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Overview for Future In-Space Operations October 2013

Overview for Future In-Space Operations October 2013. Bernard Edwards Chief, Communications Systems Engineer NASA Goddard Space Flight Center Bernard.L.Edwards@nasa.gov. Mission Statement.

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Overview for Future In-Space Operations October 2013

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  1. Overview for Future In-Space Operations October 2013 Bernard EdwardsChief, Communications Systems EngineerNASA Goddard Space Flight CenterBernard.L.Edwards@nasa.gov

  2. Mission Statement • The Laser Communications Relay Demonstration (LCRD) will demonstrate optical communications relay services between GEO and Earth over an extended period, and thereby gain the knowledge and experience base that will enable NASA to design, procure, and operate cost-effective future optical communications systems and relay networks. • LCRD is the next step in NASA eventually providing an optical communications service on the Next Generation Tracking and Data Relay Satellites

  3. Mission Overview LCRD Payload and Host Spacecraft • LCRD Flight Payload • 2 Optical Relay Terminals • 10.8 cm aperture • 0.5 W transmitter • Space Switching Unit 1244 Mbps DPSK 311 Mbps 16-PPM 1244 Mbps DPSK 311 Mbps 16-PPM Mission Concept • Orbit: Geosynchronous • Longitude TBD between 162ºW to 63ºW • 2 years mission operations • 2 operational GEO Optical Relay Terminals • 2 operational Optical Earth Terminals • Optical relay services provided • Ability to support a LEO User • Hosted Payload • Launch Date: Dec 2017 Table Mountain, CA White Sands, NM • LCRD Ground Station 1 • 1 m transmit and receive aperture • 20 W transmitter • LCRD Ground Station 2 • 15 cm transmit aperture • 20 W transmitter • 40 cm receive aperture

  4. NASA Optical Communication Technology Strategy 2017 2020 2025 2013 Near Earth Flight Terminal Technology Transfer Commercialized LLCD LADEE Demo GEO Demo – LCRD LEO Demo Near Earth Missions Commercialization Optical Module DPSK Modem Controller Electronics Deep Space Flight Terminal Candidate Deep Space Host Demo Mission Other Deep Space Missions Key DOT Technology Identification & Development SCaN Optical Ground Infrastructure Optical Comm Ground Stations (LLGT, OCTL, Tenerife) LCRD SCaN Operational Optical Ground Stations Added as Mission Needs Require (including International Space Agency Sites) Technology Investment and Development • Stabilization • Detectors • Vibration • Systems Engineering • Laser Power/Life • Pointing SNSPD arrays, photon counting space receiver, ground receiver detection array, NAF APD/nanowire det., COTS quadrant spatial-acquisition detectors Mini FOG Spacecraft disturbance rejection platform, piezo-based point-ahead mechanism CFLOS Analysis, Optical Comm Cross Support Low-noise laser PPM Laser Transmitter Flexured Gimbal Mount

  5. Leveraging the Lunar Laser Communications Demonstration (LLCD) • … • NASA’s first high rate space laser communications demonstration • Space terminal integrated on the Lunar Atmosphere and Dust Environment Explorer (LADEE) • Launched on 6 September 2013 from Wallops Island on Minotaur V • Completed 1 month transfer (possible lasercomm ops) • 1 month lasercomm demo @ 400,000 km • 250 km lunar orbit • 3 months science • 50 km orbit • 3 science Payloads • Neutral Mass Spectrometer • UV Spectrometer • Lunar Dust Experiment

  6. LLCD Flight Hardware • Optical Module • Designed and fabricated by MIT LL • Inertially-stabilized 2-axis gimbal • Fiber-coupled to Modem transmit (Tx) and receive (Rx) • Modem Module (MM) • Designed and fabricated by MIT LL • Pulse Position Modulation Only • Digital encoding/decoding electronics,1550 nm fiber Tx and Rx • Controller Electronics • Built by Broad Reach Engineering for OM, MM control • Telemetry & Command (T&C) interface to S/C All Modules Interconnected via electrical cables and optical fibers

