Asteriod 253 Mathilde

[Relative Sizes of Asteroids] [Mathilde]

Asteroid 253 Mathilde was discovered on November 12, 1885, by Johann Palisa in Vienna, Austria. The name was suggested by V.A. Lebeuf, a staff member of the Paris Observatory who first computed an orbit for the new asteroid. The name is thought to honor the wife of astronomer Moritz Loewy, then the vice director of the Paris Observatory.

Although Mathilde's existence has been known for more than a century, it wasn't until 1995 that observations with ground-based telescopes first identified the asteroid as a C-type. The 1995 observations also revealed an unusually long rotation period: 418 hours, or approximately 17 days. Orbital period is 4.30 years. Perihelion is 1.94 AU (180 million miles/290 million kilometers). Mathilde's inclination is 6.7 degrees. Geometric albedo is 0.036.

On its way to Eros, on June 27, 1997, NEAR is scheduled to pass within 1,200 kilometers (750 miles) of 253 Mathilde. Data obtained by the Infrared Astronomy Satellite has established Mathilde's diameter at approximately 38 miles (61 kilometers). This is substantially larger than the diameters of either Gaspra (10 miles/16 kilometers) or Ida (20 miles/33 kilometers), which would make Mathilde the largest asteroid to be visited by a spacecraft. This encounter with 253 Mathilde would produce the first close-up images of a C-class asteroid. During the flyby NEAR will be able to obtain images comparable to those achieved by Galileo during its flybys of 951 Gaspra and 243 Ida. The primary instrument for the encounter will be the Multispectral Imager (MSI), but measurements of Mathilde's mass will also be made. The whole illuminated portion of the asteroid will be imaged in color before and after the closest approach. As the spacecraft recedes form Mathilde, a thorough search for satellites will be made with the imaging system.

Mathilde Facts

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Diameter: 61 km
Approximate mass: 200. x 10^15 kg
Rotation Period: 418. hrs
Orbital Period: 4.31 yrs
Spectral Class: C
Semimajor Axis: 2.645 AU
Perihelion Distance: 1.94 AU
Aphelion Distance: 3.35 AU
Orbital Eccentricity: 0.2663
Orbital Inclination: 6.7 deg
Geometric Albedo: 0.036
Images of Mathilde will be available on this page when they are released after the June, 1997 flyby.
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