Cassini-Huygens is the name of a joint N.A.S.A., european space agency and the Italian space agency, Agenzia Spaziale Italiana (ASI) space craft that was sent into space to travel to Saturn. It was launched on the 15th October 1997 on a near seven year journey to Saturn which it arrived on 1st October 2004. It didn't go directly to the planet, it went first to Venus which would give it a speed momentum to help it on its way. Its primary mission length was for four years to hopefully answer a few questions about the planet and its moons. The primary missions are 2:-
Huygens Primary Objectives
Determine the abundance of the atmospheric constituents, including noble gases, establish isotope ratios for abundant elements, and constrain scenarios of formation and evolution of Titan and its atmosphere;
Observe the vertical and horizontal distribution of trace gases, search for more complex organic molecules, investigate the energy sources for atmospheric chemistry, model photo-chemistry of the stratosphere, study the formation and the composition of aerosols;
Measure the winds and global temperatures, investigate cloud physics, general circulation and seasonal effects in Titan's atmosphere, search for lightning discharges;
Determine the physical state, topography and composition of the surface and infer Titan's internal structure;
Investigate the upper atmosphere, its ionisation, and its role as a source of neutral and ionised material for Saturn's magnetosphere.
Determine the vertical structure of the atmosphere, in particular, how its composition, cloud properties, density, and temperature vary with height;
Understand the horizontal motions of the atmosphere: its waves, eddies, and storms -- where they are located and how they form, grow, evolve, and dissipate;
Determine the deep structure of the atmosphere, how it rotates, and how it relates to the upper atmosphere;
Study how the atmosphere varies with time, both on short (daily) and long (seasonal) time scales;
Investigate the relationship between the ionosphere, the magnetic field, and the plasma environment;
Investigate the sources of lightning.
Ring science objectives:
Map the composition and size distribution of ring material;
Study the configuration of the rings and the dynamic processes responsible for their structure;
Investigate the relationships between the rings and the embedded moons;
Search for new ring-embedded moons;
Study the interaction between the rings and Saturn's magnetosphere, ionosphere, and atmosphere.
Icy Satellite science objectives:
Map their surface geology and composition and determine their geologic histories;
Determine the physical processes responsible for the surface and subsurface structure;
Determine their bulk compositions and internal structure;
Investigate their interactions with Saturn's magnetosphere and ring system.
Determine the global configuration and dynamics of hot plasma in the magnetosphere of Saturn through energetic neutral particle imaging of ring current, radiation belts, and neutral clouds;
Study the sources of plasmas and energetic ions through in situ measurements of energetic ion composition, spectra, charge state, and angular distributions;
Search for, monitor, and analyze magnetospheric substorm-like activity at Saturn;
Use imaging and composition studies to determine the magnetosphere- satellite interactions at Saturn, and understand the formation of clouds of neutral hydrogen, nitrogen, and water products (such as protons, oxygen atoms or hydroxyl radicals);
Study how satellite surfaces and atmospheres are modified due to plasma and radiation bombardment;
Study Titan's cometary interaction with Saturn's magnetosphere (and the solar wind) via high-resolution imaging and in situ ion and electron measurements;
Measure the high energy (Ee > 1 MeV, Ep 15 MeV) particle component in the inner (L < 5 RS) magnetosphere to assess cosmic ray albedo neutron decay (CRAND) source characteristics;
Investigate the absorption of energetic ions and electrons by the satellites and rings in order to determine particle losses and diffusion processes within the magnetosphere;
Study magnetosphere-ionosphere coupling through remote sensing studies of the aurora and in situ measurements of precipitating energetic ions and electrons
After the four years finished, it would move onto its secondary mission known as the Equinox missions then the Solstice missions after that. The Solstice and Equinox missions are on the page linked above. The picture below is an artists impression of the craft in orbit round Saturn. It is one of the heaviest space crafts ever launched into space.
The craft's contains a dash which is to indicate that the craft is actually two crafts in one. One part, the Cassini is the craft and the Huygens is a probe that was sent into the orbit of Titan which had an atmosphere which astronomers wanted to know more about. The Huygens probe was released from its mother craft on 25th December 2004 (Christmas Day) and on the 14th January it entered the atmosphere of the moon.
Cassini is named after Giovanni Cassini who discovered both gaps between the rings of the planet but also some of its moons. Huygens is named after Dutch astronomer Christiaan Huygens who discovered Saturn's largest moon and the one it would be visiting. Huygens was built by the Europeans whilst the craft Cassini was built by the Americans.
One of the interesting discoveries was made on 3rd April 2014, that there is an underground ocean of water on Enceladus, one of the Saturnian moons. The revelation also increases the prospect that there could be micro-organisms deep below. 1.
The primary resources for the mission can be found at N.A.S.A. and E.S.A.