The Orbital Test Satellite (OTS) programme was an experimental satellite system inherited by the

European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (120 ...

(ESA) in 1975 from its predecessor, the

European Space Research Organisation The European Space Research Organisation (ESRO) was an international organisation founded by 10 European nations with the intention of jointly pursuing scientific research in space. It was founded in 1964. As an organisation ESRO was based on a ...

(ESRO). OTS was the first three-axis-stabilised

Ku-band The Ku band () is the portion of the electromagnetic spectrum in the microwave range of frequencies from 12 to 18 gigahertz (GHz). The symbol is short for "K-under" (originally german: Kurz-unten), because it is the lower part of the ori ...

satellite, and its design has inspired the conception of almost 30 other satellites in Europe. Its successors, the Maritime European Communications Satellite (MARECS) and European Communications Satellite (ECS) series of satellites, consolidated Europe's position in communications satellite technology and manufacturing.

OTS 1

The first of the pair of OTS satellites, OTS 1, was launched on 13 September 1977 at 11:31 pm UTC at the

Cape Canaveral Space Launch Complex 17 Space Launch Complex 17 (SLC-17), previously designated Launch Complex 17 (LC-17), was a launch site at Cape Canaveral Air Force Station (CCAFS), Florida used for Thor and Delta launch vehicles launches between 1958 and 2011. It was built in ...

. However, it was destroyed 54 seconds later due to its United States

Delta Delta commonly refers to: * Delta (letter) (Δ or δ), a letter of the Greek alphabet * River delta, at a river mouth * D ( NATO phonetic alphabet: "Delta") * Delta Air Lines, US * Delta variant of SARS-CoV-2 that causes COVID-19 Delta may also ...

launcher exploding. The failure was caused by a horizontal crack in the solid propellent core of one of the strap-on boosters, which caused the core gases to burn through the casing and ignite the fuel in the main tank of the launcher. The debris of the satellite landed in the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

OTS 2

OTS 2 was successfully launched on 11 May 1978 at 10:59 pm UTC at the same launch complex as OTS 1, using the same Delta

launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and system ...

. It became one of the first

geostationary A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitude ...

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. ...

s to carry six

transponders and was capable of handling 7,200 telephone circuits. With a mass of approximately , the OTS

satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are opposed to specially produced satellites. Bus-d ...

was hexagonal with overall dimensions of 2.4 by 2.1 x 1.7 m. Two

solar panels A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a photo ...

with a span of 9.3 m provided 600

watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Watt ...

s of electrical power.

British Aerospace British Aerospace plc (BAe) was a British aircraft, munitions and defence-systems manufacturer. Its head office was at Warwick House in the Farnborough Aerospace Centre in Farnborough, Hampshire. Formed in 1977, in 1999 it purchased Marconi ...

was the prime contractor from the European MESH consortium which developed the satellite. It completed its primary mission in 1984 after which the spacecraft was involved in a 6-year program of experiments, including the testing of a new

attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...

technique taking advantage of solar radiation pressure forces. In January 1991, OTS 2 was moved out of the geostationary ring and into a

graveyard orbit A graveyard orbit, also called a junk orbit or disposal orbit, is an orbit that lies away from common operational orbits. One significant graveyard orbit is a supersynchronous orbit well beyond geosynchronous orbit. Some satellites are moved into ...

References

Communications satellites European Space Agency satellites {{satellite-stub