As NEAR As You Can Get: The First Asteroid Landing
February 2001 has been a busy month for those who cover space exploration. While Atlantis delivered the module Destiny to the International Space Station, and astronauts completed the 100th spacewalk in American history, another space opera has played out in grand fashion. This particular story centers on a scrappy little space probe that simply just won’t quit. NEAR a spacecraft that has been orbiting the asteroid EROS for about a year, defied all odds by landing on it. The spacecraft was never designed for such a maneuver.
NEAR, which stands for Near Earth Asteroid Rendezvous, was the first of a series of “Discovery” missions funded by NASA. These missions are designed around the philosophy that “cheaper and faster is better.” NEAR fulfilled this promise, and was built at a cost of 233 million dollars. This may seem like a large sum of cash, but when one considers that a single shuttle launch costs around 1 billion dollars, it is a veritable bargain. NEAR was designed and constructed by the Applied Physics Laboratory (APL) at Johns Hopkins University in a little under three years. It is the first project funded by NASA to be built by an outside source.
On February 17, 1996 NEAR was boosted aboard a Delta rocket and began its long journey to the potato shaped asteroid Eros. Well before it ever reached Eros, it came within 1,000 km of another asteroid named Mathilde 253 on June 27, 1997 and took startling snapshots. In order to gain enough speed to catch up with Eros in its long orbit around the sun, NEAR had to come back to Earth in a long circular orbit and use its gravity to slingshot to the asteroid. Unfortunately, a problem occurred on its approach to Eros when a bi-propellant engine shut down too early and forced the spacecraft to skip past the asteroid. NEAR was then forced to try the approach again at a much later time.
The second rendezvous attempt occurred on February 14, 2000 when NEAR flawlessly entered orbit around Eros. It had traveled 1.9 billion miles from Earth. Since it has reached Eros, it has traveled 419 million miles along with it. At first its orbit was a sweeping 323x370 kilometers; too far away to gain important data. By April 2000, NEAR had maneuvered into a snug 100x200-kilometer orbit. This allowed the spacecraft to travel within 22 miles of the asteroid’s surface and gain fantastic images and data. Last October, it shrank its orbit and moved to within 4 miles of the surface. NEAR was designed to orbit Eros for about a year.
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