Nasa spacecraft falls to Earth after being mistaken for an asteroid

A Nasa spacecraft has safely dropped down to Earth and burnt up in its atmosphere, the space agency has said.

It safely dropped back onto Earth over the South Pacific on Saturday, burning up as it did. Nasa had assured the public before the event that it would pose "no threat to our planet – or anyone on it – and this is a normal final operational occurrence for retired spacecraft".

The old scientific craft was originally thought to be an object on an impact trajectory with Earth when it was spotted last week.

But further observations revealed it was not an asteroid but in fact a man-made object: the Orbiting Geophysics Observatory 1 (OGO-1), which was launched in 1964.

Between 1964 and 1969, Nasa sent one of the spacecraft up each year in an attempt to better understand the Earth. The spacecraft was sent on an eccentric orbit that took it around the Earth roughly every two days, flying through the radiation belts and studying the magnetosphere around the planet.

OGO-1's work lasted for five years. In 1969, it was placed in a standby mode when scientists were unable to return any more data, and the mission was fully terminated in 1971.

OGO-1, as its name suggests, was the first of the OGO spacecraft to be sent into space. But it was the last to come back, with the other five spacecraft that were part of the series having dropped down from orbit and landed in various parts of Earth's oceans.

Even though OGO-1 turned out to be a spacecraft, and not the asteroid that first observations had suggested, it will nonetheless help the space agency track future possible objects on a collision course with Earth. Nasa tracked the object's re-entry so that it could "exercise its processes for tracking and predicting impacts of natural objects on Earth’s atmosphere", it said in a statement.