Captain's Yacht
The Sovereign Class captain's yacht was a large auxiliary craft which normally docked on the ventral side of the saucer section, opposite the bridge, and immediately below the saucer torpedo launcher. When connected to the Sovereign class, only the bottom side of the yacht was exposed to space; the top of the craft was concealed by the ship and the warp Nacelles were folded against the hull. Upon launch, the Yacht's Nacelles folded downward and the entire ship dropped away from the mothership.
It contained a cockpit (with dedication plaque), a small Transporter and cargo area, and a docking port which made a direct connection to the mothership. It was capable of atmospheric flight and landing on a planetary surface. It could also generate tachyon bursts. Only one pilot was needed to fly the craft.
In 2375, Captain Jean-Luc Picard and his senior staff took the vessel to the Ba'ku planet as part of a plan to prevent the forced relocation of the Ba'ku by the Son'a. The yacht carried several weapons and transport inhibitors to the surface, which were deployed by the crew in order to keep the Son'a from removing the Ba'ku from the planet. Later, Data used the Cousteau to create a diversion by firing tachyon bursts into Ru'afo's ship's shields, forcing him to reset his shield harmonics and allowing Worf to transport the bridge crew to the Federation holoship. Ru'afo was able to seriously damage the Cousteau before he was transported from his ship. (Star Trek: Insurrection)