Orbital View: Asteroids, NEAR and Far

Eros as seen from NEAR Shoemaker (NASA)

Twenty years ago today—on February 17, 1996—NASA launched into space an unmanned aircraft named NEAR, or Near Earth Asteroid Rendezvous. Its primary mission was to gather information about asteroids, as explained on the NASA Discovery website:

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 NEAR launch didn’t immediately go as planned. From an AP report that day:

CAPE CANAVERAL, Fla. — Equipment trouble forced NASA to delay the launch of a spacecraft toward an asteroid Friday. Managers halted the countdown with less than an hour remaining because of problems with the safety system used to track ascending rockets. They said they would try again today to launch the unmanned Delta rocket from Cape Canaveral Air Force Station. Once launched, the spacecraft--called [NEAR]--will spend three years flying to the asteroid Eros and then become the first spacecraft to orbit an asteroid.

NEAR entered into orbit around Eros on February 14, 2000, and Michael Benson wrote about the union for a 2002 issue of The Atlantic. He described the craft’s landing on Eros “not unlike an adolescent confronting the object of his or her erotic fascination for the first time”:

NEAR's first image from Eros orbit (NASA)

In early 2000, in an event largely ignored by the mainstream media, the Jet Propulsion Laboratory eased [NEAR] into orbit around a twenty-one-mile-long peanut-shaped, methodically tumbling rock called Eros. NEAR was the first spacecraft ever to orbit an asteroid—no inconsiderable feat of celestial navigation, given that Eros has a gravity field so weak that an astronaut on its surface could reach escape velocity by simply jumping off. A year later project scientists maneuvered the probe to within a few hundred yards of its subject and then directed it to touch down gently. NEAR thus became the first spacecraft to land on an asteroid.

NEAR hasn’t performed flawlessly. Not unlike an adolescent confronting the object of his or her erotic fascination for the first time, the spacecraft suddenly flipped out during its initial approach to Eros, in December of 1998. Cut off from communication with Earth, acting on its own, the probe's computer managed to re-orient the spinning craft. But by the time the JPL flight engineers had figured out what went wrong, they were forced to send their charge all the way around the Sun again-a year-long trajectory-for another try.

They wouldn’t have been able to do so if NEAR hadn’t straightened up and flown right all by itself. There’s something fascinating about the increasing autonomy of these robots with which we’re populating the heavens.

NASA said goodbye to NEAR on February 28, 2001:


NEAR Shoemaker [as the craft was renamed] now rests silently just to the south of the saddle-shaped feature Himeros as the asteroid twists more and more away from the sun with each rotation, moving the southern hemisphere into its winter season and temperatures as low as minus 238 degrees Fahrenheit (minus 150 centigrade). … Tonight at 7 p.m. (EST) NASA’s Deep Space Network antennas will pull down their last Near Earth Asteroid Rendezvous (NEAR) mission data, bringing to a close the first mission to extensively study an asteroid. NEAR, which was the first mission in NASA’s Discovery Program of low-cost, scientifically focused space missions, and the first to land on an asteroid, has delighted astronomy neophytes and scientists alike.

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