Overview on Lasercom (from an MIT-LL Perspective)

Transcription

1 Overview on Lasercom (from an MIT-LL Perspective) Scott A. Hamilton Presented to: Workshop on Free Space Optical Networks 3-4 July 207 Distribution Statement A: Approved for public release: distribution unlimited.

2 Why Free-Space Optical Communications? GHz THz PHz Frequency 9 Hz 2 Hz 5 Hz vis Wavelength 0.3 m 0.3 mm 0.3 m Satcom bands UHF L X K LC Fiber telecom bands Entire Band (GHz) Typical User Band (MHz) 7 THz 50 GHz High Carrier Frequency Extremely Wide Bandwidth Short Wavelength High Beam Directionality (~ /D) System benefits High data rates in unregulated bands Efficient power delivery for low SWaP Security through narrow beams (LPD/LPI) MIT-LL Lasercom - 2

3 MIT-LL Lasercom Flight Demonstrations Technology Development (80 s-90 s) GeoLITE (200) Mars Lasercom Demo ( ) Lunar Lasercom Demo (2008-4) Lasercom Relay Demo (20-9) ALEX (2002) High-power and Low-noise Optical Amps (pre-industry) First Space-qualified > Khz Tracking Mirror Free-space Optical Comm Airborne Link (2008-) Compact Laser Transmitter (2009-4) Lasercom Terminal Integration and Fullfunctional Testing Perceived lasercom technical challenges have been solved MIT-LL Lasercom - 3

4 NASA Space Communication Challenges Tbps bps LEO SATS NEAR-EARTH MARS SATURN URANUS SATS MOON L L MERCURY JUPITER NEPTUNE PLUTO VENUS MIT-LL Lasercom - 4 Km Km light second light minute light hour GEO AU

5 NASA Space Communication Challenges Tbps Spectrum-Constrained (RF) bps LEO SATS NEAR-EARTH MARS SATURN URANUS SATS MOON L L MERCURY JUPITER NEPTUNE PLUTO VENUS MIT-LL Lasercom - 5 Km Km light second light minute light hour GEO AU

6 NASA Space Communication Challenges Tbps bps LEO SATS Space Network TDRS Near-Earth Network JWST Deep-Space Network Voyager NEAR-EARTH MARS SATURN URANUS SATS MOON L L MERCURY JUPITER NEPTUNE PLUTO VENUS MRO New Horizons MIT-LL Lasercom - 6 Km Km light second light minute light hour GEO AU

7 NASA Space Communication Challenges Tbps bps LEO SATS Space Network LCRD TDRS Near-Earth Network LLCD JWST Deep-Space Network New Horizons Voyager NEAR-EARTH MARS SATURN URANUS SATS MOON L L MERCURY JUPITER NEPTUNE PLUTO VENUS MRO MIT-LL Lasercom - 7 Km Km light second light minute light hour GEO AU

8 Lunar Laser Communication Demonstration NASA s First Lasercom Demonstration ( ) Technology demo on NASA s Lunar Atmosphere and Dust Environment Explorer (LADEE) 622 downlink from moon 20 uplink to moon Longest lasercom link ever demonstrated 4 x 40-cm Collector Photon-Counting Receiver LADEE Spacecraft 2.4 m x.8 m 383 kg -cm Transmit Aperture 0.5-W Laser Lunar Lasercom Operations Center at MITLL Presentation Name - 8 Author Initials MM/DD/YY

