Rosetta

The ESA Rosetta mission is designed to examine a cometary nucleus from close quarters as the comet approaches the Sun and then develops its tail. While clearly not a giant planet mission, understanding the composition and structure of these remnants of solar system formation is important for understanding the origin and evolution of the solar system, and the composition of all the planets.

Rosetta was launched on March 2, 2004 from French Guiana on an Ariane 5G launcher and weighed 2,970 kg (1,300 kg plus 1,670 kg of propellant) at launch. After an extended gravitationally assisted tour, Rosetta will begin its rendezvous maneuver

Figure 8.8. Artist's impression of the Rosetta spacecraft approaching its target comet. Courtesy of ESA.

with Comet 67P/Churyumov-Gerasimenko in May 2014 at a heliocentric distance of AU (during the comet's approach to the Sun) and will achieve its final close orbit with the comet by November 2014. At closest approach, the orbiter will be only 1 km above the nucleus. Active observations will be taken up until the nominal end of mission, which coincides with the perihelion passage of the comet in December 2015. The mission is named after the Rosetta Stone found by French soldiers in Egypt in 1799 and now in the British Museum in London. Inscribed on the stone is a declaration in three different languages—Greek, Egyptian Demotic, and Hieroglyphics— which were analyzed by both the English physicist Thomas Young, and the French egyptologist Jean Francois Champollion who in 1822 finally succeeded in decrypting the hieroglyphic system (Adkins and Adkins, 2000). The main structure of the Rosetta orbiter is a 2.8 x 2.1 x 2.0 m cube shown in Figure 8.8 and is powered by two solar panels each of which when fully extended has an area of 32m2 and total span of 32 m.

The Rosetta orbiter will be the first spacecraft ever to go into orbit around a comet nucleus and will be the first to observe the changes that occur in comet activity as the comet travels towards the inner solar system. The orbiter's scientific payload includes 11 experiments (listed in Table 8.1) and a small 90 kg lander, which will be the first spacecraft ever to make a soft landing on the surface of a comet nucleus and

Table 8.1. Rosetta instruments.

Instrument

Acronym

Purpose

Remote-sensing instruments

Optical, Spectroscopic, and Infrared Remote Imaging System

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