Satellite Modules & Communication Payload

Satellite Modules
The satellite’s functional versatility is imbedded within its technical components and its operations characteristics. Looking at the “anatomy” of a typical satellite, one discovers two modules.[8] Note that some novel architectural concepts such as Fractionated Spacecraft somewhat upset this taxonomy.

Spacecraft bus or service module
This first module consist of five subsystems:

The Structural Subsystems
The structural subsystem provides the mechanical base structure, shields the satellite from extreme temperature changes and micro-meteorite damage, and controls the satellite’s spin functions.

The Telemetry Subsystems
The telemetry subsystem monitors the on-board equipment operations, transmits equipment operation data to the earth control station, and receives the earth control station’s commands to perform equipment operation adjustments.

The Power Subsystems
The power subsystem consists of solar panels and backup batteries that generate power when the satellite passes into the earth’s shadow.

The Thermal Control Subsystems
The thermal control subsystem helps protect electronic equipment from extreme temperatures due to intense sunlight or the lack of sun exposure on different sides of the satellite’s body

The Attitude and Orbit Controlled Control Subsystems
The attitude and orbit controlled subsystem consists of small rocket thrusters that keep the satellite in the correct orbital position and keep antennas positioning in the right directions.

Communication Payload
The second major module is the communication payload, which is made up of transponders. A transponders is capable of :

Receiving uplinked radio signals from earth satellite transmission stations (antennas).
Amplifying received radio signals
Sorting the input signals and directing the output signals through input/output signal multiplexers to the proper downlink antennas for retransmission to earth satellite receiving stations (antennas).

Launch-capable countries
Main article: Timeline of first orbital launches by nationality
This list includes countries with an independent capability to place satellites in orbit, including production of the necessary launch vehicle. Note: many more countries have the capability to design and build satellites which relatively speaking, does not require much economic, scientific and industrial capacity but are unable to launch them, instead relying on foreign launch services. This list does not consider those numerous countries, but only lists those capable of launching satellites indigenously, and the date this capability was first demonstrated. Does not include consortium satellites or multi-national satellites.

Both North Korea (1998) and Iraq (1989) have claimed orbital launches (satellite and warhead accordingly), but these claims are unconfirmed.

In addition to the above, countries such as South Africa, Spain, Italy, West Germany, Canada, Australia, Argentina, Egypt and private companies such as OTRAG, have developed their own launchers, but have not had a successful launch.

As of 2008, only seven countries from list above ( Russia and Ukraine instead of USSR, also USA, Japan, China, India, and Israel) and one regional organization (the European Space Agency, ESA) have independently launched satellites on their own indigenously developed launch vehicles. (The launch capabilities of the United Kingdom and France now fall under the ESA.)

Several other countries, including South Korea, Iran, Brazil, Pakistan, Romania, Kazakhstan, Australia, Malaysia[citation needed] and Turkey, are at various stages of development of their own small-scale launcher capabilities, and seek membership in the club of space powers.

It is scheduled that in early 2008 South Korea will launch a KSLV rocket (created with assistance of Russia) and become the next space power. Iran already has successfully tested its own space launch vehicle (Kavoshgar 1) and is scheduled to put its first domestic satellite (Omid 1) into orbit within a year from February 4, 2008. It is expected that Brazil and Pakistan will follow in the near future

While Canada was the third country to build a satellite which was launched into space, it was launched aboard a U.S. rocket from a U.S. spaceport. The same goes for Australia, who launched on-board a donated Redstone rocket. The first Italian-launched was San Marco 1, launched on 15 December 1964 on a U.S. Scout rocket from Wallops Island (VA,USA) with an Italian Launch Team trained by NASA. Australia's launch project, in November 1967, involved a donated U.S. missile and U. S. support staff as well as a joint launch facility with the United Kingdom.[16] Kazakhstan claimed to have made their satellite independently[citation needed], but the satellite was built with Russian help, like Polish and Bulgarian ones earlier.

Attacks on satellites
For more details on this topic, see Anti-satellite weapon .
In recent times satellites have been hacked by militant organisations to broadcast propaganda and to pilfer classified information from military communication networks

Satellites in low earth orbit have been destroyed by ballistic missiles launched from earth. Both Russia and the United States have demonstrated ability to eliminate satellites.In 2007 the Chinese military shot down an ageing weather satellite followed by the US Navy shooting down a defunct spy satellite in February 2008.Russia and the United States have also shot down satellites during the Cold war.

Jamming
Due to the low received signal strength of satellite transmissions they are prone to Radio jamming by land-based transmitters. Such jamming is limited to the geographical area within the transmitter's range. GPS satellites are potential targets for jamming, but satellite phone and television signals have also been subjected to jamming

Satellite Services
Satellite Internet access
Satellite phone
Satellite radio
Satellite television
Satellite navigation