SCaN-ADD-V1

SPACE COMMUNICATIONS AND NAVIGATION PROGRAM

Space Communications and

Navigation (SCaN) Network

Architecture Definition Document (ADD)

Volume 1: Executive Summary

Revision 4

Effective Date: April 7, 2014

Expiration Date: April 7, 2019

CHECK THE SCaN NEXT GENERATION INTEGRATED NETWORK (NGIN) AT:

https://scanngin.gsfc.nasa.gov

TO VERIFY THAT THIS IS THE CORRECT VERSION PRIOR TO USE.

National Aeronautics and

Space Administration

NASA Headquarters

Washington, D. C.
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Space Communications and Navigation (SCaN) Network 

Architecture Definition Document (ADD)

Volume 1: Executive Summary

Effective Date: April 7, 2014

Approved by:

Badri A. Younes Date

Deputy Associate Administrator, SCaN Program Manager 

Space Communications and Navigation Program Office 

Human Exploration and Operations Mission Directorate

Designated Governing Authority: 

Anthony J. Russo Date

Chief Engineer 

Space Communications and Navigation Program Office 

Human Exploration and Operations Mission Directorate

Prepared by:

James S. Schier Date

Manager, Systems Engineering and Integration

S

NASA Headquarters

Washington, D. C.
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Preface

This document is under configuration management of the SCaN Program Control Board. This 

document will be changed by Documentation Change Notice (DCN) or complete revision. 

Proposed changes to this document must be submitted to the SCaN Configuration Management 

Office along with supportive material justifying the proposed change. Comments or questions 

concerning this document and proposed changes shall be addressed to:

Configuration Management Office

Qiuna.T.Harris@nasa.gov

Space Communications and Navigation Office 

NASA Headquarters

Washington, D. C.
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Change Information Page

List of Effective Pages

Page Number Issue

Title Revision 4

ii through v Revision 4

1-1 through 1-6 Revision 4

2-1 through 2-19 Revision 4

3-1 through 3-5 Revision 4

4-1 Revision 4

A-1 though A-5 Revision 4

Document History

Document Number Status/Issue Effective Date CR Number

SCaN-ADD-V1 Baseline April 20, 2009 CR000026

SCaN-ADD-V1 Revision 1 January 28, 2010 CR000049

SCaN-ADD-V1 Revision 2 October 31, 2011 CR000066

SCaN-ADD-V1 Revision 3 January 14, 2013 CR000078

SCaN-ADD-V1 Revision 4 April 7, 2014 CR000094

Change History

Revision Effective Date Description of Change

Baseline (CR000026) April 20, 2009 Initial Release

Revision 1 (CR000049) January 28, 2010 Changes to align with new SCaN 

integrated architecture vision

Revision 2 (CR000066) October 31, 2011 Changes to align with recent SCaN 

changes and with ADD Volume 2

Revision 3 (CR000078) January 14, 2013 Changes to align with Architecture 

Assessment and programmatic decisions

Revision 4 (CR000094) April 7, 2014 Updated to reflect ADM-3, ADM-3a, 2013 

Roadmap Workshop conclusions, and 

latest programmatic directions
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Contents

Preface ........................................................................................................................... ii

Section 1. Introduction .............................................................................................. 1-1

1.1 General .......................................................................................................... 1-1

1.2 Background .................................................................................................... 1-1

1.3 Driving Requirements..................................................................................... 1-2

1.4 Purpose.......................................................................................................... 1-3

1.5 Scope ............................................................................................................. 1-3

1.6 Document Overview ....................................................................................... 1-4

1.7 Architectural Goals and Challenges ............................................................... 1-4

1.8 Document Convention and Notation............................................................... 1-5

Section 2. SCaN Network Architecture Overview.................................................... 2-1

2.1 SCaN Phase 0 Network ................................................................................. 2-2

2.2 Drivers/Requirements Flow down to Capabilities ........................................... 2-3

2.3 SCaN Network Architecture in Phases 2 and 3 .............................................. 2-4

2.4 Integrated Network Service Architecture ........................................................ 2-6

2.4.1 Integrated Network Management........................................................... 2-8

2.5 SCaN Network Architecture Concept of Operations....................................... 2-9

2.6 Enhanced and New Capabilities................................................................... 2-11

2.6.1 Enhanced Near Earth Domain Capability............................................. 2-11

2.6.2 Enhanced Deep Space Domain Capability .......................................... 2-13

2.6.3 Destination Relay Capability ................................................................ 2-15

2.6.4 Mars Relay Capability .......................................................................... 2-17

2.7 Other Technology and Standards Infusion ................................................... 2-18

Section 3. SCaN Network Roadmap ......................................................................... 3-1

3.1 Security Functions of the Architecture............................................................ 3-1

3.2 Phase 1 Evolution .......................................................................................... 3-1

3.3 Phase 2 Evolution .......................................................................................... 3-3

3.4 Phase 3 Evolution .......................................................................................... 3-3
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3.5 Architecture Decision Points........................................................................... 3-4

Section 4. Summary................................................................................................... 4-1

Appendix A. Abbreviations and Acronyms............................................................. A-1

List of Figures

Figure 2-1. SCaN Network Standard Services .............................................................2-1

Figure 2-2. SCaN Phase 0 Network Architecture .........................................................2-3

Figure 2-3. Requirements & Mission Phasing, Capabilities Flow .................................2-4

Figure 2-5. SCaN Phase 3 Service Architecture ..........................................................2-7

Figure 2-6. Enhanced Near Earth Domain Capabilities..............................................2-12

Figure 2-7. Enhanced Deep Space Domain Capabilities ...........................................2-14

Figure 2-8. Destination Relay Capability (Lunar option).............................................2-16

Figure 2-9. Mars Relay Capability ..............................................................................2-17

Figure 3-1. SCaN Network Roadmap...........................................................................3-2

List of Tables

Table 3-1. ADP Descriptions ........................................................................................3-4
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Section 1. Introduction

1.1 General

The National Aeronautics and Space Administration (NASA) Space Communications and 

Navigation (SCaN) Program is responsible for providing communications and navigation

services to space flight missions located throughout the solar system. The SCaN Program 

provides user missions with services that may include transmitting data to and from user mission 

platforms (such as space vehicles); deriving information from transmitted signals for tracking, 

position determination, and timing; and measuring the Radio Frequency (RF) emission of or 

reflection from celestial bodies. 

This document, i.e., Volume 1 of the SCaN Network Architecture Definition Document (ADD), 

provides a high-level summary description of the NASA SCaN architecture. The SCaN 

Program’s challenges are to support the known NASA and approved U.S. and international 

partner mission set, and to develop and deploy new mission-enhancing capabilities (such as 

optical communications and antenna arrays) and make improvements in functionality using an 

integrated service architecture and space internetworking. This document provides an executive 

overview of the driving requirements and the technical architecture. It also explains how the 

architecture responds to challenging mission and programmatic requirements and the call for 

new, enhanced communications capabilities.

1.2 Background

In the summer of 2006, the NASA Administrator assigned management and Systems 

Engineering and Integration (SE&I) responsibilities for the Agency’s space communications and 

tracking assets to the SCaN Office in the Space Operations Mission Directorate (SOMD) (now 

the Human Exploration and Operations Mission Directorate (HEOMD)). The SCaN mandate 

centralized the management of NASA’s space communications and navigation networks: the 

Near Earth Network (NEN), the Space Network (SN), and the Deep Space Network (DSN). The 

mandate also included SCaN management of the NASA Integrated Services Network (NISN), 

but this responsibility was later reassigned to the Office of the Chief Information Officer 

(OCIO). The SCaN Program was also delegated the Agency responsibility to protect necessary 

electromagnetic spectrum, evolve efficient and interoperable telecommunications standards, and 

establish a telecommunications technology program. 

Since that reorganization other policy documents have provided further guidance to SCaN 

Program management. The SCaN Program Commitment Agreement (PCA) requires that SCaN 

evolve “services in a manner consistent with a space architecture framework and mission 

requirements and pursue cooperation, collaboration, and cross-support with industry and other 

Government agencies, including international space agencies.”

