Attachment_A_ArchBackv10.pdf

National Aeronautics and Space Administration

Space Communications and Navigation Program

Next Generation Architecture and Optical Payload Overview

8/31/2018

Contents

1 Introduction

2 Scope

3 Space Communication Networks

3.1 Earth Network

3.1.1 Earth Network Architecture: Space Segment (Relay Satellite)

3.1.2 Earth Network Architecture: SCaN Control and Ground Segment (SCGS)

3.2 Transition to Next Generation Architecture

4 Initial Architecture Deployment in 2025

4.1 Earth Relay Capability

4.2 Operations Concepts

4.2.1 Optical Services

4.2.2 RF Services

4.2.3 Latency Quality of Service Classes

4.2.4 Service Security

4.3 Optical IOC Architecture Concept

4.3.1 Payload Control

4.3.2 User Spacecraft Commanding

4.3.3 Ground Segment and User Requests

5 Optical and RF Technology Development

5.1 GSFC Optical Technology Development

5.2 Optical Terminals

5.3 Optical Payload

5.4 Optical Ground Stations

5.5 GRC Advanced RF Technology Development

6 Appendix A: Architecture-Provided User Mission Services

6.1 Communication

6.2 Navigation

6.3 Radio Science

6.4 User-Initiated Service

6.5 Time

6.6 Space Internetworking

6.7 Broadcast Service

7 Appendix B: Optical Relay Use Cases

List of Figures Figure 1: Planetary Networks Concept: Interoperable Earth, Mars, and Lunar Networks

Figure 2: Space Segment: Earth Relay Architecture

Figure 3: Current Space Communications Networks Grow into Planetary Networks

Figure 4 Initial near-Earth Communications and Navigation Architecture Concept

Figure 5 Space Service User Mission Diagram

Figure 6: System Context Diagram for Partner Relay Systems

Figure 7 GSFC’s Optical Test Facility

Figure 8: Next Generation GEO Relay Terminal

Figure 9: Engineering Model of User Terminal Optical Module

Figure 10: NASA Optical Payload

Figure 11: Optical Communications Telescope Laboratory

Figure 12: OGS-2 Telescope and Dome

Figure 13: (left) SCaN Testbed in pre-flight testing at GRC and (right) Astromesh reflector antenna characterization at GRC Near Field Range

1 INTRODUCTION

The NASA Space Communications and Navigation (SCaN) Program Office was formed in 2007 to provide a unified space communications and navigation network infrastructure capable of meeting robotic and human exploration mission needs. Today, these communication and navigation services are provided by the Near Earth Network (NEN), the Deep Space Network (DSN), and the Space Network (SN). As technologies mature and the needs of future missions change, SCaN must continually evolve its infrastructure and capabilities. Furthermore, several of NASA’s key communication systems are approaching their end-of-life and are in need of replenishment or replacement. The Next Generation Architecture is being developed to provide the strategy and architectural concept for revitalizing SCaN’s Networks through the 2040’s. The Next Generation Architecture capabilities are expected to be developed and deployed over time. Following a disaggregated services approach, initial capabilities of the Next Generation Architecture are envisioned to become operational starting in 2025.

NASA continues to expand humankind’s horizons through missions to understand the universe and extend human presence into the solar system. Space exploration in 2025 and beyond will require innovative communication solutions to support unconstrained science, autonomous operations, and increased interaction with robotic and human communication capabilities. International cooperation in space exploration is increasing, driving a need for augmented communications capabilities. Growing security threats require new approaches to secure space communications. In addition, new commercial markets in space are in development to meet the demand for commercial communications and navigation services. All of these are important considerations in the Next Generation Architecture.

NASA has an opportunity to take advantage of the commercial development to provide some or all of its increased communications needs with reduced costs. Cooperative internetworking will be part of an end-to-end system of systems that has Government, commercial, and international systems. This system of systems offers more service options for both NASA user missions and commercial customers and an overall more resilient network. The use of common standards and interfaces among communications and network elements, along with reconfigurable and adaptable system solutions, will allow missions to roam among the different service providers. User missions will have the option to select the best available, lowest cost service that meets their mission need based on availability, priority, QoS, and other scheduling controls.

2 SCOPE

The purpose of this document is to provide high level information on the current Next Generation Architecture concept to assist Offerors in developing their proposals for the Space Relay Partnership and Services Study. While the Next Generation Architecture covers all the planetary and interplanetary networks, this document provides an emphasis on the near-Earth relay satellites of the Earth Network; specifically, how NASA envisions the evolution of the Earth Network from the current networks and current government owned/operated model to cooperating government and commercial networks as part of the near term Initial Operating Capability (IOC) of 2025 followed by continuous evolution.

In addition, this document provides an overview of NASA’s optical technology, with an emphasis on optical payloads for near-Earth relay satellites that will lay the foundation for the implementation of US optical SATCOM capability.

All of the concepts described are notional at this time and open for discussion throughout the Space Relay Partnership and Services Study. NASA is encouraging commercial CONOPS approaches which could best address operations, space and ground segment interfaces, use of automation to initiate spacecraft services, security, internetworking, and service management needs with the goal of minimizing costs and minimizing user burden, yet enabling full interoperability among providers.

3 SPACE COMMUNICATION NETWORKS

Envision the solar system divided into: (a) the near-Earth domain from Earth’s surface to 2 million kilometers (M km); and (b) the Deep Space domain from 2M km to the edge of the solar system.

Regions of the solar system that have sufficient spacecraft and rich enough connectivity through space-to-space and space-to-ground links will have planetary networks. The planetary networks will grow into three segments as they emerge: 1) a Ground Segment on Earth providing network control and ground stations; 2) a planetary Space Segment with one or more orbiting spacecraft providing data relay and tracking/positioning capabilities; and 3) a planetary Orbital and Surface Segment consisting of communication terminals such as wide area networks or local area networks on orbiting spacecraft and on the planetary surface. The Space Segment’s orbiting relay spacecraft and Orbital and Surface Segment’s communication terminals multiplex and demultiplex to provide services to many orbiting user spacecraft and surface systems such as science orbiters, rovers, habitats, landing and ascent vehicles, extra vehicular activity crew, and in-situ resource utilization systems.

The future space communication and navigation network needs to provide services across the solar system and will be operated by an international set of organizations (government and commercial) that voluntarily cooperate to provide an integrated network. Figure 1 shows the concept of planetary networks with Lunar, Earth, and Mars Networks.

Figure 1: Planetary Networks Concept: Interoperable Earth, Mars, and Lunar Networks

• Strategy: Develop a flexible planetary network architecture adaptable to any celestial body to reduce development & operation cost

• User-network proximity links (space-space & space-ground/surface) provide standardized services & design for users of planetary networks

• Network-network Trunk links are internal network space-ground connections for long distance “back haul”

• International cooperation, cross support, standards: Inter-agency Operations Advisory Group (IOAG) Service Catalogs 1 & 2 approved

• Interoperability within & across Planetary Networks including government and commercial service provider networks per Internetwork

Interface and User Services Interface specifications

3.1 EARTH NETWORK

The first and largest planetary network is the Earth Network, which will consist of a set of networks each of which may have a Ground Segment with ground stations and network control centers and a Space Segment for relay and tracking spacecraft in Earth orbit. In addition, the network will include an external system for position determination such as the Global Positioning System (GPS).

Although GPS is external to NASA, it is considered here as another part of the Earth Network operated by the US Government providing time and position services to NASA and other missions.

In addition to GPS, Global Navigation Satellite Systems (GNSS) are included such as the European Galileo, Japanese Quasi-Zenith Satellite System (QZSS), and Russian GLObal NAvigation Satellite System (GLONASS).

Today, the NASA portion of the Earth Network consists of the Near Earth Network (NEN), the Space Network (SN), and the Deep Space Network (DSN). The NEN is a collection of ground stations (both NASA and commercially owned and operated) located around the world providing services to user mission spacecraft typically in Earth orbits. The Space Network is a constellation of geosynchronous satellites providing data and navigation services to user mission spacecraft in Earth orbit. In addition, the DSN ground stations on Earth communicate with and track planetary networks such as the Mars Network or individual planetary satellites. NASA’s portion of the Earth Network Ground Segment will evolve from the current SN, NEN, and DSN into NASA’s Space Communication and Navigation (SCaN)) Control and Ground Segment (SCGS). NASA will evolve its current space segment capabilities into the future Earth Relay capability. NASA’s Earth Relay may operate in Geosynchronous Earth Orbit (GEO) as well as other orbits and may include dedicated relay and tracking satellites, hosted payloads for relay and/or tracking functions, Commercial Service Providers (CSP), and other options. The Earth Network provides service in the near Earth domain (out to 2 million kilometers, Mkm). The SCGS will operate the future Earth Relay segment.

3.1.1 Earth Network Architecture: Space Segment (Relay Satellite)

Figure 2 illustrates the Earth relay architecture and the associated communication links envisioned for the next generation capability. All relay satellites possess two types of communication links:

trunk links and proximity links. A “trunk” link is a point-to-point communications link between a relay satellite and an Earth-based ground station that carries multiple user traffic flows multiplexed on the trunk line. A trunk link is internal to a network. While the trunk link for the Earth Network is typically a GEO-to-ground station link, for commonality between planetary networks, trunk links are architected to accommodate the extreme conditions of an interplanetary link, such as a link between the Earth Relay and the Lunar Relay or between a Lunar/Mars Relay and a DSN ground station. A “proximity” link is a Network-User access link between a space- or ground-based network asset and multiple individual mission platforms, through which each platform connects to the relay for traffic concentration and forwarding over the trunk link or to another platform’s proximity link.

Relay satellites will also include a “crosslink,” defined to be an internal network trunk link between two relay satellites.

