An instrument aboard the Huygens probe carried by the Cassini spacecraft, launched in 1997 and arriving at Saturn's moon Titan in July 2004. HASI consists of several sensors to measure the physical and electrical make-up of the atmosphere. These include pressure and temperature sensors as well as accelerometers which can determine atmospheric density and wind gusts, or even wave motions on a liquid surface. There is also a permittivity and electromagnetic-wave analyser to measure the electron and ion conductivities of the atmosphere and Titan's surface.