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Home , Lagrange (spacecraft), Optical communication

NASA’s Next Generation >100 Gbps Optical Relay Elizabeth A. Park Donald Cornwell David Israel Goddard Space Flight Center NASA Headquarters Goddard Space Flight Center 8800 Greenbelt Road 300 E Street SW 8800 Greenbelt Road Greenbelt, Md. 20771 Washington, D.C. Greenbelt, Md. 20771 301-286-5502 202-358-0570 301-286-5294 [email protected] [email protected] [email protected]

Abstract- NASA’s Space Communications and Navigation (SCaN) program is creating an INTRODUCTION operational optical communications network to complement its current frequency (RF) NASA is currently developing and testing optical networks. NASA is currently planning for a new communications systems to advance space optical communications relay in communications capabilities. Throughout the last geostationary (GEO) orbit to be commissioned in 50 years, NASA has primarily used standardized 2025, developed by NASA’s Goddard Space (RF) systems to bring critical Flight Center (GSFC), as evolved from science data down from space. Using optical Goddard’s Laser Communications Relay communications technologies will enable NASA Demonstration (LCRD) GEO relay payload that to support enormous volumes of data at higher will launch in 2019. The Next Generation optical rates with quicker response times more securely. relay node will serve as an initial element in a By developing a multi-satellite optical larger constellation that will communications relay system for near-Earth and consist of Government and commercial, and Lunar regions, NASA will significantly enhance international relays. NASA’s nodes will low-latency communications capabilities for aggregate traffic at data rates of up to 10 Gigabits future missions. per second (Gbps) from users on the Earth’s surface and up through suborbital, LEO, MEO, Goddard Space Flight Center (GSFC) is GEO, cislunar and even out to Earth- developing the relay payloads and the initial relay Lagrange (1.25 Mkm) distances. Users that node (relay) for NASA SCaN’s next-generation require low-latency will be serviced with an network in conjunction with our partners at MIT onboard complementary Ka-band downlink Lincoln Laboratory under the Laser Optical service. The next generation network will deploy Communications Near-Earth Satellite System > 100 Gbps space-to-ground links and also (LOCNESS) Project. LOCNESS will be one of optical crosslinks between nodes to allow for user the operational relay satellites within the multi- traffic backhaul to minimize ground station satellite relay system, enabling relay support to location constraints. user links and cross-links and at rates of tens to hundreds of gigabits per second. This paper will TABLE OF CONTENTS discuss the development of LOCNESS and the advancements provided by 1. INTRODUCTION switching to a global optical relay system. 2. NASA’s OPTICAL COMMUNICATIONS PROGRAM 3. CONCEPT OF OPERATIONS 4. OPTICAL COMMUNICATIONS PAYLOAD 5. REQUIREMENTS 6. DEVELOPMENT STRATEGY 7. CONCLUSION

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NASA’s OPTICAL COMMUNICATIONS PROGRAM: PAST AND CURRENT MISSIONS

Optical Communications: While RF technologies have been a reliable method of space communications throughout the last 50 years, recent advancements have shown that there are significant advantages to using an optical . By utilizing optical capabilities, NASA can achieve a lighter, more efficient and secure process of beaming data down to users on Earth. Figure 1: LLCD delivered 622 Mbps from the Optical technologies enable data rates that are 10 Moon, including to within 3 degrees of the Sun. to 100 times higher than standard RF systems. Additionally, optical communications systems LCRD require less size, weight, and power (SWaP), and thus can be more easily accommodated on both The next optical communications mission will be user and relay spacecraft. Furthermore, in the era NASA’s Laser Communications Relay of data security, narrow beams of , make it Demonstration (LCRD). LCRD will showcase harder for outsiders to infiltrate the data stream. the operational reliability of an optical communications relay satellite and system. LLCD LCRD will be able to communicate bi- In 2013, NASA demonstrated the use of directionally with user rates of 1.244 Gbps to and bidirectional optical communications through the from ground stations located at Haleakala, Lunar Laser Communications Demonstration Hawaii and Table Mountain in California [2]. (LLCD) on the Lunar Atmosphere and Dust Environment Explorer spacecraft (LADEE). LCRD, depicted in Figure 2, is scheduled to LLCD successfully transmitted data from the launch in late 2019 and will provide at least two Moon to Earth, 400,000 kilometers (km) at years of global high-data-rate optical download rates of 622 Megabits per second communications coverage from a geostationary (Mbps) [1]. Additionally, LLCD successfully orbit (GEO). It will demonstrate optical demonstrated an optical data upload to the communications capabilities for missions in low- LADEE spacecraft at data rates of 20 Mbps. Earth orbit (LEO). LLCD demonstrated instantaneous acquisition and operated error-free under all conditions, including to within 3 degrees of the Sun during the day as shown in Figure 1.