  7. LLCD Provides the Foundation for LCRD Lunar Lasercom Space Terminal Modem Module Lunar Lasercom Ground Terminal DL 622 Mbps UL 20 Mbps White Sands, NM Controller Electronics 1.55 um band LADEE Spacecraft DL > 38 Mbps Optical Module DL > 38 Mbps UL > 10 Mbps Table Mtn, CA Tenerife Lunar Lasercom OCTL Terminal (JPL) Lunar Lasercom Optical Ground System (ESA) LCRD will leverage designs and hardware from LLCD, with modifications to satisfy mission requirements.

  8. LCRD Design Reference Mission • Simultaneous multiple real-time user support and multiple store & forward user support multiplexed on single trunkline • Different user services: frame, DTN, … • Scheduled and Unscheduled Ground Station handovers • Number of Users, Mission Operations Centers (MOCs), and Payloads scalable • Emulation of different relay and user location and orbits by the insertion of delays and disconnections in the data paths Active optical link Future optical link User 1 S/C GS-1 GS-m User n S/C Terrestrial Internet Protocol Network User 1 MOC User k MOC LMOC

  9. LCRD Baseline • Hosted on a Space Systems/Loral Commercial Communications Satellite • Flight Payload • Two MIT LL designed Optical Modules (OM) • Two Integrated Modems that can support both Differential Phase Shift Keying (DPSK) and Pulse Position Modulation (PPM) • Two OM Controllers that interface with the Host S/C • Space Switching Unit to interconnect the two Integrated Modems and perform data processing • Two Optical Communications Ground Stations • Upgraded JPL OCTL (Table Mountain, CA) • Upgraded LLCD LLGT (White Sands, NM) • LCRD Mission Operations Center (LMOC) • Connected to the two Optical Communications Ground Stations • Connected to Host S/C MOC

  10. LCRD GS and Optical Space Terminal Location 161W 112W 63W OST Possible Location GEO Locations were chosen to ensure at least 20° above horizon for both Ground Stations

  11. LCRD Mission Architecture LCRD Payload and Host Spacecraft LCRD Flight Payload 10 cm @ 0.5 W (PPM/DPSK) DPSK at 1.244 Gbps PPM at 311 Mbps 1550 nm band 1550 nm band Environmental enclosure surrounding UL and DL telescopes 4x UL Transceivers 4x DL Receivers Host Spacecraft RF Link Chiller for cooling trailer and telescopes 18-ft Clamshell weather cover Converted 40-ft ISO container housing controls, modems, and operator console Host Mission Ops Center (HMOC) Table Mountain, CA White Sands, NM LCRD Optical Ground System (LOGS) - OCTL Based on Lunar Lasercom Ground Terminal (LLGT) NISN NISN NISN LCRD Ground Station-1 1 m @ 20 W (PPM/DPSK) LCRD Ground Station-2 1 @ 15 cm @ 20 W (PPM/DPSK) 1 @ 40 cm (PPM/DPSK) LCRD Mission Ops Center (LMOC) NASA GSFC

  12. Relay Optical Link • Relay Link Features: • Coding/Interleaving at the link edges • Rate ½ DVB-S2 codec (LDPC) • 1 second of interleaving for atmospheric fading mitigation • Data can be relayed or looped back • PPM or DPSK can be chosen independently on each leg OST-1 OST-2 Optics Modem Space Switching Unit Modem Optics Free Space Atmosphere Optics Modem Codec/ Interleave Codec/ Interleave Modem Optics Atmosphere Free Space GS-1 GS-2 LCRD Payload

