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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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lg 204 communications system

LG 204 Communications System

Amit Patel


ASTE 527

issues of current dsn
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


70m goldstone antenna
70m Goldstone Antenna
  • Upgrades needed
  • Change to 30GHz Ka-Band


need higher data rates
Need Higher Data Rates



advantages of higher frequency
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


basic concept
Basic Concept

10 Gbps links at 3 Ghz

To Whitesands Ground Teminal, etc

TDRSS or TSAT Satellites


lg204 communications system
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


lg204 communications system1
LG204 Communications System


Command Module Link

To Earth

High Gain Mesh Antenna

Laser Link 1 to observatory

Laser Link 2 to observatory

Gimbaled Solar Arrays


lunar environment considerations
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)



Link Budget Block Diagram

Moon-to-Earth Optical Data Link


2m antenna on lunar surface
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


experimental technology inflatable antenna
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)



general horizon formula
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


line of sight

To Earth









data rates
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


aggregated data rates
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


communication signal flow between spacecraft and earth for free space optical communication links
Communication signal flow between spacecraft and Earth for free-space optical communication links.




Electrostatically attaches to surfaces

Atomically sharp, abrasive

Wide range of particle distribution size

Lunar Line-of-Sight

Very rough terrain


Radiation and Solar Flares, Temperature Swings

Micrometeorites (and not so “micro”)

Antenna Pointing Accuracy

Optical Libration – Needs to be accounted for.



further studies
Further Studies
  • Laser communications
  • Large towers
  • Inflatable Antennas


future 1km tower
Future 1km Tower

To Shackleton and Schrodinger


  • 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



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.


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


4. A Vision for theNext GenerationDeep Space Network, Bob Preston, JPLLes Deutsch, Barry Geldzahler


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.


6. Using Satellites for Worldwide Tele-health and Education – The Gates Proposal. P.Edin, P. Gibson, A. Donati, A. Baker.


7. Architectural Prospects for Lunar Mission Support. Robert J. Cesarone, Douglas S. Abraham, Leslie J. Deutsch, Gary K. Noreen and Jason A. Soloff.


8. Communications Requirements for the First Lunar Outpost, Timothy Hanson' and Richard Markley.





12m antenna link from moon to earth
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



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)



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


formula s used
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