Satellite Envisat could spark 'Gravity' style debris cloud

A satellite which has lost contact with the European Space Agency could potentially pose a similar threat to that experienced by Sandra Bullock and George Clooney in the Oscar nominated 'Gravity, if it breaks up and sparks a deadly debris field, students have claimed.

Physics students at the University of Leicester have suggested that the observational satellite Envisat is at risk of colliding with other satellites and debris during the 150 years it is expected to remain in space in their final year paper.

The satellite Envisat lost contact with Earth in 2012 and now orbits free of human control at an altitude of 491 miles (790km). This altitude is where the greatest amount of space debris around the planet is found.

This close proximity means there is a slight chance of collision with other satellites and debris. Each year, two objects are expected to pass Envisat to within about 200m and one spacecraft has already had to be moved out of Envisat’s path.

The students said it was therefore possible that a collision with Envisat could lead to a chain reaction effect, known as the Kessler Syndrome, where a cloud of fast-moving debris causes other collisions with orbiting bodies around the Earth.

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A similar cloud hits Bullock and Clooney’s characters outside the International Space Station in the film ‘Gravity.’

“In the film, the cloud of space debris is caused by a missile which was supposed to destroy a non-operational satellite and sparks the chain reaction which eventually collides with Clooney and Bullock’s spacecraft. In real life this is very unlikely to happen,” said physics student Katie Raymer.

“It is even more unlikely that ESA’s Envisat could cause one of these chain reactions. However, each year two objects are expected to pass Envisat to within about 200m and other spacecraft have had to manoeuvre themselves out of Envisat’s path.

"Also Envisat orbits at an altitude where the amount of debris is greatest. So although it is unlikely to happen, de-orbiting Envisat is certainly worth considering."

Envisat was launched in 2002 as the successor to ERS and used ten instruments to observe and monitor Earth’s land, atmosphere and oceans. The Envisat mission ended on 8 April 2012, following the unexpected loss of contact with the satellite

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The fourth-year MPhys students’ paper, De-orbiting Envisat, suggests that around 140kg of fuel would be required to move the satellite to a point where it would naturally return to Earth within 25 years.

Based on the object’s cross-sectional area and its mass, the students calculated that the satellite would need to be moved to an altitude of 700km from its current position in order to return to the planet in 25 years.

Professor George Fraser, Director of the University’s Space Research Centre, said: “The Special Projects paper highlights the huge area and mass of Envisat as the major risk factors for space debris.

“The fact that Envisat is in a near-polar orbit doesn’t help either, since its path intersects most satellites’ orbits nearly at right angles. Imagine driving down the motorway and every so often a large truck cuts right across all four lanes right in front of you!”

The student’s research is published in the peer-reviewed student Journal of Physics Special Topics, run by the University’s School of Physics and Astronomy.