NextGenArch_BackgroundInfo.pdf

National Aeronautics and Space Administration

Glenn Research Center 21000 Brookpark Rd.

Cleveland, OH 44135

Space Communications and Navigation Program

Next Generation Architecture Background Information

8/22/2017

Contents

1 Introduction 3

2 Scope 3

3 Planetary Networks 3

3.1 Earth Network

3.2 Transition to Next Generation

4 Architecture-Provided User Mission Services 6

4.1 Communication

4.2 Navigation

4.3 Radio Science

4.4 User Initiated Service

4.5 Time

4.6 Space Internetworking

4.7 Broadcast Service

5 Concept of Operation 8

6 Near-Earth Architecture 10

6.1 Space Segment - Relay Orbiters

6.2 Ground Segment - SCaN Control and Ground Segment (SCGS)

7 Initial Architecture Deployment 12

7.1 Service paradigm of 2025 era

7.2 Earth Network of 2025 era

8 Optical Technology Development 14

8.1 Optical Ground Stations

8.2 Optical Terminals

List of Figures

1 Near-Earth, Mars, and Lunar Network Concept 2 Current Space Communications Networks Grow into Planetary Networks 3 2040 SCaN Network Service Provision 4 2040 SCaN Network Service Provision 5 Space Segment: Earth Relay Architecture 6 Initial near-Earth Communications and Navigation Architecture Concept 7 Optical Communications Telescope Laboratory 8 OGS-2 Telescope and Dome 9 Model of Generation-1 User Terminal 10 Generation-2 GEO Relay Terminal Components

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 Network 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 is space exploration is increasing, driving a need for augmented communications capabilities. Also, growing security threats require new approaches to secure space communications. All of these are important considerations in the Next Generation Architecture.

2 Scope

The purpose of this document is to provide high level information on the current Next Generation Architecture concept. While the Next Generation Architecture covers all the planetary and interplan-etary networks, this document provides an emphasis on the near-Earth relay satellites of the Earth Network.

3 Planetary 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 Surface Segment consisting of communication terminals such as wide area networks or local area networks on the planetary surface.

The orbiting relay spacecraft and surface communication terminals multiplex and demultiplex to provide services to many orbiting user spacecraft and surface systems such as 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 communication links for the Lunar, Earth, and Mars Network concept.

Figure 1: Near-Earth, Mars, and Lunar Network Concept

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 provided by the US Government providing time and position services to NASA missions. In addition to GPS, GNSS are included such as the European Galileo, Japanese Quasi-Zenith Satellite System (QZSS), and Russian GLObal NAvigation Satellite System (GLONASS).

Today’s 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 com-mercially 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 provid-ing data and navigation services to user mission spacecraft in Earth or lunar orbit. In addition, the DSN ground stations on Earth provide destinations for planetary networks such as at Mars or indi-vidual 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 (SCN)) Control and Ground Segment (SCGS). NASA’s Earth Network Space Segment will evolve from the current Tracking and Data Relay Satellite System (TDRSS) 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.

3.2 Transition to Next Generation

Figure 2 shows the set of space communication networks, with the evolution of NASA’s space commu-nication network shown from 2015 (green) to 2040 (orange). The initial operational capability of the SCGS and Earth Relay will occur in ∼ 2025 driven by the need to replace the capacity of TDRSS as its satellites are retired. Today’s networks gradually become the legacy architecture during the tran-sition 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 such as antennas and TDRS satellites are expected to remain operational until 2040 and beyond.

Figure 2: Current Space Communications Networks Grow into Planetary Networks

Figure 2 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) 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 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 mission operation centers (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.

4.1 Communication

Communication services move user mission data through and among SCaN infrastructure 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 SCaN ground stations on Earth

• Data to and from user satellites directly with SCaN 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.

4.2 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.

4.3 Radio Science

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

4.4 User Initiated Service

User Initiated Service (UIS) scheduling is a new service under consideration for the future network.

User-initiated service allows mission spacecraft (or MOC) to directly initiate request for asset allocation through an automated system of resource assignments.

4.5 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 increase 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 optometric 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.

