A short engine burn on April 22 started NEAR Shoemaker on a gradual journey toward its ideal scientific orbit around asteroid Eros.
At 1:50 p.m. Eastern Daylight Time, the spacecraft fired its breaking thrusters and moved down from the 62-mile (100-kilometer) orbit it occupied for the previous 11 days.
The burn — which occurred with the spacecraft about 119 million miles (190 million kilometers) from Earth — was the fifth “orbit correction maneuver” for NEAR Shoemaker since it encountered Eros on Feb. 14. On April 30, NEAR Shoemaker will begin a circular orbit 31 miles (50 kilometers) from Eros’ center.
Though all six of the spacecraft’s scientific instruments have been turned on for several weeks, this is the distance from which two of those devices — the Laser Rangefinder and X-Ray Gamma Ray Spectrometer — are designed to work best. The performance of the other instruments also improves as NEAR Shoemaker moves in for closer looks at the 21-mile-long rotating space rock.
Meanwhile, NEAR Shoemaker continued to operate nominally this past week with the spacecraft in Operational Mode with Flight Computer #1 and Attitude Interface Unit #2 in control of spacecraft attitude. The spacecraft instrument suite remained “ON” and operational this past week.
NEAR Shoemaker was in a nominal 100 km circular orbit around Eros before conducting Orbit Correction Maneuver 5 (OCM 5) that placed NEAR in a 100 km x 50 km transfer orbit.
NEAR will remain in the 100 km x 50 km transfer orbit conducting Science observations until April 30, 2000 at 16:55 UTC when Orbit Correction Maneuver 6 (OCM 6) will circularize the orbit at 50 km. Based on the performance of OCM 5, the nominal burn time for OCM 6 will be refined.
Science activities conducted last week included Eros observations by the full instrument suite: MSI, NIS, MAG, NLR and XGRS.
Upcoming Spacecraft Activities:
In addition to regular Eros Science and Optical Navigation, the following are operationally significant activities planned for the NEAR Shoemaker mission operation:
