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LG 204 Communications System

LG 204 Communications System Amit Patel amitypat@usc.com ASTE 527 Issues of Current DSN Many of the current DSN assets are obsolete or well beyond the end of their design lifetimes

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LG 204 Communications System

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  1. LG 204 Communications System Amit Patel amitypat@usc.com ASTE 527

  2. Issues of Current DSN • Many of the current DSN assets are obsolete or well beyond the end of their design lifetimes • The largest antennas (70m diameter) are more than 40 years old and are not suitable for use at Ka-band where wider bandwidths allow for the higher data rates required for future missions • Current DSN is not sufficiently resilient or redundant to handle future mission demands • Future US deep space missions will require much more performance than the current system can provide • Require ~ factor of 10 or more bits returned from spacecraft each decade • Require ~ factor of 10 or more bits sent to spacecraft each decade • Require more precise spacecraft navigation for entry/descent/landing and outer planet encounters • Require improvements needed to support human missions • NASA has neglected investment in the DSN, and other communications infrastructure for more than a decade • Compared to 15 years ago, the number of DSN-tracked spacecraft has grown by 450%, but the number of antennas has grown only by 30% • There is a need to reduce operations and maintenance costs beyond the levels of the current system Communications

  3. 70m Goldstone Antenna • Upgrades needed • Change to 30GHz Ka-Band Communications

  4. Performance Upgrade for Next Generation DSN 4 Communications

  5. Need Higher Data Rates 4 Communications

  6. Advantages of Higher Frequency • High Bandwidth due to Intrinsically High Carrier Frequency • Reduced Component Size as compared to Electronic Counterparts • Ability to Concentrate Power in Narrow Beams • Very High Gain with relatively Small Apertures • Reduction in Transmitted Power Requirements Communications

  7. Basic Concept 10 Gbps links at 3 Ghz To Whitesands Ground Teminal, etc TDRSS or TSAT Satellites Communications

  8. LG204 Communications System • For Earth-Moon link communication • 2 X 12m mesh tracking antenna • Solar Arrays sized at for 4m by 14m for 30kW solar power • Output power on HPA (High Power Amplifier) X 2 - 500 W total ie., 250W on each HPA • Power receiver from microwaves • For Moon to lunar orbit communication link • 2m tracking mesh antenna - 10W • Omni - X 3 • For lunar surface local communication • Omnis • Laser communication links to observatories - 12in aperture X 3 - high bandwidth Communications

  9. LG204 Communications System Omni Command Module Link To Earth High Gain Mesh Antenna Laser Link 1 to observatory Laser Link 2 to observatory Gimbaled Solar Arrays Communications

  10. Lunar Environment Considerations • Absence of significant atmosphere • On Earth, have to deal with Absorption, Turbulence and Link Availability • Path absorption losses minimal • Spreading Loss dominant loss mechanism • No Beam Wander, Scintillation, etc. • No Weather (Clouds, Rain, Fog) Communications

  11. Link Budget Block Diagram Moon-to-Earth Optical Data Link Communications

  12. 2m Antenna on Lunar Surface • Antenna Diameter = 2m • Frequency = 70 Ghz • Lambda = 0.00429m • Loss free space = 138.9 dB • Gain (dBi) = 40.1 dB • Received signal power (C) = -104.52 • Available (C/No) = 108.07 • Power = 10 Watts • Required (Eb/No) (bit energy/Noise power density) = 8 • Max Bit rate supported = 10.157 Gbps Communications

  13. Experimental Technology Inflatable Antenna • Combines traditional fixed parabolic dish with an inflatable reflector annulus • Redundant system prevents “all-or-nothing” scenarios • Based on novel shape memory composite structure • High packing efficiency • Low cost fabrication and inflation of an annulus antenna • Overall surface accuracy 1 mm • Negligible gravity effects • Elimination of large curve distortions across the reflector surface (i.e. Hencky curve) 2 Communications

