NASA/TM—2014–218299 

 

Unmanned Aerial System (UAS) Traffic 

Management (UTM): 

Enabling Low-Altitude Airspace and UAS Operations 

Parmial Kopardekar, Ph.D. 

Ames Research Center, Moffett Field, California 

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April 2014
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NASA/TM—2014–218299 

 

Unmanned Aerial System (UAS) Traffic 

Management (UTM): 

Enabling Low-Altitude Airspace and UAS Operations

Parimal H. Kopardekar, Ph.D 

Ames Research Center, Moffett Field, CA 94035 

 

National Aeronautics and 

Space Administration 

Ames Research Center 

Moffett Field, California 94035 

April 2014
Acknowledgments 

Note to Readers: The UTM ideas and this document were based on Parimal Kopardekar’s 

NASA Aeronautics Research Institute seedling team proposal, NASA Ames Center Innovation 

Fund/Director’s Innovation Fund proposal and award, and a filed provisional patent application 

ARC-17299-1. 

Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

This report is also available in electronic form at: 

http://www.nasa.gov 
Document Purpose 

The purpose of this document to describe initial ideas to generate discussions and multiple 

design options to enable low altitude airspace and UAS operations. The ideas expressed in this 

document offer one of the possibilities and are meant for discussion and should not be 

considered as the only option. The workshop is intended to generate discussions and explore a 

wide range of design options to enable low-altitude airspace operations. Readers are 

encouraged to provide feedback on every aspects of this document. 

Background 

Many civilian applications of Unmanned Aerial Systems (UAS) have been imagined ranging 

from remote to congested urban areas, including goods delivery, infrastructure surveillance, 

agricultural support, and medical services delivery. Further, these UAS will have different 

equipage and capabilities based on considerations such as affordability, and mission 

needs/applications. Such heterogeneous UAS mix, along with operations such as general 

aviation, helicopters, gliders must be safely accommodated at lower altitudes. However, key 

infrastructure to enable and safely manage widespread use of low-altitude airspace and UAS 

operations therein does not exist. Therefore, NASA is exploring functional design, concept and 

technology development, and a prototype UAS Traffic Management (UTM) system. UTM will 

support safe and efficient UAS operations for the delivery of goods and services. 

Lesson from History 

Today’s Air Traffic Management (ATM) system was originated as a result of mid-air collision 

over the Grand Canyon in 1956. In order to safely enable widespread civilian UAS operations 

at the lower altitudes, an ATM-like system is needed. These low-altitude UAS operations will 

occur in the same airspace where today’s gliders, general aviation, helicopter operations occur. 

Such a heterogeneous mix further justifies ATM like capability in the form of the UTM system. 

Goal 

The goal of UTM is to enable safe and efficient low-altitude airspace operations by providing 

services such as airspace design and dynamic configuration, dynamic geo-fencing, severe 

weather and wind avoidance, congestion management, terrain avoidance, route planning and 

re-routing, separation management, sequencing and spacing, and contingency 

management. Using lessons learned from today’s ATM system, UTM functions and 

requirements would be developed. UTM is essential to enable the accelerated development and 

use of civilian UAS applications, and will support UAS ranging from those with minimal avionics 

capability, to those that are highly capable and/or autonomous. 

The near-term goal (1-5 years) is to safely enable low-altitude airspace and UAS operations. 

The long-term goal (10-15 years) is to safely enable massively anticipated density of lowaltitude airspace and UAS operations. The designs for short-term and long-term goals and 

density profiles may not be the same. By one account 70,000 operations by 2035 and some 

argue even this number is underestimated (Volpe report), 

 
4

Functional Description of UTM 

Figure 1 depicts the functional description of the UTM. The UTM will support a wide variety of 

UAS from those equipped with minimalistic avionics to autonomous UAS. The inputs to UTM 

will include: UAV mission/business flight plan or trajectory, real-time weather and wind, 

predicted wind and weather, airspace constraints (dynamically adjusted), community needs 

about sensitive areas (dynamically adjusted), three-dimensional maps that include man-made 

structures as well as natural terrain. The UTM will need persistent communication, navigation, 

and surveillance (CNS) coverage to ensure and monitoring conformance to the constraints. This 

could be provided by a combination of low-altitude radar, cell, satellite, and other means. The 

important aspect of this coverage is continuous robust, reliable, and redundant coverage to 

ensure monitoring and support needed for safe operations. 

