A UK Flotilla To Study Earth-Grazing Asteroids

On 30 June 1908, the seemingly endless forests of Siberia received an unwelcome and unexpected visit by an intruder from deep space. As it plunged headlong through the Earth’s atmosphere, the incoming asteroid exploded a few miles above the tree tops, flattening the forest over an area about 50 km (30 miles) in diameter. If the 60 metre (200 ft) wide chunk of rock had arrived a few hours later, it could have destroyed a city the size of London or Paris.

Exactly how many of these threatening objects are lurking unseen in the depths of the Solar System no one knows, but scientists estimate that events such as Tunguska occur on average once every 200 years. Larger objects arrive less frequently but pack a much greater punch.

How can we find out more about these Near Earth Objects (NEOs) and possibly find a way of preventing them from sending the human race the way of the dinosaurs? One way is to send spacecraft to study them at close range.

At the UK/Ireland National Astronomy Meeting in Dublin, Simon Green (Open University) will describe SIMONE (Smallsat Intercept Missions to Objects Near Earth), a UK-led proposal to launch a fleet of low-cost microsatellites that will individually rendezvous with different types of Earth-grazing asteroids. This would be the first interplanetary microsatellite mission.

With the first spacecraft costing less than 50 million Euro and additional satellites costing 30 million Euro each, a flotilla of five could be launched as a piggyback payload on an Ariane 5 rocket for the normal budget of one spacecraft.

Each 120 kg microsatellite would be despatched to a different target, using onboard solar electric propulsion driven by lightweight, high power solar arrays, a technology in which the UK is a world leader. After rendezvous with the asteroid, five state-of-the art experiments would map its surface in great detail, in addition to determining its mass, density and composition.

“SIMONE would greatly improve our knowledge and understanding of the diverse NEO population,” said Dr. Green. “The data would be crucial for the development of effective methods to deflect different types of objects that might impact the Earth in the future.”

Assuming a launch by Ariane 5 in 2008 and arrivals 2010-11, the provisional target list includes:
1989 UQ – a C-type Aten asteroid between 560 and 760 m in diameter
2001 CC21 – an X-type Apollo asteroid with diameter between 390 and 1100 m
1996 FG3 – a 1100 m diameter C-type Apollo asteroid with a large moon
1982 DB (Nereus) – an X-type Apollo asteroid with diameter between 470 and 1330 m
1999 YB – an S-type Apollo asteroid with diameter of about 640 m

SIMONE+, a larger spacecraft built using the same design principles could provide a low-cost option for longer range interplanetary missions including Mars.