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FAQs

CASSINI-HUYGENS

When did the Cassini mission begin?
The contract was awarded, and building began, in 1990. Planning began in 1982, with advice from the National Academy of Sciences.

What is the full name of the mission?
The Cassini-Huygens Mission to Saturn and Titan. The full name of the spacecraft is Cassini-Huygens.

Why is the spacecraft called Cassini?
It's named after Italian-French astronomer Jean-Dominique Cassini (also known as Gian Domenico Cassini). He discovered four of Saturn's moons: Iapetus, Rhea, Tethys, and Dione. In 1675, he discovered the narrow gap, now known as the "Cassini Division", which splits Saturn's rings into two main parts.

What is the cost of Cassini?
The cost of the mission is $3.3 billion.

Who built Cassini?
The Cassini orbiter was built and is managed by NASA's Jet Propulsion Laboratory (JPL). The Huygens probe was built by the European Space Agency. Cassini's high-gain communication antenna was built by The Italian Space agency.

How much does the Cassini spacecraft weigh?
5,655 kg includes Huygens probe (12,467 pounds).

How big is Cassini?
Cassini is 6.8 meters (22.3 ft) tall. Its maximum diameter, the diameter of the high-gain antenna, is 4 meters (13.1 feet). It's about the size and weight of an empty 30-passenger school bus.

What is the configuration of the spacecraft?
The spacecraft consists of the Cassini orbiter and the Huygens probe. Cassini will orbit Saturn for four years, studying Saturn, it's atmosphere, the rings and moons. The Huygens probe, will descend, via parachute, to the surface of Titan to study its atmosphere and surface.

How many instruments are on board Cassini?
There are 12 instruments aboard Cassini, four of which, including UVIS, are optical remote-sensing instruments:   The Ultraviolet Imaging Spectrograph (UVIS); The Visible and Infrared Mapping Spectrometer (VIMS); the Composite Infrared Spectrometer (CIRS) and the Imaging Science Subsystem (ISS), which includes both narrow- and wide-angle cameras. Each of these optical instruments captures images with a telescope, the difference being in what part of the light spectrum it selects and what it does with the data. There are six additional instruments aboard the Huygens probe.

When was Cassini launched?
It was launched on October 15, 1997 from Kennedy Space Center in Florida.

When did it arrive at Saturn?
It entered Saturn's orbit on July 1, 2004 at 2:36 Coordinated Universal Time (UTC)--which would be June 30 at 8:36 p.m. (MDT).

How far did Cassini travel to get from Earth to Saturn?
Cassini traveled 3.5 billion kilometers (2.175 billion miles) on its way to Saturn.  

How long does it take for Cassini's data to get to Earth?
It takes about 1 hour and 20 minutes for the radio signals to reach us. The power of the transmitter is 20 watts. When received at the DSN antennas, the signal power is 10 to the -16th (0.0000000000000001) watts.

How many times will Cassini orbit Saturn?
At least 76 times.

What new information will we learn from Cassini ?
The objective of the mission is to study five main areas: Saturn's atmosphere and interior; the rings; the magnetic environment (magnetosphere); Titan; and the icy satellites. The Cassini orbiter instruments are capable of at least ten times the resolution and coverage of earlier data from missions like Voyager and Hubble. It will have the ability to study time variations in the Saturn system during the four-years it will orbit Saturn, instead of just snapshots taken during flybys of prior missions.

What happens to Cassini when the Saturn tour is over after four years?
The spacecraft will continue to orbit Saturn until it runs out of fuel, which could take many decades. There could be enough fuel and power for Cassini to take and relay data for a quite a while. However, budgetary limits will dictate how long after June 20, 2008 it will operate. When it runs out of fuel, it will spin up and break apart.

How does Cassini get its Power?
The power for the spacecraft, instruments, computers and transmitters is generated by three radioisotope thermoelectric generators (RTGs). An RTG consists of a source of heat and a system for converting that heat to electricity. The heat is generated by radioisotope fuel that becomes physically hot from its own decay.


