Marisat
Encyclopedia
Marisat satellites were the first maritime
telecommunications satellites and were designed to provide dependable telecommunications for commercial shipping and the U.S Navy from stable geosynchronous orbit
al locations over the three major ocean
regions. The three Marisat satellites, F1, F2, and F3, were built by Hughes Aircraft Corporation
(HAC) for COMSAT Corporation
starting in 1973. The satellites were designed to provide maritime telecommunications services in three large ocean areas, the Atlantic Ocean
, the Pacific Ocean
, and the Indian Ocean
, and were located at 72.5° East longitude
, 176.5° E, and 345° E in the geosynchronous orbital arc. The three-satellite Marisat system served as the initial INMARSAT
constellation.
Ownership of the three Marisat satellites was transferred to Lockheed Martin
when it bought COMSAT Corp in 2000. The Marisat-F2 satellite was acquired by INTELSAT as part of the COMSAT General Corp. acquisition in October 2004.
The three satellites were all launched in 1976 . MARISAT F1 was launched on 19 February 1976 , MARISAT F2 was launched on 10 June 1976, and Marisat F3 was launched at 22:44 GMT, 14 October 1976. Launch vehicle for the satellites was the McDonnell Douglas
2914 Delta rocket
. The satellites were launched from Cape Canaveral by the National Aeronautics and Space Administration under contract with COMSAT. In 1981 the INMARSAT
took over from the Marisat system.
) for ship communications via voice, telex
, facsimile
and high speed data, and C-band (6/4 GHz) for communications to fixed shore stations.
The Marisat satellites were a cylindrical spinning satellite design similar to earlier satellites like Syncom 1
, Intelsat I
and II
, relying on the gyroscopic forces generated by rotating at approximately 30 rpm to provide stability in the Earth's
gravitational field. They were originally designed to last 5 years, but survived much longer, with Marisat F2 operating successfully for 32 years.
The cylindrical design of satellites is good for several reasons:
The Marisat satellites weighed about 1450 pounds
(660 kilograms). Each satellite is 12 feet 6 inches (3.81 meters) in height and 7 feet 1 inch (2.15 meters) in diameter.
The UHF payload on Marisat was designed as a "gapfiller" to support the U.S. Navy. The U.S. Navy experienced a complete failure of TACSAT-1
over the Pacific Ocean in December 1972. UHF channels on Lincoln Labs Experimental Satellite LES-6 were also being used over the Atlantic Ocean, but this satellite was expected to have an end-of-life (EOL) of September 1973. This left the U.S. Navy with a potential "gap" in UHF coverage for several years until the first FLTSATCOM satellite would be available in December 1978. The U.S. Navy contracted with COMSAT in 1973 for UHF capability over the Atlantic and Pacific ocean regions (AOR and POR), and later extended the contract for coverage of the Indian Ocean region (IOR).
Marisat F3 (NSSDC ID: 1976-101A) was operated at 72.5° E until it was retired in the late 1990s and moved out to a disposal orbit (need citation).
Marisat F2 (NSSCDC ID: 1976-053A) was operated at 176° E from 1976 to 1991. It was relocated to 182 E (178° W) and operated there until 1996. It was relocated to 326.1 E (33.9º W), over the Atlantic ocean, and since 1999 F2 had been providing a wide-band data link for the National Science Foundation's
U.S. Antarctic
Program's Amundsen-Scott research station at the South Pole
. On Wednesday 29 October 2008, after 32 years of service, the longest for any commercial satellite to date, it was retired from active service . Engineers at INTELSAT used the remaining on-board fuel to raise the orbit of F2 approximately 125 miles (200 km) above the geostationary arc and place it in a disposal orbit.