The PCA assigns the SCaN Program responsibility for providing communications and navigation 

services (including systems engineering and planning) to user missions, and maintaining and 

evolving the SCaN architecture to effectively and efficiently meet user missions' present and 

future needs. 
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The PCA directs the SCaN Program to create a single NASA-wide space communications and 

navigation architecture that:

a) Controls the physical configuration and evolution of NASA’s space communications and 

navigation infrastructure

b) Defines the evolving set of standard services that the infrastructure provides to user 

missions, i.e., flight programs and projects

c) Specifies the minimum set of standards that will be used by user missions to interface 

with these services, both in space and on the ground

The PCA also directs the SCaN Program to review NASA goals, initiatives, and missions to 

identify future communication needs, and to establish and manage a set of projects that 

accomplish SCaN Program objectives within allocated resource and schedule constraints with 

priority on safety, mission success, and risk management. In recognition of the limitations of the 

present network architecture, the SCaN Program is directed to integrate its individual networks 

into a unified network which will function as a single entity to provide services to user missions.

1.3 Driving Requirements

The Strategic Management Council (SMC) reviewed and endorsed the SCaN driving 

requirements which are consistent with NASA Policy Directive (NPD) 8074.1, Management and 

Utilization of NASA's Space Communication and Navigation Infrastructure. The driving

requirements specified in the SCaN Program Commitment Agreement (PCA) are:

a) SCaN shall develop a unified space communications and navigation network 

infrastructure capable of meeting both robotic and human exploration mission needs

b) SCaN shall implement a networked communication and navigation infrastructure across 

space

c) SCaN’s infrastructure shall evolve to provide the highest data rates feasible for both 

robotic and human exploration missions

d) SCaN shall assure data communication protocols for space exploration missions are 

internationally interoperable

e) SCaN shall provide the end space communication and navigation infrastructure for lunar 

and Mars surfaces

f) SCaN shall provide communication and navigation services to enable lunar and Mars 

human missions

g) SCaN shall continue to meet its commitments to provide space communications and 

navigation services to existing and planned missions

SCaN’s Level 1 programmatic requirements are contained in the SCaN Program Plan. As part of 

the SCaN system engineering process, SCaN has defined a set of program Level 2 requirements 

in the SCaN Network System Requirements Document (SRD). Other programmatic 

requirements from the NASA directorates are defined in jointly controlled Interface Requirement 

Documents (IRD) and reflected in the Level 2 SRD.
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1.4 Purpose

The SCaN Network architecture is intentionally capability-driven, and will evolve as NASA 

makes key decisions involving technological feasibility, mission communication needs, and 

funding. The purpose of this SCaN Network ADD Volume 1 is to describe the architecture at a 

level of detail appropriate for program management in SCaN and the NASA Directorates. The 

more detailed descriptions of the target architectures of the integrated network are described in 

the ADD Volume 2 for Phases 0 & 1, and Volume 3 for Phase 2. Other ADD volumes will be 

added as needed. This document illustrates the progression of the current architecture toward 

achievement of the target architecture, and describes the evolving services and capabilities to be 

provided by the Agency’s present SCaN networks (the SN, NEN and DSN) and the planned 

transformation from the current configuration of loosely coupled networks into an integrated 

network. The ADD volumes are developed in parallel with the SCaN Concept of Operations 

(ConOps) and the SCaN SRD. The SCaN Document Tree illustrates the relationship among the 

SCaN documents. 

1.5 Scope

This document summarizes the evolution of the integrated network architecture for NASA's 

communication and navigation infrastructure for the time period 2009-2025. This plan is 

strategic in nature and defines four phases that roughly correspond to the following time periods:

Phase 0: The Independent Networks Phase represents the SCaN Network as it existed in 2010. 

In this phase, three networks and their supporting functions were independent and the definition 

of the subsequent phases began.

Phase 1: The Pre-Integrated Network Phase represents the SCaN Network with three 

independent networks, but with new capabilities that extend the functionality of the networks and 

address upcoming user mission needs. Furthermore, these new capabilities lay the groundwork 

for the next phase by beginning the implementation of key features of the Integrated Network, 

including standardized services and interfaces.

Phase 2: The Integrated Network Phase represents the SCaN Network after the three networks 

are upgraded into a unified communications and navigation infrastructure. The SN, NEN, and 

DSN will be modified to share a common architecture presenting interoperable, standardized 

services to user missions. A unified process will be established to make commitments to user 

missions for providing the services that they require.

Phase 3: The Post-Integrated Network Phase represents the next evolutionary step in the 

SCaN Network. New technologies like space internetworking and optical communications will 

be infused as required to answer the needs of NASA’s long-term exploration and science goals. 

Major objectives are to change the architecture to enable significant reductions in system 

acquisition and operations costs while improving the SCaN Network’s flexibility and scalability 

to be more responsive to changes in budget and user needs.

The architecture is driven by the mandate to develop space communications and navigation 

capabilities that will enable future user missions, and also by the aggregated requirements of 

NASA, U.S. and international partner missions. Mission needs are documented in the Space 

Communication Mission Model (SCMM), which is managed by SCaN, and reflects the NASA 

Agency Mission Planning Manifest (AMPM) managed by NASA’s Independent Program and 
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Cost Evaluation Office (IPCE). Planned capabilities meet or exceed all current and planned 

mission requirements. One of the cornerstones of the architecture is to define an approach that 

remains viable in the face of programmatic and funding volatility.

A series of trade studies and Architecture Decision Points (ADPs) have been identified that will 

refine the evolutionary path of the SCaN Network. Section 3 contains a summary of the ADPs 

and their expected need dates. The SCaN Program will perform technology development 

activities and perform the trade studies to resolve technical issues in advance of programmatic 

decisions.

The scope of this ADD is limited to NASA’s SCaN networks and does not encompass the 

architectures of external organizations, nor of supported user missions. For example, the 

terrestrial networks operated by the Communication Service Office (CSO) under the OCIO (the 

CSO Networks, formally known as NISN), are opaque to the SCaN architecture at the level 

described in this document. The SCaN architecture supports user mission navigation by 

providing tracking, radiometric, and timing services. The SCaN Program performs user mission 

navigation as a cost reimbursable service. Aside from user mission interfaces, the architecture 

described in this document does not include details regarding user mission space or ground 

system elements. The ADD may include details of external elements if necessary to describe the 

SCaN architecture (i.e. a hosted communications relay)

The scope of this document does not include descriptions of programmatic processes such as 

review and approval of requirements, architecture, and documents, nor does it describe the

implementation of such processes. These processes are all addressed separately in the SCaN 

System Engineering Management Plan (SEMP) and the SCaN Program Management Plan 

(PMP).

1.6 Document Overview

Volume 1 of the SCaN Network ADD is organized into the following sections:

a) Section 1—Introduction describing the purpose and scope of the document, the driving 

requirements, and goals

b) Section 2—Overview of the integrated network architecture, services, the concept of 

operations, and new capabilities

c) Section 3—Roadmap of the integrated network and description of how the architecture 

will be developed phase by phase, including key architecture decision points

d) Section 4—Summary

1.7 Architectural Goals and Challenges

In response to the requirements and drivers identified in guiding documents and by the SMC, 

SCaN management has identified a set of architectural goals and challenges that are 

programmatic in nature. In particular, the NASA Administrator has instructed the SCaN 

Program to go beyond responding to documented customer requirements, and to take the lead in 

developing strategic, mission-enabling capabilities in advance of identified mission 

requirements.
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The goal of this document is to provide a high level overview of the SCaN Network architecture, 

its assets, architectural options, views, and evolution until 2025 in response to NASA’s key 

driving requirements and missions. The architecture is a framework for SCaN system evolution 

and will guide the development of Level 2 requirements and designs.