The UTM will provide authentication, airspace design, airspace corridors, and dynamic geofencing, weather integration, constraint management (congestion prediction), sequencing and 

spacing as needed, trajectory changes to ensure safety, contingency management, separation 

management, transition locations and locations with NAS, and geo-fencing design and dynamic 

adjustments. The contingency management services will include but are not limited to 

emergency landing site guidance for UAS and geo-fencing segments of airspace due to wind to 

ensure safe operations, which may be unable to continue the mission. 

The UTM will be developed using autonomicity characteristics. These will include selfconfiguration, self-optimization, self-protection, and self-healing. Although the role of human 

operators needs to be carefully defined, it is anticipated that the humans will provide overall 

direction and goal-setting for the UTM system. The self-configuration aspect will determine 

whether the operations should continue given the current and/or predicted wind/weather 

conditions. The self-optimization aspect refers to given the traffic demand, how the airspace 

must be configured to make the operations most efficient in light of traffic demand. The selfprotection aspect will ensure that all sensor data related to CNS and vehicle is accurate and 

operating at the desired integrity. Should the data integrity, sensor inputs, and precision reduce, 

the self-configuration aspect will identify the appropriate strategy such as increased separation 

buffer or gradually halting the operations. The self-healing aspect refers to safely returning to 

normalcy. The human may be the ultimate decision-maker regarding the continuation and return 

to normalcy of the operations. 

The main aspect of UTM is that it will not require a human operator to monitor of every vehicle 

continuously. The UTM system will provide such monitoring, and coupled with autonomicity 

characteristics, it will provide human managers the right data to make strategic decisions related 

to initiation, continuation, and termination of airspace operations; as well as ensuring that only 

authenticated UAS operate in the airspace. 

 
UTM Types 

Two types of UTM system are envisioned. The first is the Portable UTM System, which will 

support operations such as agricultural needs. The system will be moved from one area to 

another easily. The second, the Persistent UTM System, will support low-altitude operations 

that are much more diverse and heterogeneous in nature based on multiple operators, 

missions, and range considerations. The Persistent UTM System will provide continuous 

coverage. 

Figure 1: Example Functional Description of UTM 

UTM Operational Business Models 

The current ATM system is based on a single service provider in the United States. The UTM 

System may open up several possibilities for service provider options. These include: 

1. Single service provider for the entire nation such as a government entity 

2. Single service provider for the entire nation provided by a non-government entity 

(for profit or not for profit entity) 

3. Multiple service providers by regional areas where UTM service provided by 

state/local government entities (these will be connected and compatible) 

4. Multiple service providers by regional areas where UTM service provided by nongovernment entities (these will be connected and compatible) 
6

Under all possibilities, a fee-for-service and/or route charge based model could be considered to 

support the operations, upgrade, and maintenance of UTM system. If a non-government is 

allowed to operate the low-altitude airspace operations with the UTM system, it is anticipated 

that the FAA will still need to certify the UTM system prior to its implementation and use. 

UTM Scope 

In the initial phases, UTM system is expected to support low-altitude airspace and UAS 

operations in remote areas and related applications such as wildlife monitoring and agricultural 

applications. Over period of time, the UTM system would support increasingly denser areas with 

goods and services delivery operations. Ultimately, the UTM system would support low altitude 

operations in urban areas for deliveries of goods and services. 

Partnerships 

A number of partners have expressed an interested in working with the NASA in exploring the 

research, development, prototyping, testing, and possibly implementation (if proven feasible) of 

the UTM System. These include public organizations, universities, and private organizations 

including but not limited to industry representing retailers, cargo/goods delivery operators, 

system integrators, UAS manufacturers, avionics industry, insurance industries, venture 

capitalists interested in funding UAS developers/operators, and personal vehicle manufacturers. 

Therefore, public-private-academia partnerships are expected to define and develop the UTM 

System. 

