NEAR image of the day for 2000 Mar 29
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Dancing with Eros Because of Eros' irregular shape, it is a challenge to navigate the NEAR Shoemaker spacecraft accurately through its sequence of low orbits. To help, the mission team plans and acquires sequences of images that meet objectives both for scientific mapping of the asteroid and for tracking the spacecraft's position.
Several times daily, NEAR Shoemaker's imager returns navigation images like the one shown at top, taken March 4, 2000, from a range of 203 kilometers (126 miles). The mission's Navigation Team analyzes the images to track directions to familiar landmarks like hills or craters, and thus finds the spacecraft's position relative to the asteroid. This requires very accurate knowledge of where the imager is pointed. Pointing is measured by taking images of stars, which are fixed reference points in space. Based on analysis of hundreds of star field images like the one at bottom, taken March 6, 2000, the imager's pointing is known to within about eight thousandths of a degree - approximately the size of a golf ball two hundred yards away. The combination of techniques used to navigate the spacecraft provides a high degree of accuracy in predicting future spacecraft location, so that detailed imaging sequences can be planned weeks in advance.
(Images 0127591908 and 0127755006)
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Feedback to Scott Murchie. Scott.Murchie@jhuapl.edu.
Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR-Shoemaker was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions. See the NEAR web site for more details.