Figure 2: Space Segment: Earth Relay Architecture

Relay satellites will be distributed in at least three GEO locations, or a sufficient number of non-GEO locations, with field-of-view to ensure global coverage. Additional nodal points can provide overlapping coverage areas to increase network bandwidth, availability, and resilience. Services are provided by optical and RF communication links. Trunk links are implemented with a combination of RF and optical links as required to provide the necessary bandwidth and Quality of Service (QoS).

Three methods of obtaining service are envisioned: on-demand, pre-scheduled, and User-Initiated Service (UIS). On-demand service is an on-orbit service available without a request, typically low/medium rate. Pre-scheduled service is scheduled in advance, and can be at any network-provided date rate needed by the mission. UIS is a service request initiated by the on-orbit spacecraft or Mission Operations Center (MOC). Each relay satellite is capable of supporting the return trunk line at a maximum data rate of at least 100 Gbps, as well as up to 10 Gbps for the forward trunk line. Each relay satellite has multi-rate capability to communicate with the mission platform (science or exploration spacecraft) at low rates (<10 Mbps) for disadvantaged users and up to 10 Gbps for high rate users. The relay orbiters are envisioned to have optical crosslinks at rates at nominally 100 Gbps, supporting up to 200 Gbps in the future.

Each relay satellite provides full network-layer services. These network-layer services are IP and/or Delay/Disruption Tolerant Networking (DTN) services. The implementation of the services may be distributed between the relay spacecraft and its associated ground station(s). This may allow for a simplification of the spacecraft and possible extended utility but with the penalty of increased path latency.

3.1.2 Earth Network Architecture: SCaN Control and Ground Segment (SCGS)

As shown in Figure 2 the SCGS will be comprised of a variety of ground stations for space-to-ground communications and a network management system that performs the service management and network control functions for the entire Next Generation Architecture. Ground stations could possess three types of communication links: Direct to Earth (DTE) and Direct from Earth (DFE) links, trunk links, and terrestrial links. Through the DTE/DFE links, a ground station communicates with the various user mission spacecraft to provide forward/return link-layer, network-layer, and tracking services. Through the trunk links, the ground stations communicate with the relay satellites to provide networking services for planetary networks. The ground stations also interface, via the terrestrial links, with the ground systems of user missions for delivering the services they requested, and with the network operations to conduct the network monitor and control activities. Compared to the current architecture, the SCGS will be 1) more integrated operationally; 2) support more high-frequency spectrum bands; 3) provide network-layer services (each ground station will be a IP/DTN node); and, 4) encompass both optical and RF stations.

3.2 TRANSITION TO NEXT GENERATION ARCHITECTURE

Figure 3 shows the set of space communication networks, with the evolution of NASA’s space communication network shown from 2015 (green) to 2040 (orange). The initial operational capability of the SCGS and Earth Relay will occur in ∼ 2025. Today’s networks gradually become the legacy architecture during the transition towards the future architecture. That legacy architecture remains in the picture because those spacecraft and ground stations will continue to provide service as long as they can be kept operational and as long as they have missions to support. Some legacy architecture assets may remain operational until 2040 and beyond.

Figure 3: Current Space Communications Networks Grow into Planetary Networks

Figure 3 captures the networks that NASA operates including contracted CSPs but also depicts existing and potential networks operated by international space agencies, academic institutions, and CSPs offering independent service. The open architecture of the CCSDS Solar System Internetwork (SSI, CCSDS 730.1-G-1) enables independently operated networks to collaborate voluntarily to provide cross support. Over the next 25 years, it is anticipated that communication and navigation capabilities pioneered by international space agencies will be augmented by commercial capabilities.

4 INITIAL ARCHITECTURE DEPLOYMENT IN 2025

The initial architecture deployment is an early instantiation of the Next Generation Architecture.

NASA will refine its plans over the next few years while system trade studies are conducted. NASA’s current initial 2025 concept is described below.

4.1 EARTH RELAY CAPABILITY

NASA will pursue the development of an optical relay constellation to provide optical relay services to NASA user missions. The optical relays will provide communications and navigation relay services from assets anywhere to/from the ground, air, space, and out to cislunar space, augmenting the current RF services that NASA provides.

Figure 4 Initial near-Earth Communications and Navigation Architecture Concept https://public.ccsds.org/Pubs/730x1g1.pdf

The vision for the future optical network will consist of Government and commercial relay assets as elements of a common architecture with compatible infrastructure to maximize interoperability and internetworking amongst previously disparate space-based systems, minimize operations costs, and promote the US market’s adoption of optical communications systems. The initial concept for this relay system is depicted in Figure 4, where Government relay assets, together with commercial partner relay assets, can provide services to both Government and commercial users, and route data seamlessly and transparently to the user.

Figure 5 Space Service User Mission Diagram

Figure 5 illustrates the goal of the architecture to have interoperable services among multiple relay systems, providing services to NASA missions and commercial customers. NASA envisions multiple partnerships to begin service with transitions to Non-Partner relay systems as the market matures and more providers offer service to more users. The interface to the User Mission is envisioned ideally based on a single, common, interface standard.