Stages of UTM Research, Development, Testing, and Implementation 

Table 1 shows the key activities by the fiscal year from conceptual design to the prototype 

testing and technology transfer of the UTM system for the near-term accelerated initiation of 

low-altitude airspace and UAS operations. Many aspects are very similar to the ATM system, 

however the UTM system will be unique given the challenges associated with low altitude CNS, 

different performance characteristics of UAS vehicles, mission needs, and suitability to wind and 

weather conditions. Furthermore, key capabilities such as newer and more representative 

trajectory models for UAS will have to be developed. Foundational research such as 

determination of separation minima in the vertical and horizontal directions, acceptable and 

hazardous wind and weather conditions, airspace stratification, rules of the road, and 

procedures will have to be developed. The activities listed in Table 1 can be accelerated based 

on the availability of resources, stakeholder needs, and other priorities. 

NASA expects to coordinate closely with the FAA and NOAA throughout the development 

stages of UTM system. UTM testing will also be conducted in restricted area in the beginning 

and later on in the FAA approved test sites prior to its prototype demonstration and 

implementation. 

 
Table A-1: Tentative Key Activities Associated with UTM System 

FY Tentative Key Activities (1-5 year accelerated near-term option)

2014 • Partnership building, workshop to discuss functions, issues, and 

paths to move forward 

• Identify UTM functional design options and conduct architectural 

trade studies 

• Initial analysis of the functional design vetted in autonomicity 

principles 

2015 • Develop Build #1 of UTM functionality (e.g., airspace design, geofencing, develop trajectory models) 

• Conduct safety case analysis and cost/benefit analysis of UTM 

system alternatives/architectures 

• Conduct trade studies for communication, surveillance, navigation, 

and networked needs and alternatives (e.g., radar, cell, satellite 

communications, many others) 

• Identify roles/responsibilities of human supervisor to manage UTM 

2016 • Conduct initial Live, Virtual, and Constructive (LVC) simulation study 

to test initial requirements 

• Continue to develop and mature UTM technology, Build # 2 (e.g., 

weather/wind integration, trajectory routing/rerouting, terrain/manmade object avoidance, congestion management, contingency 

management) 

• Conduct initial part-task simulation studies and analysis of UTM 

functions 

• Initial demonstrations/tests to enable low-altitude airspace 

operations with UTM system design(s) 

2017 • Continue to develop and mature UTM system functionality Build # 3 

(e.g., separation standards, separation management alternatives) 

• Conduct fast time and/or part-task simulations to demonstrate 

feasibility and benefits of UTM 

• Conduct interim demonstration/tests of UTM system design(s) 

2018 • Continue maturity of UTM Build # 3 functionality towards prototype 

• Conduct trades and analysis of surveillance, communication, 

navigation needs and finalize an architecture 

• UTM fast time analysis of degraded and off-nominal conditions 

• Conduct simulation studies to demonstrate UTM feasibility and 

maturity in LVC environment 

• Conduct interim demonstrations/tests of UTM system design(s) 
8

FY Tentative Key Activities (1-5 year accelerated near-term option)

2019 • Develop mature UTM Build # 4 prototype system (add machine 

learning component for Wx and trajectory management) 

• Conduct UTM simulations in LVC with many flights 

• Conduct UTM system demonstration in real life (portable as well as 

persistent systems) 

• Technology transfer of mature UTM system and/or its subcomponents 

2020 

and 

beyond 

• Further research based on UAS and UTM autonomy, autonomicity, 

and advanced operations and vehicles will continue to enable 

expected massive growth and demand, diverse applications, reach 

into congested urban areas, and change in city/urban design to 

accommodate UAS operations 

Workshop Breakout Goals 

1. Low-altitude missions, scenarios, use cases, and applications: 

Identify/compile various missions, use cases, vehicle types, and weight classes, 

altitudes at which these vehicles will operate. 

2. Near-term UTM Design Options: Identify alternative UTM system designs, and 

supporting research and development activities, to accelerate low-altitude 

airspace and UAS operations in 1-5 years 

3. Long-term UTM Design Options: Identify alternative UTM system designs, and 

supporting research and development activities, to accommodate massive future 

demand for low-altitude airspace and UAS operations in 10-15 years 

4. Demonstration Ideas and Stages: Identify near-term demonstration ideas that 

include heterogeneous vehicle/operations mix, missions/scenarios, alternate 

UTM design(s), and relevant metrics to safely enable low-altitude airspace and 

UAS operations. 

