NEAR Shoemaker Engine Burn puts Spacecraft on Track for Final Months in Orbit
An engine burn at 3:15 p.m. (EST) today 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. For more information on the mission, and for daily
images of Eros, visit Web site: http://near.jhuapl.edu.
