Spaceflight Now: Breaking News

Studying asteroid Eros from planning to science results
Posted: March 19, 2000

Asteroid Eros from NEAR Shoemaker. Photo: JHU/APL
Planning and acquiring observations from NEAR's Near-Infrared Spectrometer (NIS) is a complex process that requires a detailed understanding of the strange shape and the rotational state of Eros. On February 13-14, 2000, just before insertion into Eros orbit, NEAR passed between Eros and the Sun. This geometry is called a low phase angle. It is optimum for spectroscopic observations, so at that time NIS obtained some of its most valuable data.

To plan these activities in the preceding months, the NEAR science team developed a series of global NIS observation sequences like the one depicted in the left image. Here, NIS was instructed to scan its mirror back and forth across Eros while the spacecraft did a slow slew from top to bottom. The image shows the predicted coverage as viewed from directly over the north pole of a computerized "shape model" of Eros. Many such observation sequences were performed flawlessly on the spacecraft during the "low phase-angle flyby," and the highest-quality spectra were combined to show the resulting NIS coverage of Eros in the map on the right. The green and red regions show areas at high northern latitudes with the best coverage by NIS. Analysis of the NIS spectra is providing clues about the mineralogy and composition of Eros, and perhaps its early history and evolution.

Asteroid Eros from NEAR Shoemaker. Photo: JHU/APL
The Long view of Eros

This image looking down the length of Eros was taken from the NEAR Shoemaker spacecraft on March 10, 2000, from a range of 206 kilometers (127 miles). At once, it shows many of the landforms revealed in the last month to be characteristic of this tiny world. The part of the surface shown here is covered by craters of all sizes, right down to the limit of image resolution.

Many of the largest craters, such as the two at upper left, have conspicuous brightness ("albedo") markings on their interior walls. At the upper left is a portion of the ridge that nearly wraps around Eros' waist. Near the center of the image, oriented from the upper right to lower left, are several broad troughs, or grooves, about 200 meters (656 feet) wide. The three boulders on the far horizon are about 80 meters (262 feet) across - each nearly the size of a football field.

The area shown in the image is 10 kilometers (6.2 miles) high. To put the asteroid's size into human perspective, a famous New York landmark is shown inset at the lower left.

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.

Other coverage
Flashy sun -- Solar flares light Eros' surface.

NEAR Shoemaker -- NASA has renamed the probe in honor of Gene Shoemaker.

Exciting first month exploring Eros -- NEAR is astounding scientists with scientific accomplishments.

Eros terrain - Mosaic of cratered region of Eros located at the elongated end of asteroid.
Structural features - Image of the interior of Eros' saddle area.
Moving closer - NEAR shortens orbit around Eros.
Asteroid surface - NEAR shows Eros' sculptured surface with grooves.

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