  14. General Horizon Formula • The general horizon distance formula is X = (h^2 + 2hR)^1/2, where X is the distance to the horizon R is lunar radius = 1737.10 km h is height of the observer/transmitter above ground • Distance from Malapart to Shackleton = 150km • Distance from Shackleton to Schrodinger = 300km • Peak to Peak (8km) = 334km • Peak to Ground = 164km Communications

  15. Line-of-Sight To Earth 110km MonsMalapert 300km 120km Shackleton 150km Schrodinger Communications

  16. Data Rates Forward Link Requirements Data Type (Reliable Channel) Data Rates Element Speech 10 kbps Astronaut Digital Channel 200 bps Astronaut Digital Channel 2 kbps Transport / Rover / Base Data Type (High Rate Channel) Data Rates Element Command Loads 100 kbps Transport / Rover / Base CD-quality Audio 128 kbps Astronaut Video (TV, Videoconference) 1.5 Mbps Astronaut Return Link Requirements Data Type (Reliable Channel) Data Rates Element Speech 10 kbps Astronaut Engineering Data 2 kbps Astronaut Engineering Data 20 kbps Transport / Rover / Base Video 100 kbps Helmet Camera Video 1.5 Mbps Rover Data Type (High Rate Channel) Data Rates Element High Definition TV 20 Mbps Astronaut Biomedics 35 Mbps Astronaut Hyperspectral Imaging 150 Mbps Science Payload Synthetic Aperture Radar 100 Mbps Science Payload Communications

  17. Aggregated Data Rates Aggregated Return Link Requirements (Reliable Channel) User Channel Content # of Channels Channel Data Rate Total Data Rate Base Speech 4 10 kbps 40 kbps Base Engineering 1 100 kbps 100 kbps Astronaut Speech 4 10 kbps 40 kbps Astronaut Helmet Camera 8 100 kbps 80 kbps Astronaut Engineering 4 20 kbps 80 kbps Transports Video 4 1.5 Mbps 6 Mbps Transports Engineering 4 20 kbps 80 kbps Rovers Video 24 1.5 Mbps 36 Mbps Rovers Engineering 24 20 kbps 480 kbps Aggregate 43 Mbps (High Rate Channel) User Channel Content # of Channels Channel Data Rate Total Data Rate Base HDTV 1 20 Mbps 20 Mbps Astronaut Biomedics 4 35 Mbps 140 Mbps Transports HDTV 1 20 Mbps 20 Mbps Transports Hyperspectral Imaging 1 150 Mbps 150 Mbps Rovers Radar 1 100 Mbps 100 Mbps Rovers Hyperspectral Imaging 1 150 Mbps 150 Mbps Observatories Hyperspectral Imaging 3 150 Mbps 450 Mbps Aggregate 1030 Mbps Communications

  18. Block Diagram of System 5 Communications

  19. Block Diagram of Antenna 5 Communications

  20. Communication signal flow between spacecraft and Earth for free-space optical communication links. 3 Communications

  21. Dust Electrostatically attaches to surfaces Atomically sharp, abrasive Wide range of particle distribution size Lunar Line-of-Sight Very rough terrain Other Radiation and Solar Flares, Temperature Swings Micrometeorites (and not so “micro”) Antenna Pointing Accuracy Optical Libration – Needs to be accounted for. Problems Communications

  22. Further Studies • Laser communications • Large towers • Inflatable Antennas Communications

  23. Future 1km Tower To Shackleton and Schrodinger Communications

  24. Conclusion • Reliable and Sturdy communication system is critical for lunar operations • High data rate transfer is vital for the successful buildup of a lunar base. • Greater bandwidth and data rate transfers creates many possibilities for the future • People will be watching lunar activities in the highest quality video, which will lead to much greater interest in space Communications