Figure 2: Artistic Rendition of LCRD

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User Terminals for the ISS and Orion CONCEPT OF OPERATIONS Currently, NASA is developing the Integrated Nodes in the Network Low-Earth Orbit Laser Communications Relay Demonstration User and Amplifier LOCNESS will be one of at least three nodes in Terminal (ILLUMA-T), which will use LCRD to the next-generation relay network. A next relay science data from the International Space generation architecture is being developed to Station (ISS) to users on Earth at the LCRD user provide the concept of operations for evolving rate of 1.244 Gbps, with a forward link to the ISS NASA’s space communications capabilities, as of 51 Mbps. ILLUMA-T is the first of several shown in Figure 3. new user terminals that will be deployed to provide operational services to users in LEO [3]. The system differs from the TDRSS in that each node in the next generation system will be able to Laser communications capabilities will also be communicate with other nodes. In the TDRSS, onboard NASA’s human spaceflight mission to the satellites can only receive and communicate the Moon, the Orion Exploration Mission (EM)- data down to Earth, rather than pass the data to 2. EM-2 is scheduled to launch in 2023 and will another TDRS in GEO. Connectivity between the be the first spacecraft in over 50 years to take nodes is vitally important to astronauts back to the Moon. The Optical to in the next generation relay system. Optical Orion (O2O) terminal will be able to support HD communications are vastly more advantageous video links both to (20 Mbps) and from (80 for data rates, security, and mission costs, Mbps) to the Moon [3], essential to allowing the however, optical communications downlinks American public to come along for the ride. cannot be performed if the receiving ground station in under cloud coverage. By enabling the ILLUMA-T and O2O are the first space mission nodes to communicate with each other, the data terminals developed through NASA GSFC’s sent to one node can either be downlinked Laser-Enhanced Mission Communications directly to the ground or, if that ground station Navigation and Operational Services (LEMNOS) cannot be reached, the data can be further project office, which will become the pipeline for transmitted to another node, which can then send future space mission terminals developed by it to a clear ground station. This interoperability GSFC to interact with the next generation optical will allow the communication of vital science communications network. data to the ground despite weather conditions at one ground station.

Next Generation Optical Communications Network LOCNESS will primarily use optical communications to downlink data; however, if all As NASA advances further with optical ground stations within view are optically communications capabilities, a system of optical unavailable, the communications system can communication relay nodes becomes more revert to utilizing RF technologies. LOCNESS feasible. This system will complement the will host a high data rate Ka-band RF terminal to capabilities of NASA’s Tracking and Data Relay communicate with Ka-capable ground stations as Satellite System (TDRSS). Currently, NASA has a backup during weather incidents. In addition, 10 active TDRS satellites orbiting the Earth at LOCNESS will provide a weather-independent 22,000 miles in GEO. Using RF technologies, low or no-latency downlink to meet user TDRSS provides continuous global requirements. communications coverage for over a hundred missions in space. The LOCNESS relay will be LOCNESS will have a user range from Earth’s the first node in this next generation architecture surface to GEO, with limited performance at with a second node to be commercially-provided cislunar and 1 (L1) and Lagrange through a Public-Private Partnership managed by Point 2 (L2) distances. NASA’s Glenn Research Center (GRC).

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independent, and interchangeable optical terminals. The nomenclature for the relay payload is shown in Figure 4.

Figure 3: Next Generation Relay Concept with 10G user services, 100G crosslinks and space- to-ground links, and 1 Gbps Ka-band RF services for lower-rate but low-latency requirements.

