Artist's concept of the NEAR spacecraft orbiting Eros. Photo: JHU/APL

An engine burn at 3:15 p.m. (EST) yesterday put the NEAR Shoemaker spacecraft in orbit just 22 miles (35 kilometers) above Eros' center of mass in preparation for low altitude operations in January and February, just prior to the mission's end. The orbit correction maneuver lasted a minute and a half and pushed the spacecraft from an elliptical orbit approximately 120 miles (200 kilometers) above Eros at its farthest point, into its current circular orbit around the tumbling space rock.

The maneuver is the latest in the mission's five-year history that has taken the NEAR Shoemaker spacecraft on a 2-billion-mile journey and provided a unique 150,000-image photo-op since it began its orbital approach in January.

"The next two months will be the most challenging time of the entire mission for the operations team," says Dr. Robert W. Farquhar, mission director for NASA's Near Earth Asteroid Rendezvous (NEAR) program at The Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md. "We're working very closely with the navigation team at the Jet Propulsion Laboratory to ensure the success of each maneuver. The final controlled descent on Feb. 12 is one of the most complicated maneuvers to date, but the return will be worth it. We expect to get images that are 10 times better in resolution than anything we've taken so far."

NEAR Shoemaker will stay in a 22-mile (35-kilometer) orbit until Jan. 24, when three more engine burns will push it first to within 12 miles (19 kilometers) and then back to a circular 22-mile orbit, by the end of the month. During the lower orbits the spacecraft will come within 1.9 miles (3 kilometers) of the asteroid's ends.

The mission team will use the progressively lower orbits and low flyovers to collect valuable data. "This will give us an excellent opportunity for the gamma ray spectrometer to measure element abundances at low altitudes," says Project Scientist Dr. Andrew F. Cheng of the Applied Physics Laboratory. "These measurements will help us clear up some questions we have regarding how closely Eros' composition fits the pattern of ordinary chondrites. The spectrometer will also give us composition measurements from 10 centimeters below the surface and will give us a reading of natural radioactivity on the asteroid. At the same time the imager and laser rangefinder will be giving us additional low-altitude, high-resolution data to complete a global mapping of Eros."

On the final day of the mission, Feb. 12, 2001, the spacecraft will execute a series of maneuvers that will enable NEAR Shoemaker to gather high-resolution images from only 1,640 feet (500 meters) above the asteroid's surface.

NEAR Shoemaker has been in orbit around Eros since Feb. 14, 2000, conducting the first in-depth study of an asteroid. APL manages the NEAR mission and built the spacecraft.