243 Ida in the context of "Galileo (spacecraft)"

A flyby (/ˈflaɪbaɪ/) is a spaceflight operation in which a spacecraft passes in proximity to another body, usually a target of its space exploration mission and/or a source of a gravity assist (also called swing-by) to impel it towards another target. Spacecraft which are specifically designed for this purpose are known as flyby spacecraft, although the term has also been used in regard to asteroid flybys of Earth for example. Important parameters are the time and distance of closest approach.

158 Koronis is a main-belt asteroid that was discovered by Russian astronomer Viktor Knorre on January 4, 1876, from the Berlin observatory. It was the first of his four asteroid discoveries. The meaning of the asteroid name is uncertain, but it may come from Coronis the mother of Asclepius from Greek mythology. Alternatively, it may come from Coronis, a nymph of the Hyades sisterhood. The Koronis family is named after this asteroid.

From its spectrum this is classified as an S-type asteroid, indicating a stony composition. Photometric observations show a synodic rotation period of 14.206 ± 0.002 hours with a brightness variation of 0.28–0.43 in magnitude. A subsequent study at the Altimira Observatory during 2010 was in agreement with this estimate, yielding a rotation period of 14.208 ± 0.040 hours. Based on a model constructed from the lightcurve, the shape of Koronis resembles that of 243 Ida, an asteroid in the same family, although it is a bit larger. [1]

A binary asteroid is a system of two asteroids orbiting their common barycenter. The binary nature of 243 Ida was discovered when the Galileo spacecraft flew by the asteroid in 1993. Since then numerous binary asteroids and several triple asteroids have been detected.

The mass ratio of the two components – called the "primary" and "secondary" of a binary system – is an important characteristic. Most binary asteroids have a large mass ratio, i.e. a relatively small satellite in orbit around the main component. Systems with one or more small moons – also called "companions" or simply "satellites" – include 87 Sylvia, 107 Camilla and 45 Eugenia (all triples), 121 Hermione, 130 Elektra (a quadruple), 22 Kalliope, 283 Emma, 379 Huenna, 243 Ida and 4337 Arecibo (in order of decreasing primary size). Some binary systems have a mass ratio near unity, i.e., two components of similar mass. They include 90 Antiope, 2006 VW₁₃₉, 2017 YE5 and 69230 Hermes, with average component diameters of 86, 1.8, 0.9 and 0.8 km, respectively.

Johann Palisa (6 December 1848 – 2 May 1925) was an Austrian astronomer, born in Troppau, Austrian Silesia, now Czech Republic. He was a prolific discoverer of asteroids, discovering 122 in all, from 136 Austria in 1874 to 1073 Gellivara in 1923. Some of his notable discoveries include 153 Hilda, 216 Kleopatra, 243 Ida, 253 Mathilde, 324 Bamberga, and the near-Earth asteroid 719 Albert. Palisa made his discoveries without the aid of photography, and he remains the most successful visual (non-photographic) asteroid discoverer of all time. He was awarded the Valz Prize from the French Academy of Sciences in 1906. The asteroid 914 Palisana, discovered by Max Wolf in 1919, and the lunar crater Palisa were named in his honour.

Dactyl (/ˈdæktɪl/ DAK-til), formal designation (243) Ida I, is a small asteroid moon 1,200 by 1,400 by 1,600 m (3,900 by 4,600 by 5,200 ft), in size) that orbits 243 Ida, a main-belt asteroid. It was imaged by the Galileo spacecraft on August 28, 1993; Dactyl was discovered while examining the delayed image downloads from Galileo on February 17, 1994. It was provisionally designated S/1993 (243) 1. The satellite was named after the mythical creatures called dactyls, who, according to Greek mythology, lived on Mount Ida.