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You sit to watch the evening news and are alarmed by the opening story: “Asteroid Destined to Cross Earth’s Path.” You wonder what this could mean. Will it hit the Earth? You have heard in the past that the extinction of the dinosaurs sixty-five million years ago might have been linked to a devastating, asteroid impact near the Yucatan Peninsula in Mexico. You begin to wonder about these rocky fragments of space rubble. “What do they tell us about our past and how can they affect our future?
- Asteroids hold clues to the origin and evolution of our solar system and Earth. NASA has planned a number of missions to study asteroids. Its Near Earth Asteroid Rendezvous (NEAR) spacecraft is the first mission dedicated specifically to the study of an asteroid. NEAR was launched in February of 1996 and will reach its destination, the asteroid 433 Eros, in January of 1999. The mission’s investigations of Eros will directly address some of the mysteries of asteroids, their relationship to comets and meteorites, and ultimately their place in the history of our solar system.
NEAR is equipped with six instruments that will begin our first close look at an asteroid.
- The Multispectral Imager will take numerous images of 433 Eros. The
 objectives of the imager consist of mapping asteroid morphology, geologic and impact history, crater distribution, surface composition, and the determination of the size, shape and spin characteristics of 433 Eros. These objectives were achieved by NEAR during the June 1997 flyby encounter of the asteroid 253 Mathilde.
- The Laser Rangefinder is used as a laser altimeter to determine the size, bulk shape, and surface topography of the asteroid. The laser altimeter operates by transmitting a laser pulse to the surface of the asteroid; receiving the reflection of the pulse and recording the time of a round trip will provide altitude data used in mapping the surface of the asteroid.
The X-ray/Gamma-ray Spectrometer and the Near Infrared Spectrograph will be used to determine the composition of 433 Eros. By understanding the asteroid’s elemental and mineral composition, a possible link can be made between meteorites and asteroids. This link is significant in understanding what the components of our solar system were at its birth.
The Radio Science Equipment will use the telemetry system of the spacecraft to determine the mass and gravity variations of 433 Eros. Combining data from the imager and rangefinder, estimations can be made of the density of the asteroid. Determining density will provide a valuable clue as to whether the asteroid is solid rock or has internal variances.
The Near Magnetometer will be used to measure a possible magnetic field of 433 Eros. If a magnetic field is detected, this would then be a strong constraint on the composition, internal structure, and the thermal and collisional history of the asteroid.
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