The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
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Exploring our Solar System and unlocking the secrets of the Universe
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The prototype and two flight models of HEOS-1 seen in the integration hall at ESTEC.
Launch dates: HEOS-1 − 5 December 1968; HEOS-2 − 31 January 1972
HEOS-1 (Highly Eccentric Orbit Satellite-1) was the first European spacecraft to venture beyond near-Earth space, in order to study the magnetic fields, radiation and the solar wind outside of the Earth’s magnetosphere. This required an orbit stretching two-thirds of the way to the Moon and launch during a period of high solar activity. The scientific experiments also demanded a magnetically clean vehicle, another first for Europe and requiring a new facility at ESTEC for testing the integrated satellite.
HEOS-1 performed admirably for seven years, for the first time providing scientists with continuous observations of interplanetary conditions over most of a solar cycle. Precise calibration of the magnetometer meant that these data have been used ever since as a fundamental reference. Another feature – novel at the time – was the magnetometer’s memory, which allowed measurements with very high time resolution. HEOS-1 also released a canister of barium and copper oxide on 18 March 1969 some 75 000 km out from Earth – igniting it 40 km from HEOS – in order to trace distant magnetic field lines.