9 LLCD Key System Parameters and Design Choices (/4) Photons per Bit 0. Telecom, High-Rate Lasercom Coherent Photon Counting More Power Efficient More Bandwidth Efficient Quantum Limit Bandwidth Expansion (Hz/bit/s) MIT-LL Geiger-Mode Avalanche Photodiode Arrays HSQ on NbN 5 m CMOS ROIC Alumina Interposer APD with -lens ~45 % detection efficiency at 64 nm (550 nm) Speed: 350 ps timing jitter.6 s reset time MIT-LL Superconducting Nanowires HSQ on NbN 5 m NbN nanowire Radiation hard Au mirror Incident 550 nm 75 % detection efficiency at 550 nm 30 ps jitter for single photons 3 ns reset time for 3 m square device Response from UV to Mid-IR SiO 2 spacer Au contacts Sapphire /4 SiO 2 (anti-reflection) Closed-cycle Cryo-cooler 4-element SNSPD Array Key System Parameters Receiver Selection Modulation Coding & Interleaving Ground Terminal Design LLCD Design Choices Superconducting Nanowire Arrays MIT-LL Lasercom - 9

10 LLCD Key System Parameters and Design Choices (2/4) Photons per Bit Telecom, High-Rate Lasercom Coherent Photon Counting More Power Efficient More Bandwidth Efficient 6-ary Pulse Position Modulation 0. Quantum Limit Bandwidth Expansion (Hz/bit/s) Example: 6-ary PPM Bandwidth Expansion = M/log 2 M = 6 / 4 = 4 Key System Parameters Receiver Selection Modulation Coding & Interleaving Ground Terminal Design LLCD Design Choices MIT-LL Lasercom - Superconducting Nanowire Arrays Pulse Position Modulation

11 LLCD Key System Parameters and Design Choices (3/4) LLCD Uplink LLCD Downlink Atmospheric Fading Time Series Benefits of Interleaving BER without coding CER with coding Key System Parameters Receiver Selection Modulation and Coding Coding & Interleaving Ground Terminal Design LLCD Design Choices Superconducting Nanowire Arrays Pulse Position Modulation ½ rate Serially Concatenated Pulse Position Modulation (SCPPM) sec interleaver MIT-LL Lasercom -

12 LLCD Key System Parameters and Design Choices (4/4) Multiple Aperture Receiver Spatial Diversity LLCD Downlink Atmospheric Fading Time Series Ground-Based Telescope Array (LLCD) Key System Parameters Receiver Selection Modulation Coding & Interleaver Ground Terminal Design LLCD Design Choices Superconducting Nanowire Arrays Pulse Position Modulation sec interleaver Serially Concatenated Pulse Position Modulation (SCPPM) Scalable Transportable Array 4 x 40 cm MIT-LL Lasercom - 2

13 Beam Size from Moon -cm transmit aperture 5 rad beam ~0.00 deg ~6 km on Earth ~2 degrees MIT-LL Lasercom - 3

14 Beam Stabilization Disturbances * Figure from Deep Space Optical Communications, H. Hemmati, ed. Terminal distortions Spacecraft and target motions Platform vibrations Vibration Isolator 0. 0 Stabilization Methods Frequency (Hz) Passive Isolation High BW Tracking with Beacon Electro-Optic Nutator with scan MIT-LL Lasercom - 4

15 Beam Stabilization Disturbances * Figure from Deep Space Optical Communications, H. Hemmati, ed. Terminal distortions Spacecraft and target motions Platform vibrations Inertially-Stabilized Terminal 0. 0 Frequency (Hz) Stabilization Methods Celestial Sources Passive Isolation Low BW Tracking with Beacon Inertial References High BW Tracking with Beacon Small Optics with Piezo Nutator MIT-LL Lasercom - 5

16 Acquisition and Downlink Communication Performance Pointing Error ( rad) LLGT Initial Pointing Error at Acquisition Moon Elevation (deg) EL error AZ error Received Power (cts/s) Codewords Downlink Comm Performance FEC Threshold (3 ) 2-axis pointing error for elevation > 7 deg =.2 rad rms Error-free communication achieved MIT-LL Lasercom - 6

