Sunday, November 8, 2009

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. Note that some novel architectural concepts such as Fractionated Spacecraft somewhat upset this taxonomy.

Spacecraft bus or service module

This bus module consist of the following 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 (aka Command and Data Handling, C&DH)

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. Nuclear power sources (Radioisotope thermoelectric generators) have been used in several successful satellite programs including the Nimbus program (1964-1978).

  • 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 (e.g. Optical Solar Reflector)

  • 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).

End of life

When satellites reach the end of their mission, satellite operators have the option of de-orbiting the satellite, leaving the satellite in its current orbit or moving the satellite to a graveyard orbit. Historically, due to budgetary constraints at the beginning of satellite missions, satellites were rarely designed to be de-orbited. One example of this practice is the satellite Vanguard 1. Launched in 1958, Vanguard 1, the 4th manmade satellite put in Geocentric orbit, was still in orbit as of August 2009.

Instead of being de-orbited, most satellites are either left in their current orbit or moved to a graveyard orbit. As of 2002, the FCC now requires all geostationary satellites to commit to moving to a graveyard orbit at the end of their operational life prior to launch.

Launch-capable countries

Launch of the first British Skynet military satellite.

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.

First launch by country
Order ↓ Country ↓ Year of first launch ↓ Rocket ↓ Satellite ↓
1 Soviet Union 1957 Sputnik-PS Sputnik 1
2 United States 1958 Juno I Explorer 1
3 France 1965 Diamant Astérix
4 Japan 1970 Lambda-4S Ōsumi
5 China 1970 Long March 1 Dong Fang Hong I
6 United Kingdom 1971 Black Arrow Prospero X-3
7 India 1980 SLV Rohini
8 Israel 1988 Shavit Ofeq 1
- Russia[1] 1992 Soyuz-U Kosmos-2175
- Ukraine[1] 1992 Tsyklon-3 Strela (x3, Russian)
9 Iran 2009 Safir-2 Omid


  1. Russia and Ukraine were parts of the Soviet Union and thus inherited their launch capability without the need to develop it indigenously. Through Soviet Union they also are on the number one position in this list of accomplishments.
  2. France, United Kingdom launched their first satellites by own launchers from foreign spaceports.
  3. North Korea (1998) and Iraq (1989) have claimed orbital launches (satellite and warhead accordingly), but these claims are unconfirmed.
  4. In addition to the above, countries such as South Africa, Spain, Italy, Germany, Canada, Australia, Argentina, Egypt and private companies such as OTRAG, have developed their own launchers, but have not had a successful launch.
  5. As of 2009, only eight countries from the list above ( Russia and Ukraine instead of USSR, also USA, Japan, China, India, Israel, and Iran) 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.)
  6. Several other countries, including South Korea, Brazil, Pakistan, Romania, Taiwan, Indonesia, Kazakhstan, Australia, Malaysia[citation needed] and Turkey, are at various stages of development of their own small-scale launcher capabilities.
  7. South Korea launched a KSLV rocket (created with assistance of Russia) in 25 August 2009, but it failed to put satellite STSAT-2 into precise orbit and the satellite did not start to function.
  8. North Korea claimed a launch in April 2009, but U.S. and South Korean defense officials and weapons experts later reported that the rocket failed to send a satellite into orbit, if that was the goal. The United States, Japan and South Korea believe this was actually a ballistic missile test, which is a claim also made after North Korea's 1998 satellite launch, and later rejected.

Launch capable private entities

On September 28, 2008, the private aerospace firm SpaceX successfully launched its Falcon 1 rocket in to orbit. This marked the first time that a privately built liquid-fueled booster was able to reach orbit. The rocket carried a prism shaped 1.5 m (5 ft) long payload mass simulator that was set into orbit. The dummy satellite, known as Ratsat, will remain in orbit for between five and ten years before burning up in the atmosphere.

First satellites of countries

First satellites of countries including launched indigenously or by help of other
Country ↓ Year of first launch ↓ First satellite ↓ Payloads in orbit in 2008[23] ↓
Soviet Union
( Russia)
Sputnik 1
United States 1958 Explorer 1 1042
United Kingdom 1962 Ariel 1 0025
Canada 1962 Alouette 1 0025
Italy 1964 San Marco 1 0014
France 1965 Astérix 0044
Australia 1967 WRESAT 0011
Germany 1969 Azur 0027
Japan 1970 Ōsumi 0123
China 1970 Dong Fang Hong I 0083
Poland 1973 Intercosmos Kopernikus 500 0000?
Netherlands 1974 ANS 0005
Spain 1974 Intasat 0009
India 1975 Aryabhata 0034
Indonesia 1976 Palapa A1 0010
Czechoslovakia 1978 Magion 1 0005
Bulgaria 1981 Intercosmos Bulgaria 1300 0001
Brazil 1985 Brasilsat A1 0011
Mexico 1985 Morelos 1 0007
Sweden 1986 Viking 0011
Israel 1988 Ofeq 1 0007
Luxembourg 1988 Astra 1A 0015
Argentina 1990 Lusat 0010
Pakistan 1990 Badr-1 0005
South Korea 1992 Kitsat A 0010
Portugal 1993 PoSAT-1 0001
Thailand 1993 Thaicom 1 0006
Turkey 1994 Turksat 1B 0005
Ukraine 1995 Sich-1 0006
Chile 1995 FASat-Alfa 0001
Malaysia 1996 MEASAT 0004
Norway 1997 Thor 2 0003
Philippines 1997 Mabuhay 1 0002
Egypt 1998 Nilesat 101 0003
Singapore 1998 ST-1 0001
Taiwan 1999 ROCSAT-1 00009
Denmark 1999 Ørsted 0004
South Africa 1999 SUNSAT 0001
Saudi Arabia 2000 Saudisat 1A 0012
United Arab Emirates 2000 Thuraya 1 0003
Morocco 2001 Maroc-Tubsat 0001
Algeria 2002 Alsat 1 0001
Greece 2003 Hellas Sat 2 0002
Nigeria 2003 Nigeriasat 1 0002
Iran 2005 Sina-1 0004
Kazakhstan 2006 KazSat 1 0001
Belarus 2006 BelKA 0001
Colombia 2007 Libertad 1 0001
Vietnam 2008 VINASAT-1 0001
Venezuela 2008 Venesat-1 0001
Turkey 2009 ITUpSAT1[24] 0001
Switzerland 2009 SwissCube-1[25] 0001

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 (WRESAT) involved a donated U.S. missile and U. S. support staff as well as a joint launch facility with the United Kingdom.[28]

Attacks on satellites

In recent times satellites have been hacked by militant organizations 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. Russia, the United States and China have demonstrated the ability to eliminate satellites. In 2007 the Chinese military shot down an aging weather satellite, followed by the US Navy shooting down a defunct spy satellite in February 2008.


Due to the low received signal strength of satellite transmissions they are prone to 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. It is trivial to transmit a carrier to a geostationary satellite and thus interfere with any other users of the transponder. It is common on commercial satellite space for earth stations to transmit at the wrong time or on the wrong frequency and dual illuminate the transponder rendering the frequency unusable. Satellite operators now have sophisticated monitoring that enables them to pin point the source of any carrier and manage the transponder space effectively.

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