NEAR Shoemaker: The First spacecraft to orbit an Asteroid

 

Artist's illustration of NEAR Shoemaker at Eros. Credit: NASA

Launch Date: February 17, 1996

Launch Site: Space Launch Complex 17B at Cape Canaveral Florida, United States

Launch Vehicle: Delta II (7925-9 Variant no. D232)

Mission Type: Orbiter (And unplanned landing)

Targets: Eros & Mathilde

Dimensions: Unavailable

Mass: 805 Kilograms

You can build your own NEAR Shoemaker spacecraft out of LEGO here.

The goal of the Near Earth Asteroid Rendezvous (NEAR) mission was to orbit around a near Earth asteroid and study it. The target was Eros, the first near Earth asteroid discovered.

The Mission

NEAR launched on a Delta II rocket on February 17, 1996. The next year on June 27, 1997, NEAR made a flyby of the asteroid Mathilde, with a closest approach of 1200 kilometres. Mathilde is a slow-rotating main-belt asteroid rich in carbon, making it very dark. You may be wondering what NEAR is doing all the way out in the asteroid belt if its trying to orbit a near Earth asteroid. This is because Eros is on an elliptical orbit. During one part of its orbit, it's relatively close to Earth, but during most of its orbit it lies further out past the orbit of Mars.

NEAR made a gravity assist of Earth on January 23, 1998. On December 20, 1998, NEAR aborted an important engine burn, and the mission trajectory had to be modified. This meant that NEAR flew by Eros on December 23, but didn't slow down enough to enter orbit. Instead the spacecraft would have to complete another loop around the Sun, and try again over a year later.

Image of Eros from NEAR. Credit: NASA

On February 14, 2000, NEAR finally made it into orbit around Eros. This was the first time a spacecraft had gone into orbit around an asteroid. On March 14, 2000, NEAR had "Shoemaker" added on to its name, to honor Eugene Shoemaker (1928-1997), a famous geologist who made contributions to solar system research. NEAR Shoemaker made many changes to its orbit over the following months to allow different types of scientific observations to be made. Each time NEAR Shoemaker modified its orbit, it made it smaller, getting closer to the asteroid.

Near (haha, near) the end of the mission, NEAR Shoemaker lowered its orbit for a landing on Eros. The mission was never intended to land on the asteroid, but at this point NEAR Shoemaker was an old spacecraft near (did it again) the end of its mission. The options were to either leave it in orbit, or land it on the surface for extra science potential.

Credit: NASA/JPL/JHUAPL

Credit: NASA/JPL/JHUAPL

Credit: NASA/JPL/JHUAPL

NEAR Shoemaker softly touched down at a rate of 1.78 meters per second on February 12, 2001. NASA likes to proudly point out that this is the first time that an American spacecraft was the first to land on something (the Soviets landed on the Moon, Mars, and Venus before the United States). While it wasn't expected to survive the landing, the spacecraft continued to operate for two weeks on the surface of Eros. As Eros moved away from the Sun in its orbit, NEAR Shoemaker started to freeze, and last contact was made February 28, 2001. NASA tried to contact the spacecraft when Eros approached th Sun again on its orbit in December of 2002, but no contact was made.

The Targets

NEAR Shoemaker image of Eros. Credit: NASA/JPL/JHUAPL

• Date Discovered: August 13, 1898
• Designation: 433 Eros (A898 PA)
• Class: Amor [NEO]
• Radius: 8.42 Kilometres
• Rotational Period: 5.27 Hours
• Orbital Period: 643.11 Days (1.76 Years)

NEAR image of Mathilde. Credit: NASA/JPL

• Date Discovered: November 12, 1885
• Designation: 1253 Mathilde (A885 VA)
• Class: Main-Belt Asteroid
• Radius: 26.4 Kilometres
• Rotational Period: 417.7 Hours
• Orbital Period: 1574.81 Days (4.31 Years)