On April 30, at 12:15 p.m., Eastern Daylight Time, the NEAR Shoemaker spacecraft successfully completed one of
its largest orbit correction maneuvers to date. The hydrazine engine burn lasted approximately 2 minutes, 20
seconds and moved the spacecraft from a 62 X 31-mile (100 X 50 kilometer) orbit to a 31-mile circular orbit over
Eros’ north and south poles. This is the sixth time the spacecraft’s thrusters have been fired to adjust its position
since it began orbiting Eros on February 14, 2000.
The burn also successfully reduced spacecraft momentum buildup by slowing the four momentum wheels that
spin faster and faster as the spacecraft works to stay sun pointing. If the momentum isn’t reduced it can build to a
level where the guidance system can’t maintain control of the spacecraft so its autonomous systems send it into
safe mode. To avoid this, momentum dumps are routinely conducted about every week to 10 days.
For the next two months the spacecraft will remain in a 31-mile orbit, giving the imager its closest view yet of the
slowly tumbling asteroid and the Laser Rangefinder and X-Ray Gamma Ray Spectrometer instruments a chance to
begin collecting data from a distance optimum for their design. All instruments are operational at this time.
The April 30 burn left NEAR Shoemaker travelling at 7 miles per hour-a reduction of 3 miles per hour from its
previous speed. Although gravity is so slight that a baseball tossed from the surface of Eros would easily leave the
asteroid’s gravitational confines, there is still enough of a pull to influence the spacecraft’s flight. A greater
gravitational pull as the spacecraft comes closer to Eros and the closer proximity make it necessary for each engine
burn to be increasingly more accurate. The next orbit correction maneuver is expected to take place July 7.
