By: Agrima Kothari

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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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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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Laser

Light Amplification by

Stimulated Emission of

Radiation

Output is narrow beam

The beam is:

Highly coherent

Monochromatic

Directional

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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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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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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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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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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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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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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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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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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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LCRD ground segment

LCRD mission operation

center (LMOC )

Two ground stations

LCRD Ground Station 1

LCRD Ground Station 2

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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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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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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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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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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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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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Thank you !

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Queries?

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