LG 204 Communications System

1
LG 204 Communications System

• Amit Patel
• amitypat_at_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

3
70m Goldstone Antenna

• Upgrades needed
• Change to 30GHz Ka-Band

4
Performance Upgrade for Next Generation DSN
4
5
Need Higher Data Rates
4
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

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

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

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

13
Experimental Technology Inflatable Antenna
2

• 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)

14
General Horizon Formula

• The general horizon distance formula is X (h2
  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

15
Line-of-Sight
To Earth
110km
Mons Malapert
300km
120km
Shackleton
150km
Schrodinger
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

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

18
Block Diagram of System
5
19
Block Diagram of Antenna
5
20
Communication signal flow between spacecraft and
Earth for free-space optical communication links.
3
21
Problems

• 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.

22
Further Studies

• Laser communications
• Large towers
• Inflatable Antennas

23
Future 1km Tower
To Shackleton and Schrodinger
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

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 RD Efforts in Support
  of NASAs Space Exploration Vision, Robert M.
  Manning ntrs.nasa.gov/archive/nasa/casi.ntrs.na
  sa.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/presentation
  s/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/edin8
  1.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/Presenta
  tions/CesaroneR-01-PPT.pdf

26
BACKUP
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

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)
29
Transmitter Power, 1 W _at_ 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
30
Solar Power Requirements
31
Mars - .38AU 56,847,240 km
1
32
Schematic of S-band and Ka-Band Antenna
5
33
Formulas Used

• Lambda speed of light / frequency
• Loss free space 20LOG10(4PIDistance_m/lambda)
  
• Gain (dBi) 0.720LOG10(PIAntenna_Dia_m/lambda)
  
• Received signal power (C) PtGtLfsGr
• Available (C/No) C-Noise Density
• Noise Density KT
• Required (Eb/No) (bit energy/Noise power density)
  8
• Max Bit rate supported 10(0.1(C- (Eb/No)))
  /106