  13. Bus and Payload Overview Bus Overview • Existing SS/L commercial satellite bus • LCRD package is located on the S/C Earth deck, similar to a typical North panel extension • The enclosure North-facing surface is the main radiator with Optical Solar Reflectors • Secondary LCRD radiator panel is on the South side • Star trackers located on the top of the enclosure for optimal registration with OMs Radiator (back view) Star Tracker Star Tracker Optical Module Optical Module Equipment Panel& Radiator CE CE ModemB ModemA Switch 1 2 ModemA ModemB 2 1

  14. Payload Hardware Overview • Integrated Modem (qty 2) • 0.5 W transmitter; optically pre-amplified receiver • DPSK and PPM modulation • 27 kg, 130 W • Supports Tx and Rx frame processing • No on-board coding and interleaving • Optical Module (qty 2) • Gimbaled telescope (elevation over azimuth) • 12° half-angle Field of Regard • 10.8 cm aperture, 14 kg • Local inertial sensor stabilization • Space Switching Unit (qty 1) • Flexible interconnect between modems to support independent communication links • High speed frame switching/routing • Command and telemetry processor • Controller Electronics (CE) (qty 2) • OMcontrol/monitoring • Interface to Host Spacecraft • 7 kg, 151 W

  15. Flight Payload Functional Diagram Space Switching Unit Frame Switching Command & Telemetry Processing Controller Electronics 1 Integrated Modem 1 Controller Electronics 1 Integrated Modem 2 Host S/C 1553 Host S/C 1553 Optical Data & Frame Processing Optical Data & Frame Processing Host S/C 1 PPS Host S/C Interface Load Drivers Host S/C Interface Load Drivers Host S/C 1 PPS Transmitter Receiver Transmitter Receiver Sensor Processing PAT Processing Sensor Processing PAT Processing fiber fiber Optical Module 2 Optical Module 1 Pointing & Jitter Control Pointing & Jitter Control Optical Telescope Optical Telescope To & From Ground or LEO Terminals To & From Ground or LEO Terminals SpaceWire Downlink communication signal High Speed Serial Uplink communication signal Analog Uplink acquisition beacon signal

  16. Two Ground Stations • JPL will upgrade the JPL Optical Communications Telescope Laboratory (OCTL) to form the LCRD Optical Ground Stations (LOGS) • This is a single large telescope design • Adaptive Optics and support for DPSK will be added • LCRD will upgrade the Lunar Laser Communications Demonstration (LLCD) Ground Terminal developed by MIT Lincoln Laboratory • This is an array of small telescopes with a photon counter for PPM • Adaptive Optics and support for DPSK will be added • Both stations will have atmospheric monitoring capability to validate optical link performance models over a variety of atmospheric and background conditions

  17. Ground Station Components

  18. DPSK Modulation/Demodulation In the DPSK system, each slot contains an optical pulse with phase = 0 or π. Data carried as a relative phase difference between adjacent pulses. DPSK Transmitter The average power-limited transmitter allows peak power gain for rate fall-back via “burst mode” operation. At the DPSK receiver, the original sequence is demodulated using a fiber delay-line interferometer to compare the phase of adjacent pulses. DPSK Receiver

  19. PPM Signaling • For PPM, the binary message is encoded in which of M=16 slots contains a signal pulse. • Optical modulation accomplished with the same hardware that implements burst-mode DPSK, with the applied phase irrelevant for PPM PPM Signaling • PPM demodulation is accomplished by comparing the received power in each slot with a (controllable) threshold value • Uses the same pre-amplifier and optical filter as the DPSK receiver, but by-passes the delay-line interferometer PPM Receiver threshold