The SCaN architecture must respond to a number of challenges, including:

a) Forming a fully integrated network from three pre-existing individual networks

b) Resource constraints

c) Addressing requirement-driven, capability-driven, and technology-driven approaches 

simultaneously

d) Interoperability among compliant NASA, U.S., and foreign spacecraft and networks and 

commercial systems

e) Uncertainty in timing and nature of future user mission communications requirements

f) Requirements for support of user missions already in operation, as well as those to which 

support commitments have already been made

g) Changes in high level requirements and direction

1.8 Document Convention and Notation

To distinguish between the networks as systems and the organizational entities that currently 

operate the networks, this document uses new terminology to refer to the systems that comprise 

the SCaN Network. The set of organizational elements managed by Goddard Space Flight 

Center (GSFC) that are required to operate and maintain the SN is known as the Earth-Based 

Relay Element (EBRE). Examples of organizational entities that are included in the EBRE 

include the SN project, the Network Integration Management Office (NIMO), and functions of 

the Flight Dynamics Facility (FDF) that are required to operate the Tracking and Data Relay 

Satellite System (TDRSS) fleet. The set of organizational elements managed by Goddard Space 

Flight Center that are required to operate and maintain the NEN is known as the Near Earth 

Element (NEE), including the NEN Project and NIMO. The set of organizational elements 

managed by the Jet Propulsion Laboratory (JPL) that are required to operate and maintain the 

DSN is known as the Deep Space Element (DSE) and includes the DSN project and the DSN 

Mission Services Planning & Management Office (DMSP&M). These new terms (EBRE, NEE, 

and DSE) will be used exclusively in this document, as well as the SCaN SRD and SCaN 

ConOps. Each element may contain development projects, such as the EBRE’s SN Ground 

System Sustainment (SGSS) Project and the Tracking and Data Relay Satellite (TDRS) K/L/M

Project. Each element is responsible for the architecture of their respective development 

projects. Future development projects may be independent of the current elements, and will 

develop their own documentation to describe their architecture and interfaces with the SCaN 

Network. In Phase 2, NIMO and DMSP&M are reorganized into the SCaN Mission 

Commitment Office (MCO), which operates the new Customer Service Management Element

(CSME). EBRE, NEE, and DSE will continue to operate the SN, NEN, and DSN, respectively. 

In Phase 2, EBRE, NEE, and DSE are referred to as Operational Network Elements (ONEs).

Common equipment and software will be developed and deployed to the EBRE, NEE, DSE and 

CSME.
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For purposes of this document, dates associated with elements that are funded and have programplanned dates, are externally imposed milestones, or are mission commitments are treated as 

“firm” dates and are underscored in the text. All other dates are notional (indicated by italics in 

the text) and represent the best-estimated dates for planning purposes.
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Section 2. SCaN Network Architecture Overview

The SCaN Network architecture defines what must be done at the Program level to realize the 

concept of a “single, unified space communications and navigation architecture,” as defined in 

the SCaN PCA and NPD 8074.1: Management and Utilization of NASA's Space Communication 

and Navigation Infrastructure. Central to this architecture is a baseline set of core services, as 

shown in Figure 2-1, that are provided by all of the SCaN Network assets to user missions. 

These services are standardized and provided by common interfaces across the SCaN Network.

Figure 2-1. SCaN Network Standard Services

The services shown in Figure 2-1 are interoperable with those provided by networks of other

organizations, both national and international, and are preferentially based upon internationally 

agreed standards, such as those developed within the Consultative Committee for Space Data 

Systems (CCSDS).

From a physical perspective, the SCaN Program has engineered an integrated network 

architecture that will be responsive to both future user mission requirements and availability of 

advanced technology. This architecture features:

a) Aggressive, yet systematic, infusion of optical communications to complement the RF 

baseline (i.e., Phase 3 for near Earth and deep space)
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b) Migration toward high-frequency RF links (e.g., Ka-band during Phases 1-3)

c) Adoption of standard services and integrated network management starting in Phase 1 

and full integration of the networks by the end of Phase 2

d) Development of a Destination Relay capability for exploration and science missions in 

Phase 3 and enhancement of the Mars Relay (MR) capability

e) Augmentation and replacement of existing aging infrastructure (e.g., the ground segment 

at the White Sands complex during Phase 1, and 70-m antennas by Phase 3)

f) Growth into new performance realms (e.g., increased performance in data rates to meet 

projected demand and provide enabling capabilities during Phases 1-3)

g) Application of other communications technologies (e.g., Software Defined Radio (SDR), 

Disruption Tolerant Networking (DTN), standard communications, and physical security 

measures) during Phases 1-3

h) Compatible with existing user missions and legacy interfaces

The following sections contain a summary of the Phase 0 “As-Is” SCaN network, followed by an 

analysis of the flow of user mission drivers and requirements down to the future architecture 

capabilities, and a description of the notional future SCaN Integrated Network architecture,

including its services, operational concepts, and future capabilities.

2.1 SCaN Phase 0 Network

NASA currently operates a complex space and ground infrastructure that supports the Agency’s 

own space missions, as well as missions operated by partner agencies (both national and 

international) and by the private sector. The current NASA space communications architecture, 

shown in Figure 2-2, embraces three operational networks that collectively and effectively 

provide communications services to supported user missions using space-based and groundbased assets:

a) EBRE (i.e. the SN) – constellation of geosynchronous relays (TDRS) and associated 

ground systems

b) DSE (i.e. the DSN) – large aperture ground stations spaced around the world providing 

coverage of spacecraft from Geosynchronous Earth Orbit (GEO) to the edge of our solar 

system

c) NEE (i.e. the NEN) – NASA, commercial, and partner ground stations and integration 

systems providing space communications and tracking services to lunar, orbital and 

suborbital missions

Each of these networks is optimized to support user missions in specific operational domains 

where the communications and tracking requirements are quite distinct. The NASA space 

communications infrastructure as a whole offers a very extensive repertoire of services, 

including launch/tracking range support, early orbit tracking, forward and return data delivery, 

RF science, radiometric, and emergency services. Customers include robotic and human 

missions at locations ranging from near Earth to deep space. The present architecture is very 

capable, but is also complex because of the heterogeneous nature of the network assets and the 

lack of consistent service offerings, interfaces, and interoperability.
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The Phase 0 NASA space communication networks, i.e., EBRE, NEE, and DSE, have been 

evolving independently for as long as four decades on their own respective paths, providing 

services to user missions. The resulting levels of integration and interoperability are less than 

optimum. User missions that only need services from one network are well served, but user 

missions that need services from more than one network face inevitable operational and testing 

complexities, and in some cases even need different equipment to communicate using the 

existing assets and services. This situation will be burdensome, inefficient, and not cost effective 

for new exploration and science user missions that will require services from all three networks.

Figure 2-2. SCaN Phase 0 Network Architecture

2.2 Drivers/Requirements Flow down to Capabilities

Figure 2-3 shows the SCaN driving requirements aligned with the time periods in which they 

need to be addressed. The figure also shows the most significant NASA mission drivers.

Significant analysis was performed to identify the supporting capabilities needed to address these 

requirements and mission drivers. Figure 2-3 illustrates how the requirements and drivers flow 

down to the supporting capabilities listed at the bottom of the figure for each time period.

The current architecture has served NASA well, but is not optimum to provide tomorrow’s 

science and exploration mission support. The proposed plan includes an integrated architecture 
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with integrated network management, standard service interfaces, and integrated service 

execution. It also includes new technologies such as antenna arraying, optical communications, 

and new navigation capabilities, and also provides space networking (Internet Protocol (IP) and 

DTN protocols in space), which will enable new mission concepts. Collectively, these elements 

will provide NASA missions with seamless use of the SCaN Network assets, cooperating 

national and international networks, and compatible space assets. These new capabilities are 

necessary to efficiently execute future science and exploration missions.

Figure 2-3. Requirements & Mission Phasing, Capabilities Flow

2.3 SCaN Network Architecture in Phases 2 and 3

The vision for the future SCaN Network architecture is to build and maintain a scalable and 

integrated infrastructure that provides comprehensive, robust, and cost effective space 

communications services at order-of-magnitude higher data rates to enable NASA's science and 

exploration missions. This infrastructure can readily evolve to accommodate new and changing 

technologies and will preserve current capabilities to support user mission critical events and 

emergencies.

The future SCaN Network architecture, as illustrated in Figure 2-4, unlike the current SCaN 

networks, will function as a single integrated network by implementing an architecture that 
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includes a consistent suite of international standards, interfaces and processes, and is referred to 

as the SCaN Integrated Network. While the different operating domains and unique customer 

needs will require some distinct capabilities, the integrated network will use common 

crosscutting standards and implementations to the greatest extent possible. An integrated 

network management function will serve as the interface for all NASA SCaN Network 

customers. In addition to existing physical, information technology, and communications 

methods, NASA will adopt new standardized security measures for managing access control and 

ensuring confidentiality, system integrity, and availability.

