From the publishers web site:

Expansion to the space exploration game HIGH FRONTIER, adds a fifth player (the UN), and adds an extension to the map that includes Jupiter, Saturn, main belt comets, centaurs, and Trojan asteroids. The expanded rules include slingshots, radiation belts, piracy, combat, solar flares, and space politics and governments. There are also 48 new patent cards, representing reactors, generators, and radiators. The expanded scenarios include alien invasions, the solitaire game, and two short games.

Comment: There are in fact 24 new cards, giving 48 additional patents.

expands High Frontier