4.6 Space Internetworking

Space Internetworking services under consideration as a new service in the future network have the potential to significantly increase the operational flexibility and robustness of missions, as well as enabling mission classes otherwise untenable. In addition, networked communications offers 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 to route data offer many advantages to traditional point-to-point communications. This comes at a cost, however, in that the assets providing the relay service must also themselves be deployed and operated.

Internetworks will handle the handover of data from one satellite to another or from one ground station to another, ensuring continuous data flow from spacecraft to mission center. Responsibility for data is shared among the participating elements providing for retransmissions, prioritizations, buffering, and automatic rerouting based on failures.

Network layer services will allow missions to have network layer interfaces (e.g. IP packet or DTN bundle) which will deliver data to its destination by the SCaN Network. These services will eliminate the need for mission-unique gateways and protocol conversions.

Reference: Solar System Internetwork Architecture, Consultative Committee for Space Data Stan-dards, Green Book, July 2014.

4.7 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 simultaneously to all users. A variety of mission aids such as network information and navigation aids will be available to all SCaN missions without the need for scheduling. The broadcast service may also include low data rate forward messages for on-demand service and user-initiated scheduled service. Features of this service would be to share timing and GPS correction information, space weather, network and service assignments, network status, and other operational advancements.

5 Concept of Operation

The SCaN Network will provide services in a manner that combines the best attributes of the SCaN service provisioning of today, along with best attributes of commercial telecomm service provisioning.

Figure 3 shows a schematic of how the mission’s platforms and ground systems will interact with the SCaN ground segment (SCGS) and the space segments of the Earth Network, Lunar Network, and Mars Network when scheduling and receiving service. The general concept of operations will be the same in all three space segments, but the specific details may vary to suit the specific needs in each region.

SCaN and its service interfaces will become highly automated in service provisioning, greatly reducing the labor required for both SCaN and the missions. For instance, link connections will become adaptive (e.g. using cognitive techniques), changing parameters such as coding, data rate, etc, for optimal throughput. The system will provide three methods for scheduling and providing services to the missions: on-demand service; pre-planned service; and user-initiated service. Pre-planned service will be highly automated for scheduling, while on-demand and user-initiated service will be completely automated.

Figure 3: 2040 SCaN Network Service Provision

On-demand service provides low date rate forward and return services via relay for TT&C and other uses. It will be available in regions serviced by the Earth, Lunar, and Mars Networks. Service will be initiated by the mission platform or ground system, and the SCaN Network will set up the service nearly instantaneously. On-demand service can be configured to be “always listening” and can be available without a request. Sufficient capacity will be available to provide very high availability according to the QoS agreed to with the missions. The implementations of these services are expected to be optimized for availability, so the necessary trades are expected to lead to lower performance, such as data rates, as compared to other parts of the network.

Pre-planned service will be an evolution of the current method of scheduling, using an automated algorithm using inputs such as mission priority, data criticality, etc, to develop the schedule for com-munication, metric, and science services. Pre-planned service is initiated from the mission ground system via a request to the SCaN Service Request System (SRS). It is intended for use in areas where user-initiated service is not available (such as in deep space DTE links) to cover known service needs such as critical events, and when it best fits the mission needs. It also covers other services such as Navigation, Science, and Calibration Services that do not require direct interaction with the mission platform.

User-intiated service (UIS) is a new scheduling method that allows the mission to schedule service within a short scheduling window from both the mission platform and ground system. The UIS request can come from either the mission platform to the SCaN space segments or from the mission ground system to the SCGS depending on the mission need. UIS can provide service through any SCaN Network assets, including relays and ground stations. The UIS request will include information on the service required such as data volume, latency requirements, radio parameters, etc, that allow SCaN to provision the service, along with positional information such as ephemerides in order to establish the link connection. The SCaN Network will have enough capacity to support the UIS requests according to a QoS agreed to during the mission planning. Only high priority UIS requests such as emergencies may be able to override existing service schedules. Figure 4 shows a simplified concept of operations for UIS in the Earth regime.

Figure 4: 2040 SCaN Network Service Provision

Broadcast service provision is currently envisioned through the space segments as the means to provide full orbital coverage, but some features could be provided from the ground via SCGS. The broadcast signal design itself may provide the means for mission onboard autonomous navigation through radiometric or optometric means. Other data carried on the broadcast service may provide other information to enable autonomous user operations, such as network status, GPS corrections, and space weather data or warnings.

