEO).

Competition to provide reliable, affordable launch services to the LEO, MEO, and GEO markets has led to growth and complexity in the commercial space transportation industry. New commercial space vehicle concepts (e.g., reusable launch vehicles, aerospace planes), new commercial launch applications (e.g., overland flight, launch operations conducted from airports), and new infrastructure developments (e.g., commercial spaceports, space-based navigation and surveillance systems) are reshaping the industry and placing new demands on the NAS. 1997 marked the first year that the number of commercial space missions exceeded the number of military missions. Market forecasts indicate that approximately 1200 space launches will occur worldwide in the next ten years. Finally, launch rates are anticipated to grow to more than 60 per year, or by more than 1 per week, by 2005.

1.2 Scope

This Concept provides a high-level description of future commercial space operations within the NAS. Moreover, it focuses on how space vehicles are managed in 2005 as they transition through the NAS to and from space. The ideas presented in this document are intended to drive new NAS technology and lay the groundwork for NAS transitional phases subsequent to 2005. This Concept evolved from discussions with various government and industry stakeholders, and research and analyses performed and sponsored by the FAA. The 2005 time frame represents the first opportunity to incorporate fundamental changes in the delivery of NAS services based on technological capabilities (e.g., decision-support tools, advanced CNS systems) and operational initiatives (e.g., Free Flight, Airspace Re-design) that are currently being developed.

1.3 Intended Use
Figure 1 - Relationship Among Operational Concepts

This document complements the ATS Operational Concept for the NAS in 2005, which focuses on NAS service provider operations and the associated NAS architecture. This document, in conjunction with the ATS Concept will be used to derive lower-level concepts (i.e., Level II CONOPS) for technical areas such as communication, navigation, surveillance, and automation. The relationship among operational concepts is illustrated in Figure 1. To ensure its usefulness, this document is intended to be a living instrument that will be subject to ongoing evaluation, validation, and refinement. Throughout this process, the FAA and the user community will use the maturing document to plan, develop, and coordinate activities related to user and service provider operations in the NAS. Additionally, the commercial space transportation operational concept provides support towards realization of a modernized NAS. FAA organizations may use the information provided in the concept as follows:

  • Commercial Space Transportation (AST) may use this concept to shape regulatory guidelines and policies for commercial space operations and to identify future space system development initiatives.
  • Air Traffic Service (AAT) and Airway Facilities Service (AAF) may use this document as a source to define NAS operational needs and to guide improvements in NAS infrastructure management.
  • Air Traffic Requirements Service (ARS) may use this document as a source to define requirements for new technologies and to influence investment decisions required to make efficient operations a reality.
  • Aircraft Certification Service (AIR) and Flight Standards Service (AFS) may use this document to craft certification and regulation guidelines, to support certification of new systems, and to develop standards to implement the shared infrastructure of 2005.
  • Office of System Architecture and Investment Analysis (ASD) may use this document to define the NAS architecture for 2005 and the associated communications, navigation and surveillance capabilities.
1.4 Organization

This document conceptually describes commercial space operations by phases of flight, and is organized as follows:

  • Section 1.0, Introduction - describes the background and scope of this document, provides projections regarding future commercial space operations, and outlines the need for a concept of operations to accommodate both air traffic and space traffic.

  • Section 2.0, Operational Environment in 2005 - Describes space vehicles, spaceports, airspace, technologies and automation support, collaborative decision making (CDM) functions, and licensing and certification needs that will comprise the operational environment in the 2005 timeframe.

  • Section 3.0, Commercial Space Operations - Describes the manner in which commercial space operations are accommodated in the NAS of 2005, covering operational phases such as mission planning, launch, transition to space, re-entry, and transition to base.

The 2005-15 timeframe sees the completion of the National Airspace Re-design, replacement of the Host en route automation system, transition to satellite navigation, and introduction of new display platforms and decision support capabilities. It encompasses completion of the first phase of transition to the technologies and airspace structures required for Free Flight. With some of these technologies fully deployed, and others under limited deployment, subsequent development is under way to complete the transition to a full Free Flight environment.

Commercial space launches are more commonplace than today, with at least one launch typically occurring every week. A variety of launch vehicles exist, ranging from those with conventional aircraft capabilities, to more traditional rocket-types. The performance of expendable launch vehicles (ELVs) is enhanced (e.g., evolved expendable launch vehicles (EELVs) to lift large and/or multiple payloads). Reusable launch vehicles (RLVs) offer mission reliability and cost savings. Coastal, inland, and sea-based commercial spaceports are used by both ELV and RLV operators. In addition, some conventional airports accommodate commercial space operations that utilize space vehicles with performance profiles similar to conventional aircraft for transition through the NAS.

A CDM approach is utilized that ensures user participation in key operational decisions that impact delivery of services. Decision support systems [1] and enhanced displays expedite the information exchange among NAS systems, service providers, and users. This creates a 'shared situational awareness' that improves the planning and decision-making process. Based on safety, workload, and efficiency as the driving forces, human factors analyses and operational assessments have determined the appropriate allocation of tasks between service providers, users, and automation. As a result of the new systems available in 2005, NAS throughput has increased significantly without a proportional increase in the controller workforce. Contention for NAS resources is minimized through the use of improved technologies to precisely predict and manage aviation and space traffic.

Figure 2 - Factors Influencing Space Transportation Operations

Operational variables that influence the co-existence of space operations and aviation operations in the NAS are depicted in Figure 2, and discussed further below.

  • Traffic & workload within the NAS influences the options for accommodating the vehicle during its launch and re-entry. Traffic variables such as demand/capacity, dynamic density, volume, and complexity will moderate controller workload and define the resources available for handling the mission.

  • The environment may place constraints on commercial space operations. These factors include sector configurations, airport/spaceport configuration, weather conditions, noise abatement requirements, etc. For example, airports/spaceports have limitations as to the types of space vehicles they can accommodate, while airspace sectorization moderates capacity and influences controller workload.

  • The vehicle profile determines the viability of traffic management options. Determinations of these options are based on the vehicle's ability to comply with air traffic control (ATC) clearances. Vehicles that cannot comply with clearances are provided reserved airspace for their transitions to and from space. More responsive vehicles may also be provided reserved airspace; but these vehicles are candidates to be worked by ATC in the traditional manner, depending on a variety of traffic and environmental factors.