Shipping
Shipping has multiple meanings. It can be a physical process of transporting commodities and merchandise goods and cargo, by land, air, and sea. It also can describe the movement of objects by ship.Land or "ground" shipping can be by train or by truck...
telecommunications satellites and were designed to provide dependable telecommunications for commercial shipping and the U.S Navy from stable geosynchronous orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
al locations over the three major ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
regions. The three Marisat satellites, F1, F2, and F3, were built by Hughes Aircraft Corporation
Hughes Aircraft
Hughes Aircraft Company was a major American aerospace and defense contractor founded in 1932 by Howard Hughes in Culver City, California as a division of Hughes Tool Company...
(HAC) for COMSAT Corporation
COMSAT
The Communications Satellite Corporation is a global telecommunications company, based in the USA, and with branches in Brazil, Argentina, Colombia, Mexico, Peru, Venezuela and several other countries in the Americas. It is present also in Turkey...
starting in 1973. The satellites were designed to provide maritime telecommunications services in three large ocean areas, the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, and the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, and were located at 72.5° East longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
, 176.5° E, and 345° E in the geosynchronous orbital arc. The three-satellite Marisat system served as the initial INMARSAT
Inmarsat
Inmarsat plc is a British satellite telecommunications company, offering global, mobile services. It provides telephony and data services to users worldwide, via portable or mobile terminals which communicate to ground stations through eleven geostationary telecommunications satellites...
constellation.
Ownership of the three Marisat satellites was transferred to Lockheed Martin
Lockheed Martin
Lockheed Martin is an American global aerospace, defense, security, and advanced technology company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It is headquartered in Bethesda, Maryland, in the Washington Metropolitan Area....
when it bought COMSAT Corp in 2000. The Marisat-F2 satellite was acquired by INTELSAT as part of the COMSAT General Corp. acquisition in October 2004.
The three satellites were all launched in 1976 . MARISAT F1 was launched on 19 February 1976 , MARISAT F2 was launched on 10 June 1976, and Marisat F3 was launched at 22:44 GMT, 14 October 1976. Launch vehicle for the satellites was the McDonnell Douglas
McDonnell Douglas
McDonnell Douglas was a major American aerospace manufacturer and defense contractor, producing a number of famous commercial and military aircraft. It formed from a merger of McDonnell Aircraft and Douglas Aircraft in 1967. McDonnell Douglas was based at Lambert-St. Louis International Airport...
2914 Delta rocket
Delta rocket
Delta is a versatile family of expendable launch systems that has provided space launch capability in the United States since 1960. There have been more than 300 Delta rockets launched, with a 95 percent success rate. Two Delta launch systems – Delta II and Delta IV – are in active use...
. The satellites were launched from Cape Canaveral by the National Aeronautics and Space Administration under contract with COMSAT. In 1981 the INMARSAT
Inmarsat
Inmarsat plc is a British satellite telecommunications company, offering global, mobile services. It provides telephony and data services to users worldwide, via portable or mobile terminals which communicate to ground stations through eleven geostationary telecommunications satellites...
took over from the Marisat system.
Design
The satellites were designed to be identical, with three communications payloads on board; an ultrahigh frequency UHF (240 to 400 MHz) payload for the U.S. Navy, L-band (1.5 to 1.6 GHzGHZ
GHZ or GHz may refer to:# Gigahertz .# Greenberger-Horne-Zeilinger state — a quantum entanglement of three particles.# Galactic Habitable Zone — the region of a galaxy that is favorable to the formation of life....
) for ship communications via voice, telex
Telex
Telex may refer to:* Telex , , a communications network** Teleprinter, the device used on the above network* Telex , a Belgian pop group...
, facsimile
Fax
Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...
and high speed data, and C-band (6/4 GHz) for communications to fixed shore stations.
The Marisat satellites were a cylindrical spinning satellite design similar to earlier satellites like Syncom 1
Syncom
Syncom started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by Hughes Space and Communications...