5. Business Models and other Considerations: Identify alternative business 

models to manage UTM system, and management strategy for issues such as 

privacy, insurability, security, and public perceptions. 
Summary 

Many civilian applications of low-altitude airspace and UAS have been imagined. Learning from 

the history of ATM, to safely enable diverse operations, a management system is needed. 

NASA is exploring the research and development of a UTM system to enable low-altitude 

airspace and UAS operations. The UTM system will be based on autonomicity characteristics 

with self-configuration, self-optimization, self-protection, and self-healing properties. The UTM 

system will consider input related to real-time and predicted winds and weather, 3-D mapping, 

low-altitude CNS, community needs related to airspace, and other constraints. The human 

manager is supposed to set the goals of UTM system based on the inputs from various sensors. 

The UTM system could function in two modes: portable and persistent mode. The UTM system 

operations may offer opportunities to examine different service provide options and fee-forservice and/or route charge options. Many committed partners are willing to work with NASA to 

research, develop, test, and implement the UTM system. Public-private-academia partnerships 

are expected throughout the development phase of UTM system with a tight collaboration with 

FAA. A prototype UTM system technology transfer is expected by 2019, which can be 

accelerated based on the resources and stakeholder needs. Further, long-term UTM system 

design options must be identified to accommodate the expected massive number of operations 

in this airspace. The initial near-term UTM design options targeted for 1-5 year implementation 

and long-term UTM design options targeted for 10-15 year implementation would provide 

continued research and development needs. 

 
10

Appendix A: Selected UTM Related Requirements 

Appendix B: Selected UTM Related Research Questions 

 
Appendix A: Selected List of UTM System Requirements 

System Requirements related to airspace design, geo-fencing, separation management/sense 

and avoid, trajectory management, contingency management, severe wind/weather avoidance, 

communication, navigation, and surveillance must be identified. 

Authentication 

1. Able to authenticate UAS that meet minimal equipage considerations 

2. Able to detect UAS that are “rogue” and will not meet minimal equipage 

considerations 

3. If there is a vehicle identification number (VIN) equivalent to all UAS then VIN 

should be verified 

Airspace Design, Dynamic Airspace Adjustments, and Geo-fencing 

1. Able to create airspace corridors and dynamically adjust them (e.g., lanes in 

the sky) with altitude for direction rules for nominal separation (similar to the 

right altitude for direction rules in the NAS) and efficiencies. In the beginning 

separation in 100 ft. height (number chosen by analysis) increments and 

could gradually decrease over time 

2. Set up rules of the road and right altitude for direction of traffic based on 

changing needs 

3. Able to dynamically create and adjust geo-fencing areas which will need to be 

avoided due to special needs such as community concerns, security, fires, 

etc. 

Communication, Navigation, and Surveillance, Prediction and Separation Management 

including sense and avoid 

1. Able to provide persistent communication, navigation, and surveillance 

coverage under day and night time (e.g., VMC and IMC) conditions 

2. Able to provide coverage under poor visibility conditions. Able to provide 

communication, navigation, and surveillance coverage under all visibility 

conditions 

3. Able to sense, detect and track every moving objects up to 10,000 ft. Most of 

the UAS for package delivery, wildlife monitoring, fire fighting, crop dusting, 

and other applications will operate much lower altitudes. A starting point is 

Class G airspace under 2000 ft. 

4. Able to provide predict potential collisions between UAS, UAS and other 

moving objects including but not limited to birds, gliders, helicopters, model 

aircraft, general aviation, personal air vehicles, special purpose balloons, jet 

wind turbines, etc. 

5. Predict the trajectory for next mile and/or within 5 minutes which ever is 

higher 
12

6. Able to monitor separation among UAS and predict conditions where the 

crossing or separation minima will be violated. The horizontal separation 

minima be set to 1 mile in the beginning and will be reduced over time. 

