It's a bird! It's a plane! No, wait … it's the Ørsted satellite! Since February 23, 1999, when it was launched from California, a Danish satellite has been circling the Earth in a low orbit nearly in sync with the sun. Named in honor of Danish physicist Hans Christian Ørsted, who discovered electromagnetism in 1820, Denmark's first satellite is considered a microsatellite (weighing in at just 62 kg), built jointly by several Danish space companies. Once it became operational, the daily oversight and maintenance of the satellite became the responsibility of the company Terma A/S and the Danish Meteorological Institute.
The main mission of the Ørsted satellite was to observe and map the magnetic field of the Earth, continuing the work started by the satellite Magsat, launched in 1979 as a joint venture of NASA and the U.S. Geological Survey. The main body of the Ørsted satellite was equipped with three primary instruments: a pair of GPS receivers that provide detailed information on the satellite’s position and on atmospheric conditions, and a particle detector. Magnetometers, which measure magnetic fields, are located at the end of a boom 8 meters long; the distance keeps the satellite’s electrical system from interfering with the instruments.
Data obtained by the Ørsted sensors have revealed some interesting information. Scientists at the Danish Space Research Institute have determined that not only are the Earth’s magnetic poles shifting, but they are doing so at an increasing rate. This suggests to some researchers that the Earth may be in the process of experiencing a complete magnetic pole reversal. This possibility and the potential impact it could have on plants and animals have been the subject of numerous scientific articles in recent years.
Such a reversal is not unexpected. Scientists say the Earth’s magnetic field flips, give or take, about once every 200,000 years. Still, this interval can vary quite a bit; the last time it happened was some 780,000 years ago.
Where does this magnetic field come from? According to scientists, it is a result of the molten iron churning at the core of the planet. An intensely hot inner core of solid iron heats up an outer core of liquid iron; the liquid expands and contracts as it warms up and cools down, and that moving iron generates the magnetic field that makes the Earth one big magnet, with its own North and South poles.
The primary mission of the Ørsted satellite is complete (it was originally foreseen to last a year), but the spacecraft is still orbiting and collecting data. It continues to provide detailed accounts of the Earth’s magnetic field to the research community.