Satellite space segment

From Wikipedia, the free encyclopedia
Jump to: navigation, search
A telecommunications satellite. The space segment comprises the uplink, the satellite itself, and the downlink
A large parabolic antenna in a satellite Earth station

The space segment of an artificial satellite system is one of its three operational components (the others being the user and control segments). It comprises the satellite or satellite constellation and the uplink and downlink satellite links.

Contents

1 Introduction

2 Power Supply

3 Attitude Control

4 Station Keeping

5 Transponders

6 Telemetry, Tracking and Command (TTC)System

7 Thermal Control

8 Antenna Subsystem

Introduction[edit]

Geostationary Communication satellite is very complex system that comprises several subsystems. These subsystem may be divided into two groups, namely (i) Communication subsystem and (ii) Common subsystem. Communication sub system consists mainly of repeater and antennas, and it performs the primary function. The common subsystems are power supply, stabilization, propulsion, orbital station-keeping, Attitude control,Telemetry, Tracking and Command (TTC),Thermal Control, Structure and Reliability.

Power Supply[edit]

In Communication Satellite the electric power supply system the electrical energy needed to run the spacecraft and the communication system. When the satellite is in stationary orbit, electrical power is obtained from solar cell. The power for modern satellites comes from the sun, and is inexpensive. Approximately 1000W of sunshine reaches the satellite surface, perpendicular to sun. Solar cells which are used to convert sunshine into more electricity. Solar arrays on satellites are built up by attaching solar cells about 2 square cm to a panel. The cells are made of doped silicon crystals. they are connected in parallel and series as to meet the voltage and current requirements of the satellite. To generate 100W power, more than 2000 cells are needed, occupying about a square metre of surface and weighing about 5 pounds. In most communication satellites, the cells are attached around their cylindrical operating and it must carry storage batteries, which are charged by the solar panels.