6 Near-Earth Architecture

6.1 Space Segment - Relay Orbiters

Figure 5 illustrates the Earth relay architecture and the associated communication links. All relay orbiters possess two types of communication links: trunk links and proximity links. A “trunk” link is a point-to-point communications link between a relay orbiter and an Earth-based ground station that carries multiple user traffic flows that “share” the trunk line. A trunk link is internal to a network, designed specifically for the extreme conditions of an interplanetary link. A “proximity” link is an access link between a space- or ground-based network asset and multiple individual mission platforms, through which each platform connects to the orbiter for traffic concentration and forwarding over the trunk link or to another platform’s proximity link. Relay orbiters may also include a “crosslink,” defined to be an internal network link between two relay orbiters.

Figure 5: Space Segment: Earth Relay Architecture

Relay satellites will be distributed in at least three GEO locations, or a sufficient number of MEO locations, with field-of-view to ensure global coverage. Additional nodal points can provide overlapping coverage areas to increase network bandwidth, availability, and resilence. 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 provided: on-demand (available without a request), pre-scheduled, and User-Initiated Service (UIS). Each relay orbiter is capable of supporting the return trunk line at a maximum data rate in excess of 200 Gbps, as well as 10 Gbps for the forward trunk line. Each relay orbiter communications with the mission platform (science or exploration spacecraft) at a maximum of 10 Gbps. The relay orbitors are envisioned to have optical crosslinks at rates upto 200 Gbps.

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

6.2 Ground Segment - SCaN Control and Ground Segment (SCGS)

As shown in Figure 5, 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. All ground stations 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, and tracking services. Through the trunk links, the ground stations communicate with the Earth, Lunar, and Mars relay orbiters to provide networking services for the three 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 DTN node)

4) encompass both optical and RF stations.

7 Initial Architecture Deployment

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

NASA will refine its plans over the next few years as the existing relay satellite system changes and system trade studies are conducted. NASA’s current initial 2025 concept is described below.

7.1 Service paradigm of 2025 era

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 SCaN Network will continue to provide services to existing missions using the current methods as required. Two new relay satellites around Earth are envisioned. User-initiated service and on-demand service will be available via the Earth relay nodes, and those nodes can forward requests to the new common SCaN Service Request System for scheduling of existing assets. Single-point, automated service request scheduling will be implemented for pre-planned services for all SCaN ground stations and relays. New metric and broadcast services will be available on the new Earth relay.

• Network-layer service: In compliance with the CCSDS DTN standard, some network assets (relays and ground stations) in the deep space communication and navigation are designated as DTN nodes to provide network-layer services. While space link layer services, previously char-acterized by directionality as separate forward and return services with different protocols, are still available, they are only exposed to missions for certain anomalous events. “Last Hop/First Hop” interfaces are provided to integrate non-DTN nodes into the network-layer services.

• Timing service: This new service includes the end-to-end time correlation and time synchro-nization functions available to all deep space missions.

• Positioning service: This new SCaN Network service includes the position determination of orbital mission spacecraft for missions of the Mars Network and Lunar Network.

• Service management: The service management function based on the CCSDS Cross Support Service Management (CSSM) standard is in place for interoperability.

• Broadcast service: An initial operational capability of a broadcast service could be real-ized using the existing second and third generation Tracking and Data Relay Satellite System (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 opera-tional 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: Further study is required before the final definition of these services, including aspects of acquiring and maintaining the on-demand links, and onboard autonomous navigation.

7.2 Earth Network of 2025 era

The initial deployment will start in approximately 2025, driven by the need to replace the capacity of TDRSS as its satellites are retired. Today’s networks gradually become the legacy architecture during the transition to the future architecture. The legacy architecture remains while the TDRSS satellites and ground stations continue to provide service to missions. Some legacy architecture assets such as antenna and TDRS satellites are expected to remain operational until 2040 and beyond.

