The Huygens Probe will be delivered to Titan, Saturn's largest satellite, by the Cassini Orbiter in 2004. After an interplanetary journey of 6.7 years - during which Huygens will be dormant except for health checks every six months - its aeroshell will decelerate it in less than three minutes from an entry speed of 6 km s^-1 to 400 m s^-1 (Mach 1.5) at about 160 km altitude. From then on, a pre-programmed sequence will trigger parachute deployment and heatshield ejection. The main scientific mission can then begin, lasting for the whole 2 - 2.5 hour descent.

Built by an industrial consortium led by Aerospatiale, the Probe System comprises two principal elements:

• the 318 kg Huygens Probe, which enters Titan's atmosphere after separating from the Saturn Orbiter
• the 30 kg Probe Support Equipment (PSE), which remains attached to the Orbiter after Probe separation

The Probe itself consists of the Entry Assembly (ENA) cocooning the Descent Module (DM). The ENA provides Orbiter attachment, umbilical separation and ejection, cruise and entry thermal protection, and entry deceleration control. It is jettisoned after entry, releasing the Descent Module.

The DM comprises an aluminium shell and inner structure containing all the experiments and Probe support subsystems, including the parachute descent and spin control devices.

The PSE consists of:

• four electronic boxes aboard the Orbiter: two Probe Support Avionics (PSA), a Receiver Front End (RFE) and a Receiver Ultra Stable Oscillator (RUSO)
• the Spin Eject Device (SED)
• the harness (including the umbilical connector) providing power and RF and data links between the PSA, Probe and Orbiter.

Mechanical & Thermal Subsystems