  25. References 1. RF and Optical Communications: A Comparison of High Data Rate Returns From Deep Space in the 2020 Timeframe, W. Dan Williams, Michael Collins, Don M. Boroson, James Lesh, Abihijit Biswas, Richard Orr, Leonard Schuchman and O. Scott Sands. http://gltrs.grc.nasa.gov/reports/2007/TM-2007-214459.pdf 2. An Overview of Antenna R&D Efforts in Support of NASA’s Space Exploration Vision, Robert M. Manning ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070032056_2007033090.pdf 3. Development of an End-to-End Model for Free-Space Optical Communications, H. Hemmati tmo.jpl.nasa.gov/progress_report/42-161/161H.pdf 4. A Vision for theNext GenerationDeep Space Network, Bob Preston, JPLLes Deutsch, Barry Geldzahler www.lpi.usra.edu/opag/may_06_meeting/presentations/next-gen.pdf 5. NASA Ground Network Support of the Lunar Reconnaissance Orbiter, Steohen F. Currier, Roger N. Clason, Marco M. Midon, Bruce R. Schupler and Michael L. Anderson. sunset.usc.edu/GSAW/gsaw2007/s6/schupler.pdf 6. Using Satellites for Worldwide Tele-health and Education – The Gates Proposal. P.Edin, P. Gibson, A. Donati, A. Baker. http://www.esa.int/esapub/bulletin/bullet81/edin81.htm 7. Architectural Prospects for Lunar Mission Support. Robert J. Cesarone, Douglas S. Abraham, Leslie J. Deutsch, Gary K. Noreen and Jason A. Soloff. http://sci2.esa.int/Conferences/ILC2005/Presentations/CesaroneR-01-PPT.pdf 8. Communications Requirements for the First Lunar Outpost, Timothy Hanson' and Richard Markley. ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=465752 Communications

  26. BACKUP Communications

  27. 12m Antenna Link from Moon to Earth • Antenna Diameter = 12m • Power = 30kW power array = 240W front end • Frequency = 3 Ghz • Lambda = 0.01m • Loss free space = 157.3 dB • Gain (dBi) = 30.7 dB • Received signal power = -102.7 • Available (C/No) = 110.42 • Required (Eb/No) (bit energy/No) = 8 • Max Bit rate supported = 10.46 Gbps Communications

  28. Moon - to - Earth Distances and Associated Propagation Losses Minimum: 364,800 km (Propagation Loss = - 314.8 dB) Nominal: 384,00 km (Propagation Loss = - 315.3 dB) Maximum: 403,200 (Propagation Loss = - 315.7 dB) Communications

  29. Transmitter Power, 1 W @ 830 nm 0 dBW Transmitter Antenna Gain, 1 m Dia. 131.6 dBi Transmitter Optical Losses - 6.0 dB Space Propagation Losses -315.3 dB Losses in Vacuum 0 dB Spatial Pointing Losses - 1.0 dB Receiver Antenna Gain, 1 m Dia. 131.6 dBi Receiver Optical Losses - 6.0 dB Spatial Tracking Splitter Losses - 1.0 dB Receiver Sensitivity 84.0 dBW Link Margin 17.9 dB Assume: 100 Mbps, 10-6 BER Link Budget Calculation Communications

  30. Solar Power Requirements Communications

  31. Mars - .38AU = 56,847,240 km 1 Communications

  32. Schematic of S-band and Ka-Band Antenna 5 Communications

  33. Formula’s Used • Lambda = speed of light / frequency • Loss free space = 20*LOG10(4*PI*Distance_m/lambda) • Gain (dBi) = 0.7*20*LOG10(PI*Antenna_Dia_m/lambda) • Received signal power (C) = Pt*Gt*Lfs*Gr • Available (C/No) = C-Noise Density • Noise Density = K*T • Required (Eb/No) (bit energy/Noise power density) = 8 • Max Bit rate supported = 10^(0.1*(C- (Eb/No))) /10^6 Communications

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