Contact was regained with the $129 million Nasa spacecraft, after 24 hours of silence following an incomplete engine burn last Sunday. Near was only weeks away from its destination, the asteroid Eros.

Near will make a close fly-by of Eros at 1.43pm Wednesday. It will take a few pictures of it and make some magnetic measurements.

Eros is moving faster so will soon overtake Near. However in May 2000 the two will be in the right position for Near to enter Eros orbit.

The probe, intended to be the first ever to orbit an asteroid, appears to be physically intact. But the data returned to Earth is missing the crucial moments when communication was lost.

Contact has been made but the crucial data is missing

"It was not exactly where we thought it would be, probably because the rocket burn did not take place," said Dee Reese, a spokesperson for the Johns Hopkins University Applied Physics Laboratory in Maryland, USA, which built and manages the craft.

She told BBC News Online, "We're really hoping we can save this mission."

Contact was lost late on Sunday when Near's rockets were about to fire in the first of four intended bursts to adjust its speed and direction. These are to guide it into orbit around Eros, a 25 mile (40 km) long asteroid, 240 million miles (385 million km) from Earth.

A two-minute process of settling the fuel was apparently successful, but communications blanked out during an 18-minute procedure to fire Near's large engine.

First signal

The first signal was spotted by Nasa's Deep Space Network of monitoring devices at about 0100 GMT on Tuesday. It is likely that the signal was being transmitted all long and that mission control were looking for it in the wrong place, following the failed manoeuvre which caused the probe to go off course.

The Near Earth Asteroid Rendezvous (Near) probe was launched in February 1996 and was expected to reach the asteroid Eros on 10 January 1999. But that rendevous date has now been scrapped. The next possibility is 6 February 1999, but that depends on the condition of the probe, said Reese.

The probe has a "safe mode", an automatic shutdown procedure designed to protect it if something goes wrong. This, believe mission controllers, means that it may well be possible to safely re-awaken the craft.

Billion mile journey

Six instruments will enable the most detailed study of an asteroid ever

The probe had travelled 1.4 billion miles on its indirect route to Eros and was only 150,000 miles (242,000 km) short when the break in communication occurred.

The Near probe was intended to orbit nine miles (15 km) above Eros for a year, mapping its magnetic and gravitational fields and analysing its rock composition. Scientists had hoped to bring the craft to within feet of the surface and possibly even attempt a soft landing.

The challenges of manoeuvring a spacecraft to within such close distances of a tumbling, irregularly-shaped body are significant.

But Dr. Joseph Veverka of Cornell University, Science Team Leader for the mission, said that, if successful, "This will be the first detailed characterisation, not only of the surface of an asteroid, but of the interior of the asteroid. We will also learn about the history of this asteroid based on its surface characteristics and materials composition."

The Near spacecraft was launched on 17 February 1996. Its flight past asteroid Mathilde on 27June 1997 at a distance of 750 miles (1200 km) was the closest approach to an asteroid ever made by a spacecraft. This provided the program's first scientific results, more than 500 pictures.