A one-tonne satellite is falling out of control and is likely to crash into the Earth sometime during the weekend, scientists have warned.

The Gravity Field and Steady-State Ocean Circulation Explorer was launched in March 2009, to study changes in sea level, ocean circulation and the planet's gravitational field.

It has now run out of fuel and is spiralling back to Earth.

The European Space Agency says it cannot predict exactly where, or when, but that it is highly unlikely to cause any casualties.

Tim Allman reports.