|NEAR - |
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The NEAR mission was the first launch in NASA's Discovery Program, and was to be the first spacecraft ever to orbit an asteroid. The vehicle was intended to rendezvous with the asteroid 433 Eros and perform up-close observations for about one year. The primary scientific goals were to measure the asteroid's: (1) bulk properties (size, shape, volume, mass, gravity field, and spin state); (2) surface properties (elemental and mineral composition, geology, morphology, and texture); and (3) internal properties (mass distribution and magnetic field).
Spacecraft: 3-axis stabilized.4 deployed, non-articulating fixed solar panels provide 1600 watts at 1 AU. Fixed 1.5 m diameter high gain antenna. X-band communications using via DSN with selectable data rates between 1 and 27 kbps. Passive thermal control.1 Gbit solid state data storage. Hydrazine propulsion system with one 100 lbf, four 5 lbf, and seven 1 lbf thrusters provide a total delta-V of 1425 m/s. Mission control provided by JHU APL with navigation support from JPL.
Payload: The instrument payload totals 55 kg and 48 watts. MultiSpectral Imager (MSI) - a refractive telescope with passively cooled Si CCD array (244 x 537) that will determine the overall size, shape, and spin characteristics of the asteroid, map the morphology and composition of the surface, and search for satellites of Eros.2.25 x 2.9 deg FOV, 10-16 meter resolution from 100 km altitude, sensitive between 400 and 1100 nm. X-Ray/Gamma-Ray Spectrometer (XGRS) - containing two sensors (an X-ray fluorescence spectrometer and a gamma-ray spectrometer), XGRS will be used to determining the surface/near-surface elemental composition of the asteroid. Near-Infrared Spectrograph (NIS) - a spectrometer covering 800-2700 nm, NIS is designed to map the mineralogical composition of Eros. Magnetometer - a three-axis fluxgate sensor that will be used to measure Eros' magnetic field. These measurements will help determine the internal composition of the asteroid. NEAR Laser Rangefinder (NLR) - an altimeter that uses a solid-state pulsed laser to measure the distance between the spacecraft and the surface of the asteroid. It will be used to make will make accurate measurements of the asteroid's shape and detailed surface structure. Nd-YAG laser operating at 1.064 mm wavelength, 6 meter resolution, 50 km range. Radio Science - uses the satellite's telemetry system to map Eros' gravity field.
$ 650 million original estimated cost in May 1992 reduced to $ 210 million. This includes the Delta launch for $ 55 million plus $ 122 million for the satellite.
Design Life: 4 years. Total Length: 2.8 m. Maximum Diameter: 1.7 m. Total Mass: 818 kg.
Near Earth Asteroid Rendezvous (NEAR) mission was the first of NASA's Discovery missions, a series of small-scale spacecraft designed to proceed from development to flight in under three years for a cost of less than $150 million. The spacecraft's mission was to rendezvous with and achieve orbit around the asteroid Eros in January, 1999, and study the asteroid for one year. Prior to its encounter with Eros NEAR flew within 1200 km of the C-class asteroid Mathilde on 27 June 1997. It then flew by the Earth on 23 January 1998. A problem caused an abort of the first encounter burn and the mission had to be rescoped for a later encounter. NEAR finally entered orbit around Eros on February 14, 2000. Orbit insertion was at 15:34 GMT into a 323 x 370 km initial orbit with a period of 27 days. The renamed NEAR-Shoemaker probe moved into a 100 x 200 km orbit around Eros on April 2 at 0200 GMT. NEAR returned spectacular detailed pictures of the surface over the next several months. Studies were made of the asteroid's size, shape, mass, magnetic field, composition, and surface and internal structure. Periapsis of the orbit would be as low as 24 km above the surface of the asteroid during the final days of the mission.