UVIS

Who Built UVIS?
An international team led by principal investigator Larry Esposito of the Laboratory for Atmospheric and Space Physics (LASP), which is a research organization at the University of Colorado in Boulder, built UVIS.

How big is UVIS?
The UVIS instrument is 18.5" long x 9.2" wide x 11.8" tall and weighs 15.43 kg.

What is the cost of UVIS?
Funded by NASA, the UVIS instrument cost $12.5 million to build.

What will the UVIS instrument learn?
UVIS will measure ultraviolet light in the Saturnian system. Data from UVIS will provide information on the atmospheric composition and photochemistry of Saturn and Titan, and the nature and history of Saturn's rings. The UVIS science objectives include investigation of the chemistry, aerosols, clouds, and energy balance of the Titan and Saturn atmospheres; neutrals in the Saturn magnetosphere; the deuterium-to-hydrogen ratio for Titan and Saturn; icy satellite surface properties; and the structure and evolution of Saturn's rings.

What were the first results from UVIS?
UVIS discovered neutral oxygen atoms orbiting Saturn, that Saturn's rings become more icy further from the planet, and that Saturn's moon Phoebe is an object from the outer solar system with an icy surface.


SATURN

What is Saturn made of?
Saturn is about 75% hydrogen and 25% helium with traces of water, methane and ammonia. Saturn's interior consists of a rocky core, a liquid metallic hydrogen layer and a molecular hydrogen layer. Traces of various ices are also present. Saturn is the least dense of the planets and would float if you could find an ocean large enough to put it in.

What are Saturn's rings made of?
The rings are mostly water ice particles, with some rock mixed in. The particles range in size from grains of sand to the size of a house.

Why does Saturn have rings?
Other planets, like Jupiter, Neptune and Uranus have rings also, but Saturn's rings are more breathtaking. It's believed that Saturn's rings were formed when small moons were broken apart by collisions with meteoroids, comets, small asteroids, or other small moons that orbit around Saturn. Over time the gravitational pull of larger moons and of Saturn's equatorial bulge flattened the pieces into the thin disk we now see.

What is the atmosphere of Saturn and its moons like and could we breathe it?
Although the mostly hydrogen and helium gases in Saturn's atmosphere aren't poisonous to humans, they don't provide the oxygen we need to breathe. Titan is the only one of Saturn's moons that has an atmosphere. It consists mainly of nitrogen (like Earth's), however, it also doesn't have enough oxygen for humans to breathe.

What is the gravity like on Saturn?
Saturn's surface gravity is 107% of that of Earth at the cloud tops.

What is the temperature on Saturn?
The mean temperature on Saturn, at the cloud tops, is 88 K (-185° C; -290° F).

What color is Saturn?
Saturn's natural colors are muted yellows and browns with some whites and reds. Sometimes you will also see pictures that have been "color-enhanced". This method is used when the images have been taken in a wavelength of light humans can't see (like UVIS takes Ultraviolet data). We assign colors to the different the wavelengths so that we can see a picture that's understandable to us.

What is the length of a day and year on Saturn?
A day on Saturn is 10.2 Earth hours long (one rotation on it's axis). A year on Saturn is 29.46 Earth years long (one orbit around the Sun).

How many moons does Saturn have?
There are at least 34 moons orbiting Saturn and we always seem to be discovering more. Titan is the biggest moon and the only one with an atmosphere--which is thick with nitrogen. It's 5,150 kilometers in diameter and bigger than the planet Mercury, which is 4,878 km in diameter. Saturn's moons are usually named after characters in Greek and Roman mythology. Some of the names are (including the year they were discovered): Pan (1990), Atlas (1980), Prometheus (1980), Pandora (1980), Epimetheus (1980), Janus (1966), Mimas (1789), Enceladus (1789), Tethys (1684), Telesto (1980), Calypso (1980), Dione (1684), Helene (1980), Rhea (1672), Titan (1655), Hyperion (1848), Iapetus (1671), and Phoebe (1898). Other moons are known by plain letter and digits codes, such as S/2000 S4 and S/2000 S5.

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