4.2 OPERATIONS CONCEPTS

The service paradigm of the 2025 era will provide services using a combination of the existing methods and the first steps toward the full Next Generation Architecture methods. The NASA Network will continue to provide services to existing missions using the current methods as required. A minimum of two new relay satellites around Earth are envisioned to provide the initial optical relay capability. Furthermore, user-initiated and on-demand services will be available via the Earth relay nodes. Single-point, automated service request scheduling will be implemented for pre-planned services for all SCaN ground stations and relays. Additional description of new services is provided in Appendix A: Architecture-Provided User Mission Services.

• Network-layer service: Internetworking services are envisioned using IP and DTN. In compliance with the CCSDS DTN standard, some network assets (relays and ground stations) are designated as DTN nodes to provide network-layer services adapted for the characteristics of space links. While space link layer services, previously characterized by directionality as separate forward and return services with different protocols, are still available, they are only exposed to existing users and new missions for certain anomalous events.

• Service management: the service management function will be based on open standards such as CCSDS 902.1-B-1, Cross Support Service Management (CSSM), for interoperability.

• Broadcast service: An initial operational capability of a broadcast service could be realized using the existing second and third generation TDRSS spacecraft in the near-Earth domain. A prototype of this capability, known as the TDRSS Augmentation Satellite Service (TASS), has already been demonstrated using operational SN/TDRSS assets. An initial deployment using current SCaN assets will inform specific design of such a service for later use by planetary networks.

• On-demand service and User-Initiated Service: A new service access protocol under consideration, known as UIS, involves the automated use of narrowband multi-access link resources to request wideband single access link resources.

4.2.1 Optical Services

The optical relay system concept provides a multi-rate return link up to 10 Gbps and up to 2.5 Gbps forward link service. The system will support CCSDS-compliant High Data Rate and High Photon Efficiency standards at 1550 nm wavelength. Beyond high data rate optical communications services, the relay network will also support data-clock ranging and range rate computations, angular tracking, as well as a goal of supporting optical carrier accuracy range rate computations.

Ranging services are limited to coherent modulations where phase recovery is accomplished and require user terminals to have their transmit clock tied to the recovered receive clock.

4.2.2 RF Services

The NASA Network will continue to provide RF services to mission users, through Government or commercial services. NASA’s systems will continue to use S-band for low rate, on-demand, multiple access, and navigation (e.g. timing, Doppler) services and Ka-band for high rate services.

4.2.3 Latency Quality of Service Classes

The optical service is focusing on three primary classes of service regarding latency. However, some users may levy constraints on where the data may flow (i.e., security requirements, only using optical paths, only using government-owned assets, or Space/Ground Link (SGL) only to US territory), which may impact service availability for them. QoS classes under consideration include:

1. Latency-intolerant, High availability: High priority data transfer from user platform to the ground via relay satellite. User data rate is limited by the capacity of the RF SGL (assumed to be higher availability than an optical link), which will be at least 1.2 Gbps for the return link (based on legacy LCRD performance).

2. Latency-intolerant, Lower availability: Routine priority data transfer from user platform to the ground via relay satellite. User data rate is limited to the capacity and availability of the optical SGL. This will be dominated by the cloud-free line of site for the various optical ground station locations.

3. Latency-tolerant, guaranteed delivery: Routine data transfer from user platform to the ground via relay satellite. User data rates are subject to the capacity and availability of the optical links, and limited by the onboard memory capacity implemented for DTN. Each relay node is envisioned to have sufficient on-board storage to support the store and forward capability of the protocol and to buffer through weather outages of the ground terminals.

https://public.ccsds.org/Pubs/902x1b1.pdf

Integration of commercial partner nodes with Government nodes should expect to, at a minimum, meet these identified latency QoS classes, though the implementation of which could be left to the commercial partner based on respective service management implementations.

Appendix B: Optical Relay Use Cases provides various Use Cases for expected user links requiring services from the optical relay. The optical service, modulation, and latency service class is provided in the table.

4.2.4 Service Security

The security of each user will be managed through the service management subsystem and will identify the specific assets that are available to support data relay functions. The mission users are assumed to provide protection/encryption for their mission payload and TT&C data. The relay provider will pass through user data, but control and secure its relay TT&C data to ensure end-to-end protection. NASA will provide protection of its payload TT&C data. The user data must be encrypted prior to encoding to ensure that any on-board decoding will not impact the format of the data that is transported and allow the on-orbit platform to optimize transmission to get the highest possible throughput.

4.3 OPTICAL IOC ARCHITECTURE CONCEPT

The Government’s initial optical node, developed by the NASA SCaN Program will consist of several optical terminals and be developed and launched through a spacecraft development effort, rideshare, or hosted payload provision, designated NR1 (NASA Relay) in Figure 7. NASA plans to initially operate this spacecraft and payload from its network control center at the White Sands Complex (WSC) with optical ground stations located at WSC and in Hawaii.

