There is only one file type that uses the .UBOX extension:
Universe Sandbox Data File
Saved data file created by Universe Sandbox, an interactive astronomy application; saves a simulation through space and can include planets, stars, moons, man-made objects, orbital motions, and other simulated data; used for sharing and playing back universe explorations.
UBOX files are .ZIP files renamed with the ".ubox" extension. The compressed file contains XML data that specifies the parameters of the simulation.
Updated: April 11, 2012