  • The space vehicle's mission profile helps determine the impact of launch/re-entry on traffic flow through the NAS. The impact of the mission on the NAS is determined by the launch/re-entry plans (e.g., departure location/trajectory, re-entry location/trajectory, landing location), launch/re-entry window sizes, instantaneous impact points (IIPs) [2], etc. The payload may also influence traffic management strategies. For example, vehicles with hazardous payloads (e.g., nuclear, biological, chemical, explosive materials) require increased buffer zones, and/or trajectories that minimize the ground footprint over populated areas. The combination of the mission profile and vehicle profile also dictates the options available in case of an aborted mission - i.e., whether the vehicle can return to base and, if not, whether it may be destroyed.
  • Figure 3 - Interaction Between Air Traffic and Space Traffic (Adapted from VPI Study)

    Figure 3 illustrates some of these variables and the resulting impact on air traffic management and control. As shown, a given level of traffic complexity yields a workload level that varies directly with the both the temporal launch window size and the physical size of reserved airspace. The balance of this section discusses specific elements of the overall operational environment in 2005. These elements are 1) space vehicle characteristics, 2) spaceports, 3) airspace characteristics, 4) technologies and automation support, 5) NAS CDM functions, and 6) regulations. Together, these elements describe the operational framework that drive the evolution of the modernized NAS.

    2.1 Space Vehicles

    RLVs are commonplace in 2005, benefiting from operational and economic advantages such as relatively low cost, improved reliability, and decreased mission risk (i.e., ability to return to base if the mission is aborted). There are a variety of RLV concepts. For example, some concepts are based on spacecraft that take off and re-enter under power on conventional runways. Other concepts are based on spacecraft that are ferried to high altitudes (e.g., 50K feet), launched from the air, and re-enter under power. Figure 4 compares the basic launch and re-entry concepts - horizontal take off, vertical launch, powered flight back to base, gliding flight to base, and ballistic return using parachutes or other such devices to manage the descent. The primary factor influenced by each concept is the ability (or the lack of it) for ATC to control the vehicle. Vehicles that cannot comply with ATC clearances are provided a Space Transition Corridor (STC). Aviation traffic is then separated from the STC, which is sterilized airspace (similar to a moving altitude reservation (ALTRV)) that is dynamically reserved and released based on the vehicle's trajectory as it transitions through the NAS. Vehicles that can comply with ATC clearances may be managed using positive ATC techniques (i.e., speed, heading, altitude clearances). However, other factors (e.g., traffic and environmental) may dictate the use of STCs for these types of vehicles as well.

    Figure 4 - Launch and Re-Entry Concepts

    Factors other than launch and re-entry technique also affect a vehicle's ability to comply with ATC clearances. These factors include:

    • Vehicle performance. Vehicles that perform comparably to conventional aircraft may be controlled via positive ATC techniques. These vehicles incur reduced risk in the event of an aborted mission by increasing the probability of the vehicle's safe return to base. Vehicles with extremely high performance or ballistic profiles (e.g., rocket-type vehicles) are not amenable to positive ATC, and therefore require reserved airspace to ensure separation during transition to/from space and in the event of aborted mission.

    • Vehicle pilotage. Autonomously piloted (e.g., pre-programmed) vehicles are provided reserved airspace. Piloted and remotely piloted vehicles may also be provided reserved airspace - however, these vehicles are candidates for positive ATC, depending on a variety of traffic and environmental factors.

    • Vehicle equipage. The electronic systems used by the vehicle (e.g., CNS systems , etc.) factor into the vehicle's ability to respond to ATC, and the precision with which the vehicle can be monitored or tracked.

    • Trajectory predictability. Vehicle performance and reliability, mode of pilotage, and tracking capability determines accuracy of NAS trajectory predictions for traffic planning and conflict detection processes.
    2.2 Spaceports

    In 2005, commercial spaceports are in operation at various locations in the U.S. and abroad, and include coastal, inland, and sea-based spaceports. Spaceports, like airports, vary as to the types of commercial space operations they can support. Spaceport infrastructure, noise abatement concerns, hazard risks, launch and re-entry concepts, etc., determine the types of space vehicles that can be accommodated at a given spaceport. Payload processing and fuel requirements (e.g., solid, liquid) are additional factors that may constrain operations to certain spaceports. Finally, there are joint-use facilities that handle both aviation and commercial space operations. Spaceports rely primarily on space-based surveillance to support the mission. Additional support services provided by spaceports include communications (e.g., voice, data link, etc.), telemetry, specialized weather forecasting and advisories, and payload/vehicle processing. These services are provided for launch/takeoff, re-entry, and landing phases. Factors that may determine a preference for a particular spaceport include:

    • Destination/mission objective (e.g., launching a satellite into LEO, MEO or GEO) and the preferred trajectory for accomplishing the mission.
    • Ability of the spaceport to accommodate the vehicle performance/support requirements.
    • Spaceport scheduling assurance and flexibility.
    • Range turn-around time (e.g., time to process successive launches and/or re-entries).
    • Environmental constraints (e.g., noise abatement requirements, hazard concerns).
    • Economics (e.g., launch costs).
    • Weather trends (i.e., the probability that weather patterns/trends will present a risk to the launch window).
    • Traffic flow patterns (i.e., the constraints that must be dealt with due to contention for NAS resources).
    2.3 Airspace

    Today, the NAS has no defined upper limit. In 2005, the NAS may have a defined (but currently unspecified) upper limit, to clearly define the FAA's responsibility for accommodating space vehicles transitioning to and from space. Within the NAS, three methods of airspace management that facilitate commercial space operations are:

    • Dynamic Airspace Configuration. Airspace design and underlying sector configurations are no longer constrained by the current geographic boundaries, particularly for very high altitudes. Seamless communications and coordination, coupled with the NAS-Wide Information System (NAS-WIS), allow dynamic reconfiguration of airspace between facilities to increase traffic management flexibility and to better accommodate contingencies (e.g., space mission operations, equipment outages, workload imbalances, etc.). Upon completion of the National Airspace Re-design, tools and procedures are in place for frequent evaluation of the airspace structure and anticipated aviation and space traffic flows, with adjustments made accordingly. Due to this increased flexibility, workload is more equitably distributed among sectors and facilities, rather than being predominantly driven by institutional requirements. Current sector combinations and boundary configurations are depicted on the displays at all relevant operational positions. Planned combinations and configurations are available to the supervisor and traffic manager.

    • Space Transition Corridors. These dynamically reserved and released airspace areas allow space vehicles to transition through the NAS. STCs are determined for each spaceport based on the types of vehicles the spaceport serves, typical traffic flows, and typical trajectories to and from space. STCs may be tailored as mission needs or ATC needs dictate, and provide more flexibility than today's special-use airspace (SUA). Disruptions to air traffic are minimized by tailored STCs and improved precision of launch and re-entry windows. STC schedules and status information are output to controllers, supervisors, traffic management, and airline operations centers (AOCs), and may be accessed via the NAS-WIS. Aircraft with cockpit display of traffic information (CDTI) may also view STC information.

    • Flexible Spaceways. Routes similar in function to today's airways and jet routes are designated to service traffic transitioning to and from space. These routes, referred to as 'flexible spaceways,' are dynamically designated to meet specific space mission objectives, such as transitioning to airborne launch points, aerial refueling, etc. The use of spaceways is predicated on traffic density and controller workload. Spaceways may be used to segregate different types of missions, concurrently accommodate different mission phases (e.g., launches vs. re-entries), and help ensure safety in case of an off-nominal event. Depending on the mission and vehicle profile, the spaceway may be used in conjunction with an STC. Spaceway data is available via the NAS-WIS and can be displayed at controller and traffic manager positions.
    2.4 Technologies & Automation Support

    NAS modernization is based on an incremental implementation of new technologies that can be leveraged to manage aviation and space operations. Technology enhancements assist in the management and control of these operations by helping to absorb the increased demand for NAS resources, minimizing the impact of space operations on the ATC system, and enhancing productivity. This approach maintains safety as the first priority, while also increasing capacity, flexibility, and productivity in balance with airspace, airport/spaceport, and controller workload considerations. The following enhancements are the catalysts for improved NAS services:

    • Mission Planning Tools. An archive of NAS performance information is consistently maintained to provide inputs for operations planning aids (e.g., graphical depictions of airspace, trajectories, reserved airspace, traffic flows, planning charts/diagrams, etc.) and data visualization tools that can graphically show the anticipated impact of space launch operations for various traffic profiles. These mission planning tools enhance CDM and expedite communication, coordination, and analysis.

    • Trajectory Modeling/Simulation Tools. To complement the database described above, predictive simulation tools enable traffic managers and mission planners to anticipate conflicts between space traffic and air traffic, including conflicts with active space transition corridors or spaceways. Improved strategic planning is achieved by providing mission planners with the capability to 'trial plan' trajectories (launch and re-entry) against projected air traffic, and provide an added level of fidelity to apply in mission planning. Using this preview capability, contention for airspace can be anticipated prior to filing a mission plan with traffic management. These 'what if' scenarios can be performed in fast-time to allow mission planners to explore alternative profiles. Outputs can be used in CDM between traffic management and mission planners to identify and review solutions given specific user needs and priorities.

    • Conflict Prediction & Resolution. Automated trajectory modeling assists mission planners and traffic managers to predict and resolve conflicts between spacecraft, aircraft, airspace, and weather. Trajectories of aircraft and spacecraft are continuously probed across the length of the route for early detection of conflicts. For space vehicles provided with an STC, conflict prediction is based on conflicts with active airspace, and not the vehicle. Controllers may also perform trial planning to preview the potential effect of re-routes, etc., prior to implementing control initiatives. Finally flight deck systems such as collision and avoidance systems, cockpit display of traffic information, etc., assists pilots in maintaining flight safety.

    • NAS Wide Information System. The NAS-WIS drives the exchange of information among NAS users and service providers. It expedites dissemination of information such as: 1) Static data, including maps, charts, airport & spaceport guides, and Notices to Airmen, 2) dynamic data such as current and forecast weather, radar summaries, traffic loading, hazardous condition warnings/advisories, airport and airspace capacity constraints, STC schedules and status, launch/re-entry window schedules and coordinates, and infrastructure status 3) aircraft information, including the flight information posting (FIP), estimated departure and arrival times, first movement of the aircraft, wheels-up, position data in flight, and flight cancellations, and 4) space flight information, including the mission information posting (MIP), launch/re-entry windows and coordinates, STC coordinates/status/schedule, vehicle profile, payload, and trajectory.

    • CDM Tools. 'Shared situation awareness' among users and service providers offers an efficient alternative to the parochial problem-solving process. Improved information displays that support the integration of air traffic, space traffic, weather, and airspace information - coupled with access to common sets of information and better information sharing mechanisms - enhance CDM among users and service providers. Digital communications (e.g., datalink) augment this information exchange. The ability to preview mission profiles and flight profiles creates a shift from reactive, tactical decision-making to proactive, strategic decision-making. For situations such as demand-capacity imbalances or severe weather avoidance, this capability supports strategic planning to determine when, where, and how to transition to temporary route structures to accommodate contingencies. Airspace status data are also provided to pilots to augment situational awareness and ensure separation from active STCs.

    • Decision Support Tools. Advances in communications, navigation and surveillance systems present an abundance of real-time data that must be integrated to maintain situational awareness. Task performance is no longer data-limited (or constrained by the timeliness and precision of information), but rather resource-limited (or constrained by the operator's ability to assimilate information to execute decisions). Therefore, decision support systems (DSSs) are used to assist service providers in assimilating, interpreting, and exchanging information. DSSs provide advisories/heuristics to help reduce the burden of routine tasks, allowing service providers to apply more cognitive resources to the primary task of evaluating traffic situations and planning appropriate responses. This increases productivity and offers greater flexibility to user operations, which is especially important given the potential for reduced vertical separation minima and increased traffic density /complexity given the increases in air and space travel.

    • Workload/Traffic Load Management Capabilities. Automation and DSS capabilities include the prediction and display of traffic demand/capacity, dynamic density, user-preferred trajectory data, and workload information. DSSs assimilate and correlate traffic parameters (e.g., current and predicted traffic demand, density, trajectories, etc.) and workload measures (e.g., communications workload, manual workload, etc.) to derive workload projections to compliment traffic projections. This information is used by controllers and traffic managers to ensure that the demand does not exceed airspace, airport, spaceport, or controller resources. Automation assistance provides traffic managers and controllers with strategic advisories (e.g., task prompts, event prompts) to facilitate proactive air/space traffic management and control.

