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Friday, 3 March, 2000, 22:47 GMT
Near zaps Eros
The laser impact point on a 3-D image of Eros
By science editor Dr David Whitehouse

The Near spacecraft has begun probing the darkest corners of the asteroid Eros.

It is using a laser rangefinder device to look at the regions on the space rock that are in shadow and hidden from its main camera.

The first laser reflections were picked up at a distance of 290km (180 miles) from the asteroid. This has thrilled researchers because the rangefinder was designed to operate at a distance of 50km (31-mile).

The combination of this data and the photographs sent back by Near will enable scientists to measure more accurately the differences in height and depth in the various grooves and craters that make up the asteroid's surface.

Closer orbit

The Near (Near Earth Asteroid Rendezvous) team say they are going to have a lot of fun over the next few weeks.

The images sent back by Near continue to thrill scientists
A 15-second engine burn on 3 March will nudge the spacecraft into a 200km (124 mile) orbit around Eros.

Over the next four weeks, Near will collect images and data for a detailed global surface map, a topographic model and a more precise estimate of gravity on Eros.

"We expect to resolve a lot of the features that we've only seen glimpses of so far," said Louise Prockter, a member of Near's imaging team.

Gravity field

Near's multispectral imager will take enough pictures to compile colour and monochrome maps of Eros's surface. By measuring the distance between Near and Eros, the laser rangefinder will begin to shape three-dimensional perspectives of the craters, ridges and various other features that have already been picked up in the stunning images sent back to Earth.

The craft's radio science equipment will use the closer orbit to get a better reading of the asteroid's gravity field. With a little help from the Sun, the satellite could also get its first readings of the asteroid's elements. Near's x-ray spectrometer detects fluorescence from elements that react to solar x-rays.

"A lot depends on solar activity," said Ralph McNutt, X-ray/gamma ray spectrometer instrument scientist. "If there is a strong solar x-ray event, the instrument will get a good measurement."

On 1 April, another short engine burn will gradually move Near into a 100km (60 mile) orbit.

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See also:

21 Feb 00 |  Sci/Tech
Eros is 'no ordinary rock'
15 Feb 00 |  Sci/Tech
Near probe gets down to business
04 Jan 00 |  Sci/Tech
Saving the world from asteroids
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