The document discusses the Laser Communications Relay Demonstration (LCRD) project between NASA and MIT Lincoln Laboratory to demonstrate high-data rate optical communications from space. The LCRD flight payload includes an optical module, modem, and electronics to transmit and receive laser signals. The payload will use differential phase-shift keying (DPSK) for near-Earth missions and pulse-position modulation (PPM) for deep-space. The LCRD ground segment consists of two ground stations and a mission operations center to coordinate activities. The goals are to advance optical communication technologies to provide higher bandwidth capabilities with lower mass, power and volume requirements.

1. By: Agrima Kothari
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2. Content
 Introduction
 Laser
 Why laser?
 Objectives
 Flight payload
 Flight Optical Communications Module
 Flight modem
 DPSK
 PPM
 High speed electronics
 LCRD ground station
 LCRD ground station1
 LCRD ground station2
 LMOC
 Advantages
 Application
 Conclusion
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3. Introduction
 LCRD is a joint project between
 NASA/GSFC (Goddard space flight center)
 MIT/LL (Massachusetts Institute of Technology / Lincoln Laboratory)
 Demonstrating how optical communications can meet NASA’s
growing need for higher data rates
 Provide two years of continuous high data rate
 Lower power, lower mass communications systems on
spacecraft.
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4. Laser
 Light Amplification by
Stimulated Emission of
Radiation
 Output is narrow beam
 The beam is:
 Highly coherent
 Monochromatic
 Directional
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5. Why laser?
 Used in optical communication.
 Basic idea was
 Establish a communication link between earth and satellite
 to increase the data rates
 For same mass, power, and volume higher data rates
achieved.
 For same data rate will require less mass, power, and
volume.
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6. Objectives
 Near Earth applications
 Following were demonstrated:
 High rate bi-directional communications between Earth and
GEO.
 Real-time optical relay between 2 Ground Stations.
 Pulse Position Modulations.
 DPSK Modulations.
 Performance testing.
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7. Flight Payload
 Optical communications terminal
 An optical module
 A modem
 An optical module controller
 High speed electronics
 To interconnect the two optical modules.
 Perform network and data processing.
 To interface to the host spacecraft.
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8. Flight Optical Module construction
 Two optical communication
terminals
 Each optical module is a 4-inch
reflective telescope
 It houses a spatial acquisition
detector
 Telescope mounted on a 2 axis
stand & stabilized by MIRU
 Optical fibers couple the
optical module to the modems
 Each optical module is held and
protected during launch with a
cover and one time launch
latch.
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9. Flight Optical Module working
 Transmit and receive optical signals.
 When transmitting
 To efficiently generate optical power
 Encode, format, and interleave incoming electronic data
 Modulate the optical beam
 Amplify and transmit
 Aim the very narrow beam at the ground station
 When receiving
 Large collector
 Couple light onto low noise efficient detectors
 Synchronization, demodulation and decoding
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10. Flight modem
 Two types of mission
 Deep space mission
 Near earth mission
 Differ in range and data rates
 Different modulation techniques are used
 LCRD will demonstrate both techniques
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11. DPSK
 Used for near earth mission
 A bit is encoded in the phase difference between
consecutive pulses
 2.88 GHz Clock rate
 Data rate from 72 Mbps to 2.88 Gbps.
 In future data rates beyond 10 Gbps.
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12. PPM
 Used in deep space mission
 2.88 GHz clock rate
 Downlinks up to 100 Mbps
 Uplinks up to 1Gbps
 Maximum data rate is 360 Gbps
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13. High Speed Electronics
 Objective is to demonstrate advanced relay operations
 Challenge is the susceptibility to cloud cover.
 Significant amount of data storage in order to demonstrate
store and forward relay services.
 HSE will support delay tolerant network (DTN) protocols.
 Implement required decoding and de-interleaving so the
payload can process and route the data.
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14. LCRD ground segment
 LCRD mission operation
center (LMOC )
 Two ground stations
 LCRD Ground Station 1
 LCRD Ground Station 2
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15. LMOC
 LCRD Mission Operations Center
 LMOC coordinates all optical communications activities
 LMOC communicates with all segments:
 Two ground stations
 Space segment
 The LMOC will provide services such as:
 Planning and scheduling
 Control
 Status Monitoring
 Reporting and Accountability
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16. LCRD Ground Station 1
 OCTL is located in the San
Gabriel Mountains of southern
California
 The large aperture readily supports
the high data rate
 Required to operate 24/7 in the
presence of winds
 OCTL telescope enclosed in a
temperature controlled dome
 The Laser Safety System at the
OCTL will ensure safe laser beam
transmission
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17. LCRD Ground Station 2
 MIT Lincoln Laboratory
designed the Lunar
Lasercom Ground
Terminal (LLGT) in
Hawaii
 The LLGT is an array of
 Four 40-cm receive
reflective telescopes
 Four 15-cm transmit
refractive telescopes
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18. Advantages
 Relatively simple, yet
highly reliable.
 Six times faster in
delivering data.
 Increase in bandwidth of
five to six orders of
magnitude.
 Mass, weight and power
are reduced.
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19. Application
 High resolution images of
interstitial objects
 Able to stream high
definition video
 Telepresence
 Carry more fuel or other
equipments
 Military operations
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20. Conclusion
 In time, space communication will extend humanities
reach into space.
 Doing this demonstration will allow initial operational
capability (IOC) of an optical service on the first next
generation satellite.
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21. Thank you !
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22. Queries?
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