The NEAR mission

The NEAR mission team was mostly from the Johns Hopkins University Applied Physics Laboratory.

NASA began work on the Near-Earth Asteroid Rendezvous (NEAR) spacecraft in 1993 as part of its Discovery program of low-cost interplanetary exploration missions. NEAR left Earth on February 17, 1996. The spacecraft whizzed past the asteroid 253 Mathilde at a distance of 753 miles (June 27, 1997), then flew past Earth (January 22-23, 1998) to bend its course toward its primary goal, asteroid 433 Eros. On December 20, 1998, NEAR suffered a malfunction which caused its computer to shut down its engine, so it missed its planned Eros rendezvous. Controllers quickly redesigned the mission. NEAR collected data as it flew past Eros (December 23, 1998), then fired its engine to ensure that it would reach Eros in February 2000, after completing one orbit around the Sun. On February 14, 2000, NEAR fired its engine and entered Eros orbit. The spacecraft completed its primary exploration mission in January 2001. By the time it landed on Eros (February 12, 2001), NEAR had traveled some 2 billion miles. The entire mission cost only $225 million.

NEAR was a small interplanetary spacecraft, with a total weight of only 1775 pounds. Of this, 717 pounds was propellant for its rocket engine and 124 pounds was scientific instrumentation. Instruments included a Multispectral Imager for taking pictures of the surface, Near-Infrared and X-Ray/Gamma-Ray Spectrometers for determining rock composition, a Laser Rangefinder for precisely measuring Eros’ lumpy shape, and a Magnetometer for measuring any magnetic fields. The Multispectral Imager took its last picture of Eros from a height of only 394 feet, showing details as small as a half-inch wide. After landing on Eros, NEAR’s 1.5-meter-diameter radio antenna no longer pointed directly at Earth. This made sending pictures impossible; the X-Ray/Gamma-Ray Sepectormeter was, however, able to provide detailed compositional information on NEAR’s landing place.

Robinson described the landing of the NEAR spacecraft: “The landing was never part of the original mission, and the spacecraft was not designed to land anywhere. . . The intent was really just to get some very high-resolution pictures as we were descending to the surface. I think there was probably only one or two people who really believed the spacecraft would still operate once it landed because again, it wasn’t desgned to land — it was very fragile the way it was landing. . . We started getting pictures over the last 15 or 20 minutes, and they were the highest-resolution pictures taken from orbit of any body, except maybe CIA spy satellite images of Earth . . . We were just stunned by what we were seeing. . . As soon as we touched down, I heard this big uproar in the back of the room. . . indicating to us that we were still getting data from the spacecraft after it had set down. We didn’t get any more images. . . But the spacecraft was still alive and healthy. Apparently there was absolutely no damage whatsoever at all. So it had set down on the surface at about awalking pace.

Robinson continued, “It appeared that we actually landed on one of these interesting ponded deposits. That may have helped the spacecraft survive the impact because it was sort of like landing in a sandbox. The ground would give, as opposed to landing on a solid slab of rock.”

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