NEAR's Laser Rangefinder records the first range returns from an asteroid. Photo: JHU/APL

Now the fun starts.

A 15-second engine burn at 1 p.m. EST on March 3 will nudge NEAR into a 124-mile (200-kilometer) orbit around Eros, giving the spacecraft its best scientific look at the asteroid so far. 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," says Louise Prockter, a member of NEAR's imaging team.

NEAR's Multispectral Imager will snap enough photos to create color and monochrome maps of Eros' 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 in the images. 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. The X-Ray Spectrometer detects fluorescence from elements that react to solar x-rays. "A lot depends on solar activity," says 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."

Moving three miles an hour relative to Eros, NEAR will circle the rotating space rock three full times during this orbit. NEAR operates at this range until April 1, when another short engine burn will gradually move it into a 60-mile (100-kilometer) orbit. The asteroid and spacecraft are about 152 million miles (almost 245 million kilometers) from Earth.

The NEAR team will analyze and present its findings from the orbit over the next several months, including a potential first look at the data during a March 13 press briefing at the Lunar and Planetary Science Conference in Houston.