The true nature of Eros becomes a bit clearer -- literally -- as NEAR Shoemaker moves into a lower orbit this weekend. Shortly after 9 p.m. EST on Saturday, the spacecraft fired its thrusters for 36 seconds and began gradually descending into position to start a 62-mile (100-kilometer) orbit on April 11.

Since March 3, NEAR Shoemaker has been in a nearly circular orbit some 127 miles (205 kilometers) from the center of Eros. NEAR team members say the new orbit will yield sharper images of the asteroid's abundant geological features, and more information about its many ridges, grooves and craters.

Lighting and viewing geometries make a huge difference in the appearance of Eros' surface features. One of the most striking examples is the 2.7-kilometer (1.68-mile) diameter crater shown in these two images. The image at left, looking at the crater nearly edge-on, was taken February 16, 2000, from a range of 341 kilometers (212 miles). The image at right was taken high over the crater on March 2, 2000, from a range of 226 kilometers (140 miles). In the first image the only visible part of the crater's interior is the far, bright wall, which at the time was well-lit. The lighting, in combination with the particular viewing angle, make the crater appear stunningly bright. In the second view, the brighter material occupies only part of the slightly-shaded interior, greatly reducing the overall brightness contrast between the crater and the surrounding terrain. Photo: JHU/APL

Earlier than expected, the team is also gathering information on the asteroid's elemental makeup. With the help of three solar flares on March 22 and 23, the spacecraft's X-Ray/Gamma Ray Spectrometer (XGRS) picked up additional fluorescent "signatures" of magnesium, aluminum, silicon, calcium and iron on the Eros surface. The readings were similar to those detected during a solar flare on March 2 -- from four times the instrument's designed operating distance.

"From that distance, the readings verify that the instrument has the sensitivity we need," says Dr. Jacob Trombka, XGRS instrument team leader from NASA's Goddard Space Flight Center. "They continue to show us that the calibration is on target and the instrument is working as it should." NEAR Shoemaker is about 134 million miles (215 million kilometers) from Earth, moving just under 3 miles per hour around Eros. The spacecraft is six weeks into its historic, yearlong mission to study the asteroid.

Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR-Shoemaker was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions.