NEAR Encounter with Asteroid 433 Eros

Images of Eros

Eros' bland butterscotch colors

These color images of Eros was acquired by NEAR on February 12, 2000, at a range of 1800 kilometers (1100 miles) during the final approach imaging sequence prior to orbit insertion. A five and one-half hour long sequence of images covering visible and infrared wavelengths was taken at that time, to provide a global overview of the color and spectral properties of the asteroid. The images show approximately the color that Eros would appear to the unaided human eye.

Eros' subtle butterscotch hue at visible wavelengths is nearly uniform across the surface. Two days after these images were taken, mapping by NEAR's infrared spectrometer showed that Eros exhibits a great deal more variety at longer wavelengths. These variations could be due to differences in texture or composition of the surface. Both NEAR's multispectral imager and infrared spectrometer will be used extensively during the month of March to map Eros' color and spectral properties from an altitude of 200 kilometers (120 miles). The images to be returned will show details as small as 20 meters (68 feet) across, providing a new perspective on the asteroid's many fascinating landforms discovered so far by NEAR.

Eros in color

This color image of Eros was acquired by NEAR's multispectral imager on February 12, 2000, at a range of 1100 miles (1800 kilometers). It is part of the final approach imaging sequence prior to orbit insertion and is intended to map the color properties of Eros across all of the illuminated surface. The image shows approximately the color that Eros would appear to the unaided human eye. Its subtle butterscotch hue is typical of a wide variety of minerals thought to be the major components of asteroids like Eros. (Color composite of images 0125766469, 0125766471, 0125766473)

On February 12, 2000 during the final stage of approach to Eros, NEAR acquired a 780 frame rotation sequence using its MSI camera. Images were taken every 26 seconds to capture slightly over one rotation. These data not only serve as critical optical navigation aids, but give scientists a dynamic look at changing shadowing and shading of surface features. By examining features with different illumination conditions analysts can easier interpret their origin. This is a small sampled version (one frame every 13 minutes) of the full movie. (Images 0125726525-0125746779)

NEAR's last image returned before orbit insertion

On February 12, two days before NEAR's insertion into orbit around Eros, the spacecraft's camera took this image of Eros from a range of 970 miles (1570 kilometers). This was the last image returned to Earth prior to NEAR's insertion into Eros orbit.

Features as small as a 520 feet (160 meters) across can be seen. This face of Eros is dominated by a huge, hollowed-out gouge which may also have been caused by an impact. The feature which from a greater distance appears heart-shaped (at lower left) is resolved in this view as three impact craters which rims shallow depression. (Image 0125766481)

Eros' global morphology

On 12 February, 2000, the NEAR spacecraft obtained a sequence of 780 images of Eros from a range of about 1800 km (1100 miles). This sequence covered one complete revolution of the asteroid at 0.5 degree intervals. In these views of opposite hemispheres of the asteroid, groups of images slightly apart in time were digitally processed to bring out local details. The processed data showing Eros from slightly different perspectives can then be combined as anaglyphs or stereo pairs. The processing of the data highlights the topography of small-scale features, but makes the gross shape of the asteroid appear flattened.

Computer processing brings out Eros's details

The NEAR camera's ability to show details of Eros's surface is limited by the spacecraft's distance from the asteroid. That is, the closer the spacecraft is to the surface, the more that details are visible. However mission scientists regularly use computer processing to squeeze an extra measure of information from returned data. In a technique known as "superresolution", many images of the same scene acquired at very, very slightly different camera pointing are carefully overlain and processed to bright out details even smaller than would normally be visible. In this rendition constructed out of 20 image frames acquired Feb. 12, 2000, the images have first been enhanced ("high-pass filtered") to accentuate small-scale details. Superresolution was then used to bring out features below the normal ability of the camera to resolve. (Mosaic of images 0125957025 and 0125957087)

NEAR enhanced image - composite of 20 images coregistered to 0.2 pixel.

On February 12, two days before NEAR's insertion into orbit around Eros, during a five-hour time span the spacecraft's Multispectral Imager recorded these pictures of the asteroid spinning on its axis. This view, looking down toward the rocky body's north pole, is generally similar to sequences taken on February 6, 10, and 11. But the spacecraft was much closer to Eros (about 1,800 kilometers or a little over 1,100 miles), so the pictures are much sharper.

Features as small as a 590 feet (180 meters) wide can be seen. The most prominent, sharp-rimmed impact crater is on the opposite side of Eros from a huge, hollowed-out gouge, which may also have been caused by an impact. Between these features, and towards the ends of the "fat banana" shape of Eros, the asteroid's surface is covered with smaller craters.

(Images 0125726525, 0125734325, 0125742125, 0125728085, 0125735885, 0125743685, 0125729645, 0125737445, 0125745245, 0125731205, 0125739005, 0125732765)

Close up of images 0125726525, 0125728085, 0125745245, 0125732765.

This montage shows a selection of images of the asteroid 433 Eros that were acquired from the NEAR spacecraft over three weeks from January 22 through February 12, 2000, as the spacecraft's distance from its target shrank from 18,000 to 1260 miles (29,000 to 2025 km). As the spacecraft closed in on its target, the resolution of the images increased from 1.7 to 0.12 miles (2.8 to 0.19 km) per pixel. At 20x8x8 miles in size (33x13x13 kilometers), Eros is the second largest near-Earth asteroid and spins on its axis once every 5 hours, 16 minutes.

