Circling the Sun

Ulysses, like its mythological namesake, is on an epic voyage

The European space probe Ulysses has completed its first full orbit of the Sun. The journey of nearly four billion kilometres took almost eight years.

Ulysses was launched from the US Space Shuttle Discovery to explore the atmosphere of our nearest star and investigate how it influences conditions on Earth.

Martin Redfern of BBC Science said at first the probe's path took it away from the Sun and out towards Jupiter.

There, it used the giant planet's gravity to swing it, like a slingshot, back towards the Sun and up, above the plane in which the planets orbit, over the Sun's poles.

Now Ulysses has come full circle, after an epic voyage of 3.8 billion kilometres and is again crossing Jupiter's orbit.

That planet is now far away, on the opposite side of the Sun, so Ulysses will continue on like a comet, making another swoop over the Sun's poles.

A mission of discovery

It will investigate the solar wind of particles that constantly blows from the Sun, sometimes disrupting communications on Earth, causing power surges, damaging satellites and possibly affecting the climate.

As it passes the Sun's south pole for a second time, late in the year 2000, solar magnetic activity will be at its 11-year maximum.

Ulysses is likely to be buffeted by gusts of electrically charged particles.

The insights it gains may help scientists to understand and possibly predict conditions on Earth.