What launch vehicle sent Cassini-Huygens toward Saturn in 1997?

Cassini–Huygens was launched toward Saturn aboard a Titan IVB/Centaur on October 15, 1997.

The vehicle was a U.S. Air Force Titan IVB, a powerful heavy-lift rocket, topped by a liquid-hydrogen-and-liquid-oxygen Centaur upper stage. The launch took place from Space Launch Complex 40 at Cape Canaveral, Florida. The Centaur supplied the final push that sent the spacecraft onto its interplanetary trajectory.

Cassini was not aimed directly at Saturn by a single straight rocket burn. Its voyage used gravity assists from Venus twice, Earth, and Jupiter to build speed efficiently. After nearly seven years in transit, it entered orbit around Saturn on July 1, 2004.

The answer is sometimes shortened to “Titan IV-B,” but “Titan IVB/Centaur” is the more complete launch-vehicle designation. Ariane 5, Delta II, and Atlas V were not used for this mission.