Elysium

Elysium is the planet that was the setting for Wrong Way Up until partway through the 5th week. It is placed right up against Perseii such that their gravity fields and atmospheres overlap, allowing vehicles to transition between them without space travel, usually by accident.
The mod for the planet was created by Steam user wolf4243, and can be found on the Steam Workshop here: https://steamcommunity.com/sharedfiles/filedetails/?id=2490230295