By BBC News Online Science Editor Dr David Whitehouse

Scientists have gone onto high alert as the Near Earth Asteroid Rendezvous (Near) spacecraft closes in on asteroid 433 Eros. It will be the first time that a spacecraft has ever gone into orbit around an asteroid.

It is a tense time for the researchers. Last year's attempt to circle the Asteroid failed and Near now has a rare second chance.

In December 1998, Near's computer shut down the rocket motor after only two seconds of firing, which was far too short to get into orbit around Eros. Instead, it sailed past the space rock sending back many pictures of the tiny irregular world.

Thanks to the quick actions of the Near mission control, the spacecraft was placed on a trajectory that would take it back to Eros just over a year later. Now, on 14 February, 13 months later than planned, Near will try again.

Near's science operations have moved into high gear as the spacecraft approaches to within 41,000 km of Eros. Images of the asteroid have confirmed its location and scientists say the spacecraft's approach is going exactly as planned.

Own moon

Near's images of Eros have also been used to measure the brightness variations caused by the rotation of the irregularly-shaped world.

The images are also being scrutinised to see if Eros has any natural moons of its own. Some other asteroids, Ida and Eugenia, have their own satellites. If Eros does have a moon, mission controllers will want to know all about its motions before Near attempts to go into orbit.

Launched in February 1996, Near is the first Nasa planetary mission to be carried out by a non-Nasa space centre. The Applied Physics Laboratory at Johns Hopkins University designed and built Near in only 26 months at a cost of $108m.

If all goes well, mission operators will fire the spacecraft's set of thrusters on 2 February to begin orbital insertion. Because of the previous problems, it has been decided to use Near's thrusters and not its main motor.

It is planned that Near will orbit Eros for a year in ever closer orbits. It has even been suggested that the probe may attempt a landing on the asteroid.