Interoperability Figure 4: Optical Communications Payload LOCNESS, which is planned to operate for a minimum of five years, will be a dedicated NASA The gimbaled telescope for each optical terminal asset. However, SCaN’s goal is to have an will have a 22 cm diameter aperture. The interoperable system of optical communications unobstructed Field of Regard (FOR) for the next relays comprised of NASA, commercial, and generation payload’s four optical modules is other government agencies’ assets. Parts of the anticipated to be +/- 120 degrees in elevation and next generation system can be created through +/- 175 degrees in azimuth. This will enable the public-private partnerships to assist in obtaining maximum opportunity for the terminals to view constant, global coverage for missions in space. users in all of the required orbits, regardless of the platform on which they reside. The controller To ensure interoperability between the initial command all of the functions of the nodes the payloads provided by GSFC will have optical terminal, including the pointing, the same design. The initial space mission acquisition, and tracking. terminals also use the same design architecture as the node payloads. The node payloads are Two are associated with each terminal. required to maintain backward compatibility with One will receive up to 10 Gbps data from mission LCRD users for continuity of service. Use of the users, and the other will have approximately 100 Consultative Committee for Space Data Systems Gbps capability for the downlink and crosslink (CCSDS) standards, currently under functions. The 100 Gbps modem leverages development, throughout the network will enable highly-integrated commercial off-the-shelf continued interoperability nationally and technology from the fiber internationally as the optical communications industry based on a silicon photonic integrated industry grows. circuit and a coherent Digital Processor Application Specific Integrated Circuit that has been OPTICAL COMMUNICATIONS space-qualified and will be demonstrated in LEO in 2019 [5, 6]. PAYLOAD AND SPACE MISSION TERMINALS The payload electronics manage the functions of the payload external to the optical terminal. These Relay Payloads include the payload controller and data handler, In the next generation network, each relay will local data storage, a controller for disruption have one optical payload. The government relay tolerant networking (DTN), and a switch/router. payload is planned to have four identical, The latter moves data from the receiving terminal

4 to the optical downlink, the cross-link, or to the [7]. The most significant aspect of DTN is the Ka-band RF system for downlink. The switch Bundle Protocol (BP) capability. BP, using a may also move designated data to the DTN store-and-forward approach, allows the data, in system to be stored and forwarded later. The Ka- the form of DTN bundles, to be routed and if, band system is to the payload and is for necessary, stored at relay nodes within the next the payload’s use. generation system. A user can deliver data reliably to the relay. The relays then can either route the data immediately if the link is available Space Mission Terminals or store the bundle until a link is restored. The The space mission terminals, located on user user can send its data without concern for whether missions, will provide the link from a user or not there are any disruptions along the path. mission to an optical communications relay or Before DTN onboard the relay, if direct to Earth to an optical ground station. The communications beyond the relay were disrupted nomenclature, shown in Figure 5, is similar to a mid-transfer, the spacecraft would have to ensure payload optical terminal. The telescope aperture that the data was retransmitted, causing will vary in size based on the link budget additional communications costs. [8] requirements of the mission. The modem data rate may also vary between the 1.244 Gbps An additional advantage to the DTN technology ILLUMA-T modems and the relay ~10 Gbps user is the network-layer functionality. DTN enables modem. the data being downlinked to ground stations to automatically send the data to the end user based only on the received data headers instead of a priori configuring data paths. Furthermore, DTN includes automatic rate buffering to accommodate rate mismatches between space links and terrestrial data lines. [7]

Figure 5: Optical User Terminal By incorporating DTN into LOCNESS and the entire next generation relay system, transmitting REQUIREMENTS data becomes more automated and reliable. Users that are latency tolerant may choose to CCSDS route their data through the DTN system while To achieve an international interoperable system, latency intolerant data can be routed directly to the Optical Communications Working Group ground. DTN capabilities can be seen in Figure 6. (OCWG), within the international Consultative [9] Committee for Space Data Systems (CCSDS) organization, is developing a set of standards for optical communications technologies. A commercial entity or other government agency intending to build optical communications satellites should consider following the CCSDS’ guidelines, ensuring interoperability with the next generation relay system.

