Robotic Missions in Sun-Earth Space - Nasa's Discovery Program
near asteroid spacecraft orbit
The Discovery program allows scientists to conduct small space investigations that complement NASA's larger and more expensive interplanetary missions. Each Discovery mission must have a fast development time (less than thirty-six months) and relatively low cost (less than $299 million). NASA calls it the "faster, better, cheaper" approach to space science. The program focuses on specific research objectives related to planets, moons, comets, and asteroids.
NEAR (Near Earth Asteroid Rendezvous) was the first mission under the Discovery program. On February 17, 1996, NEAR was launched into space to meet up with the asteroid 433 Eros. Asteroids are small celestial bodies that orbit larger ones. Most of the asteroids in the solar system are found in a massive asteroid belt that circles around the Sun between the orbits of Mars and Jupiter. 433 Eros is twenty-one miles long and has an elliptical orbit that carries it outside the Martian orbit and then in close to Earth orbit. On February 12, 2001, the NEAR spacecraft softly touched down on the asteroid. It was the first time in history that a spacecraft had landed on an asteroid. When it happened, 433 Eros was 196 million miles from Earth.
NEAR orbited 433 Eros for nearly a year before landing and returned dozens of high-resolution photographs of the asteroid. The spacecraft was built by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, which also managed the mission for NASA. Before it landed the spacecraft was renamed NEAR Shoemaker in honor of the late geologist Dr. Eugene M. Shoemaker. The first Discovery mission was considered an overwhelming success.
There are ten other missions in the Discovery program, as shown in Figure 6.2. Two of them ended during the late 1990s or early 2000s. As of March 2004 the others are ongoing or still in development.