The expected commercial optical relay IOC is planned to consist of one or more nodes of a potential future commercial relay constellation, wherein the first node, designated PRS1/PR1 (Partner Relay System 1/Partner Relay 1) in Figure 6. The first node(s) of the commercial IOC, will be developed as part of a public-private partnership with NASA in which NASA supplies an optical payload as part of the partnership. Based on an assessment of market conditions, the commercial partner may choose to enhance their optical services capability, leveraging the NASA optical communications technology to expand their network. NASA may partner with a second commercial provider to develop PRS2 who will also be provided with NASA’s optical payload for the first node and who will also have the option to add additional commercial nodes of their network. The commercial operator(s) and NASA will jointly develop the capabilities of the initial Partner Relays based on mutually agreed objectives.

Figure 6: System Context Diagram for Partner Relay Systems

Interoperability among the providers, whether Government or commercial, will be a key objective for NASA as the IOC is developed. For NASA to use commercial services, multiple providers need to exist and offer services to mission users. Market diversity enables service providers to compete and creates options for NASA (and other customers) ensuring the user needs are met at competitive prices. NASA is considering multiple partnerships to foster the growth of these new services.

Interoperability among providers allows users to “roam” or transition operations among Government or commercial providers as conditions warrant; e.g. to best meet mission needs, remain cost competitive, accommodate a provider exiting the marketplace or ending a service(s) for any reason, while minimizing any impact to the mission while continuing to meet the performance requirements specified in the service agreements.

Within the architecture, there are two key interfaces between the commercially provided nodes (PRSn) and other systems. The right side of Figure 6 illustrates the User Services Interfaces which are identical for all PRSs. For example, the user mission may also operate with the NASA Network over the Network-User space and ground interfaces. The architecture also provides for interoperability of the inter-satellite links from one relay provider to another (e.g., commercial-commercial, commercial-government) and the space-to-ground links from one provider relay satellite to another provider’s ground stations (e.g., commercial-government, possibly commercial-commercial). These features will allow providers a means to improve availability through additional site diversity and provide redundancy.

As a contribution to the partnership, NASA will provide an optical payload (depicted as NASA P/L in Figure 6), consisting of several optical terminals to the commercial partner to support user links or network crosslinks. These payloads will facilitate interoperability among the first set of Government and commercial nodes. The NASA Network will operate its relay satellites and ground infrastructure. The commercial node(s) are expected to route to and be managed by commercial ground stations and operations centers. Flexibility of the commercial node(s) to access NASA ground stations for test purposes can also be discussed as a possibility. The commercial partners’ use of the NASA payload or the sole use of additional optical terminals will be discussed through the services partnership study.

4.3.1 Payload Control

Based on the NASA optical payload design, the optical terminals can be commanded either through the optical or RF SGL directly with the payload, or through a secure spacecraft bus interface with the payload. The primary means of commanding the optical payload on the government nodes will be through the optical or RF SGL. NASA will require control of its payload for certain NASA users.

The commercial partner may operate the payload for its own uses, commercial customers, or other NASA users as discussed with NASA during the Partnership and Services study. The onboard switching and routing unit on the NASA optical payload will have the capability to receive, store, and route data through any of the available optical terminals, as well as the RF SGL. This will allow for re-utilization of optical terminals for user links, SGLs, and crosslinks.

The ability to command and receive telemetry over the optical SGL allows Government or commercial relay spacecraft to forward commands to another node using crosslinks and receive another node’s telemetry and housekeeping information, in addition to the user traffic, for certain scenarios. These services may have to be pre-coordinated or provided via special configuration to ensure no interruption/interference between individual Government or commercial/partner operations.

4.3.2 User Spacecraft Commanding

User spacecraft will need to obtain information regarding ephemeris, pointing angles, and scheduled access times with the optical relay to initiate optical data transfer. It is expected that the user ground segment may either directly, or through the Government or commercial partner ground or space segments, provide this commanding to establish high rate service via low rate RF service prior to relay optical or high rate RF link acquisition. Once links are established with the optical payload, TT&C can then be sent via the relay service. In addition, the broadcast service will disseminate ephemerides and other navigation-related data for use by user spacecraft and relay spacecraft.

4.3.3 Ground Segment and User Requests

Government and commercial ground segments are expected to provide commanding, telemetry, and data transmissions to/from their respective relay nodes. The interconnection of these the ground segments form an enterprise architecture of the Government and commercial infrastructure. User requests and network responses and notifications to/from either spacecraft or MOC will require coordination between these various ground stations, implying a level of defined interfaces, standards, or commonality between Government and commercial service management schemes and systems. One such interface could be the establishment of a User Services Coordination Center that can provide an overall system planning and management interface between the user and the Government/commercial networks.

In contingency situations, it may be desired to have an additional level of interoperability such that Government nodes and commercial nodes could communicate with the other’s ground stations, allowing for an increased level of redundancy should system or channel impairments prevent the establishment of communication links. This may require additional commonality between infrastructure and architectures for this scenario to be feasible.

5 OPTICAL AND RF TECHNOLOGY DEVELOPMENT

5.1 GSFC OPTICAL TECHNOLOGY DEVELOPMENT

Goddard Space Flight Center is NASA’s Center of Excellence for near-Earth optical communications.