Disruption Tolerant Networking

The next generation network will have DTN capabilities onboard the relays. DTN uses Figure 6: LOCNESS versus LCRD DTN interoperable protocols to provide routing and Capabilities data security. DTN technology ensures reliable data delivery despite intermittent link availability

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Data Security out to industry while developing the initial network. With an increase in industry providers, In the era of hacking, data security will need to be a systematic supply chain will be created for built into the system design of the next generation interoperable optical terminals for future optical network. Using optical communications is communications missions. The technology inherently more secure, as the data is encoded transfer from NASA to industry is crucial to meet into beams of light rather than transmitted future user demand and for an interoperable next through radio frequency, which could potentially generation relay system. be accessed. Even with the security advantages of optical communications systems, security should be implemented into the network at each layer CONCLUSION through encryption methods. NASA’s next generation relay system will

provide constant, global, high-data-rate DTN provides an added layer of security as well. communications services for hundreds of future A security protocol will secure data within each missions. This multi-satellite optical bundle. This protocol will add protection for the communications relay system will complement bundles being transmitted as well as protect links the current capabilities of NASA’s RF relay to relays. [9] system, TDRSS.

DEVELOPMENT STRATEGY Currently, GSFC is developing the flight payloads for two of the relay nodes within the The development plan for the next generation system. As NASA intends this network to be fully network is currently underway. The GSFC team interoperable, optical communications standards developing the LOCNESS mission is performing are being developed within the Optical multiple spacecraft bus studies including multiple Communications Working Group (OCWG) industry approaches. The goal is a reduced-cost within the CCSDS, enabling commercial bus with the potential to launch on a ride-share companies and other government agencies to opportunity. Toward the end of 2018, NASA will develop additional optical relay nodes and space decide on the approach for the spacecraft bus. mission terminals for the network.

As NASA’s Center of Excellence for optical Utilizing optical communications systems will communication, GSFC is also solely in charge of significantly increase NASA’s data capabilities. developing the flight payloads for the next The optical terminals within this system will generation system. Building on the partnership provide up to 10 Gbps relay services to users and with MIT Lincoln Laboratory and recent design > 100 Gbps relay crosslinks and space-to-ground advancements, GSFC plans to build a prototype services. Additionally, the use of optical payload from enhanced LEMNOS designs with communications technologies provides a more industry providers. After testing the prototype, secure method of data transfer, and lower the GSFC team will start developing two flight spacecraft costs for missions in LEO, GEO, payloads, one for LOCNESS and one for the cislunar and Earth-Sun L1/L2 distances. GRC node. These flight payloads will be built in parallel to enable a robust, two-node start to the GSFC, with SCaN and GRC, is in the process of optical communications network. developing this operational optical communications relay node system and plans to launch the first node, LOCNESS, by 2025. Commercialization Plan

The next generation relay system will evolve beyond the initial three relays. With this evolution, demand for optical communications technology is expected to increase. NASA plans to push the optical communications technology

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BIOGRAPHY David J. Israel is the Exploration and Space Betsy A. Park is the Communications Projects Exploration and Space Division Architect and the Communications (ESC) Principal Investigator for the Project Manager for next- Laser Communications generation relay satellites. Relay Demonstration She began her career at (LCRD) at Goddard Space NASA’s Goddard Space Flight Center. He has been working on various Flight Center in 1987 and throughout her career aspects of space communications systems, since she worked on all phases of the mission lifecycle. joining NASA in 1989. He received a B.S.E.E Park has been involved with flagship missions, from the Johns Hopkins University in 1989 and such as the International Ultraviolet Explorer, M.S.E.E. from the George Washington , Earth Observing University in 1996. He has led the development Systems, International Space Station, and Joint of various Space Network/Tracking and Data Polar Satellite System. In 2002, Betsy moved to Relay Satellite System (TDRSS) operational NASA Headquarters where she worked in the systems and has been the principal investigator Office Biological and Physical Research, and for multiple communications technology then the Exploration System Mission Directorate. activities concerning advanced space Her work has earned her a multitude of awards, communications concepts and networking including the Goddard Exceptional Achievement protocols, including the LPT CANDOS Award. Park began at GSFC after earning her experiment on STS-107 and Disruption graduate degree in astronomy from The Ohio Tolerant Network demonstrations on the Lunar State University in 1987. Laser Communications Demonstration.

Dr. Donald M. Cornwell is the Agency lead for advanced communications and navigation technology development at NASA. Prior to moving to NASA Headquarters, Don served as the Mission Manager for the historic Lunar Laser Communication Demonstration in 2013 on NASA’s LADEE mission to the Moon. Previously, Don served as the Vice President of Systems Engineering for a fiber telecom start-up, Corvis Corporation, where he was awarded eight patents for his work in Raman amplifier technology and was instrumental in the development and deployment of two nationwide fiber optic networks. Dr. Cornwell has a Ph. D. in from the University of Maryland College Park and has been awarded the NASA Outstanding Leadership Medal and the National Space Club’s Nelson P. Jackson Award.

