This artist's conception shows Titan's surface. Then, in January of 2005, at just 45 minutes before the spacecraft reaches the atmosphere of Titan, timers will wake up the Huygens probe. Its programming must then be smart enough to work automatically, as the distance from Earth is too great to provide signals and commands. During the probe's rapid descent onto Titan's surface, the robotic controls will then fire a pilot parachute to pull out the main parachute, and within a minute the probe will slow down from 20,000 km per hour (12,427 miles per hour) to just 300 km per hour (186.4 miles per hour). In order to survive the harsh conditions at Titan, the Huygens probe needed more advanced technologies than probes on other missions. Built like a shellfish, the probe has a hard surface and a rather delicate interior. The shell will act as a braking device as well as an advanced thermal shield, designed to protect the probe by the extreme heat generated by the probe's rush into Titan's atmosphere at about 6 kilometers per second (13,400 miles per hour). Temperatures upon descent will soar up to 1,700 degrees Celsius (3,000 degrees Fahrenheit), and could be reached in less than a minute. However, to ensure instruments' functionality, the tile thickness on the front shield of the probe is calculated to ensure that the structure will not exceed 150 degrees Celsius (302 Fahrenheit), which is below the melting temperature of lead. Therefore, tiles similar to those used to protect the Space Shuttle are used to cover the heat shield. They are made of a material known as AQ60, a low density "mat" of fibers. The rear side of the probe will reach much lower temperatures during the probe's descent - thus, a spray-on layer of a silicon-based foam called "Prosial" was used. The total mass of the probe's thermal protection system is more than 100 kilograms (220 pounds) - about one-third of the entire probe's mass. Huygens Decent Profile In addition, the parachute system onboard Huygens is designed to work in conjunction with the thermal protection system to ensure the probe will survive entry into Titan's atmosphere. The main parachute is nearly 9 meters (28 feet) in diameter and will deploy at an altitude of 170 kilometers (105 miles) above the surface. Thirty seconds after parachute deployment, the probe's heat shield system will also be deployed, significantly lightening the load. The bulk of the data will be captured during the probe's descent into Titan's murky atmosphere. The descent is expected to last between two and two and half hours. The data acquired by the six instruments on board of the probe will be transmitted to the Cassini orbiter, and then subsequently back to Earth. << Previous

Titan Facts Distance from Saturn: 1,226,000 kilometers Responsible Agencies: ESA: The Huygens Probe NASA: The Cassini Orbiter Period of Orbit ( A Day on Titan): 15.95 Days Mean Distance from the Sun: 120-150 minutes Diameter of Titan: 5150 kilometers Science Payload: 6 instruments, 48 kg Diameter including Upper Atmosphere 5550 kilometers Diameter (shield): 2.7 meters Mass: 1/45 of Earth's mass Deployment toward Titan's Atmosphere: December, 2004 Arrival at Titan: January, 2005 DDensity Compared to Water: 1.881 Surface Temperature: -180 degrees Celsius, (+94 Kelvin) Operations on Surface of Titan: 3-30 minutes Atmospheric Pressure at Surface: 1.5 times Earth's