17 LLCD System International community understands how to build interoperable ground terminals MIT-LL Lasercom - 7

18 Lasercom Operations in the Presence of Clouds LLCD Oct Nov Ops Block Block 2 Block 3 Block 4 Day GT Elev GT Elev OGS OGS OGS OGS Elev GT T Clou DSN gt OGS femod 2 GT GT GT GT GT OGSt cloudogs OGS GT GT DSNGS clouogsgs clou 3 GT GT GT GT OGS GT GT OGS OGS GT GT DSNGS clouogsgs clou 4 GT OT GT GT GT EDAC OGS T clou GT GT GT OT GT GT GT 5 OT GT OT GT GT GT GT OGS GT GT OT OT/GT GT GT GT 6 GT GT OT OT GT GT GT OT GT SEP OT GT OT GT GT 7 OT OT Elev OT OT OT GT OT OT SEP OT Clo GT OT femod GT 8 Elev Elev Elev Elev ElevGT to O GT T Clou GT SEP T Clou GT OT femod GT 9 Elev Elev Elev Elev Elev Elev Elev Elev Elev SEP T Clou Elev OT femod GT Thin Cirrus Clouds Reduce data rate Downlink data rates from 39 to 622 Uplink data rates /20 Intermittent Clouds Mid-pass handover between ground stations Delay / disruption tolerant network Thick Cloud Cover Use alternate ground station! Operations Clouded out Not available % passes clouded out % alternate ground station used All solutions were demonstrated during LLCD MIT-LL Lasercom - 8

19 NASA Space Communication Challenges Tbps bps LEO SATS Space Network LCRD TDRS Near-Earth Network LLCD JWST Deep-Space Network New Horizons Voyager NEAR-EARTH MARS SATURN URANUS SATS MOON L L MERCURY JUPITER NEPTUNE PLUTO VENUS MRO MIT-LL Lasercom - 9 Km Km light second light minute light hour GEO AU

20 Space Lasercom Operational Pathfinder Qualified Subsystems being Integrated at MIT-LL Optical Module Multi-Rate Modem Qualified Subsystems being Procured from Industry Payload Configuration International Standards Pointing Processor (Moog BRE) Digital Processor (SEAKR Eng., Inc) Modem Electronics (Aeroflex Cobham) Optical Subassembly (ITT-Exelis) Inertially-Stable Platform (ATA) Gimbal & Latch (Sierra Nevada Corp ) Solar Window Assembly (L3-SSG) MIT-LL Lasercom - 20

21 NASA s Next Generation Near-Earth Space Comm and Nav Network LCRD with 2 Optical Heads in GEO on STPSat Return Link 5- Forward Link 80- DownLink 20- UpLink Orion EM-2 At Cis-Lunar Orbit Ka-band RF > from LEO in.8u Volume 209 Mission Users in LEO with high data volume: Total Return 56 Tb/day CONUS Hawaii JPL TMF LMOC WSC PI Site 3 4 Optical Ground Stations with PPM Support and A-O or Coherent Combining MIT-LL Lasercom - 2

22 Next Generation Terminal (NGT) Optical Module Latch and Gimbals SCALABLE MODULAR Telescope and Relay Optical Bench NextGen Terminal (NGT) estimated 3 kg mass Modular Scalable Leverages heritage programs LEO User Terminal ( cm) GEO Terminal (20 cm) Deep Space Terminal (30 cm) Subassemblies for initial NGT prototype are being developed by industry MIT-LL Lasercom - 22

23 NASA Space Communication Challenges Tbps bps Revolutionary New Technology Short-range optical Ultra-high data rates LEO SATS Space Network LCRD TDRS Near-Earth Network LLCD JWST Deep-Space Network New Horizons Voyager NEAR-EARTH MARS SATURN URANUS SATS MOON L L MERCURY JUPITER NEPTUNE PLUTO VENUS MRO MIT-LL Lasercom - 23 Km Km light second light minute light hour GEO AU

