NEAR Credit - NASA

NEAR (Near Earth Asteroid Rendezvous) was the first spacecraft ever to orbit and then (improvisationally) land on an asteroid. The vehicle went into orbit around the asteroid 433 Eros and performed up-close observations for one year.

The NEAR mission was the first launch in NASA's Discovery Program. 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. However as it flew by the Earth on 23 January 1998, a problem caused an abort of the first encounter burn. The mission had to be rescoped for a later encounter, but NEAR successfully entered orbit around Eros on Valentine's Day 2000 and ended the mission by gently landing on its surface on 12 February 2001.

The primary scientific goals were to measure the asteroid' bulk properties (size, shape, volume, mass, gravity field, and spin state); surface properties (elemental and mineral composition, geology, morphology, and texture); and internal properties (mass distribution and magnetic field).

The spacecraft was 3-axis stabilized and used passive thermal control. Four deployed, non-articulating fixed solar panels provided 1600 watts at 1 AU. A fixed 1.5 m diameter high gain antenna provided X-band communications via the Deep Space Network with selectable data rates between 1 and 27 kbps. 1 Gbit solid state data storage was provided. The hydrazine propulsion system had one 100 lbf, four 5 lbf, and seven 1 lbf thrusters provided a total delta-V of 1425 m/s. Mission control was by JHU APL with navigation support from JPL.

The instrument payload totaled 55 kg and 48 watts and consisted of:

• MultiSpectral Imager (MSI) - a refractive telescope with passively cooled Si CCD array (244 x 537) that would 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. It had a 2.25 x 2.9 deg field of view, 10-16 meter resolution from 100 km altitude, was sensitive between 400 and 1100 nm.
• X-Ray/Gamma-Ray Spectrometer (XGRS) - contained two sensors (an X-ray fluorescence spectrometer and a gamma-ray spectrometer), XGRS was used to determining the surface/near-surface elemental composition of the asteroid.
• Near-Infrared Spectrograph (NIS) - a spectrometer covering 800-2700 nm, NIS was designed to map the mineralogical composition of Eros.
• Magnetometer - a three-axis fluxgate sensor that would be used to measure Eros' magnetic field. These measurements would help determine the internal composition of the asteroid.
• NEAR Laser Rangefinder (NLR) - an altimeter that used a solid-state pulsed laser to measure the distance between the spacecraft and the surface of the asteroid. It would be used to make would make accurate measurements of the asteroid's shape and detailed surface structure. The Nd-YAG laser operated at 1.064 mm wavelength, 6 meter resolution, 50 km range.
• Radio Science - used the satellite's telemetry system to map Eros' gravity field.

The $ 650 million original estimated cost in May 1992 was reduced to $ 210 million via massive project reformulation to fit within Discovery program low-cost guidelines. This included the Delta launch for $ 55 million plus $ 122 million for the satellite.

Design Life: 4 years. Typical orbit: Eros orbit. Length: 2.75 m (9.02 ft). Maximum Diameter: 1.70 m (5.50 ft). Mass: 818 kg (1,803 lb). Associated Launch Vehicle: Delta 7000.

• 1996 February 17 - NEAR - Program: Discovery. Launch Site: Cape Canaveral. Launch Vehicle: Delta 7000. Mass: 818 kg (1,803 lb).

  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. However as it flew by the Earth on 23 January 1998, a problem caused an abort of the first encounter burn. The mission had to be rescoped for a later encounter but successfully entered orbit around Eros on Valentine's Day 2000 and ended the mission by gently landing on its surface on 12 February 2001.

• 1997 June 27 - NEAR, Asteroid Mathilde Flyby -

  Prior to its first flyby of the Earth on the way to Eros, NEAR flew within 1200 km of the C-class asteroid Mathilde.

• 2000 February 14 - NEAR, Asteroid Eros Orbit Insertion -

  NEAR finally entered orbit around Eros on Valentine's Day, 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 02:00 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.

• 2001 February 12 - NEAR, Asteroid Eros Landing -

  Periapsis of the orbit was as low as 24 km above the surface of the asteroid during its final days. At the end of its mission, NEAR touched down on the surface of Eros at 20:01:52 GMT on 12 February 2001. The spacecraft obtained 69 high-resolution images before touchdown, the final image showing an area 6 meters across. NEAR apparently came to rest with the camera and gamma-ray spectrometer pointing towards the ground and the solar panels and low gain antenna pointing generally towards the Earth and Sun. NEAR was not designed as a lander, but survived the low-velocity, low-gravity impact, a signal continued after the "landing" using the omni-directional low-gain antenna as a beacon.

• National Space Science Center Planetary Page, As of 19 February 1999.. Accessed at: http://nssdc.gsfc.nasa.gov/planetary/planetary_home.html.

• McDowell, Jonathan, Jonathan's Space Report (Internet Newsletter), Harvard University, Weekly, 1989 to Present. Essential internet newsletter recording worldwide weekly space events. Accessed at: http://www.planet4589.org/jsr.html.

• JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Accessed at: http://msl.jpl.nasa.gov/home.html.