Regia Solis was a satellite used for the reflection of solar rays onto Terragrigia. The word "Solis" was a portmonteau of "Solar Integrated System.
The Regia Solis was used to concentrate solar rays to power the solar panels powering the Terragrigia city. The satellite was carefully controlled so it won't radiate too much rays from the sun.
During the Terragrigia Panic of 2004, the satellite was used by the Federal Bioterrorism Commission (FBC) to reflect the maximum amount of rays directly at the city, subliming much of the city's support structure, causing a total collapse. The following year, the FBC again tried to perform the action against a biohazard; this time the Queen Zenobia. With BSAA agents Jill Valentine and Parker Luciani still onboard and unable to get to safety, they proceeded to use one of Il Veltro's UAVs to confuse the satellite's targeting system, thereby saving the ship from immediate destruction.
It is unknown if the satellite is still left drifting in the outer space, or is controlled by the BSAA after the FBC was transferred following Morgan Lansdale's arrest.