A US spacecraft will today try a historic unmanned touchdown on the surface of the asteroid 433 Eros, scientists with NASA said.
NEAR Shoemaker - NEAR stands for Near Earth Asteroid Rendezvous - has been orbiting Eros for a year and during that time collected 10 times more data than originally expected in its five-year $223-million-dollar mission.
Now the craft is almost out of fuel and its final approach toward the asteroid it has long gazed at - not originally planned as part of the mission - is "bonus science" according to NEAR mission director Mr Robert Farquhar.
"It might not be a very soft touchdown. The unknown nature of the surface makes it hard to predict what will happen to the spacecraft, especially since it wasn't designed to land," he said.
The controlled descent, set to start at 4.31 p.m., will enable NASA to practise landing manoeuvres ahead of future missions to other small celestial bodies, space officials said.
NEAR is currently orbiting Eros at 35 km altitude. On touchdown it will fire its thrusters six times during a four-hour descent to slow to one-to-three metres per second, Mr Farquhar said.
Asteroid 433 Eros is 33 kilometers long and 13 kilometers across and lies 196 million miles from Earth.
During its year-long orbit of the asteroid NEAR transmitted some 160,000 images of the rocky surface.
AFP