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ACRONYMS BP = Bundle Protocol CCSDS = Consultative Committee for Space Data Systems DTN = Disruption Tolerant Networking EM = Exploration Mission FOR = Field of Regard GEO = Geosynchronous Orbit GBPS = Gigabits per second GRC = Glenn Research Center GSFC = Goddard Space Flight Center ILLUMA-T = Integrated Low-Earth Orbit Laser Communications Relay Demonstration User Modem and Amplifier Terminal ISS = International Space Station L1/L2 = Lagrange Point 1 / 2 LADEE = Lunar Atmosphere and Dust Environment Explorer LLCD = Lunar Laser Communications Demonstration LCRD = Laser Communication Relay Demonstration LEO = Low Earth Orbit LEMNOS = Laser-Enhanced Mission Communications Navigation and Operational Services LOCNESS = Laser Optical Communications Near-Earth Satellite System MBPS = Megabits per Second MEO = Medium-Earth Orbit O2O = Optical Communications System OCWG = Optical Communications Working Group RF = Radio Frequency SCaN = Space Communications and Navigation SWaP = Size, Weight, and Power TDRSS = Tracking and Data Relay Satellite System

REFERENCES [1] Boroson, Don M., Bryan S. Robinson, Daniel V. Murphy, Dennis A. Burianek, Farzana Khatri, Joseph M. Kovalik, Zoran Sodnik, and Donald M. Cornwell. "Overview and results of the lunar laser communication demonstration." In Free-Space Laser Communication and Atmospheric Propagation XXVI, vol. 8971, p. 89710S. International Society for and , 2014.

[2] Edwards, Bernard L., Dave Israel, Keith Wilson, John D. Moores, and Andrew S. Fletcher. "The laser communications relay demonstration." In Proc. International Conference on Space Optical Systems and Applications (ICSOS) 2012, 1-1, pp. 9-12. 2012.

[3] Israel, David J., Bernard L. Edwards, and John W. Staren. "Laser Communications Relay Demonstration (LCRD) update and the path towards optical relay operations." In Aerospace Conference, 2017 IEEE, pp. 1-6. IEEE, 2017.

[3] Robinson, B. S., T. Shih, F. I. Khatri, D. M. Boroson, J. W. Burnside, O. Guldner, S. Constantine et al. "Laser communications for human space exploration in cislunar space: ILLUMA-T and O2O." In Free-Space Laser Communication and Atmospheric Propagation XXX, vol. 10524, p. 105240S. International Society for Optics and Photonics, 2018.

[5] Boroson, Don M., Bryan S. Robinson, Curt M. Schieler, Farzana I. Khatri, Steven Constantine, Bryan M. Reid, and Donald M. Cornwell. "A new optical communication architecture for delivering extremely large volumes of data from space to ground." In AIAA SPACE 2015 Conference and Exposition, p. 4658. 2015.

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[6] Robinson, B. S., D. M. Boroson, C. M. Schieler, F. I. Khatri, O. Guldner, S. Constantine, T. Shih, D. Cornwell, "TeraByte Delivery (TBIRD): a demonstration of large-volume direct-to-Earth data transfer from low-Earth orbit." In Free-Space Laser Communication and Atmospheric Propagation XXX, vol. 10524, p. 105240V. International Society for Optics and Photonics, 2018.

[7] “Rationale, Scenarios, and Requirements for DTN in Space.” Report Concerning Space Data System Standards, CCSDS 734.0 G-1. Green Book. Washington, D.C. CSDS, August 2010.

[8] Israel, David J., Donald Cornwell, Gregory Menke, and W. John Guineau. "Demonstration of Disruption Tolerant Networking across Lunar Optical Communications Links." In 32nd AIAA International Systems Conference, p. 4481. 2014.

[9] David J. Israel, Christopher J. Roberts, Robert M. Morgenstern, Jay L. Gao, Wallace S. Tai. “2018 Space Operations Experience, Mission Systems, and Advanced Concepts.” Space Mobile Network Concepts for Missions beyond Low Earth Orbit. November 2018.

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