The Near Earth Asteroid Rendezvous, or NEAR, was the first space probe to orbit and perform an in-depth investigation of an asteroid and then safely land on it.
The mission was designed to answer many fundamental questions about the nature and origin of asteroids, which are of great interest both because of their potential for colliding with Earth and for the clues they hold about the formation and evolution of our solar system.
The spacecraft was renamed NEAR Shoemaker to honor Dr. Eugene M. Shoemaker, the renowned geologist who influenced decades of research on the role of asteroids and comets in shaping the planets.
Dr. Andrew Cheng
The NEAR mission was managed by the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, MD. The Project Scientist was Dr. Andrew Cheng of APL. The spacecraft was designed and built at APL.
NEAR Shoemaker captured this movie from orbit 125 miles above Eros. Covering a full rotation of the 21-mile-long asteroid, it opens at one of Eros' battered ends and sweeps over the depression named Himeros. The sequence then includes a view of a large boulder patch before swinging over the opposite end and providing a stunning view of a sunset inside Psyche, the asteroid's large, 3-mile impact crater.
NEAR Shoemaker's multispectral imager (MSI) captured these images during the spacecraft's controlled descent to Eros. Starting from 3 miles above the surface, the camera moves over cracked and jagged rocks, boulder patches, craters filled with dust and debris, and mysterious areas where the surface seems to have collapsed. The final frame, taken 422 feet above Eros, shows features a few inches across.
Diagram showing location of NEAR science instruments.
NEAR’s primary target was asteroid 433 Eros, the second largest of the “near-Earth asteroids” whose orbits cross that of Earth's. NEAR’s payload of six highly specialized instruments each contributed in different ways to accomplish the mission objectives:
• Measure shape, mass, density, gravity field, magnetic field, and spin state
• Determine elemental and mineralogical composition
• Identify physical, geological and morphological characteristics
In this montage, asteroid Mathilde (at left) and Eros are shown at the same scale. Mathilde is 35 miles across, and Eros is 21 miles long, 8 miles wide. Mathilde's brightness is greatly exaggerated for viewing purposes -- it's actually six times darker than Eros, with about the same reflectivity as soot.
The NEAR mission launched on February 17, 1996, aboard a Delta II rocket from Cape Canaveral Air Force Station, Florida. As the first Discovery Program mission launch, NEAR led the way with a new paradigm for planetary missions that could be designed and built within cost and schedule constraints, minimizing risk and maximizing science capability.
On the way to Eros, NEAR flew past the main-belt asteroid 253 Mathilde, providing the closest view of an asteroid to date and the first look at a C-type asteroid, the dark, carbon-rich, most common type. On June 27, 1997, hurtling through space at 22,000 mph, NEAR flew within 750 miles of the highly cratered Mathilde, taking images and measurements for 25 minutes – the first Discovery science data return.
NEAR entered into a year-long orbit around Eros on February 14, 2000. The spacecraft circled 21-mile-long potato-shaped space rock at altitudes from 2 to 35 miles, revealing it to be much more exciting and geologically diverse than scientists had expected.
One of the most striking features on Eros' surface is the abundance of very large boulders. This image of the saddle region from a range of 125 miles shows a particularly boulder-rich area. Many of the huge rocks are 164 feet or more in diameter. They are believed to be fragments of Eros' native rock, shattered over the eons by formation of impact craters.
This image of a crater on Eros (left), is displayed next to and at approximately the same scale as Meteor Crater in Arizona. The late Dr. Eugene Shoemaker did pioneering work at Meteor Crater, documenting the effects of impact cratering as a planetary process. When part of a comet or asteroid strikes a planet or another asteroid, the resulting shock wave and excavation of rock and soil leave a characteristic landform, as illustrated by this comparison.
Combining digital images and data from the laser rangefinder, scientists built the first detailed map and three-dimensional model of an asteroid.
Scientists previously theorized that asteroids were either solid iron or cosmic rubble piles, but Eros is neither. Data suggests that Eros is a cracked but solid rock, with a density similar to Earth’s crust. Scientists believe it is a fractured chip off a larger body, made of some of the most primitive materials in the solar system.
Eros is geologically active with grooves, ridges, and many craters altered by mass motions of dust and rocky debris, called regolith, believed to be up to 300 feet deep. Data indicate the regolith has moved downhill, smoothing over rough areas and spilling into craters. The intriguing square craters and scarcity of small craters surprised scientists. More than 100,000 craters wider than 50 feet have been counted. The quantity of boulders was a surprise, with about one million house-sized or larger. Another unexpected finding was “ponds” of smooth, flat deposits of fine regolith.
After a journey of more than two billion miles and achieving all its planned science goals, NEAR Shoemaker gently landed on Eros on February 12, 2001. The spacecraft snapped 69 detailed pictures during the final three miles of its descent, the highest resolution images ever obtained of an asteroid, showing features as small as one centimeter across. It operated for two more weeks, taking measurements of surface composition and conducting the first gamma-ray experiment on a surface other than Earth.
The NEAR mission returned more 160,000 detailed images. The final images show clusters of boulders, an area where the surface appears to have collapsed, and extremely flat, sharply delineated areas in some crater bottoms, indicating the story of Eros's composition is still emerging.
The wealth of data, shared with scientists all over the world, revealed new and surprising details about asteroids and raised more questions: What are the processes that determine the surface geology and internal structure of asteroids? How do they depend on asteroid size? Perhaps the Dawn mission will supply answers.
NEAR science results were published in five articles in Nature, September 21, 2001; four reports in Science, September 21, 2000; and two reports in Science, April 20, 2001.
For further information, visit the National Space Science Data Center, NASA's permanent archive for space science mission data.
Spectacular view of the northern polar region of Eros taken by NEAR Shoemaker, showing the 3.3-mile diameter crater at the top, the saddle at the bottom, and a major ridge system between the two.
One of the last Eros images, taken from 820 feet on the way to landing. The cluster of rocks at the upper right measures 5 feet across.
Use of the Internet for communicating with the public through Project Scientist Andy Cheng’s regular Science Updates during orbit, the first science mission blog, and posting NEAR Images of the Day
The NEAR mission team received two prestigious awards:
National Air and Space Museum 2001 Current Achievement Trophy for outstanding achievement in scientific or technological endeavors relating to air and space
Popular Science magazine 2001 "Best of What's New"Award in aviation and space, honoring the world's most outstanding breakthrough products and technologies that improve the quality of life through advancing human knowledge