SSP Implementation: GEO vs. LEO

Reza Zekavat

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GEO  Orbit  SBSP  

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Cost? Maintenance? Environmental?

Solar storm?

Installa1on  and  Launching  Costs    

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GEO:  35786  km  (22300  Mile)  Interna1onal  Space  Sta1on:      278 km (173 mi) and 460 km (286 mi)

GEO  Orbit  Conges1on  à  Limited  Units  

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Coverage Closer to the Equator  

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LEO?  

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LEO  Implementa1on:  Direct  Transmission  

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•     Lower  al3tudes  à  lower  power  loss  •     Lower  transmission  power  per  unit  •     Higher  reliability  •     Lower  cost  of  launching      •     Complex?  •     Handoff  Process  •     Synchroniza3on  •     Rou3ng  if  a  cluster  is  not  in  ground  sta3on  field  of  view    

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Multi-Satellite Synchronization? •  Different Doppler •  Different distance to ground

LEO Implementation: Direct Transmission

Follower  –  Leader  Op1on    

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PCBS visibility zone

/ cone   Follower Satellite

Leader Satellite

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Follower-Leader Option

Synchronization may not required if each spacecraft orbit in formation is carefully designed

But how about conversion loss? •  RF to DC •  DC to RF

MEO-­‐LEO  (Tethered  Op1on)  

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Transmission Line Structures (TLS) Ionosphere

Atmosphere Orbital Control Situation Awareness Power Distribution High Gain Comm.

Power Relaying Security

Reliability

Solar  Power  Harves1ng  Units  (SOPHU)

   LEO  Satellite        Ground  PCBS

     The  Earth

Ci1es  in  the  Equator    Transmission  Line  Needed  

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Captured Power

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TX Antenna Aperture Area (Km2) Pt(dB) Captured

Power GEO 5000Km 1000Km

500m (88dBi)

4 98 100 MW 1 TW 3 TW 1 91 20 MW 200 GW 600 GW

0.01 71 200 KW 2 GW 6 GW 250m (82dBi) 0.01 71 33 KW 340 MW 1GW

( ) ( )32.45 20log 20logDirect Km MHz Ion Atm EclL d f L L L= + + + + +

Atmospheric  Loss  

Eclipse  Loss  

Ionosphere  Loss  

•  Transmission frequency: 5GHz •  The power harvested by solar cells: 1400W/m2

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GEO LEO DISTRIBUTION Central Distributed

ACCESSIBILITY Near Equator Everywhere (Orbit Design)

EFFICIENCY (POWER) Lower Higher

RELIABILITY Low High COST/KWATT High Low

HAZARD Higher Lower SIGNAL

PROCESSING Simpler Complex !

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Cost LEO   GEO  

Launch  •  Launch cost is a significant portion; •  Several launches will be needed ; •  The launch to lower orbits is much lower than to the GEO;  

Lower Launch cost   Higher Launch cost  

Ground Stations  

•  Several smaller units are needed  •  All units are identical, •  Production cost per unit is lower  

One huge unit is needed  

Lower Ground Station Cost Higher Ground Station Cost Ground Power

distribution   No distribution is needed   Distribution is needed  

Not applicable   Significant Cost  

With Tether  •  Several studies tethers have been conducted. •  Commercially available.  

Technology is available   Not applicable  

Satellite  Several small identical units;

lower production cost per unit; Similar harvesting area to GEO  

One huge unit  

Lower cost   Higher cost  

Research Areas 1. Analysis and comparison of already proposed techniques: a. Expected Efficiency; b. Expected Cost; c. Expected Space Needed on The Ground; d. Expected Reliability; e. Expected Durability;

2. The best techniques for absorbing solar energy in the space? a. Forming the Structure of Satellites; b. Designing the best Orbit; c. Solar Sensors;

3.  Energy Transfer from the atmosphere to the earth surface (Wireless; Laser; Cable)

a. Wireless Transmission Scheme (Modulation, Beam-forming) b. RF – Optical Systems? c. Antenna structures (Number of Antennas, Antenna Design) d. Selecting the transmission parameters

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Research Areas

4.  Ground Receivers a. The Ground Antenna Structure (Size, Distribution, etc); b. Passive or Active Receiver? c. High Aperture Antenna Beam-forming

5.  Energy Conversion (How energy should be converted to the City Electricity?) Whether Rectantennas are the best options?

6. Channel Modeling The effect of Ionosphere on the RF Signal and Ionosphere baser on their power; 7.  Environmental Effects The Effect of High Energy Laser or RF signal on Ionosphere; 8.  Cyber Systems a. The Control Process of the Whole Structure; b. Directing power from one satellite to another;

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References

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1.  S. G. Ting and S. A. Zekavat, “Space-based Solar Power via LEO Satellite Networks: Synchronization Efficiency Analysis,” proc. IEEE Aerospace Conference, Big Sky, MT, March 03-09, 2013.

2.  S. G. Ting, S. A. Zekavat, and O. Abdlekhalik, “Space-Based Wireless Solar Power transfer via a network of LEO satellites: Doppler Effect Analysis” proc. IEEE Aerospace Conference, Big Sky, MT, March 03-09, 2012.

3.  S. G. Ting, O. Abdelkahlik, and S. A. Zekavat, “Constraint Estimation of Spacecraft Positions,” AIAA Journal of Guidance, Control, and Dynamics, Journal of Guidance, Control, and Dynamics, vol. 35, no. 2, 2012.

4.  S. G. Ting, O. Abdelkhalik, and S. A. Zekavat, “Implementation of Differential Geometric Filter for Spacecraft Formation Orbit Estimation,” International Journal of Aerospace Engineering, vol. 2012, Article ID 910496, 13 pages, 2012. doi:10.1155/2012/910496, 2012.

5.  S. G. Ting, O. Abdelkhalik, and S. A. Zekavat, “High Performance Spacecraft Formation Orbit Estimation using WLPS-based Relative Position Measurements: Signal Transmission Time Delay Modeling,” EURASIP Journal on Navigation and Observation, vol. 2011, Article ID 654057, 12 pages, doi:10.1155/2011/654057, 2011.

6.  S. A. Zekavat, and O. Abdlekhalik, “An Introduction to Space-Based Power Grids: Feasibility Study,” proc., IEEE Aerospace Conference, Big Sky, MT, Mar. 06-12, 2011.

7.  S. A. Zekavat, O. Abdelkhalik, S. G. Ting, and D. Fuhrmann, “A Novel Space-Based Solar Power Collection via LEO Satellite Networks: Orbital via a Novel Wireless Local Positioning System,” proc. IEEE Aerospace Conference, March 07 – 12, Big Sky, MT, 2010.

8.  S. G. Ting, O. Abdelkhalik, and S. A. Zekavat, “Differential Geometric Estimation for Spacecraft Formations Orbits via a Novel Wireless Positioning,” proc. IEEE Aerospace Conference, March 07 – 12, Big Sky, MT, 2010.

Question?

Thank you

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