Encounter Ambassador
The Ambassador is a large derelict ship which can spawn if the "Random Encounters" option is enabled in your world. It can be found by following the "SPRT MAYDAY" signal, which flashes on the player's HUD for 1s every minute, from a distance of ~25 km.
Engineers should aproach with some caution, as there are a few still active battery-powered interior turrets mounted on the ships hull.
Contents
It contains a broken Cryo Chamber, a mix of hydrogen thrusters and ion thrusters, a reactor with 10 kg of Uranium. As this ship is in a really bad state, it does not contain any notable cargo, only components from salvaging the wreck (steel plates, construction components, and a few metal grids). It is possible to restore the ship, however it would be a real challenge in survival mode.
The Original Ship
The original ship (Steam) was part of the first campaign in the game. A refitted version of it can be found on Steam by Aragath.