Goddard has developed significant missions in this field over the last two decades, starting with the Lunar Laser Communications Demonstration (LLCD), launched in 2013 in partnership with MIT’s Lincoln Laboratory. LLCD made history, transmitting data from lunar orbit to Earth at a rate of 622 megabits per second (Mbps) and to lunar orbit at 20 Mbps. That download rate was more than six times faster than previous state-of-the-art radio systems flown to the moon.

Goddard followed up this success with the development of the LCRD, again in partnership with Lincoln Laboratory. A majority of the payload was built in-house at Goddard. Recently, LCRD has completed its environmental testing and is waiting for satellite integration for an expected 2019 launch. LCRD will provide a space-based technology demonstration platform for bidirectional optical communications, demonstrating that optical communications can meet both NASA’s and other agencies’ growing need for higher data rates and enable lower-power, lower-mass communications systems on spacecraft. LCRD will provide user link services from 2 Mbps to 1.24 gigabits per second (Gbps).

Optical user terminals are now being developed by Goddard and MIT Lincoln Lab. The first terminal will fly on NASA’s Orion mission to the moon and communicate directly with a ground terminal, and the second terminal will be on the International Space Station, communicating through the LCRD relay. These terminals are the first units of multiple terminals planned for the future.

As NASA moves into the operational phase of optical communications with the next generation relays, Goddard is responsible for the relay payloads and user terminals that will provide up to 10 Gbps user services and 100 Gbps GEO-GEO crosslinks and space-to-ground links. Leveraging its previous work, Goddard continues to maintain sophisticated optical test sets, ground support equipment, integration facilities and engineering expertise to develop and validate the Next Generation relay payloads and user terminals (Figure 7). Goddard will provide a government node with a four-terminal payload for the initial Next Generation Network.

Figure 7 GSFC’s Optical Test Facility

An overview of the NASA’s optical terminals, optical payload, and ground stations is described in the following sections.

5.2 OPTICAL TERMINALS

NASA is currently developing optical terminals for both GEO relays (20 cm telescope) and user terminals (10 cm) (Figure 9 and Figure 8). The first GEO optical relay payload will be flown on the LCRD mission, and is capable of 1.24 Gbps using Differential Phase Shift Keying (DPSK) modulation, and 622 Mbps with Pulse Position Modulation (PPM). A corresponding user terminal, the Integrated LCRD LEO User Modem and Amplifier Terminal (ILLUMA-T) will be installed on the International Space Station (ISS) to demonstrate relay laser communications with LCRD1. The next generation of optical terminals, beginning development in 2018, will be capable of up to 10 Gbps for the user terminal (10 cm), and 100 Gbps for the GEO relay terminal (20 cm).

Figure 8: Next Generation GEO Relay Terminal

Figure 9: Engineering Model of User Terminal Optical Module

5.3 OPTICAL PAYLOAD

The Optical Communications Payload (OCP) shown in Figure 10 consists of notionally four (4) [TBR] Optical Relay Terminals (ORT), the Ka band system, and the Payload Electronics. The ORTs are identical, interchangeable, and operate independently. Each has a hemispherical field of regard to accommodate users in Earth orbit, at Sun-Earth L1 or L2, and in cislunar orbits. Each ORT consists of the Optical Module (OM) (20 cm telescope), two 1550 nm modems (10 and 100 Gbps), a high-power optical amplifier transmitter and beacon, and Controller Electronics to provide the pointing, acquisition, and tracking (PAT) control. The Payload Electronics consists of units for data storage, data processing, a switch/router, and the OCP Controller.

The Space Switching Unit interconnects the two optical terminals and the spacecraft's high rate RF system. In addition to realtime relay operations, the electronics will allow scenarios where one link uses DPSK signaling and the other PPM. A known challenge with optical communication through the atmosphere is the susceptibility to cloud cover. Thus the Space Switching Unit can use the high rate RF system in addition to an optical downlink when necessary. The link operations will be configurable to allow support for a variety of scenarios.

1B. S. Robinson, T. Shih, F. I. Khatri, D. M. Boroson, J. W. Burnside, O. Guldner, S. Constantine, J. Torres, T. M. Yarnall, C. E. DeVoe, W.

Hubbard, D. J. Geisler, M. L. Stevens, O. Mikulina, N. W. Spellmeyer, J. P. Wang, R. Butler, M. Hogan, T. King, A. Seas, "Laser communications for human space exploration in cislunar space: ILLUMA-T and O2O," Proc. SPIE 10524, Free-Space Laser Communication and Atmospheric Propagation XXX, 105240S (15 February 2018)

The Payload Secure Interface Module (PSIM) isolates the optical payload, in an Information Assurance (IA) point of view, from the spacecraft. IA technology prevents unauthorized access, use, disclosure, disruption, modification, inspection, recording, or the destruction of information within the payload. IA gets the right information to the right people at the right time while protecting that information from eavesdropping or corruption. IA is critical in preserving the integrity and confidentiality of future operational relay satellite systems. With the PSIM, the optical payload could be hosted on an untrusted non-US government spacecraft and maintain complete information assurance.