Figure 2-4. SCaN Phase 3 Network Architecture (circa 2025)

The future SCaN Network architecture has the following features:

a) Solar system-wide coverage

b) Anytime, anywhere connectivity for Earth, Moon, and Mars

c) Integrated service-based architecture and network management 

d) New technology (optical, arraying, SDR) infused into the SCaN Network

e) International and commercial interoperability using standard interfaces
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The future architecture includes a baseline of highly reliable low to high rate microwave links, 

and augments them with very high data rate optical links to provide direct-to-Earth and relayed 

communications for user missions. The following sections describe the new capabilities that 

deliver these services, along with the corresponding mission drivers, specific infrastructure 

enhancements, and performance benefits.

The SCaN Program has adopted and/or adapted internationally standardized protocols and 

interfaces to ensure interoperability among the SCaN assets, and with space and ground assets of 

NASA, U.S., and international partners and commercial providers. NASA has commonly 

selected CCSDS space communications and data exchange standards where available. In 

addition, other international standards (such as the IP suite and surface wireless standards such as 

Institute of Electrical and Electronic Engineers (IEEE) 802.xx) may be used. The SCaN Program 

works closely with the CCSDS and other international standards bodies to evaluate and adopt 

effective, interoperable standards as well as conduct development activities in areas where new 

standards are required. The end result is a standards-based infrastructure with defined 

compliance points for interoperability. The nominal assumption in the architecture is that any 

external systems—including those of other agencies and commercially provided systems—will 

be compliant with these internationally agreed and supported standards and interfaces. 

To the extent practical and efficient, the SCaN Network will use integrated services and common 

implementations for similar functions, thereby reducing the costs of developing, operating, and 

sustaining unique systems. These changes will facilitate a seamless and efficient interface for 

SCaN customers and increase efficiency of network systems. Evolution of the SCaN Network 

will be driven by both mission requirements and insertion of new, mission-enabling 

technologies. Customers will be strongly encouraged to use the available standard services 

whenever possible. 

Through system upgrades and insertion of microwave arraying, the SCaN Program will improve 

the performance of NASA’s RF-based assets to support 1.2 Gbps in the Earth domain, and 150 

Mbps in the deep space domain1. Arraying will also improve the reliability and flexibility of 

SCaN services by providing sub-array capabilities and soft failure (failure of a single antenna in 

the array will not result in service loss, but will result in a slight degradation of the performance 

of the system). NASA will use a combination of RF and optical assets synergistically to enable 

future Agency missions. This portfolio of diverse capabilities will allow mission designers to 

efficiently realize new science and exploration mission concepts.

2.4 Integrated Network Service Architecture

The SCaN Network will transition into an integrated network service architecture in Phase 2 and 

continuing into Phase 3 and beyond, illustrated in Figure 2-5, providing SCaN customers with 

the capabilities to seamlessly use any of the available SCaN assets to support their missions. It 

will also allow the SCaN Program to optimize the application of its assets to efficiently meet the 

collective needs of Agency missions. The service-based architecture will include: common 

services; common processes for network assets and user missions; internationally interoperable, 

 

1Analysis has shown that this is achievable at one Astronomical Unit (AU), assuming 180W 

spacecraft transmitting power for Ka-band using a 3-m high-gain antenna, and three arrayed 34-

m ground-based antennas.
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standard services; and integrated network management and data delivery elements to maximize 

access to all of the SCaN Program’s capabilities.

The Phase 3 integrated network service architecture shown in Figure 2-5 will include the 

network assets of NASA’s current EBRE, NEE, and DSE as well as future expansions, and 

includes CSME added in Phase 2. These assets are shown grouped by mission domain. As with 

the current NEN, the Near Earth Element of the SCaN Network will include both NASA-owned 

ground stations and contracted commercial stations. The figure shows separately the assets of 

other agencies and of commercial vendors not under contract to the SCaN Network. The use of 

internationally interoperable, standard services will enable user missions to interface seamlessly 

to the SCaN Network as well as these external entities. SCaN may interface with other agencies 

via the standard service management and execution interfaces. User Mission Ground Systems

may interface with SCaN or other agencies via the standard service management and execution 

interfaces.

Barring real world physical constraints and limitations of the communications assets, all of the 

standard SCaN services will be available from all assets of the SCaN Network. The SCaN 

Program will publish a standard catalog of services and ensure secure access to services via a

consistent set of interfaces for planning, requesting, delivering, managing and reporting.

Figure 2-5. SCaN Phase 3 Service Architecture
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SCaN Network services are categorized as follows:

a) Forward Data Delivery Services transmit the data received from the user mission 

ground system to the user mission platform. Data transmitted typically are commands, 

sequence loads, and flight software loads, but may also include any other types of data 

elements. Corresponding to the various levels of data units processed and radiated, 

different service types have been defined for this service group in Phase 2. They are 

Command Link Transmission Unit (CLTU), frame, file, and IP service.

b) Return Data Delivery Services acquire the data transmitted by the user mission platform 

over the space link and deliver them to the user mission ground system. Corresponding to 

the various levels of data units processed and delivered, different service types have been 

defined for this service group in Phase 2. They are beacon tone, return all frames, return 

channel frames, packet, file, and IP service.

c) Radiometric Services provide radiometric observables from which the position and 

velocity of the user mission platform can be derived. Three types of service have been 

defined for this service group in Phase 2. They are Raw Radiometric Data service, 

Validated Radiometric Data service, and Delta Differential One-way Ranging (DeltaDOR) service.

d) Science Services use the assets available in the SCaN Network to provide measurements 

on celestial bodies and characterize the intra-solar system media. These services include 

radio science, radio astronomy and radar science in Phase 2.

e) Calibration Services provide more precise Earth Orientation Parameters (EOP) 

referenced to the terrestrial and celestial frames, and adjustments to signal delays due to 

the Earth's troposphere and ionosphere.

SCaN will continue to provide legacy services (such as Return Bitstream) to existing user 

missions. See the SCaN Service Catalog for detailed service descriptions. These service 

definitions, particularly Forward and Return Data Delivery Services, may have to be refined as 

SCaN adds capability in Phase 3. For example, Phase 3 may include data delivery from one user 

mission platform (such as a astronaut or rover) through a SCaN relay to another user mission 

platform (such as a exploration vehicle or habitat). Such data delivery service does not currently 

fit the current definitions.

2.4.1 Integrated Network Management

The SCaN Network will provide a common set of services and interfaces across the network. 

Although some user missions only use one network asset, many user missions require the 

services of more than one asset. To reduce the customer burden, improve SCaN integration, and 

enable an integrated service commitment process, the SCaN Program will offer an integrated 

network management function (portrayed in Figure 2-5) that will provide access to all of the 

services provided by the SCaN Network, plus the compliant services offered by national, 

international, and commercial partners/providers. User missions would use the single common 

network management function, as negotiated in accordance with NPD 8074.1, to access the 

services that they require.

The integrated network management interface will maximize commonality for essential service 

and network management functions among the integrated network assets and future Phase 3 
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capabilities such as the Destination and Mars Relays and optical communication (relays are 

described in Sections 2.6.3 and 2.6.4). The integrated network management interface will 

provide user missions with a set of standard service management functions, and will offer these 

functions using secure interfaces. The integrated network management function will provide 

user missions with standard data delivery services using similarly secured interfaces.

2.4.1.1 Mission/Program Drivers

In particular, exploration missions and many near-Earth Science Mission Directorate (SMD) 

missions currently require the services of multiple SCaN networks. The driving requirements 

call for a unified network infrastructure capable of meeting user mission needs. To fulfill this 

requirement at best value to NASA, SCaN requires a service architecture with integrated network 

management across all asset domains, which is expected to maximize operations efficiency and 

reduce Operations & Maintenance (O&M) costs. Provision of seamless interfaces for service 

requests to user missions is critical to reduce the number of different interface options—both 

space and ground—that must be developed and operated.

2.4.1.2 Infrastructure Enhancements

Infrastructure enhancements include:

a) Standard service management functions 

1. Service planning

2. Service request scheduling

3. Service accountability reporting

b) Common network control functions 

1. Network scheduling

2. Network asset configuration and control

3. Network asset monitoring

4. Space Internetworking management

c) SCaN Service Catalog accessible at the network management interface

2.5 SCaN Network Architecture Concept of Operations

By the end of Phase 1, the operational concept will primarily involve the establishment of a 

common set of service and service management interfaces between the EBRE, NEE, and DSE

and their customers. The key feature of this concept for operations is the introduction of 

common internationally interoperable interfaces, protocols, and processes across the three 

networks and the initial implementation of integrated network management and integrated 

service execution. This commonality of interfaces and processes will allow the SCaN Program 

to assist customers through a common planning and scheduling interface, regardless of the SCaN 

assets that eventually serve a customer. The use of common protocols across the networks will 

also allow NASA to employ a common set of test equipment and procedures for customer 

communications system compatibility verification and validation, and employ commercial 

service providers that use compliant interfaces. NASA must implement these changes to achieve 

a SCaN integrated network architecture and set the stage for the Agency to provide high-layer 
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routed and store-and-forward internetworking services. Additionally, this phase includes the 

addition of dedicated communications resources into the SCaN infrastructure such as the 

additional 34-m antennas in the DSN Aperture Enhancement (DAE) Project.

By the end of Phase 2 all of the existing SCaN networks will be completely integrated into the 

SCaN Integrated Network. This network architecture will include integrated service 

management functions, common network control functions, and common service interfaces. It 

will also include adoption of common and/or centralized control and data delivery services 

across the network. The end state of the Phase 2 Integrated Network is still being refined as a 

result of architecture trade studies and analyses. Architecture Decision Memorandum-2 (ADM2), released after the November 2011 SCaN Phase 2 Architecture Assessment, documents the 

management positions and decisions, including that the "Phase 2 development should be based 

on an incremental development approach." ADM-3a documented the decision that a new CSME

will be established to integrate the functions of the GSFC NIMO and JPL DMSP&M. ADM-3a 

also splits Phase 2 into Phase 2a that implements CSME and completes upgrades to support early 

exploration missions and Phase 2b that completes the network integration.

The introduction of relay assets, such as the Destination Relay and space internetworking nodes, 

into the SCaN Network in Phase 3 will extend SCaN services beyond line of sight from Earth, 

and will be a major addition to the SCaN operational concept. The relay assets will provide 

interfaces to the surface elements developed by other directorates, and will provide high-rate 

communications and high-precision navigation services for regions out of line-of-sight of Earth, 

filling a coverage gap. Operational details of the Destination Relay assets within the SCaN 

Program are still being refined, as upcoming mission architectures and requirements are defined. 

A Space-Based Relay (SBR) will become operational in Phase 3. The SBR will augment/replace 

the TDRSS as the first and second generation satellites are retired. The capabilities for the SBR 

are still in definition, but will include optical communications.

Optical terminals and optical relay services will have some different operational considerations 

when compared to today's RF ground and relay systems. Optical systems will require more 

rigorous pointing, acquisition, and tracking due to the smaller beamwidth and restriction of 

operations to minimize interference from sunlight, and more frequent mitigation of weather 

interruptions (due to cloud cover for Earth-based systems) through handovers, as compared to

RF systems. A combined RF/Optical system may be employed to help mitigate some of these 

issues.

The concept of operations for Phase 3 builds upon the previous capabilities in various additional 

ways including: support of a possible human exploration outpost, support of a possible human 

mission to a Near Earth Object (NEO), extension of optical links to Mars, addition of spacebased optical array capabilities to relay signals between the Earth and Mars, transition of a Mars 

Relay capability from SMD to the SCaN Program, and any modifications of the MR required for 

SCaN to provide the standard data relays required for Mars missions. 

A permanent human exploration outpost or NEO campaign will have different communications 

requirements than individual user missions that only require services during certain time 

windows. Communications link scheduling services will require alteration or expansion to 

accommodate the surface systems. 
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The addition of orbiting optical relays implies that the SCaN Program will need new technology 

and modified and/or new operations centers. The Phase 3 orbiting relays, however, could 

eliminate the weather-induced operational challenges encountered with Phase 2 Earth-based 

optical systems if a RF downlink is employed.

Mars-orbiting relays will require support for DTN store-and-forward networking services and 

on-demand network access without human scheduling or intervention. 

2.6 Enhanced and New Capabilities

Enhanced and new capabilities that need to be implemented in the three phases of the 

architecture evolution plan are presented below. These capabilities are designed to provide new, 

mission-enabling functionality and to meet and exceed the requirements of the aggregate set of 

supported user missions. NASA missions are predominantly cited for reference; however, 

international partner missions may be supported, as well.

Activities to extend capability and capacity in the near Earth domain include the addition of 

TDRS K, L, and M, and the completion of SGSS by the end of Phase 1. For the deep space 

domain, activities include the DAE Project with additional 34-m antennas with arraying 

capability starting in Phase 1 and migration to higher frequencies (such as Ka-band) extending 

through Phase 3. New capabilities will also be required to support the new human spaceflight 

missions in late Phase 2 and Phase 3.

2.6.1 Enhanced Near Earth Domain Capability

The near Earth domain, shown in Figure 2-6, encompasses operational assets serving user 

mission platforms on and near the Earth, up to lunar and Sun-Earth Lagrange distances. The 

mission/program drivers for changes in this capability are described below.
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Figure 2-6. Enhanced Near Earth Domain Capabilities

2.6.1.1 Mission/Program Drivers

Science missions such as Soil Moisture Active Passive (SMAP) are near-term drivers that 

require high-rate return links in earth orbits. Human exploration missions require: robust 

communication for human flight/safety, high rate trunk lines, near continuous tracking coverage, 

and seamless user mission support by all of the SCaN Network assets. Science spacecraft such 

as the James Webb Space Telescope (JWST) and the Wide-Field Infrared Survey Telescope 

(WFIRST) require high-rate science data return at Sun-Earth Lagrange Point 2 (L2) distance. 

Other mission types such as large format imagers, Synthetic Aperture Radars (SAR), Lagrange 

point and Earth-orbiting sensor webs will benefit from high data rate downlinks and space 

internetworking.

2.6.1.2 Infrastructure Enhancements

Planned Infrastructure enhancements include:

a) Optical Initial Operational Capability (IOC): flight and ground terminals

b) Earth-orbiting optical relay for higher availability

c) RF capacity and performance upgrades

1. Additional ground stations

2. Ka-band upgrades
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d) TDRSS

1. TDRS K, L, and M

2. Multiple aperture arraying

e) SGSS

f) Blossom Point Ground Terminal (BPGT)

g) Launch Communications Stations (LCS)

h) Space-Based Relay

i) Destination Relay

j) Integrated Network Management and Integrated Service Execution

k) Space internetworking nodes with IP and DTN

2.6.1.3 Performance

Within the near Earth domain, the near Earth optical IOC (2022) will provide at least 1.2 Gbps 

on the return link to Earth, and 100 Mbps on the forward link. RF return link enhancements will 

provide at least 150 Mbps at L2 using Ka-band, and at least 1.2 Gbps for Low Earth Orbit 

(LEO)/Middle Earth Orbit (MEO) using Ka-band. RF forward link enhancement will provide 

between 25 to 70 Mbps for user missions at locations from LEO through lunar distances using 

Ka-band.

Near Earth domain assets provide anytime, anywhere connectivity within Earth line-of-sight and 

global Earth coverage. Standard services will be used across the SCaN Network.

2.6.2 Enhanced Deep Space Domain Capability 

Through system upgrades and insertion of antenna arraying, the SCaN Program will improve the 

performance of NASA’s RF-based assets to provide robust support for Mars exploration and user 

missions to outer planets (see Figure 2-7). Capabilities will include higher sensitivity for future 

heliospheric missions, interstellar probes, and other user missions, as well as higher data rates. 