  20. Line of Sight and CFLOS • The first consideration in link establishment is whether a line of sight between the source and destination exists. • Free space laser communications through Earth’s atmosphere is nearly impossible in the presence of most types of clouds. • Typical clouds have deep optical fades and therefore it is not feasible to include enough margin in the link budget to prevent a link outage. • Key parameter when analyzing free space laser communications through the atmosphere is the probability of a cloud-free line of sight (CFLOS) channel. • A mitigation technique ensuring a high likelihood of a CFLOS between the source and destination is needed to maximize the transfer of data and overall availability of the network. • Using several laser communications terminals on the relay spacecraft, each with its own dedicated ground station, to simultaneously transmit the same data to multiple locations on Earth • A single laser communications terminal in space can utilize multiple ground stations that are geographically diverse, such that there is a high probability of CFLOS to a ground station from the spacecraft at any given point in time. • Storing data until communications with a ground station can be initiated • Having a dual RF / laser communications systems onboard the spacecraft. • NASA has studied various concepts and architecture for a future laser communications network. The analysis indicates ground segment solutions are possible for all scenarios, but usually require multiple, geographically diverse ground stations in view of the spacecraft.

  21. Network Availability • A ground station is considered “available” for communication when it has a CFLOS at an elevation angle to the spacecraft terminal of approximately 20° or more. • The network is “available” for communication when at least one of its sites is “available.” • Typical meteorological patterns cause the cloud cover at stations within a few hundred kilometers of each other to be correlated. • Stations within the network should be placed far enough apart to minimize these correlations • May lead to the selection of a station that has a lower CFLOS than sites not selected, but is less correlated with other network sites. • Having local weather and atmospheric instrumentation at each site and making a simple cloud forecast can significantly reduce the amount of time the space laser communications terminal requires to re-point and acquire with a new ground station. • In addition to outages or blockages due to weather, a laser communications link also has to be safe and may have times when transmissions are not allowed.

  22. Optical Communications Network Operations Center (NOC) • In order to provide all of this flexibility for users, the relay network operations center must assume the responsibility for the user data flows. • The NOC must now keep an accounting of the user data in transit within the provider system (onboard the relay or within a ground station). • Any handovers or outages that require retransmissions or rerouting within the provider network must all be managed by the NOC transparently to the users. • The NOC must also be able to provide the necessary insight to resolve any lost data issues reported by users. • The LCRD Mission Operations Center (MOC) acts as a future NOC in the demonstration

  23. Essential Experiments and Demonstrations • Experiments will begin immediately following launch and Payload checkout • During the first six months, the highest priority experiments will demonstrate technology readiness for the next generation TDRS infusion target • Laser Communications Link and Atmospheric Characterization • Earth-Based Relay (Next Generation TDRS) • The remaining mission time will continue the essential experiments to collect additional data and also include: • Development of operations efficiency (handover strategies, more autonomous ops, etc.) • Planetary/Near-Earth Relay scenarios (additional delays, reduced data rates, non-continuous trunkline visibility) • Low Earth Orbit (LEO) - real or simulated 23

  24. SCaN’s Optical Communications Strategy for Near Earth • SCaN has made a considerable investment in the 10 cm optical module design being used on both the Lunar Laser Communications Demonstration (LLCD) and the Laser Communications Relay Demonstration (LCRD) • In the optical module there are minor differences between the two • The major difference is in the modem (DPSK at 1.244 Gbps for LCRD and PPM at 622 Mbps for LLCD) • SCaN would like to re-use that design as much as possible: • Future Low Earth Orbit (LEO) compatible terminal • Future lunar missions (far side exploration) • Next Generation TDRS (perhaps with an upgraded higher rate modem) • For missions deeper in the solar system, SCaN has made a limited investment in the Deep Space Optical Terminal (DOT) concept being worked on at JPL 24

  25. Summary • The LCRD optical communications terminal leverages previous work done for NASA • With a demonstration life of at least two years, LCRD will provide the necessary operational experience to guide NASA in developing an architecture and concept of operations for a worldwide network • Unlike other architectures, it will demonstrate optical to optical data relay • LCRD will provide an on orbit platform to test new international standards for future interoperability • LCRD includes technology development and demonstrations beyond the optical physical link • NASA is looking forward to flying the LCRD Flight Payload as a hosted payload on a commercial communications satellite • NASA can go from this demonstration to providing an operational optical communications service on the Next Generation Tracking and Data Relay Satellites

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