During the early stages of NEAR's approach, Eros appeared as a small blob only a few pixels across. The apparent size of Eros and the resolution of the pictures increased continuously, at first only slowly and later dramatically day by day until, on February 9, the level of detail visible exceeded that during NEAR's first flyby of Eros on December 23, 1998. In the last images shown here, details of Eros's surface have become visible. Heavy cratering has pockmarked the irregular asteroid's surface. One side is dominated by a scallop-rimmed gouge, and the opposite side by a conspicuous, raised-rimmed crater.

On February 10, four days before NEAR's insertion into orbit around Eros, the spacecraft's Multispectral Imager took this movie of the asteroid's rotation over one 5.27-hour Eros "day", from a range of 2050 miles (3300 kilometers).

Features as small as a 1100 feet (330 meters) across can be seen. The most prominent, sharp-rimmed impact crater is on the opposite side of Eros from a huge, hollowed-out gouge, which may also have been caused by an impact. Between these features, and towards the ends of the "fat banana" shape of Eros, the asteroid's surface is covered with smaller craters. (Images 0125647625-0125686773)

Just in time for its Valentine's Day date with 433 Eros, the Near Earth Asteroid Rendezvous (NEAR) spacecraft snapped this photo during its approach to the 21-mile-long space rock. Taken Feb. 11, 2000, from 1,609 miles (2590 kilometers) away, the picture reveals a heart-shaped depression about 3 miles (5 kilometers) long. Scientists at the Johns Hopkins University Applied Physics Laboratory - which manages the NASA mission - processed the image on Feb. 12. Photos taken from closer in during the next few days will help the NEAR team unravel the mystery of this shadowy feature. (Image 0125693155)

Image of Eros without the arrow

On February 9, the Multispectral Imager on NEAR acquired these four images of the asteroid 433 Eros as the spacecraft closed to within 2500 miles (4100 km) of its target. The pictures were taken at approximately equal time intervals over the course of one 5.27-hour rotation of the asteroid. Thus the upper left image shows nearly the same view of the asteroid as the lower right image. In just this time, NEAR shaved another 120 miles (200 kilometers) off the remainder of its journey, so that the last view of the asteroid is measurably larger than the first.

Over the last few days new details of Eros's surface have become resolved. Craters as small as a couple of kilometers across are now becoming visible. By the time of orbit insertion on February 14, features as small as 330 feet (100 meters) in size will be distinguishable. (Images 0125513653, 0125501173, 0125507413, and 0125494933)

Approximately one day after its first rendezvous burn, NEAR imaged Eros every 15 degrees of rotation over a period of about 5.8 hrs. At this time the distance between the asteroid and spacecraft was approximately 4638 miles (7730 km). These images taken during approach to the asteroid are used by mission navigators and operators to make the proper corrections in the spacecraft's trajectory during the critical burns coming up on Feb. 8 and Feb. 14.

As an added bonus, these "OpNav" (optical navigation) images provide an increasingly detailed view of surface features on the asteroid. The resolution has increased to about 0.5 miles (0.8 km) per pixel, revealing the presence of 3 small craters on the surface. Over the next 10 days our view of the surface will become increasingly detailed and will allow for nearly global low resolution mapping of the asteroid before NEAR goes into orbit about Eros on Valentine's Day, Feb. 14. Once in orbit, NEAR's suite of scientific instruments will allow for global mapping of the asteroid at very high resolution. (Images 0125057110 - 0125075950)

On February 6, the Multispectral Imager on NEAR acquired the two right-hand views of the asteroid Eros as it closed to within 4200 miles (6800 km). This distance is just greater than the distance at which NEAR imaged Eros during a flyby of the asteroid on Dec. 23, 1998 (images on left). The differences in Eros's appearance at the two times result from seasonal variations in solar illumination and from NEAR's viewing angle when the two sets of images were taken. Last year NEAR approached from the north when the asteroid was experiencing southern hemisphere summer and thus the north pole was in shadow, resulting in a mostly shadowed, crescent asteroid. Now, nearly 14 months later, Eros is experiencing northern summer. Now the spacecraft is again over northern latitudes, but because of the difference in illumination it views a mostly sunlit, gibbous Eros. Images of Eros taken with different illumination and viewing are needed to piece together a global view of the asteroid's geology. For example, in the flyby views at left, the shading accentuates a low linear feature that runs the length of the asteroid. The recent approach images at right show northern hemisphere features not visible during the flyby. By combining images taken with very different viewpoints a complete history of the asteroid's surface can be compiled. In order to build up this complete view, at very high resolution, NEAR will orbit the asteroid for about one Earth year.

NEAR Eros orbital images
NEAR Eros Science Returns

More information on asteroid 433 Eros
Asteroid Fact Sheet
NSSDCA Asteroid Home Page

Information on the Multispectral Imager
Information on the NEAR Mission Profile and Trajectory

Images from the Eros and Mathilde Flybys
NEAR Eros Images - Applied Physics Lab, JHU

NSSDCA NEAR Home Page
Detailed information on NEAR from the NSSDCA Master Catalog
NSSDCA Planetary Home Page

NASA Official: Dr. Ed Grayzeck, edwin.j.grayzeck@nasa.gov
Last Updated: 18 December 2001, DRW