Optical communications will be added to augment RF for higher rate data return.
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Figure 2-7. Enhanced Deep Space Domain Capabilities

2.6.2.1 Mission/Program Drivers

NASA is considering a number of new missions to Mars and the outer planets, including Mars 

Sample Return, which will require higher radiometric accuracy for precision rendezvous and 

docking; Mars Atmosphere and Volatile EvolutioN (MAVEN), which will extend reliable 

communications for the MR; Interior Exploration using Seismic Investigations, Geodesy and 

Heat Transport (InSight), which needs the MR and high-rate trunk line; Outer Planet missions 

which require long distance links to Jovian or Saturnian spacecraft and are survival-time limited 

missions; and New Frontiers missions, which will need extreme distance return link and 

emergency Tracking, Telemetry & Command (TT&C). Many of these missions will be 

collaborative ventures with European or other international agencies. 

2.6.2.2 Infrastructure Enhancements

Planned Infrastructure enhancements include:

a) Optical IOC: flight and ground terminals

b) Deep space optical relay for higher availability

c) RF ground stations

1. Additional 34-m antennas with arraying capability from the DAE Project 

2. Capacity and performance upgrade

d) Integrated Network Management and Integrated Service Execution
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e) Space internetworking nodes with DTN

2.6.2.3 Performance

The deep space communication capability will continue to provide robust standard services and 

emergency communication services using RF frequencies, but will emphasize the use of Ka-band 

for high rate data return. A scalable array of RF antennas will provide robust emergency X-band 

TT&C and high-power uplink capability, and will deliver anytime, anywhere connectivity within 

the Earth’s line-of-sight. Arraying will also improve the reliability, sensitivity, and flexibility of 

SCaN services by providing sub-array capabilities and soft failure functionality.

To deliver the highest performance data return, balanced against reduced spacecraft mass and 

power, a new deep space optical IOC will be developed offering at least 100 Mbps return data 

rates at one AU that will be extensible to one Gbps, and forward rates greater than two Mbps. 

Optical communications performance may be constrained, however, by weather effects, as well 

as sensitivity of the electronics to solar energetic particle events. Pathfinder missions will be 

used to mature the technology and evaluate these potential constraints.

2.6.3 Destination Relay Capability

The introduction of Destination Relay assets into the SCaN Integrated Network will significantly 

increase SCaN services to user missions at lunar and NEO distances and beyond. The 

configuration, evolution, and destination of these relay assets within the SCaN architecture are 

based on emerging communication and navigation requirements of NASA exploration and 

science missions, as well as SCaN Program driving requirements. The relay architecture, shown 

in Figure 2-8, shows trunk links between Earth and relay assets using RF and/or optical 

technologies, as well as orbit-to-surface links. The introduction of Destination Relay assets into 

the SCaN Network architecture will respond to NASA’s exploration and science mission plans. 

The termination point of the SCaN architecture resides at the interface from the Destination 

Relay to user mission surface and orbiting elements.
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Figure 2-8. Destination Relay Capability (Lunar option)

2.6.3.1 Mission/Program Drivers

The primary driver for the Destination Relay capability is high data rate return for potential 

human exploration missions in Phase 3. 

2.6.3.2 Infrastructure Enhancements

Planned Infrastructure enhancements include:

a) Optical IOC: flight and ground terminals

b) Earth-orbiting optical relay for higher availability

c) Destination Relay satellites

d) Space internetworking nodes with IP and DTN

e) Integrated Network Management and Integrated Service Execution

2.6.3.3 Performance

The Destination Relay architecture will be scalable to provide varying coverage depending on 

customer requirements, the number of orbital assets, and selected geometry. The Destination 

Relay assets will provide high-rate forward and return capabilities via RF and optical links, as 

well as radiometric capabilities for precision approach and landing and support of surface roving.
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The Destination Relay assets will enable international and commercial collaboration and 

interoperability, and will also provide multiple access communications techniques and protocols 

to provision simultaneous communications to multiple orbiting and surface elements. 

2.6.4 Mars Relay Capability

The present MR, which is currently developed and operated by NASA’s SMD, provides an 

initial communication relay capability for user missions on the surface and in the vicinity of 

Mars by including relay communications payloads on science orbiters. In the future it is 

expected that exploration vehicles and science spacecraft operating on or near the Mars surface 

will receive communication, navigation, and timing services via MR assets, which may be 

developed and operated by SCaN (to be decided at the NASA Agency level). The future MR

architecture will be incorporated into the SCaN Integrated Network, and may continue use of 

relay communications payloads on science orbiters, or use dedicated relay satellites with storeand-forward, space internetworking, and system capabilities evolved from the early MR designs

(see Figure 2-9). Two significant changes from current practice will be:

a) uniform adoption of a standard file relay and internetworking communications 

architecture, and

b) management and operation of the relay communications assets as essential elements of 

the SCaN service framework.

Figure 2-9. Mars Relay Capability
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2.6.4.1 Mission/Program Drivers

The near-term primary drivers for the MR are the upcoming missions to Mars, which include: 

Mars Science Laboratory (MSL) (long distance rover), MAVEN (extends reliable 

communications for Mars Relay), InSight, and other international agency partner missions. Mars 

Sample Return may drive higher navigation performance in Phase 3 because the mission requires 

higher radiometric accuracy for precision rendezvous and docking. Human exploration 

precursor missions are possible beyond the Phase 3 timeframe, which could drive requirements 

for dedicated Mars communication/relay orbiters. 

2.6.4.2 Infrastructure Enhancements

Infrastructure enhancements include:

a) Hybrid science/communication orbiters: relay payloads on science spacecraft

1. Telecommunications, data relay, navigation, and timing services

2. Store-and-forward file networking and initial space internetworking

b) Dedicated communication/relay orbiters: scaled for higher availability

1. Extended space internetworking services

c) Space internetworking nodes

d) Integrated Network Management

2.6.4.3 Performance

While the exact implementation plan and ownership of these MR assets is yet to be decided, the 

defined architecture is scalable and can easily evolve to support the human exploration phase and 

the use of higher data rate instruments like synthetic aperture radars and hyperspectral imagers. 

Based on easily achievable spacecraft designs, near-term return data rates of up to six Mbps RF 

are being delivered from Mars at one AU; up to 150 Mbps will be achievable in the long term, 

using more powerful transmitters and arrayed antennas. For the optical trunk lines to Earth, rates 

of at least 600 Mbps (Mars closest approach) can be achieved. Radiometric and new optimetric 

(i.e., observables derived from the optical link) capabilities will be provided to support precision 

approach, landing, and surface roving.

The MR and its services will be implemented in compliance with international standards such as 

CCSDS standards and Interagency Operations Advisory Group (IOAG) space internetworking 

cross support recommendations to maximize interoperability between NASA-developed assets 

and those developed by international partner agencies. This approach will also maximize 

commonality in service/network management amongst the relay and landed assets. The use of 

SDRs that embed this internetworking service functionality will reduce customer burden and 

enable delivery of interoperable DTN and file relaying services.

2.7 Other Technology and Standards Infusion 

To implement the future SCaN Network architecture, several technologies need to achieve at 

least Technology Readiness Level (TRL) six, and several key standards need to be established. 
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The SCaN Program’s Technology and Standards functions are carrying out these tasks and 

maturing targeted technologies where needed.

Key optical technologies will be required for the successful implementation of the optical 

communication link capability, including demonstration of efficient direct-to-Earth optical links 

utilizing photon counting receivers. Additional technologies needed include inertial stabilization 

and space-based photon counting receiver technologies, which will enable the Earth-orbiting 

optical relay satellites. Adaptive and lightweight optics technologies will enable the deep space 

optical communications IOC. SDR technologies will be needed to facilitate the Destination 

Relay implementation. The SCaN Program’s Spectrum function obtained an additional 

frequency allocation in the 22 GHz band, and will protect current SCaN frequencies in the 37-38 

GHz band for use by all the network assets. DTN technologies will be needed to enable 

internetworking throughout the solar system and beyond. 

The development of a series of international standards as well as new technologies will enable 

the SGSS modernization efforts. The SCaN Standards group is developing a suite of 

internationally approved communications standards, including IP over CCSDS, DTN, Low 

Density Parity Check (LDPC) Codes, and multiple access standards to enable international 

collaboration and interoperability. The SCaN Program will use these and other international 

standards to further support network integration, space internetworking, and human exploration 

missions. 
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Section 3. SCaN Network Roadmap

The SCaN Program has created a SCaN Network Roadmap (Figure 3-1) to show how NASA 

will develop the integrated network and its capabilities over time. The roadmap depicts an 

orchestrated timeline of phased evolution toward the target SCaN integrated network 

architecture, identifies major ADPs, and shows the relationships among the drivers, network 

assets, and activities. It provides NASA with guidelines for budget planning and technical 

efforts. This roadmap shows all planned, potential technology maturation and infusion paths, but 

not all of these paths will necessarily eventuate. The intent of the ADPs is to permit evaluation 

and selection of options at key points to decide the final path that is to be taken. The evaluations 

are based on technology maturation, feasibility, mission set, costs, and other relevant technical 

and programmatic concerns. 

