NEAR Mission Extended Through February

NASA has given the go-ahead for the NEAR mission to
collect data from the surface of Eros through Feb. 28,
tacking four days onto an extension granted after the
NEAR Shoemaker spacecraft’s historic landing on the
asteroid last week.

The extension gives NEAR Shoemaker’s gamma-ray
spectrometer additional time to observe the elemental
composition on and below Eros’ surface, and the NEAR
team at least two more opportunities to download this
information through NASA’s heavily used Deep Space
Network of antennas.

“This allows us to build a much better sample,” says
Jacob Trombka, of NASA’s Goddard Space Flight Center,
team leader for NEAR Shoemaker’s X-ray/Gamma-ray
Spectrometer. “The longer you accumulate data the more
you can reduce the uncertainty of your results. When you
look at a little bit of data you see clues, but when you
get more data down you can be a bit more definitive.”

Touching down on Eros certainly hasn’t kept NEAR
Shoemaker from touching base with NEAR scientists. The
spacecraft has returned readings from its magnetometer,
and today mission team members are downloading the
latest information from the gamma-ray spectrometer.

The gamma-ray instrument can measure elemental
composition to a depth of about 4 inches, and is much
more sensitive on the surface than it was in orbit.
Mission engineers fine-tuned the device last week to
account for things it hadn’t encountered in orbit; it
operates at a higher temperature near the surface, for
example, because it can no longer radiate heat into
space.

“We optimized the instrument for collecting science in
its new environment,” says John Goldsten, of the Johns
Hopkins Applied Physics Laboratory (APL), lead engineer
for the gamma-ray spectrometer. “Now that we know how
well it’s operating . . . the data we expect from here
on is prime science data.”

While Trombka says they’ll need months to interpret that
data, it won’t take nearly as long for mission
scientists to get a clearer picture of the asteroid’s
magnetic properties – or lack thereof. NEAR Shoemaker’s
magnetometer found no evidence of magnetism at its
landing site. Having returned data from the surface, the
instrument’s work is done and it has been turned off.

“We already knew there was no global magnetic field, but
measuring this close dramatically increased our ability
to see if there was evidence for localized ‘hot spots’
on the surface,” says Brian Anderson, magnetometer
instrument scientist at APL. “The landing site shows no
evidence for an intrinsic magnetic field. Since the
sensor is only two meters above the surface this is a
pretty definitive measurement.”