Figure 10: NASA Optical Payload

The OCP can operate independent of the spacecraft. Data may be downlinked either through the high speed optical space-to-ground link or the payload Ka band downlink. Data may also be cross-linked to other nodes in the network through another ORT high speed optical link.

The OCP current best estimate of mass and power plus 25% margin (not including the Ka-band subsystem) is listed in Table 1.

Table 1: OCP Mass and Power

Optical Communications Payload Total Mass (kg) Total Power (W)

Payload Electronics 96 371

Optical Relay Terminal (4 units) 440 1334

Total Payload 536 1705

5.4 OPTICAL GROUND STATIONS

The NASA/JPL Optical Communication Telescope Laboratory (OCTL) was built for dedicated research and development toward supporting free-space laser communications from space. The facility (Figure 11) has been used to support multiple optical communication technology demonstrations in the past, and is currently undergoing major upgrades to support future tests. As the upgrades are completed, the OCTL will become Optical Ground Station 1 (OGS-1) to support NASA’s future optical communication needs. The 1 m diameter aperture provides adequate collection area for expected laser signals from near-Earth, lunar and Lagrange point satellites. The OCTL facility is located at the Table Mountain Observatory near Wrightwood, CA.

A second ground station, OGS-2 (), will be located in Maui, Hawaii. OGS-2 will have a 60 cm receive aperture, a 15 cm transmit aperture, and be located within an approximately 5.5 meter diameter dome.

Both OGS-1 and OGS-2 are being outfitted to support the LCRD, flying in 2019.

Figure 11: Optical Communications Telescope Laboratory

Figure 12: OGS-2 Telescope and Dome

5.5 GRC ADVANCED RF TECHNOLOGY DEVELOPMENT

Glenn Research Center (GRC) is NASA’s Center of Excellence for Advanced RF communications. Over the last three decades, GRC has had a storied legacy in advanced RF technologies and communications system development, particularly in the Ka-band, with the advent of the Advanced Communications Technology Satellite (ACTS). The ACTS satellite made history demonstrating Ka-band technologies, spot-beam architectures, and conducting atmospheric propagation characterization that made possible the prolific use of Ka-band by the commercial satellite communications industry today.

Following the successes of the ACTS program, GRC became the lead center for the development of SCaN Testbed. Launched in 2012, the SCaN Testbed represents NASA’s first demonstration hardware for standards-compliant software-defined radios (SDRs) on board the International Space Station.

The flexibility permitted by SDRs allowed mission operators to demonstrate in-flight changes in functionality of radio communications hardware through software programming.

The work performed on SCaN Testbed (Figure 13) has now evolved to GRC becoming the lead NASA center for cognitive communications, which is developing the algorithms and flexible antenna technologies to utilize machine learning and artificial intelligence in communications systems. This cornerstone technology will be critical to NASA’s Next Generation Architecture by optimizing communications system performance while autonomously responding to dynamic changes in user needs, system security, and environmental conditions.

GRC is also working closely with industry for the development and demonstration of next generation RF user terminals with wideband, reconfigurable performance characteristics to result in low-cost electronically scanned array payloads for dual government and commercial use in the Ka-band.

Beyond these specific space-flight projects, GRC maintains world-renowned expertise in RF propagation channel measurements, space-qualified traveling wave tube amplifiers, novel antenna technologies (i.e., deployable antennas, reflectarrays, multi-beam antennas, and phased arrays), and on-board processing, and houses three anechoic chambers for antenna metrology. Leveraging this experience and facilities, GRC will provide the test and validation capabilities to support NASA’s Next Generation RF payload and architecture development and will work with industry partnerships to augment the Government optical nodes with commercial partner nodes as part of the next generation relay capability.

Figure 13: (left) SCaN Testbed in pre-flight testing at GRC and (right) Astromesh reflector antenna characterization at GRC Near Field Range.

6 APPENDIX A: ARCHITECTURE-PROVIDED USER MISSION SERVICES

The Next Generation Architecture will be seen from the mission perspective to be a standard set of services and interfaces available from a variety of provider access nodes. Similar to the terrestrial mobile networks, system complexity will be hidden “inside the box” and the specific implementation done by the provider will not be seen by the mission. This will allow the provider to evolve the implementation as technology and funding allow. As the implementation evolves, the mission may see increased availability, new or enhanced services, new or enhanced interfaces, and/or reduced operations costs and complexity.

The end-state architecture will provide the future missions with enabling services that minimize burden and constraints placed upon the mission. In the near-Earth environment, communication and navigation services will be available on-demand or, in the case of high rate and critical services, by schedule. Recognizing the trend towards increasing system autonomy, the scheduled services may be requested autonomously by mission platforms or MOCs and may become available within seconds or minutes of a request.

The SCaN Program offers a range of space communication and navigation services and capabilities to enable the next generation of NASA’s science and exploration missions and global collaborations.

