From the introduction:
This is the Space Era, where humanity has finally started expanding into space with colonies. With the arrival of Meteor 3 in 179, containing alien technologies referred to as Extra Over Technology, technology has advanced significantly. This came with a price however, as the scientist Dr. Bian Zoldark, head of the Extra Over Technology Institute, discovered that the aliens who owned this technology, codenamed by the Earth Federation as the Aerogaters, would come to invade Earth. As a result, the Earth Federation began developing robots, known as Personal Troopers, as preparation for this event. Other companies also began developing PTs, alongside more massive and powerful robots titled simply as Super Robots.