During routine operations on May 13, the Near-Infrared Spectrometer (NIS) inexplicably began drawing excessive current from the spacecraft's power supply and stopped sending data.

Engineers shut down the instrument and began examining potential causes, but after a minute-long "turn on" test June 5 showed the problem remained, the NEAR team opted to keep the instrument off until it could gather more information.

Robert Gold, NEAR Shoemaker payload manager at the Johns Hopkins University Applied Physics Laboratory - which manages the mission for NASA - says the spacecraft itself is fine and that "NEAR Shoemaker's other instruments are operating extremely well."

Designed to map the mineral composition of the asteroid's surface by measuring the reflected spectrum of sunlight, NIS has already contributed much to this historic mission.

Its best data came from a low-angle flyby of Eros on Feb. 13, when it mapped the minerals on the asteroid's northern hemisphere under near-perfect lighting conditions. So far, the instrument has gathered more than 58,000 "spectra" - or separate infrared readings - covering more than 60 percent of the asteroid.

"We have a fantastic data set because, to this point, the instrument has operated beautifully," says Joseph Veverka, of Cornell University, who leads NEAR's Multispectral Imager/NIS team. "We have a vast number of spectra to analyze, and we gathered everything and more than we expected from the northern hemisphere."

That information will help the team examine Eros' southern hemisphere, which over the next few months will slowly emerge from the shadows and into the sunlit view of NEAR Shoemaker's imaging tools.

"It appears the surface is pretty uniform in terms of spectral reflectance," Veverka says. "By correlating the NIS data from the northern hemisphere with what we gather from the Multispectral Imager [digital camera] and the X-ray/Gamma-Ray spectrometers [which detect surface elements], we should be able to address the remaining questions of how different the south polar regions are from what we've already seen."

Four months after becoming the first spacecraft to orbit an asteroid, NEAR Shoemaker is working 85 million miles (136 million kilometers) from Earth, circling 31 miles (50 kilometers) above Eros at just under 7 miles per hour.

On July 7, the spacecraft begins moving in for its closest look at Eros yet - a 10-day orbit just 22 miles (35 kilometers) from the rotating space rock. NEAR Shoemaker also carries a Laser Rangefinder to determine the asteroid's precise shape, and a Magnetometer to search for a magnetic field. The yearlong mission ends in February 2001.