    • Enhanced Weather Information. There is increasingly accurate weather data available to service providers and users, including hazardous weather alerts for wind sheer, microbursts, gust fronts, and areas of precipitation, icing, and low visibility. Enhanced steps for avoiding convective weather are made as weather prediction capabilities are improved and integrated into the decision support tools. Aircraft and spacecraft are both the consumers and sources of weather data. Improved weather 'forecasting' and 'nowcasting' increases scheduling precision (for air traffic operations, space launches, and re-entry operations) and overall air traffic and space traffic management. Detailed weather information is available via the NAS-WIS, and is selectively presented on sector displays and flight deck displays.

    • System Performance Analysis Tools. There are improved methods and tools to measure NAS performance and to identify user requirements, including the daily archiving of the NAS wide information system. Performance tracking and measurement tools include a space operations database and archive that allows post-hoc operational analyses to be performed and used in subsequent mission planning exercises. System performance analysis tools are geared toward 'mining' a vast array of data, integrating and assimilating information, and presenting this information in meaningful, readily accessible forms. Analytic capabilities include summary statistics for delays, conformance to optimal routes/trajectories, traffic loading and density information, etc. Outputs may be customized (e.g., based on airspace, time, spacecraft/aircraft type, airline, mission, etc.) to examine specific issues and consider alternative scenarios. These performance measurement and data visualization capabilities allow traffic managers and flight/mission planners to refine methods and strategies based on objective performance analyses.

    • Enhanced CNS Capabilities. Electronic communications (e.g., datalink) provide a non-verbal means of disseminating information between users and service providers. The combination of Global Positioning System (GPS) and aircraft-broadcast position reports increases navigational accuracy and more precise ATC. These systems facilitate increased use of pilot self-separation, and improve conflict prediction and resolution capabilities. Finally, surveillance has transitioned from ground-based to air- and space-based systems. More precise tracking also enables the use of dynamic STCs, which are reserved and released as vehicles transition through the NAS to/from space.

    • Infrastructure Management Tools. Since it is recognized that infrastructure components will fail, the NAS design provides a fault-tolerant system that maintains a balance between reliability, redundancy and procedural backups. This is achieved through safety and risk analyses that identify areas requiring higher reliability and backup. Thus the design provides a system that is not only available, but one that also requires minimal time to restore failed functionalities. To facilitate the management of infrastructure operation, there are improved methods for collecting and processing infrastructure data. These data are available as an integral part of the NAS-WIS, and are used to prioritize and schedule NAS infrastructure activities. Users and service providers collaborate in this prioritization and scheduling, utilizing DSSs that provide information regarding the coverage and status of NAS infrastructure components.
    2.5 CDM Functions

    In concert with Collaborative Air Traffic Management initiatives (e.g., initiatives pioneered by RTCA Special Committee 191), CDM provides the basis for safely and efficiently accommodating increased demands for NAS resources. The AST CDM model discussed here expands on the traditional CDM paradigm, and includes both the aviation commercial space users.

    Figure 5 - Collaborative Decision Making Model

    The CDM model is illustrated in Figure 5. The model depicts the functions/organizations involved in the planning of space missions, and the operational integration of those missions into the overall air traffic environment.

    The balance of this section provides a high level description of the major functions involved in the CDM process (inclusive of space operations), while the detailed interactions involved in planning and implementing commercial space operations are described in section 3.0.

    • Launch Safety Operations (LSO). A major spaceport function during the launch phase is the monitoring of all factors related to the go/no-go decision, and the assurance of vehicle safety during initial ascent. The spaceport therefore provides the personnel necessary to execute the range-safety functions necessary to help assure the safety of people and property, and vehicle flight safety in the event of an abort.

    • Mission Operations Center (MOC). Each space transportation company may institute a MOC which is analogous to the AOCs of today's airlines. The MOC is comprised of three major functions, as follows:

      • Mission Planning (MP). The MP Specialist (MPS) works with ATS and the spaceport to define and file a mission plan that accommodates the preferred launch/re-entry windows and trajectories, based on anticipated demand for NAS services, TM options, and the inherent flexibility of the mission.

      • Mission-Control (MC). Vehicle pilotage is conducted by an on-board flight crew, by mission controllers in the MOC, or by a combination of the two. This vehicle flight control function is referred throughout this concept as 'mission control,' or 'MC.'

      • Mission Management (MM). The MM function provided by each company's MOC provides oversight and management of the real time operation of the company's fleet.

    • Traffic Management System (TMS). The TMS integrates the new traffic management and ATC functions required to organize space transportation operations within the overall NAS environment.

      • Air Traffic Control (ATC). The ATC system provides separation assurance to space traffic while it transitions through the NAS to and from space. For some space vehicles (i.e., those with responsiveness and performance similar to conventional aircraft), ATC may provide aircraft-to-vehicle and/or vehicle-to-vehicle separation. For space vehicles operating in STCs, ATC provides separation assurance by separating other traffic from the vehicle's reserved airspace.

      • Space Operations Control (SpOC). This is a new national traffic management entity that expands on the current functions at the Air Traffic Control System Command Center (ATCSCC). The SpOC collaborates with commercial space operators to de-conflict space missions, and it coordinates with traffic managers to integrate space transportation operations and air traffic.

      • Traffic Management (TM). Local and national traffic managers organize major air traffic flows in order to prevent demand capacity imbalances on NAS resources, and they coordinate with the SpOC to integrate space transportation operations and air traffic.

    • International Space Flight Organization (ISFO). The ISFO is analogous to the International Civil Aviation Organization (ICAO), in that it is a unified body that represents international space mission interests. In 2005, the ISFO serves as the focal point for international collaboration and information exchange for:

      • Hypersonic point-to-point international flights requiring advanced planning and notification to mitigate contention for airspace, and

      • Commercial space flights bound for orbit, originating in the U.S. but terminating at international locations (or vice versa). End-to-end mission planning is required for these flights to ensure that all components of the mission can be accommodated, including contingency plans.
    2.6 Regulation of Commercial Space Transportation

    In 2005, segments of the commercial space transportation industry are supported and regulated by a structure similar to that which is currently in place for the aviation industry. Space operations in 2005 are performed from commercial spaceports operated by civilian personnel. The current system of licensing launches has evolved to meet the changes resulting from the increased frequency of piloted, over-land space operations. Accepted levels of vehicle safety and public risk are identified for commercial space vehicles in 2005. Based on these safety and risk levels, some space vehicles are evaluated for safety in a manner similar to that performed for commercial aircraft. The commercial space transportation infrastructure, including spaceports and CNS systems, is safety-approved in a manner analogous to today's communications and navigation facilities. And finally, civilian space operations personnel such as launch safety specialists, mission planners, mechanics, and MCs (including on-board spacecraft pilots), receive FAA-monitored training, authorization, and medical qualification in a manner similar to that received by aircraft pilots, dispatchers, and mechanics.