24 Coherent Optical Receiver Technology 25 QPSK 25 GHz Symbol Clock Rate-/2 FEC Stronger FEC / Lower Data Rate 40 QPSK 25 GHz Symbol Clock Rate-4/5 FEC Weaker FEC / Higher Data Rate 45 QPSK 25 GHz Symbol Clock Rate-9/ FEC Quadrature-Phase (a.u.) Quadrature-Phase (a.u.) Quadrature-Phase (a.u.) xlog(count) (a.u.) In-Phase (a.u.) In-Phase (a.u.) In-Phase (a.u.) High-sensitivity scalable multi-aperture receivers High data-rate communications leveraging fiber-optic communications technology MIT-LL is developing high-rate efficient coherent modem technologies for lasercom applications MIT-LL Lasercom - 24

25 Low-Earth Orbit Direct-to-Earth Optical Links Transmitter 0.5 W, 2-cm Telescope Large data volume many Terabytes per day! Small space terminal CubeSat scale! Small, low-cost ground terminal widely deployable! 200 Downlink from LEO can deliver 7 Terabytes per day to single ground station MIT-LL Lasercom - 25 Receiver 40-cm Telescope

26 DTE Risk Reduction Efforts 3U CubeSat Concept for.8u lasercom payload being developed with NASA SCaN Working with NASA STMD to procure a CubeSat Space qualification of COTS Space components qualification of COTS components Vacuum Vacuum Thermal Thermal Vibration Vibration Radiation Radiation Compact Beam Director -2 cm aperture 0.5 kg Hemispherical field of regard End-to-end comm testbed Fading channel emulator High-bandwidth data buffer inch MIT-LL Lasercom - 26

27 NASA Space Communication Challenges Tbps bps Revolutionary New Technology Short-range optical Ultra-high data rates LEO SATS Space Network LCRD TDRS Near-Earth Network LLCD Revolutionary New Technology Multi-aperture coherent combining JWST Deep-Space Network New Horizons Voyager NEAR-EARTH MARS SATURN URANUS SATS MOON L L MERCURY JUPITER NEPTUNE PLUTO VENUS MRO MIT-LL Lasercom - 27 Km Km light second light minute light hour GEO AU

28 Large Scientific-Class Ground Terminals Historically require fixed-site high-cost installations Typically utilize large >-m telescope apertures Coupled via coudé path to laboratory class optical tables Examples include: JPL s Mount Palomar Hale 5.-m Telescope JPL s -m Optical Communication Telescope Laboratory (OCTL) ESA s -m Teide Observatory in Tenerife, Spain Mt. Palomar 5.-m Hale Telescope Table Mountain -m OCTL Telescope Teide Observatory -m Telescope MIT-LL Lasercom - 28

29 Next-Generation Optical Gateway Concepts Which solution is best for large area optical ground stations? Cost for equivalent performance Daytime operation and pointing near the sun Lossless Coherent Combining NASA Integrated Telescope 2-m aperture diameter ~ Hexagonal segmented mirrors Dedicated for optical communications Coherent Multi-Aperture Array Leverage COTS telescopes and telecom components Develop custom DSP algorithms to support multiaperture arrays for next generation optical ground terminals MIT-LL Lasercom - 29

30 Summary Findings: Lasercom offers higher rates and reduced SWaP for space communications Requires cloud-free line-of-sight Lasercom has been matured to at least TRL-6 and is ready for transition to operations Space-to-air/space and space-to-ground has been matured to TRL-6 or beyond Lasercom is an enabling technology for other important links Air-to-air, LEO and deep-space Recommendations: Insert lasercom into program-of-record, e.g. relay Invest in manufacturability Continue R&D on other links MIT-LL Lasercom - 30

31 Distribution Statement A: Approved for public release: distribution unlimited. This material is based upon work supported by the National Aeronautics and Space Administration under Air Force Contract No. FA C-0002 and/or FA D-000. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Aeronautics and Space Administration. 207 Massachusetts Institute of Technology. Delivered to the U.S. Government with Unlimited Rights, as defined in DFARS Part or 704 (Feb 204). Notwithstanding any copyright notice, U.S. Government rights in this work are defined by DFARS or DFARS as detailed above. Use of this work other than as specifically authorized by the U.S. Government may violate any copyrights that exist in this work. MIT-LL Lasercom - 3