Montage of our solar system

Scientists at NASA's Jet Propulsion Laboratory developed new approach to old radar data and determined the shape of the large Earth-approaching asteroid, Eros.

Dr. Steven Ostro who, with two colleagues, wrote paper entitled "The Shape of Eros," said the radar observations were made at NASA's Goldstone facility in the California desert between Jan. 19 and 26, 1975.

Ostro's co-authors were Dr. Raymond Jurgens and Keith Rosema. The paper, accepted for publication in the science journal Icarus, was scheduled for presentation Dec. 6 before the Fall Meeting of the American Geophysical Union in San Francisco.

Eros was discovered in 1898 and was subsequently found to cross the orbit of Mars. It made its closest approach to Earth in this century in January 1975 at 14 million miles and was, few months later, favorably placed for observation with available astronomical techniques including radar.

It was determined that Eros is nearly 22 miles long by 9 miles wide and 8 miles thick and rotates about its short axis so it appears to be tumbling end-over-end through space every 5 hours and 16 minutes.

Ostro and his colleagues developed new theoretical approach to the 1975 radar data, called echo spectra, to define its shape as like rounded trapezoid, that is, with one of its long sides longer than the other. He said their work showed how to estimate the shape of the asteroid, develop error-analysis techniques, and study the relation between the accuracy of their estimate and the 1975 data set's signal-to-noise ratio.

The earlier observations determined the asteroid has an iron-bearing silicate composition similar to minority of main belt asteroids and is probably identifiable with ordinary chondrites that make up the majority of Earth-striking meteorites.

The research on Eros was carried out by the Caltech-JPL scientists under contract with NASA.

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