The following sections contain descriptions of the SCaN integrated service architecture for each 

of the three time phases of deployment. The discussion includes the complete chronological set 

of ADPs identified for each phase. The section also contains a brief overview discussion of 

security considerations.

3.1 Security Functions of the Architecture

Security considerations are discussed only at a high level in the preceding sections, but they are a 

key part of the overall SCaN integrated architecture. Security functions addressing end-to-end 

confidentiality, integrity, and availability are present at many levels in the architecture, and 

include traditional physical and perimeter security, access control and authentication per NASA 

Procedural Requirement (NPR) 2810.1, data encryption and digital signatures where required, 

link and network layer communications security, and use of separate security domains and a 

layered deployment architecture to provide protection against a variety of attack vectors. Further 

security details are found in SCaN ADD Vol. 2.

3.2 Phase 1 Evolution

One of the most significant early steps in the SCaN architecture evolution plan is to provide a 

common set of standard services, interfaces, processes, and protocols for user missions, which 

will allow SCaN customers to interface seamlessly to all of the network services. The adoption 

of the initial integrated network management interface and standard services across the network 

will facilitate customer access to all assets of the SCaN architecture, enabling more efficient and 

effective user mission support. These services will be internationally interoperable to facilitate 

future international science and exploration missions. These new standards will be developed 

during Phase 1 and implemented in Phases 1 and 2.
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Figure 3-1. SCaN Network Roadmap
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The first phase also includes significant increases in microwave data throughput, providing at 

least 1.2 Gbps in the near-Earth (LEO) domain. Additionally, the SCaN Program plans several 

pathfinder missions to demonstrate technologies such as optical communications near the Moon, 

use of DTN, and SDRs. These pathfinders are designed to retire risk and allow NASA to gain 

operational experience before these technologies are put into operational use. Finally, this first 

phase involves the replenishment and modernization of aging SCaN Program systems, including 

targeted capacity and robustness increases to maintain highly reliable SCaN services for our 

Nation’s space missions.

3.3 Phase 2 Evolution

The deployment of the second phase of SCaN architecture evolution will integrate the three 

existing elements into one unified network. The second phase will enable increasingly 

sophisticated lunar science missions, and progressively more complex Mars and planetary 

science missions will also occur in this timeframe. The incremental implementation of Phase 2 

capabilities overlaps with the end of Phase 1.

Phase 2 evolution will provide the following major SCaN Network capability changes: 

a) Additional antennas from the DAE Project in anticipation of the eventual retirement of 

the 70-m Subnet.

b) Space internetworking with DTN and IP employed by selected user missions

c) Integrated Network Management and Integrated Service 

Building on expected successes in Phase 1, the Agency will execute Mars optical relay 

pathfinders to enable future technology insertion. NASA will also continue to augment 

microwave arraying to improve the reliability and flexibility of SCaN services by enhancing soft 

failure and sub array capabilities. Transition of the separate SCaN networks to an integrated 

network management structure will improve end-to-end operability and cost effectiveness of 

network management functions for the Agency. 

3.4 Phase 3 Evolution

The deployment of the third phase of SCaN architecture evolution will enable sophisticated 

robotic science missions with hyperspectral imaging or SAR instrumentation near Mars and 

beyond. NASA plans to develop and launch pathfinders for near Earth and deep space optical 

communications and tracking systems, demonstrating 100 Mbps throughput or more at one AU, 

and sub-meter-level ranging measurements for deep space science missions. Robust support for 

human exploration, Mars exploration, and missions to outer planets will be provided. Data 

throughput of at least 100 Mbps from Mars via highly available trunk lines and a dedicated (or 

improved) Mars relay system will dramatically increase exploration efficiency around the red 

planet. Size, weight, and power requirements for missions will be significantly reduced as 

optical communications capabilities evolve. Navigation improvements will include optimetric 

measurements with ranging at the centimeter level, including Doppler-equivalent observables. 

The deployment of space internetworking with DTN and IP across the SCaN architecture will 

provide seamless transitions between SCaN capabilities. Space internetworking with DTN and 

IP will be implemented throughout the solar system, with the SCaN Network providing the IP 

management infrastructure. Data confidentiality and uplink security will be implemented within 
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the space internetwork. NASA will continue enhancements of the SCaN architecture and 

retirement of aging or obsolete microwave systems (such as the 70-m antennas) in this phase. 

3.5 Architecture Decision Points

Table 3-1 lists the ADPs required to define the SCaN Architecture and their current status.

Table 3-1. ADP Descriptions

Year Architecture Decision Point Descriptions Status

2009 DS-1: Deep Space Antenna Array – resolve the outstanding 

tactical and strategic issues concerning the deep space antenna 

array, such as optimal antenna size, spectrum bands, uplink 

arraying

Complete: Implement array of four 

34-m Ka-band antennas per site; one 

34-m antenna per site with 80kW 

transmitter; receive and transmit 

performance equivalent to 70-m

2009 ER-1: New Earth Relay Services – determine which new 

services should be included into the Earth Relay element, and 

when they should be provided

Complete: Decided not to implement 

augmented TDRSS position 

determination and on-demand 

Multiple-Access forward capabilities; 

Approved TDRS antenna arraying 

for increased performance by 2016

2009 NE-1: Near Earth upgrades for Constellation ascent –

define the implementation approach to meet the Constellation 

launch requirements including dissimilar voice and 

Developmental Flight Information

Complete: Constellation Program 

cancelled and SCaN implementation 

cancelled

2010 ENT-1: Unified Service Pricing Approach – establish an 

approach for unified service pricing, cost accounting, and 

attribution across the SCaN network.

Cancelled: Programmatic Decision 

not to fund study

2011 MR-1: SCaN responsibility for Mars Relay 

Communications Payload – determine whether the SCaN 

Program will take responsibility for developing and/or 

operating the Mars Relay communications payload

Cancelled: SMD retained 

responsibility

2011 LR-1: Coverage and Orbits of Lunar Relay Satellites –

determine the orbital configuration of the Lunar Relay 

Satellites and cislunar vicinity coverage based exploration 

missions requirements

Cancelled: Study was completed but 

Constellation Program was cancelled

and no formal decision was made

2011 TDRS-1a: Exercise TDRS M option – determine whether to 

exercise the contract option to procure an additional thirdgeneration TDRS

Complete: SCaN exercised the 

TDRS M option, but deferred launch 

until 2018

2012 NE-4: Near Earth Ka-Band – determine how to implement 

Ka-band for near Earth Missions

Complete: Upgrade White Sands 1 

(WS1) for multi-mission use, scar 

new antennas for Ka-Band, don't 

upgrade existing sites unless mission 

drivers emerge

2012 MR-2: Configuration of near term Mars Relay 

communications payload – determine the capability and the 

configuration of an integrated communications payload and 

support its development for the Mars Relay

Cancelled: SMD retained 

responsibility

2012 NE-2: Ka-band uplink to support lunar operations –

decide if a Ka-band uplink is necessary to meet Constellation 

and science mission requirements

Cancelled: Constellation Program

was cancelled

2014 OPT-1: Lunar Trunk Line: Optical or RF Ka-band Link –

decide if the lunar relay trunk should be implemented via 

Cancelled: Constellation Program 

was cancelled and International 
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optical or RF technology and define an optical IOC (if needed) Lunar Network deferred

2014 NE-3: Upgrades to Support the Lunar Trunk – determine 

how to upgrade the Near Earth element to support the lunar 

relay space to ground link

Cancelled: Constellation Program 

was cancelled

2013 IN-1: Integrated Network Decision – make decisions 

regarding the configuration and deployment of the integrated 

network including integrated network management, integrated 

service execution, and space internetworking

Complete: ADM-3 added CSME 

and allocated network integration and 

allocated network integration 

responsibility. Revised in ADM-3a 

splitting Phase 2 into Phases 2a and 

2b to meet budget constraints.