    This paragraph discusses the following commercial space mission phases of flight: [3]

    • Mission Planning.
    • Launch/Takeoff.
    • Ascent Through The NAS.
      • Ascent Through An STC To The Upper Limit Of The NAS.
      • Positive ATC To A High-Altitude STC.
    • Re-entry.
    • Descent Through The NAS and Landing.
      • Descent Through An STC To The Surface.
      • Positive ATC From A High-Altitude STC.
    • Hypersonic point-to-point international missions.
    3.1 Mission Planning

    The objective of the mission planning process is to develop and coordinate a mission plan that accommodates user priorities while being sensitive to TM conditions and constraints. This process involves end-to-end mission analysis and collaboration among the launch operator's Mission Planning Specialist (MPS), ATS, and AOCs to identify and exploit the flexibilities of the NAS. Advanced simulation and trajectory modeling capabilities, which integrate both vehicle performance modeling and current/forecast weather and wind information, allow the analysis of the feasibility and risks of specific launch and landing schedule windows. The product of the mission planning process is the Mission Information Posting (MIP), which includes the following information:

    • Payload/Manifest (e.g., passengers, hazardous cargo)
    • Mission duration
    • Vehicle type/Class
    • Launch window (primary, secondary)
    • Flight profile/Preferred route/trajectory (launch & re-entry)
    • Re-entry window (primary, secondary)
    • Launch location
    • Estimated Trajectory/Initial heading & azimuth
    • Destination (e.g., LEO, MEO GEO, pt-pt)
    • Air Defense Identification Zones (ADIS) penetrated
    • Point of re-entry
    • STC information (e.g., coordinates, schedule)
    • Landing location
    • Instantaneous Impact Point (IIP)
    • Traffic loading at time of launch & re-entry-by stratum
    • Weather (current & forecast)
    • Airspace configuration (e.g., active MOAs, etc.)
    • Space & Solar Conditions (solar flares, etc.)

    The MIP is defined by the MPS before mission support services are contracted with the spaceport, since this information is necessary to perform safety analyses required in the licensing process. The MIP is used to determine mission support service requirements such as radar coverage, weather information/services, surveillance requirements, payload processing requirements, etc. The MPS coordinates with the spaceport and ATS to define operational and supportability requirements. Since many missions are recurring and involve re-use of the same vehicles, the planning process becomes more concise for subsequent missions since baseline information exists in a space operations database. This information includes both the trajectory and performance of the vehicle, and the initiative(s) used to accommodate the mission (e.g., STCs, coordinates for transitioning to/from space, etc.).

    Shared access to all commercial spaceport schedules (U.S. and international) is provided via the NAS-WIS. Military range schedules are also available to selected service providers based on security requirements, to avoid contention with DoD missions. This integrated set of spaceport schedules allows MPSs to synchronize their operations and mission support services. They also provide ATS with a global view of the projected demand generated from space operations. DSSs and data visualization tools assist the MPS and the user in mining and integrating scheduling data for spaceports and air traffic operations. In this way, the viability of desired trajectories, launch and re-entry windows can be determined from the outset of the mission planning process.

    The MPS works with ATS to define a plan that accommodates the preferred launch and re-entry windows and trajectories, considering the anticipated demand for NAS services, ATM options, and the inherent flexibility of the mission. Several factors influence mission flexibility, as follows:

    • Launch time flexibility is dependent on the payload's destination - LEO, MEO, GEO - and whether the payload must be put into a specific 'slot' in a constellation of satellites or simply a particular orbit.
    • Launch window size is influenced by the vehicle's ability to adjust for the movement of the earth and fly to its target destination.
    • Preferred launch locations and trajectories are influenced by the payload's destination and laws of physics.

    Fast-time simulations allow the MPS to preview launch trajectories and air traffic flows. These predictive tools are used to analyze variables such as vehicle performance, vehicle trajectory, traffic loading, dynamic density, and forecasted weather and atmospheric conditions. Upon analyzing the interactions between these variables, the DSS integrates the information and provides graphical outputs to the MPS, including trajectory, scheduling and buffer zone advisories to ensure safety of flight. This information is essential for subsequent coordination with ATS.

    DSSs assist the MPS in evaluating alternative mission scenarios and contingency plans to mitigate potential constraining factors such as adverse weather conditions, traffic loading, etc. [4] Contingency plans are developed in the event the primary launch & re-entry windows are unavailable (e.g., due to weather), if an off-nominal event occurs, or if the mission must be aborted. This precise and proactive planning reduces turn-around time between missions, optimizes spaceport capacity, minimizes schedule 'churning' - the ripple effect created by cancelled/rescheduled launches and re-entries - and reduces the complexity of accommodating transition to/from space. Airspace requirements, mission scenarios, and availability of NAS resources are evaluated. The results of these evaluations are input into the CDM model as previously discussed.

    Upon completing the pre-mission analysis and developing a candidate mission profile, the MPS coordinates this information with ATS to finalize the mission plan. The ATCSCC serves as the focal point for this coordination, with affected local ATC facilities also being involved in the planning process. This collaboration occurs well in advance of mission commencement to allow notification to be disseminated to other NAS users and pertinent organizations (domestically and internationally). The required lead time depends on the mission profile and vehicle profile. [5] The NAS-WIS expedites the dissemination of information to ensure timely notification is provided to domestic and international users and service providers.

    When a mission profile is filed by the MPS, the SpOC function of the ATCSCC reviews the NAS operational requirements in conjunction with affected ATC facilities. Based on this review, the mission profile is revised, as needed, based on the predicted status of the NAS - projected traffic flows, dynamic density (including other space missions), weather, and infrastructure status. Users and service providers collaborate to identify traffic flow flexibilities, as well as launch/re-entry windows and trajectories, that can be utilized to accommodate all concerns. System assisted coordination facilitates this process by allowing MPS to supply analysis and modeling information generated as part of mission planning. The SpOC has equivalent DSS capabilities that assist in reviewing the mission plan, and supplementing it as required. If the mission involves international concerns, or will penetrate international airspace, the SpOC collaborates with the ISFO to alleviate conflicts and finalize the mission profile.