, Intelsat I
Intelsat I
Intelsat I was the first communications satellite to be placed in geosynchronous orbit, on April 6, 1965...
and II
Intelsat
Intelsat, Ltd. is a communications satellite services provider.Originally formed as International Telecommunications Satellite Organization , it was—from 1964 to 2001—an intergovernmental consortium owning and managing a constellation of communications satellites providing international broadcast...
, relying on the gyroscopic forces generated by rotating at approximately 30 rpm to provide stability in the Earth's
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
gravitational field. They were originally designed to last 5 years, but survived much longer, with Marisat F2 operating successfully for 32 years.
The cylindrical design of satellites is good for several reasons:
- early satellites did not have high power computers and attitude control systems of more modern satellites, and the spinning design provides a good basic method for maintaining a known attitude in orbit about the earth,
- the cylindrical design maximized the size of the satellite which could fit inside the nose cone (fairing) of the launch vehicle (rocket), and
- the cylindrical design was a simpler design for a spacecraft which would have a rotating body with a de-spun payload module to allow the antennaAntenna (radio)An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
to point continuously at the same target on the earth (see NadirNadirThe nadir is the direction pointing directly below a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface there. Since the concept of being below is itself somewhat vague, scientists define the nadir in more rigorous...
pointing).
The Marisat satellites weighed about 1450 pounds
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...
(660 kilograms). Each satellite is 12 feet 6 inches (3.81 meters) in height and 7 feet 1 inch (2.15 meters) in diameter.
Payload
The UHF payload provided one 500 kHz wide-band channel and two 25 kHz narrow-band channels.The UHF payload on Marisat was designed as a "gapfiller" to support the U.S. Navy. The U.S. Navy experienced a complete failure of TACSAT-1
TacSat-1
TacSat-1 is an experimental satellite built by the Naval Research Laboratory on behalf of the United States Department of Defense Office of Force Transformation . The second satellite in the series, TacSat-2, has already been launched. It is the planned payload of the sixth launch of the SpaceX...
over the Pacific Ocean in December 1972. UHF channels on Lincoln Labs Experimental Satellite LES-6 were also being used over the Atlantic Ocean, but this satellite was expected to have an end-of-life (EOL) of September 1973. This left the U.S. Navy with a potential "gap" in UHF coverage for several years until the first FLTSATCOM satellite would be available in December 1978. The U.S. Navy contracted with COMSAT in 1973 for UHF capability over the Atlantic and Pacific ocean regions (AOR and POR), and later extended the contract for coverage of the Indian Ocean region (IOR).
Solar array
Because of the spinning design of the satellite, the exterior of the cylinder body of the satellite was covered with solar cells, forming a solar power generating array. As the satellite spun in orbit, some part of the array would always be lit by the sun and provide power to the satellite power bus. On Marisat the cylindrical solar panel, covered with approximately 7000 solar cells, supplies each satellite with primary power of 330 watts.Service
Marisat F1 (NSSDC ID: 1976-017A) was operated at 345° E (15° W) from 1976 to 1990. It was relocated to 254° E (106° W) over the Americas until 1997, when it was retired from active service and moved out to a disposal orbit.Marisat F3 (NSSDC ID: 1976-101A) was operated at 72.5° E until it was retired in the late 1990s and moved out to a disposal orbit (need citation).
Marisat F2 (NSSCDC ID: 1976-053A) was operated at 176° E from 1976 to 1991. It was relocated to 182 E (178° W) and operated there until 1996. It was relocated to 326.1 E (33.9º W), over the Atlantic ocean, and since 1999 F2 had been providing a wide-band data link for the National Science Foundation's
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...
U.S. Antarctic
Antarctic
The Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...
Program's Amundsen-Scott research station at the South Pole
South Pole
The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...
. On Wednesday 29 October 2008, after 32 years of service, the longest for any commercial satellite to date, it was retired from active service . Engineers at INTELSAT used the remaining on-board fuel to raise the orbit of F2 approximately 125 miles (200 km) above the geostationary arc and place it in a disposal orbit.