2013 TDRS-1b: Exercise TDRS N option – determine whether to 

exercise the contract option to procure an additional thirdgeneration TDRS3.5.1 Expired: Contract option 

allowed to expire due to budget 

constraints

2015 INR-1: Integrated Network Relay procurement – decide the 

capabilities and schedule for the Earth-based relay capability 

that succeeds TDRSS

2015 MR-3: Configuration of mid-term Mars Relay 

communications payload – determine the capability and the 

configuration of a mid-term integrated communications 

payload and support its development for the Mars Relay

2015 COM-1: Internetworking Architecture Deployment –

make decisions regarding the communications protocol 

architecture and deployment of secure space internetworking 

services (DTN and IP) within the SCaN Program and between 

the SCaN Program and its user missions and partners

2017 OPT-1: Lunar Trunk Line: Optical or RF Ka-band Link –

decide if the lunar relay trunk should be implemented via 

optical or RF technology and define an optical IOC (if needed)

2019 OPT-2: Mix of space- and ground-based optical systems 

for the Earth domain - determine the optimum 

implementation mix of Earth-based optical stations and Earthorbiting optical relays for the near-Earth domain optical 

communications capability

2019 OPT-5: Destination Relay: Optical or RF Ka-band Link –

decide if the Destination Relay should be implemented via 

optical or RF technology and define an optical IOC (if needed)

2020 MR-4: Configuration of long term Mars Relay 

communications payload - determine the capability and the 

configuration of a long-term integrated communications 

payload and support its development for the Mars Relay

2020 OPT-3: Mars trunk decision - decide if the Mars Relay

trunk should be implemented via optical or RF technology and 

define the deep space domain optical IOC implementation (if 

needed)

2022 OPT-4: Mix of space- and ground-based optical terminals 

for the deep space domain - determine the optimum mix of 

space relay and Earth-based ground terminals for the deep 

space optical capability

2022 DS-2: Deep Space 70-m Subnet Retirement – determine 

if/when the 70-m subnet should be retired
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Section 4. Summary 

The SCaN Program has defined an integrated network architecture that fully meets the 

Administrator’s mandate to the Program, and will result in a NASA infrastructure capable of 

providing the needed and enabling communications services to future space missions. The 

integrated network architecture will increase SCaN operational efficiency and interoperability 

through standardization, commonality and technology infusion. It will enable NASA missions 

requiring advanced communication and tracking capabilities such as:

a) Optical communication

b) Antenna arraying

c) Destination and Mars Relays

d) Integrated Network Management and Integrated Service Execution

e) Enhanced tracking for navigation

f) Space internetworking with DTN and IP

g) End-to-end security

h) Enhanced security services

Moreover, the SCaN Program has created an Integrated Network Roadmap that depicts an 

orchestrated and coherent evolution path toward the target architecture, encompassing all aspects 

that concern program-level architecture (i.e., new capabilities, new & decommissioned facilities, 

major developments, and upgrade efforts). This roadmap identifies major NASA ADPs, and 

shows dependencies and drivers among the various planned undertakings and timelines. The 

roadmap is scalable to accommodate timely adjustments in response to Agency needs, goals, 

objectives and funding.

Future challenges to implementing this architecture include balancing user mission needs, 

technology development, and the availability of funding within NASA’s priorities. Strategies for 

addressing these challenges are to: define a flexible architecture, update the architecture 

periodically, use ADPs to evaluate options and determine when to make decisions, and to engage 

the stakeholders in these evaluations. In addition, the SCaN Program will evaluate and respond 

to mission need dates for technical and operational capabilities to be provided by the SCaN 

integrated network. In that regard, the architecture defined in this ADD is scalable to 

accommodate programmatic and technical changes
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Appendix A. Abbreviations and Acronyms

Acronym Definition

ADD Architecture Definition Document

ADM Architecture Decision Memorandum

ADP Architecture Decision Point

AMPM Agency Mission Planning Manifest

AU Astronomical Unit

BPGT Blossom Point Ground Terminal

CCiCap Commercial Crew integrated Capability

CCSDS Consultative Committee for Space Data Systems

CLTU Command Link Transmission Unit

ConOps Concept of Operations

CR Change Request

CSME Customer Service Management Element

CSO Communication Service Office

DAE DSN Aperture Enhancement

Delta-DOR Delta Differential One-Way Ranging

DCN Documentation Change Notice

DESDynl Deformation, Ecosystem Structure and Dynamics of Ice

DFE Direct From Earth

DMSP&MO DSN Mission Service Planning & Management Office

DSE Deep Space Element

DSN Deep Space Network

DTE Direct To Earth 

DTN Disruption Tolerance Network(ing)

EBRE Earth-Based Relay Element
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Acronym Definition

EM Exploration Mission

EOP Earth Orientation Parameters

EUMETSAT European Organisation for the Exploitation of Meteorological 

Satellites

EVA Extra Vehicular Activity

FAR Final Acceptance Review

FDF Flight Dynamics Facility

GEO Geosynchronous Earth Orbit

GSFC Goddard Space Flight Center

HEOMD Human Exploration and Operations Mission Directorate

HST Hubble Space Telescope

IEEE Institute of Electrical and Electronic Engineers

InSight Interior Exploration using Seismic Investigations, Geodesy and Heat 

Transport

IRIS Interface Region Imaging Spectrograph

IOAG Interagency Operations Advisory Group

IOC Initial Operational Capability

IP Internet Protocol

IPCE Independent Program and Cost Evaluation Office

IRD Interface Requirement Document

ISS International Space Station

JPL Jet Propulsion Laboratory

JPSS Joint Polar Satellite System

JWST James Webb Space Telescope

L2 Lagrange Point 2

LADEE Lunar Atmosphere and Dust Environment Explorer

LCRD Laser Communications Relay Demonstration

LCS Launch Communications Stations
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Acronym Definition

LDPC Low Density Parity Check

LEO Low Earth Orbit

LLCD Lunar Laser Communications Demonstration

LRO Lunar Reconnaissance Orbiter

MAVEN Mars Atmosphere and Volatile EvolutioN

MCO Mission Commitment Office

MEO Middle Earth Orbit

MESSENGER MErcury Surface, Space ENvironment, GEochemistry, and Ranging

MetOp-B Meteorological Operational - B

MPCV Multi-Purpose Crew Vehicle

MR Mars Relay

MRO Mars Reconnaissance Orbiter

MSL Mars Science Laboratory

NASA National Aeronautics and Space Administration

NEE Near Earth Element

NEN Near Earth Network

NEO Near Earth Object

NGIN Next Generation Integrated Network

NIMO Network Integration Management Office

NISN Network Integrated Services Network

NPD NASA Policy Directive

NPR NASA Procedural Requirement

O&M Operations & Maintenance

OCIO Office of Chief Information Officer

ONE Operational Network Element

PCA Program Commitment Agreement

PMP Program Management Plan
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Acronym Definition

RF Radio Frequency

SAR Synthetic Aperture Radar

SBR Space-Based Relay

SCaN Space Communications and Navigation

SCMM Space Communication Mission Model

SDO Solar Dynamics Orbiter

SDR Software Defined Radio

SE&I Systems Engineering & Integration

SEMP System Engineering Management Plan

SGSS SN Ground Segment Sustainment

SLS Space Launch System

SMAP Soil Moisture Active Passive

SMC Strategic Management Council

SMD Science Mission Directorate

SN Space Network

SOHO Solar and Heliospheric Observatory

SOMD Space Operations Mission Directorate

SRD System Requirements Document

SRS Space Research Service

STEREO Solar TErrestrial RElations Observatory

STS Space Transportation System

SWOT Surface Water Ocean Topology

TDRS Tracking & Data Relay Satellite

TDRSS Tracking & Data Relay Satellite System

TRL Technical Readiness Level

TT&C Tracking, Telemetry & Command

U.S. United States
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Acronym Definition

WFIRST Wide-Field Infrared Survey Telescope

WMAP Wilkinson Microwave Anisotropy Probe

WS1 White Sands 1

WSC White Sands Complex