    After reviewing the mission profile, SpOC, MPS, ISFO, AOCs, and ATC coordinate any TM initiatives (e.g., STCs, resectorization, traffic flow modulation, etc.) needed to accommodate the mission.[6] When the mission profile is complete, SpOC disseminates the MIP via the NAS-WIS to notify airmen, mariners, the military, and the ISFO of the impending mission. AOCs and FAA Flight Advisory Services (FAS) also receive this information. Notification of the approved MIP is accompanied by event prompts that provide positive notification when updated information is received. NAS users and service providers access this information as necessary.

    3.2 Launch/Takeoff

    Space vehicles make either a vertical or horizontal departure. Vehicles making 'vertical departures' include rocket types that operate from a launch pad, and spaceplanes that operate from a runway and immediately begin a vertical ascent. Vehicles making 'horizontal departures' include spaceplanes that depart from a runway and climb out in the manner of a conventional aircraft, and vehicles that are carried/towed by a conventional aircraft to an airborne launch point. General pre-departure actions for both vertical and horizontal departures are as follows:

    • When a MIP is filed, DSSs facilitate the integration of the mission into the overall TMS. TM previews departure schedules for space vehicles. Sequencing and scheduling tools provide TM advisories and ensure that the launch is well coordinated with other arrival and departure traffic.

    • The NAS-WIS enables domestic and international users and service providers to access MIPs and related STC data. Airline pilots and AOCs access this data during flight planning. Visual Flight Rule (VFR) flights may contact FAS, or access STC data via the NAS-WIS, to ensure that flight plans are conflict free.

    • The MC controls departure activities to ensure that the departure will conform to the MIP. At a predetermined time before departure, the MC provides a status report to the SpOC, which in turn provides the information to relevant ATC facilities. The MOC and TM establish the necessary communication links, and review the TM initiatives that will be instituted - e.g., STCs, spaceway routes, temporary routes for aircraft, positive ATC, etc. Depending on the departure location, this activity may occur several hours in advance so that oceanic and international traffic can receive timely notification.

    • Departure status is displayed to TM and controllers. Event prompts signal the need to activate STCs and clear traffic from the airspace. ATC then monitors STC status and separates traffic from active STCs. Conflict prediction tools assist ATC in detecting aircraft that will conflict with the STC.

  • Upon departure, the MC monitors vehicle status and TM/ATC monitors the traffic situation. [7] TM, ATC, and MC collaborate to implement the appropriate contingency plan if a compromise to safety is detected.
    3.3 Ascent Through the NAS

    Entry to orbit requires a nearly vertical, high-acceleration ascent phase that precludes the use of positive ATC techniques. For vertical departures, this ultra-high-performance ascent begins immediately, while horizontal departures make a conventional transition through the NAS to an airborne launch point (i.e., the point at which high-acceleration/vertical-ascent is initiated). The vertical ascent of all missions is accommodated with an STC. Thus the STC for vertical departures extends from the surface to the upper limit of the NAS. However, the conventional portion of the trajectory for horizontal departures may be handled either with an STC or through positive ATC. The following paragraphs describe the basic options for handling ascents through the NAS.

    3.3.1 Positive ATC From The Surface To A High-Altitude STC
  • Vehicles that fly to an airborne launch point may be eligible for positive ATC for initial ascent. If positive ATC is used, the vehicle is cleared on flexible spaceways to the point at which the vertical ascent begins. The mission is then protected by an STC to the upper limit of the NAS. The decision to use positive ATC is made by TM during mission planning. For positive ATC to be used, the vehicle must be piloted by an MC, either onboard or at the MOC. The vehicle must also be able to be tracked,[8] and the MC must have direct voice or datalink communications with ATC. Finally, positive ATC is used only when traffic and environmental conditions yield acceptable levels of controller workload.

  • Positive ATC During Initial Ascent. Upon departure, vehicle position is tracked on ATC situation displays. ATC issues clearances to the MC to assure separation for the vehicle while it transitions to the point at which the vertical ascent is initiated. Conflict prediction capabilities recognize the vehicle's performance envelope, and provide appropriate resolutions.[9] If the vehicle is carried or towed to altitude, or involves aerial refueling, MOC is responsible for the separation of the vehicles in the manner of today's 'military assumes responsibility for separation of aircraft' (MARSA) procedures. Collision avoidance systems used by aircraft also recognize the vehicle and its performance profile to provide conflict advisories on the flight decks of other air traffic. CDTI-equipped aircraft monitor the vehicle and may perform self-separation, as directed by ATC.
  • Final Ascent Through A High-Altitude STC. As the vehicle approaches the point for vertical ascent, a high altitude STC is activated. The STC is tailored to the MIP and vehicle characteristics. The STC data is depicted on TM and controller displays, along with weather and traffic data to provide a complete view of the situation. Controllers of the sectors that contain the STC communicate with the MC to ensure that the STC is activated and clear of traffic.[10] To ease the burden of monitoring STC information, controllers receive event prompts that signal STC status changes. In addition, conflict prediction and resolution advisories provide notification of flights that are predicted to conflict with the STC. Carried/towed space vehicles advise ATC of impending disengagement. ATC assesses the traffic situation, issues approval for disengagement, and issues a clearance for vertical ascent. The MC then assumes responsibility for separating the vehicle and host aircraft, in the manner of today's MARSA. The STC is released when the upper limit of the NAS is reached.
  • Upon departure, vehicles that are not controlled by positive ATC are generally protected by an STC from departure to the upper limit of the NAS.[11] They may be cleared point-to-point or on flexible spaceways. Although the STC size and schedule are tailored to the MIP and vehicle characteristics, baseline STCs exist for each class of vehicles at the respective spaceports. The vehicle's ascent is conducted as follows:

    • The vehicle's position and STC status is available on situation displays at ATC, TM, and SpOC positions. STC strata are reserved and released as the vehicle progresses through its flight trajectory. STC schedule, status, and coordinates are depicted on integrated TM and controller displays, and complemented by weather and traffic information to provide a comprehensive view of the current and impending situation.

    • The sectors containing the STC communicate with TM to ensure that the STC is clear of traffic. To ease the burden of monitoring the STC, controllers receive event prompts for STC status changes. In addition, conflict prediction and resolution advisories provide notification of flights that conflict with the STC. Using DSS advisories and advanced situation displays, ATC anticipates future airspace status and directs flights through or away from the airspace based on its availability.