7. Able to provide persistent, redundant, coverage by sensors to areas where 

operations will be conducted 

Severe Weather and Wind Monitoring, Prediction, and Integration 

1. Able to real-time access and process data about winds and weather 

conditions and predictions 

2. Able to send changes to the trajectories to avoid severe wind and weather 

conditions. The weather and wind severity conditions need to be defined 

which will need to be avoided by these UAS 

Terrain, Man-made Objects Avoidance 

1. Able to maintain update terrain, maps, tall structures, power lines, etc. data 

base that every UAS trajectory needs to avoid 

Autonomicity Considerations 

1. Able to self-configure system under the poor sensor/surveillance conditions 

due to reduced accuracy (e.g., sensors reduced accuracy in poor visibility, 

fog, etc. conditions) where the separation buffers could be increased 

2. Able to operate on four key properties of autonomicity: self-configuration, selfoptimization, self-protection, and self-healing. Self-configuration will be used 

to operate under most efficient or degraded conditions (higher separation 

minima, dynamic geo-fencing, etc.) Self-optimization will be used to generate 

most efficient trajectories given the demand and optimize overall throughput 

while maintaining individual vehicle level efficiencies. An extreme example of 

self-protection is the kill switch where the UTM system could not provide the 

necessary support for operations. It will involve detecting degraded 

conditions (e.g., severe weather, impaired synthetic visibility) letting selfconfiguration decide how it would operate under such degraded conditions. 

Self-healing will be gradually moving towards normalcy after an off-nominal 

event 

Last 50 feet consideration (safety considerations to humans and other moving parts on 

the ground) 

1. Last 50 feet consideration – Able to deliver the cargo safely and at a safe 

location without impacting any other objects or people in the vicinity. Need 

vision system on board or off-board at the receiving end. There may need a 

shake-hand and authentication to ensure the cargo is delivered to the right 

location 

 
Business Models, Insurability and Underwriting 

1. Able to insure the UTM system operations 

2. Able to consider different business models where UTM could be operated by 

a third party vendor once the UTM system is certified 

Contingency Management 

1. Able to support a UAS find an appropriate and safe landing spot in case of 

UAS on-board emergency for events such as energy drop at UAS, cargo mishandling, etc. 

2. Able to return to home location when link is lost (special altitude zone may be 

needed for all lost link recovery, like a curb on highway) 

3. Able to communicate with UAS and/or operations centers and monitor all 

UAS at once to provide a “all-land at once scenario” (e.g., 9/11) to the nearest 

safe place. This will ensure that that the rouge UAS be identified and 

appropriate action be taken to take the rouge UAS “out of the system” should 

a need arises 

Congestion Detection, Prediction, and Management 

1. Able to congestion prediction and management guidance to UAS (could be to the 

operator) so that alternative trajectories, speeds, and altitudes be provided and 

used 

2. Able to provide sequencing and spacing under tight airspace corridors by 

creating required time of arrivals (schedule based system to strategically manage 

traffic and deconflict original trajectories) 

Heterogeneous Mix of Vehicles 

1. Able to accommodate UAS that are autonomous as well as non-autonomous and 

be dependent on the UTM to provide route/trajectory guidance 

2. Able to generate nominally conflict-free and efficient trajectories based on arrival 

and departure locations (latitude/longitude) and any specified time constraints 

and/or able to accept business trajectories provided by the 

operator/owner/retailer/renter of the UAS – This functionality may be needed to 

support small UAS operators as opposed to fleet managers (Airline Operations 

Center vs Flight Service Station analogy) 

 
14

Security 

1. Secure software/hardware from cyber security threats, must be able to detect 

that an intrusion has occurred and to the extreme operations will need to be 

halted. 

2. Able to provide redundant operations, should one system is unable to provide 

functionality 

3. Protect business confidential trajectories 

4. Able to operate without human intervention for sustainable operations but allow 

human to stop the operations should there be an event that needs kill switch 

Overall UTM Design 

1. Able to provide redundant operational support 

2. Able to be minimalistic 

3. Able to record trajectories of operations for research, analysis, and operationally 

challenging events 

4. Able to connect with other NAS airspace to support operations in/out of lowaltitude UTM managed airspace and other National Airspace System 

 
Appendix B: Selected Research Questions 

Comprehensive research questions must be compiled for both near-term 1-5 year accelerated 

implementation as well as long-term 10-15 year estimated massive volume, and scalable 

operation. 

Note: Research will address how the requirements can be met, when there is more than 

one way to address same requirement or operational need, or feasibility is unknown we 

translate that into a research need. 

Airspace Design, Geo-fencing 

1. Where do focus low-altitude airspace operations initially– Class G, up to 2000 

feet? 

