  
Overview and Objectives: The Cassini Mission
The Launch
The current development plan calls for the Cassini/Huygens spacecraft to be launched in October 1997 by a Titan IV/Centaur rocket from Cape Kennedy. Weighing more than five tons at launch, the spacecraft is too heavy to be injected directly into a Saturn-approach trajectory and requires several planetary boosts.
The interplanetary trajectory includes gravity assists from Venus (in April 1998 and June 1999), Earth (in August 1999), and Jupiter (in December 2000). This launch opportunity makes it possible to reach Saturn in about seven years. Other launch opportunities (degraded because they do not include a Jupiter flyby) exist in December 1997, and in 1998 and 1999, but are less desirable both in terms of launch performance and scientific returns.
Arrival at Saturn
Arrival at Saturn of the Cassini/Huygens spacecraft is planned to take place in June 2004. The probe is to be released from the Saturn Orbiter during the initial orbit around Saturn, nominally 22 days before Titan encounter. Shortly after probe release, the Orbiter will perform a deflection maneuver to set up the radio communication geometry between the probe and itself during the probe descent phase. This maneuver will also set up the initial conditions for the satellite tour after completion of the probe mission. Huygens' entry into the atmosphere of Titan is planned for November 27, 2004.
The Orbiter will act as a relay station during the Huygens Probe mission. During the probe mission, the Orbiter will point its high-gain antenna (HGA) at the probe. The Huygens Probe data will be received via the HGA. The Saturn orbiter's high-gain antenna is the crucial link between the Orbiter, Huygens and Earth. Its development is the result of a major contribution by the Italian Space Agency under a bilateral NASA/ASI agreement.
With the HGA pointed at the probe, there will not be a real-time link between the Orbiter and Earth during this phase of the mission.
The probe data will be stored onboard the Orbiter in two solid-state recorders for later transmission to the Earth after the probe mission. A Titan encounter scenario after the probe mission involves remote sensing observations of Titan's atmosphere near the probe entry site from the Saturn Orbiter. Simultaneous global remote-sensing observations from the Orbiter and local in-situ observations from the probe will make it possible to place the Huygens observations in their global context.
Four-Year Tour
After the end of the probe mission phase, the Saturn Orbiter will start its four-year tour of the Saturnian systems, the so-called satellite tour. This consists of more than 40 Saturn-centered orbits, connected by Titan gravity-assist flybys or propulsive maneuvers. The size of the orbits, their orientation to the Sun/Saturn line, and their inclination to Saturn's equator are dictated by the various scientific requirements, which include: Titan ground-track coverage, icy-satellite flybys, Saturn, Titan or ring occultation, magnetosphere coverage, orbit inclinations and ring-phase crossings. Also a major target for the Saturn Orbiter is Titan, which will be observed during each Titan flyby.
Scientific Objectives
Saturn
--Thermal structure, cloud properties, and composition of the atmosphere--Atmospheric dynamics and general circulation of the atmosphere
Rings
--Configuration and composition of the ring system, dynamic processes in the rings, interrelation of the rings and satellites.
Titan
--Thermal structure and composition of the atmosphere, with special emphasis on physiochemical processes driving prebiotic chemistry. Nature and location of aerosols and clouds, search for lightning.--Atmospheric dynamics and general circulation of the atmosphere.--Investigation of topography, state history, and composition of the surface and the nature of the atmosphere -- surface interactions.--Interaction of Titan with the solar wind.
Satellites
--Surface properties and bulk composition of satellites to determine origins, resources of internal activity, ad processes responsible for surface modification. Comparative studies within the satellite system.
Magnetosphere
--Configuration and generation of the nearly axially symmetric magnetic field and its relation to the modulation of Saturn Kilometric Radiation (SKR).--Current systems composition, sources and sinks of thermal and energetic charged particles, and dynamics of the magnetosphere of Saturn and its interactions with the solar wind, the satellites and the rings.
Targets of Opportunity
--Definition of asteroid and/or comet properties from flyby with existing payload en route to Saturn.--Post-impact studies of Titan's surface and atmosphere by the probe.
For the latest developments and news on the mission visit:
NASA - National Aeronautics and Space Administration
ESA - European Space Agency
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