    • STC information is available on the flight decks of aircraft that are equipped with traffic displays. Aircraft using CDTI may use this capability to monitor and self-separate from active STCs. VFR flights access real-time STC status information by contacting FAS, or via NAS-WIS/Datalink.

    • The MC informs ATC when the vehicle exits the NAS, and the STC is released.
    3.4 Re-Entry

    Throughout the mission, the MC uses advanced CNS and weather forecasting tools to provide mission updates to the SpOC. This status information may be accessed by NAS users for strategic planning. For short duration missions (e.g., one week or less), the re-entry plan is included in the initial MIP. For longer missions, the re-entry plan is coordinated at a predetermined time period prior to the re-entry.[12] If a re-entry plan was included in the initial MIP, the MC contacts the SpOC at a predetermined time prior to re-entry and confirms the re-entry window and trajectory. If the re-entry plan must be modified, the MC coordinates the revised plan with the SpOC, AOCs, military, and international ATC. Current re-entry information is disseminated to domestic and international users and service providers via the NAS-WIS, along with notices to airmen, mariners, and the military.[13] Shortly before re-entry, the MC contacts SpOC and requests clearance to re-enter the NAS. The re-entry is conducted as follows:

    • Re-entry plans are used by TM to define appropriate STCs. Like the STCs used for transitions to space, baseline STCs exist to support typical vehicle re-entries from various points in space. These STCs are dynamically reserved and released, and may be tailored to satisfy specific mission or vehicle profiles.

    • SpOC performs fast-time scheduling analyses to determine the re-entry plan's feasibility, and coordinates with the appropriate sectors. ATC then issues the re-entry clearance. For unpowered returns, re-entry clearance is an implied clearance to land, since the vehicle is committed to its return upon de-orbiting.

    • The SpOC disseminates notification to airmen, mariners, military, AOCs, FAS, and ISFO via the NAS-WIS. Affected sectors are notified by SpOC of the re-entry and STC activation. STC event prompts assist in establishing situation awareness of the traffic situation. Conflict prediction and resolution capabilities help controllers mitigate conflicts between air traffic and active STCs, and to resume use of the airspace as STC strata are released, while sequencing and scheduling advisories assist in managing traffic flows.

    • NAS users may access mission and STC information via the NAS-WIS. VFR flights receive information on low-altitude STCs by remotely accessing the NAS-WIS, or by contacting the FAS.

    • When the vehicle re-enters the NAS, the MC ensures that the vehicle's trajectory conforms to the designated STC. The vehicle's position and STC status is available on situation displays at ATC and TM positions, at the SpOC, and on cockpit displays of traffic information.
    3.5 Descent Through the NAS & Landing

    Descent through the NAS is managed in one of two ways; either 1) the vehicle is protected by an STC for the entire transition from the upper limit of the NAS to the surface, or 2) it is protected by an STC from the upper limit of the NAS to a point at which it assumes the performance characteristics of a conventional aircraft, and positive ATC techniques are then used to work the vehicle back to its base. The application of one of these options to a mission is largely determined by the re-entry profile of the vehicle. Three classes of re-entry profiles are addressed in this Concept - powered (i.e., conventional) flight, gliding flight, and ballistic return. In general, vehicles that fly conventionally back to base are eligible for positive ATC, but the option exists to protect even these vehicles by an STC for the entire return. STC protection for the entire return is the only option available for gliding and ballistic returns. The following paragraphs discuss the two options for handling descents through the NAS.

    3.5.1 Positive ATC From A High-Altitude STC To The Surface

    A fully maneuverable spacecraft that flies to base under power may be accommodated through the use of an STC for the entire transition from space and back to base, or through a combination of an STC for initial re-entry to the NAS, and positive ATC as it assumes the performance characteristics of conventional aircraft. If positive ATC is to be used for the final descent phase, the vehicle is cleared on flexible spaceways through a high-altitude STC, to the point at which the vehicle assumes conventional performance characteristics. Thereafter the vehicle receives route, vector, and speed clearances that are typical of positive ATC operations. The decision to use positive ATC is made by TM during mission planning. For positive ATC to be used, the vehicle must be able to be tracked,[14] and it must have direct voice or datalink communications with ATC. Finally, positive ATC is used only when traffic density and environmental conditions yield acceptable levels of controller workload.

    • Initial Descent Through High Altitude STC. As the vehicles enters the NAS, the MC ensures that its trajectory conforms to the STC. With the assistance of conflict prediction and resolution advisories, ATC ensures that aircraft do not penetrate active STCs. STC schedule and status information is accessible to NAS users and service providers via the NAS-WIS, and is actively monitored by the TM, ATC, and MOC. As the vehicle descends, ATC monitors STC status to ensure maximum airspace utilization by aircraft as STC airspace is released. The STC is completely released when the vehicle's vertical velocity decreases and it transitions to a conventional performance profile.
    • Final Descent Managed by Positive ATC. As the vehicle exits the STC, DSSs assist controllers in integrating the vehicle into en route and arrival traffic flows. This sequencing and scheduling assistance continues throughout the vehicle's return. If the vehicle will land at an airport, it is managed by ATC as it transitions through terminal airspace. Terminal controllers provide a runway assignment and issue an approach clearance. The vehicle is then transferred to the tower, which issues a landing clearance and taxi instructions. If the vehicle will land at a dedicated spaceport, ATC communicates with the MC for the transition through terminal airspace, then terminates air traffic services and transfers the vehicle to the appropriate authority for landing instructions.
    3.5.2 Descent Through An STC From The Upper Limit Of The NAS To The Surface

    Powered vehicles that are eligible for positive ATC may be accommodated by an STC for their entire return, based on the operational decision of the relevant traffic manager. Unpowered vehicles (i.e., gliding or ballistic) are always accommodated by an STC for the entire transition from space to the surface.

    • Powered Return. As the vehicle enters the NAS, the MC ensures that it conforms to the STC. With assistance of conflict prediction and resolution advisories, ATC ensures that aircraft do not penetrate active STCs. STC information is accessible to users and service providers via the NAS-WIS, and is monitored by the TM, ATC, and MOC. As the vehicle progresses, ATC monitors STC status data to ensure maximum airspace utilization by aircraft as STC airspace is released. As the vehicle approaches terminal airspace, sequencing and scheduling advisories are provided to ATC, in order to create an arrival slot for the vehicle. In contrast to today's static SUA, the dynamic nature of STCs minimizes impact on air traffic since higher altitude STC strata may be released as the vehicle begins its descent and final approach. Before beginning final descent, the MC of a powered vehicle contacts the tower for clearance to land. 'Managed arrival reservoirs' designated for space operations may be used to ensure that final descent into the airport can be coordinated with ATC.
    • Gliding Return. Positive ATC is not an option for a gliding return since the vehicle cannot respond to the full range of ATC clearances. Upon re-entry, these vehicles have a higher descent rate than powered vehicles, and they must anticipate any constraints to landing, since alternative trajectories must be exercised early in the re-entry. Trajectory modeling identifies the point at which the spacecraft is committed to landing at the primary airport. This point represents the final opportunity to invoke any contingency plan to route the spacecraft to an alternate landing site if operational conditions are undesirable at the primary site. The MC and TM maintain direct communications in case contingency plans have to be implemented. When the spacecraft reaches its commitment point, it is handled as a priority vehicle since it does not have the option of deviating from its landing plan. DSSs provide sequencing and scheduling advisories to create an arrival 'slot' to accommodate the landing. If the vehicle lands at an airport, ATC issues taxi instructions to the vehicle. If the vehicle lands at a dedicated spaceport, the appropriate authority assumes this responsibility.
  • Ballistic Return. Vehicles with ballistic returns will free-fall to a predefined altitude, and then use a parachute or other mechanism to slow the vertical velocity for landing.[15] Positive ATC is not an option for handling these returns, since the vehicle has no ability to comply with ATC clearances. Due to the relatively slow vertical descent, STCs must be reserved for a longer time, requiring more extensive planning and collaboration among users and service providers. In addition, ballistic returns are constrained to landing at ports that can support the unique descent profile with minimal impact to arrival and departure traffic. Once the vehicle deploys a mechanism to slow its descent rate, narrower STCs are dynamically reserved and released, and ATC provides horizontal and lateral separation of aircraft from these STC. When the vehicle touches down, the MC issues notification that the mission has been completed, and this notification is disseminated via the NAS-WIS.
    3.6 Hypersonic Point-to-Point

    'Hypersonic point-to-point' refers to missions involving ultra-high-altitude international transit of passengers and/or cargo. These operations may involve transition through the NAS, entry into international airspace, and return to base; this sequence is reversed for flights originating from other countries. These international missions involve reusable vehicles that are essentially very fast, very high-altitude, very long range airplanes that operate several times a day to regularly scheduled destinations. Since some of these missions involve the carrying of passengers, the reliability and safety of these vehicles is comparable to conventional aircraft. The concepts described below illustrate the collaboration and coordination that accompanies these international missions.

    Like today's air carriers, commercial 'aerospaceline' companies coordinate flight plans and ensure that the vehicle's operation conforms to these plans. During the mission-planning phase, the aerospaceline's MOC collaborates with the SpOC and ISFO to develop a MIP for international travel. This collaboration includes the use of trajectory modeling to analyze the vehicle's trajectory, identify transition points at airspace boundaries, specify Air Defense Identification Zones (ADIZs) that will be penetrated, and define the ATM/ATC strategies that will be used to ensure safety of flight. Because of the recurring nature of these missions, nominal trajectories between specific origins and destinations are available as a baseline. These baseline MIPs streamline the mission planning process, and may be tailored to unique mission requirements. Coordination and dissemination of the MIP is expedited by the NAS-WIS, which facilitates international collaboration, notification, and information exchange to ensure that the trajectory and schedule are achievable.

  • The balance of this discussion describes missions departing from a U.S. point of origin for an international destination.[16] For these flights, the MC requests departure clearance from ATC. After ensuring the applicable TM initiatives are in place, ATC clears the flight to depart. As the flight transitions through the NAS, DSSs update scheduling information, which is available internationally via the NAS-WIS. Satellite-based surveillance allows the flight to be tracked and monitored throughout its trajectory. International communications are in place between the ISFO, SpOC, AOCs, ATC, and the spacecraft to facilitate both silent and verbal coordination. The ability to exchange information electronically improves the timeliness and accuracy of international communications, reduces the communications workload burden, and reinforces/clarifies verbal instructions that may be confounded due to language barriers, etc.

    The en-route trajectories for hypersonic missions departing from the U.S. may involve 1) ultra-high altitude flight within the NAS, and a transition directly to international airspace, or 2) flight above the NAS and re-entry into international airspace. For flights cruising within the NAS at ultra-high altitudes, large ultra-high sectors provide positive ATC. These missions may request VFR (with or without flight following), VFR-On-Top, or IFR. The MIP includes the trajectory, a defined ultra-high-altitude transition point within each Center, scheduled time of arrival at these transition points, spaceway routes, STC coordinates and schedules (if applicable), and any special operating procedures that the flight requires (e.g., aerial refueling). Ultra-high sector controllers provide ATC services, as requested, considering the vehicle class and flight profile. U.S. ATC coordinates with international ATC for approval for the flight to enter its airspace at pre-planned coordinates included in the flight's MIP.

    For flights operating above the NAS, the MIP also includes 1) the vehicle's targeted point for insertion into space, and the corresponding STC coordinates and schedule, and 2) the re-entry point and corresponding STC coordinates and schedule. Once the MIP is approved and disseminated, DSSs factor the mission into arrival and departure schedules. If dynamic STCs are used, their schedules are probed to mitigate conflicts with reserved airspace. When the flight is ready to depart the upper limit of the NAS, the MC informs ATC of its intent to launch into space. ATC uses conflict prediction and resolution tools to ensure that the STC is clear of traffic and clears the flight to launch. Once the flight accomplishes insertion into space, the appropriate international authority assumes TM responsibility. Mission status updates are available to the ISFO, SpOC, ATC, military and other interested users and service providers. Prior to the flight's re-entry, the MC coordinates with the ISFO and international ATC for approval to re-enter at specified coordinates included in the MIP. This coordination is performed at a predetermined time before re-entry. Upon re-entering international airspace, coordination between the MC and international ATC continues until the flight reaches its destination.

    P G Smith (ed P G Smith), 1999, "Concept of Operations in the National Airspace System in 2005", FAA.
    Also downloadable from of operations in the national airspace system in 2005.shtml

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