2. Where do we need airspace restrictions, direction of traffic, 

arrival/departure/cruise corridors? 

3. Where do we need geo-fencing? Do we need to completely avoid Class A, B, C, 

D, and E airspace? 

UAS Equipage Considerations (there are many activities and standards that are being 

developed so we can leverage that work) 

1. What is the minimum equipage requirement on the UAS? 

Separation Management/Sense and Avoid (there are many activities in this area which we 

will leverage solution/designs) 

1. What is the minimum separation between UAS and other operations in the 

airspace? 

2. How do we maintain safe separation among UAS, gliders, helicopters, model 

aircraft, general aviation, and in future personal air vehicles? 

3. What is the separation minimum among different types of UAVs, UAV and 

general aviation and other vehicles operate in the same airspace? 

4. What is the (minimum) requirement on UAS for detect/sense and avoid and 

collision avoidance? 

5. What are different designs (ground-based and UAS based) for sense and avoid, 

and how they would work together? 

6. What are different sense and avoid architectures to provide persistent coverage 

to area? 

7. What are different sensor options, redundancies, sensor data integrity needs? 

Weather and Wind Detection, Prediction, and Modeling for low-altitudes 

1. What is the low-altitude weather modeling and prediction system required to 

accurately detect and predict eddies, wind shear, speed and direction among 

urban and remote areas? 
16

Contingency Management 

2. What are the procedures to manage emergencies including energy depletion? 

3. What are the procedures and technology solutions to manage lost-link 

scenarios? 

4. What are to procedures to handle bird-strike to an UAS? 

5. What are the procedures to manage multiple vehicles crashing into each 

other? When is it a real accident? 

Policy, Community, and Business Model Considerations 

1. What community concerns that must be addressed and what are different 

ways of addressing them? 

2. What are the concerns about insurers and how to satisfy them? 

3. What the concerns about privacy and liability, and how must be they be 

addressed particularly from vehicle design, certificate of approval, and UTM’s 

conformance monitoring? 

4. What are different business models (e.g., commercial fee for service) that 

should be considered in developing and maintaining UTM infrastructure? 

5. Should there be any clear approval of applications that UAS and UTM 

support? Should these applications verification (self-reported) be part of the 

UTM system? 

6. Should there be a limit on the cargo weight and type, if so, what’s the 

maximum cargo load allowed? 

Communication, Navigation, Surveillance 

1. Is the aviation-approved frequency coverage a requirement, can other CNS 

architectures and capabilities be leveraged? 

2. What are different ways to provide communication, navigation, and 

surveillance of the UAS operations? – cell, satellite, low-altitude radar, etc. 

3. Will the aviation frequency spectrum be a limiting factor to accommodate 

future demand? 

Overall System Design 

1. What is the level of redundancy needed? 

2. What are the functional allocation and architecture options for UAS, UTM, and 

networked/cloud system? 

3. What is the minimum functionality of the UTM in terms of airspace design, 

geo fencing definition, self-configuration, weather/wind integration, congestion 

management, trajectory management, and separation assurance? What are 

inputs, outputs, and processing functions of UTM? 

4. How portable UTM and persistent UTM differ in their functionality? 

5. What are different architectural alternatives to build and maintain UTM 

system? 
6. What kinds of safety and cost-benefit analysis need to be conducted for UTM 

system and its operational value in enabling low-altitude airspace and UAS 

operations? 

Contingency Management, Authentication, and Security 

1. How should authentication be performed to ensure that unauthorized UAVs are 

identified? How should these unauthorized UAS be managed? 

2. How would the large-scale cyber security physical intrusion (e.g., 9-11 

equivalent) be addressed procedurally, technically, and operationally? 

3. What kind of alerting, emergency management (e.g., parachutes) should be part 

of the UAS? 

4. What are cyber security related considerations for UTM system and operations? 

Does it need a “kill” switch to shut off operations in case of extreme intrusion? 

How would operations gracefully degrade under those conditions? 

Last 50 feet Descent Operation 

1. What are the most effective ways (e.g., technology, authentication, receptacle 

design) of managing the last 50 feet of descent to the ground in the safest 

manner? What are different ways of accomplishing in first 1-5 years and how 

would it look like in 10-15 years from now? 

 
18