These services allow missions to share the costs of critical space infrastructure and eliminate individual and costly mission facilities providing a cost-effective national resource for space exploration. In the end-state of the Next Generation Architecture, missions will receive common services across near-Earth and deep space. The interfaces and protocols used will be common across all networks to the fullest extent practical, taking into account the physics, mission constraint, and operational differences between near-Earth and deep space missions.

6.1 COMMUNICATION

Communication services move user mission data through and among network elements.

Communication services cover a wide range of functions and capabilities depending upon the mission need.

• Data to and from user satellites through relay satellite to ground stations on Earth

• Data to and from user satellites directly with ground stations on Earth (DTE, DFE)

• Data from one user platform to another through a relay satellite (e.g. one Mars rover to another through a Mars relay satellite)

• Data moved among a planetary wireless network among rovers and habitats.

6.2 NAVIGATION

Next Generation navigation services will provide improved availability and accuracy by expanding and enhancing the services available today. Metric tracking data will be provided on any microwave or optical carrier that carries data. Observations will be formed on space-to-space, space-to-ground, and ground-to-space physical links and then delivered to consumers of metric tracking data according to new protocols. Optimetrics will provide order of magnitude improvements in ranging, Doppler, and pointing (angular) observation accuracy. Non-coherent observation types, specifically one-way forward ranging (new service provided by SCaN) and Doppler, will facilitate autonomous navigation on-board the mission platform. In areas of high mission concentration, a navigation beacon may be provided as the basis of a stand-alone service. Navigation observables will be tied to a common time scale and will be compatible with GNSS in the near Earth domain.

6.3 RADIO SCIENCE

Radio science services provide users a unique measurement capability of the integrated network infrastructure (e.g., ground stations). Services may include very long baseline interferometry, radar services, and forward/return RF carrier signal transmission/reception.

6.4 USER-INITIATED SERVICE

A new service access protocol under consideration, known as UIS, involves the automated use of narrowband multi-access link resources to request wideband single access link resources. This protocol enables significant improvements in user service request disposition and service event execution response times. Using the UIS, all users send service requests (via on-demand link) and receive network responses (e.g., broadcast link) through a dedicated control signaling plane that supports multiple access flow processing. Requested services are typically provided through single access service (on heritage TDRSS), providing higher rate links, considered to be part of the data plane. In general, the user request contains the information about the requested service type, priority/urgency or QoS, acceptable service characteristics, and quantity of data to downlink.

Likewise, the response from the network contains response type (e.g. simple acknowledgement or other), scheduled asset (for antenna tracking planning), contact scheduled day/time, and network access information.

6.5 TIME

Time transfer services are also under consideration as a new service, and will enhance operations, complement navigation services, and enable new science. Precise time synchronization of the network and missions allows for the application of new multiple access techniques and thereby increases the number of simultaneous missions supported by the network. Transition to one-way range and Doppler tracking data also requires synchronization but will allow for new processing/routing relay satellite designs in place of bent-pipe relays. A reduction in timing errors is necessary to translate the accuracy of optimetric observations to accuracy in orbit determination.

Radio and optical science applications will benefit from an increase in time and frequency precision of the network and the mission.

6.6 SPACE INTERNETWORKING

The Space Internetworking services under consideration as new services in the future SCaN network have the potential to significantly increase the operational flexibility and robustness of missions, as well as enabling mission classes otherwise untenable. Already implemented and flight proven in several commercial satellite communications systems, networked communication systems offer additional redundancy and resiliency to a failure of an individual asset or to conditions that do not permit line-of-sight communication with Earth. Communication networks which use relays and relay crosslinks to route data offer many advantages to traditional point-to-point, direct space-to-Earth communications.

With cross links, relay satellites can route data from a mission user spacecraft anywhere in orbit to a local ground station and the terrestrial Internet, ensuring continuous data flow from the spacecraft to its respective MOC. Networks in space can also transfer data (both commands and payload sensor data) from one user mission spacecraft to another in space, enabling cross-platform operations and automated tip-and-queue (reducing system latency and enabling entirely new types of science mission data collection and operations). In addition, science data can be shared with multiple ground location sites simultaneously (i.e., multicast data distribution), enabling autonomous, cloud-based data processing, fusion, storage, and distribution spanning multiple, world-wide providers and users.

Network layer services will allow mission developers to utilize IP-based interfaces on board their mission spacecraft, eliminating the cost, complexity, and additional test requirements associated with accommodating mission unique interfaces. Network layer services at ground sites will allow the use of generic network layer interfaces and low cost commercial hardware which can reliably deliver data to its destination by any network (SCaN, OGA, or commercial) without the need for expensive mission-unique gateways or protocol conversions. For missions with data rate mismatches or intermittent connectivity (e.g., a NASA rover on the back side of the moon), store, carry, and forward services (such as those provided by DTN) can ensure that data is delivered reliably to its final destination over multiple, independent transmission hops, separated in time.

6.7 BROADCAST SERVICE

Broadcast services are a new service under consideration for the future network. Broadcast services provide both general and specific state and network (e.g., management) information to user spacecraft, transmitted…