NEAR Team Seeks Clues in Close Orbit

Boulders or big dirt piles? Still dust or shifting particles? The NEAR team
hopes the high-resolution pictures NEAR Shoemaker sends back from its
current 22-mile (35 kilometer) orbit around Eros can answer the range of
questions they have about the asteroid’s surface.

“This is the closest we’ve ever been, giving us a more detailed view of Eros
than we’ve ever had,” says NEAR Project Scientist Andy Cheng of the Applied
Physics Laboratory. “We’re very interested in getting a closer look at the
size and shape of the boulders, the texture of the surface, and finding out
whether the regolith – the layer of dust – is moving across the surface.”

Since completing a four-day gravity experiment on July 17 – and gathering
critical data for designing low-altitude maneuvers later in the mission –
the NEAR team has shifted its attention to imaging and other scientific
activities. Though 22 miles from the center of Eros, the orbit actually
brings NEAR Shoemaker anywhere from 12 to 18 miles (19 to 30 kilometers)
from the asteroid’s surface, which is prime positioning for the
X-ray/gamma-ray spectrometer to analyze Eros’ elemental composition.

NEAR Shoemaker could also be close enough for its magnetometer to detect a
magnetic field from Eros – should the asteroid have one. “The solar wind
carries its own magnetic field, which reflects the magnetic field at the
surface of the sun where the wind originated,” says magnetometer instrument
scientist Brian Anderson of the Applied Physics Laboratory. “Because the sun
rotates and because of solar magnetic activity, the solar wind magnetic
field is quite variable in space. Our challenge is trying to detect a
possible Eros magnetic signature against the variable background of the
solar wind field.”

The spacecraft will keep its current position until July 24, when a short
engine burn will send it back toward an orbit 31 miles (50 kilometers) from
the Eros. By then, NEAR Shoemaker will have circled Eros 14 times in its
current orbit.