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How Asteroids Work


NEAR Lands on Eros
The path of NEAR's descent from orbit
The path of NEAR's descent from orbit
Photo courtesy NASA/JHUAPL

After a year orbiting Eros, NEAR was about out of fuel. It was only designed to orbit the asteroid and eventually crash onto the surface. Because all of its scientific objectives had been accomplished, NEAR's scientists decided to try to land the spacecraft rather than let it crash (because NEAR was never designed to land, it was not equipped with landing legs). The landing procedure would allow scientists to test complex maneuvers for a spacecraft, as well as get close-up pictures of the surface. These pictures would allow scientists to see objects as small as 4 inches (10 cm) in diameter.

Scientists ordered NEAR to slow from its circular orbit and execute a series of braking turns as it approached the surface. The landing site was in the saddle-shaped middle of the asteroid.

NEAR's landing site (yellow)
NEAR's landing site (yellow)
Photo courtesy NASA/JHUAPL

NEAR approached the surface and sent back pictures of Eros taken from ranges of 1,650 feet (500 m) down to 396 feet (120 m).

The surface of Eros, from 3,795 feet (1,150 m)
The surface of Eros, from 3,795 feet (1,150 m)
Photo courtesy NASA/JHUAPL

 

NEAR's last picture of the surface of Eros, from 396 feet (120 m)
NEAR's last picture of the surface of Eros, from 396 feet (120 m)
Photo courtesy NASA/JHUAPL

The temperature on the asteroid varies from 212 degrees Fahrenheit (100 degrees Celsius) during the day to -238 F (-150 C) at night. The gravity is weak, with an escape velocity of a mere 22 mph (Earth's escape velocity is 25,000 mph), but it could hold NEAR, which survived the landing and could still radio information back to Earth.

For more information on asteroids and NEAR, see the links on the next page.


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