Huygens Descent Module

Spacecraft nº:

ESA spacecraft nº: 37

Launch data: Designation  A04759 / 97061 Launch date  15 Oct 1997 - 08:43 UT Launch site  CC, LC-40 Launch vehicle  Titan-4B/Centaur-T Mission  Venus-Flyby, Earth-Flyby, Titan lander Operator   Heliocentric orbit Perihelion / Aphelion   Incl. to ecliptic   ° Period   min

Spacecraft data: Prime contractor  Aerospatiale, Cannes, France. Platform  Cassini spacecraft Operator  ESA Mass at launch   kg Dry Mass   kg Basic shape   Dimension   Solar array   Stabilization   DC power

Description:

• The Huygens probe, supplied by the European Space Agency (ESA) and named after the 17th century Dutch astronomer who first discovered Titan, Christiaan Huygens, scrutinized the clouds, atmosphere, and surface of Saturn's moon Titan in its descent on January 14, 2005. It was designed to enter and brake in Titan's atmosphere and parachute a fully instrumented robotic laboratory down to the surface.
• The probe system consisted of the probe itself which descended to Titan, and the probe support equipment (PSE) which remained attached to the orbiting spacecraft. The PSE includes electronics that track the probe, recover the data gathered during its descent, and process and deliver the data to the orbiter that transmits it to Earth. The data was transmitted by a radio link between Huygens and Cassini provided by Probe Data Relay Subsystem (PDRS). As the probe's mission could not be telecommanded from Earth because of the great distance, it was automatically managed by the Command Data Management Subsystem (CDMS). The PDRS and CDMS were provided by the Italian Space Agency (ASI).

Mission details:

• The Huygens Titan lander separated from Cassini on Dec 25, 2004.
• Following its release from the Cassini mothership on 25 December 2004, Huygens reached Titan's outer atmosphere after 20 days and a 4 million kilometre cruise. The probe started its descent through Titan's hazy cloud layers from an altitude of about 1270 km on 14 Jan 2005 at 09:06 UT, and entered the atmosphere protected by its heat shield. During the following three minutes, Huygens had to decelerate from 18 000 to 1400 km per hour.
  By 09:10 UT the entry was complete and at about 160 km altitude the pilot parachute deployed, followed two seconds later by the aft cover and the main 8.3-meter diameter parachute. The probe's scientific instruments were exposed to Titan's atmosphere for the first time and Huygens started to transmit its radio signal to Cassini at 09:12 UTC (spacecraft event time). The Huygens radio signals also arrived on Earth, but 67 min later as a faint tone that was detectable by large radio telescopes. At around 09:10 UT the heat shield was jettisoned and the initial parachute descent began, ending at 09:25 UT when the main parachute was jettisoned (at about 120 km altitude) and a smaller 3.0-meter diameter stabilizer parachute took over. The DISR camera snapped remarkable images of an apparent coastline during the ensuing slower 2-hour descent to the surface. The Huygens radio signal was detected on Earth at about 11:20 CET by the 110-m Robert Byrd Green Bank Telescope in West Virginia. About 2 hours later, the probe's signal was picked-up by telescopes in Australia, which indicated that Huygens had landed and continued to transmit after landing. Cassini listened to Huygens for 4h 36 min and then transmitted the Huygens data to Earth via NASA's Deep Space Network once the Huygens mission was over. The first scientific data arrived at ESA's European Space Operation Centre (ESOC) in Darmstadt at 17:19 CET, having also taken 67 min to travel across space.
• Touchdown on the Titanian surface was at 11:38 UT, at latitude 11 S longitude 192W. Huygens continued to transmit signals till at least 14:48 UT when the spacecraft set as seen by the Parkes radio telescope, which received the last bits of data 67 minutes later.
• It was mankind's first successful attempt to land a probe on another world in the outer Solar System.

artist's impression of Huygens on Titan's surface