Figure 6: Initial near-Earth Communications and Navigation Architecture Concept

Figure 6 depicts the early deployment of the near-Earth architecture including the new service offerings through a combination of upgrades to existing systems and launch of the initial Next Gen-eration relay satellite nodes. New services include optical communications, internetworking using IP and DTN, use of the CCSDS Universal Space Link Protocol (USLP) for both forward and return link layer protocol, broadcast service, asynchronous end-to-end messaging, and UIS service. These services may have limited coverage and capacity until full deployment is reached.

The initial deployment features high-rate (∼10 Gbps) optical terminals to support a minimum of two (TBR) simultaneous user mission spacecraft in low earth orbit. Onboard the optical relay satellite, high-rate (∼100 Gbps) optical crosslinks are used between relays to bring the data to ground stations located in the US. The same (∼100 Gbps) capacity is available for the optical space-to-ground link to bring the data to the gateway ground station. To complement the optical link, a high-rate Ka-band (or other suitable RF frequency band) is available as backup for the data relay to the gateway ground station. A Ka-band or S-band link will be used for satellite command and control. On-board data processing and routing among communication links will be used to enable space internetworking.

Open commercial and international standards will be used for interoperability among commercial and partner assets (e.g. relays, ground stations). Satellite control and data communication links will be secure and resilient.

8 Optical Technology Development

NASA is developing optical communication technology and operational capabilities in order to meet the Next Generation Architecture objectives, as described below.

8.1 Optical Ground Stations

The NASA/JPL Optical Communication Telescope Laboratory (OCTL) was built for dedicated re-search and development toward supporting free-space laser communications from space. The facility (Figure 7) has been used to support multiple optical communication technology demonstrations in the past, and is currently undergoing major upgrades to support future missions. As the upgrades are completed, the OCTL will become Optical Ground Station (OGS)-1 to support NASA’s future optical communication needs, and ultimately become an operational capability. 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.

Figure 7: Optical Communications Telescope Laboratory

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 Laser Communication Relay Demonstration (LCRD), flying in 2019.

Figure 8: OGS-2 Telescope and Dome

References: Roberts, W.T., Ansos, D., Croonquist, A., Piazzolla, S., Roberts, L. C. Jr., Garkanian, V., Trinh T., Wright M. W., Rogalin, R., Wu, J., and Clare, L., ”Overview of Optical Ground Station 1 of the NASA Space Communication and Navigation Program”, Proc. SPIE, 9739.

8.2 Optical Terminals

NASA is currently developing optical terminals for both GEO relays (20 cm) and user terminals (10 cm). Generation-1 of this technology will be demonstrated on the LCRD mission for the GEO optical relay, and the Integrated LCRD LEO User Modem and Amplifier (ILLUMA) for a user terminal on the International Space Station (ISS). The Gen-1 terminals will be capable of 1.24 Gbps, using DPSK modulation.

Figure 9: Model of Generation-1 User Terminal

The Generation-2 terminals, beginning development in 2018, will be capable of 10 Gbps for the user terminal (10 cm), and 100 Gbps for the GEO relay terminal (20 cm). Compared to the Generation-1 terminals, these will have consolidated modem and controller electronics, and will incorporate com-mercial off-the-shelf integrated photonics modems for reduced size and power consumption.

Figure 10: Generation-2 GEO Relay Terminal Components

Acronyms

CCSDS Consultative Committee for Space Data Standards.

CSP Commercial Service Provider.

DFE Direct from Earth.

DSN Deep Space Network.

DTE Direct to Earth.

Gbps Gigabits per second.

GEO Geosynchronous Earth Orbit.

GLONASS GLObal Navigation Satellite System.

GPS Global Positioning System.

ILLUMA Integrated LCRD LEO User Modem and Amplifier.

LCRD Laser Communication Relay Demonstration.

LEO Low Earth Orbit.

MEO Medium Earth Orbit.

MOC Mission Operation Center.

NEN Near-Earth Network.

OCTL Optical Communication Telescope Laboratory.

SCaN Space Communication and Navigation.

SCGS SCaN Control and Ground Segment.

SN Space Network.

TASS TDRSS Augmentation Satellite Service.

TDRS Tracking Data and Relay Satellite.

TDRSS Tracking Data and Relay Satellite System.

UIS User-initiated Service.

USLP Universal Space Link Protocol.