Ariel 4, known pre-launch as UK 4, was a British

ionospheric The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays ...

research

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

, which was operated by the

Science and Engineering Research Council The Science and Engineering Research Council (SERC) and its predecessor the Science Research Council (SRC) were the UK agencies in charge of publicly funded scientific and engineering research activities, including astronomy, biotechnology and bi ...

. It was launched 11 December 1971, aboard an American Scout rocket. Experiments were designed to meet one scientific objective, making it the first mission-oriented satellite for the UK. It was also the first satellite in the

Ariel programme Ariel was a British satellite research programme conducted between the early 1960s and 1980s. Six satellites were launched as part of the programme, starting with the first British satellite, Ariel 1, which was launched on 26 April 1962, an ...

to contain an American experiment. Ariel 4 decayed from orbit on 12 December 1978

Design

Development

Ariel 4 leveraged both the design and hardware of

Ariel 3 Ariel 3 (UK 3 or United Kingdom Research Satellite 3) was a satellite in the Ariel programme, a satellite partnership between the US and UK. Three of the onboard experiments continued research from the first two missions and two experiments wer ...

to reduce costs. Ariel 4 used pieces of its predecessor's flight backup unit and spare parts. The satellite cost about 1.25 million pounds.

Operation

British Aircraft Corporation The British Aircraft Corporation (BAC) was a British aircraft manufacturer formed from the government-pressured merger of English Electric, English Electric Aviation Ltd., Vickers-Armstrongs, Vickers-Armstrongs (Aircraft), the Bristol Aeroplane ...

was the prime contractor. Ariel 4 had a launch mass of . It was the first satellite in the

to be able to perform attitude maneuvers.

Sensors

It was the first satellite of the Ariel programme to have a mission-orientated payload, where all of the experiments are designed to research one scientific objective. The scientific objective was to "...study the interaction between high energy charged particles and electromagnetic radiation in the upper ionsphere and magnetosphere. Three of the five experiments on Ariel 3 were to determine a single scientific objective, so those three were improved for use on Ariel 4 and an additional experiment was added. Experiments accounted for of the spacecraft's mass. It was also the first in the program to carry an American experiment.

Mission

Launch

The launch of Ariel 4 occurred at 20:47:01 GMT on 11 December 1971, from Space Launch Complex 5 at the

Vandenberg Air Force Base Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in Key West, Florida * Vandenberg S ...

. It was conducted by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

, using a Scout B-1 rocket.

Operations

Ariel 4 was placed into a

low Earth orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...

, with a perigee of , an apogee of , 82.9 degrees of

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

and an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of 95.3 minutes as of 10 January 1972. It decayed from orbit on 12 December 1978.

Notes

References

* * {{Use dmy dates, date=January 2014 1971 in spaceflight Space programme of the United Kingdom Satellites formerly orbiting Earth British Aircraft Corporation Spacecraft launched in 1971 Spacecraft which reentered in 1978