Need of satellite for long distance communication

Satellite pictures

October 1957, the first artificial satellite Sputnik -I was launched by former Soviet Russia.

The first artificial passive satellite Echo-I of NASA was launched in August 1960.

In July 1962 active satellite Telstar was developed and launched

Elements

• Two major elements of Satellite Communications

Systems are:

–  Space Segment

– Ground Segment

• Space Segment includes:

– Satellite (transponders etc)

– Means for launching satellite

– Electrical Power System

– Mechanical structure

– Communication Antennas

– Attitude and orbit control

system

Means for launching satellite

Launch Vehicle

Launch Vehicle

Summary of LaunchersSummary of Launchers

Sea LaunchSea Launch

At the Equator

equator

11 day travel, 3 days on site, 9 days back1. and 2. stage fueled on launch site; 3. stage and satellite fueled in Long Beach

Sea Launch

The Launch Service Alliance

ArianeSpace, Boeing Launch Services, and Mitsubishi Heavy Industries

↪ mutual backup to mitigate schedule risks, range issues, etc.

Launching Satellites• How does a satellite stay in it’s orbit?

Launching cntd…

The launch process can be divided into two phases:

• The Launch Phase

- Satellite placed into the transfer orbit.

• The Orbit Injection Phase

- Satellite transferred from elliptical transfer orbit to

geosynchronous orbit.

Launch Vehicle

• Function-Place the satellite into the desired Orbit.

• Two types

Expandable

• Launch vehicles can be used only once.

• Most of the satellite are of this type.

Reusable

• Only one reusable launch vehicle available.

Satellite ejected from the cargo compartment.

• The Space Shuttle performs the functions of the first two stages of an expendable launch vehicle.

• The satellite and third stage assembly are ejected after reaching elevation of 150 to 200 miles.

Launching contd….• By riding on a rocket or in the cargo bay of the Space Shuttle.

• At about 120 miles (193 km) up, the rocket's navigational system fires small rockets, just enough to turn the launch vehicle into a horizontal position.

• Inertial guidance system mechanism is used to calculate adjustments to tilt the rocket

Electrical Power System

Satellite Power SystemsSatellite Power Systems• Main source of power is solar cell panels - new solar cells

are increasingly efficient

• The solar cell system is backed up by battery system that provides energy during solar eclipses and other periods of outages.

• Typical power levels of 2 to 5 KWs for Fixed Satellite Systems and 10 to 12 KWs for Mobile and Broadcast Satellite Systems.

Batteries• latest battery technology is represented by Lithium Ion

systems that can provide a greater power density for longer periods of time and survive a greater depth of discharge

• Satellite Control Centre function:

– Tracking of the satellite

– Receiving data

– Eclipse management of satellite

• The ground segment consists of

– Earth Stations

– User terminals and interfaces

– Network control centre

– Transmit equipment.

– Receive equipment.

– Antenna system.

User terminals and interfaces

Network control center

Satellite Communications System

Uplink Down Link

Transmit Earth Station Receive Earth Station

IDU IDURFT RFT

RF

ConceptTransponder

Earth station (site A) Earth station(site B)

IRRADIUM

downlinkdownlink

uplinkuplink

downlinkdownlink

uplinkuplink

Propagation Delay

Single Hop 270 ms Double Hop 540 ms

Ground Station _ Anatomy

Indoor Unit(IDU)

Outdoor Unit(ODU)

Antenna Sub-System

IFL

70/140MHz

C/Ku