Liberate Dust Sector.
You need to take down the EDF Control over dust and complete all the missions in dust.
EDF Control: Do certain guerrilla actions like raid and defend or go around taking down low EDF areas ( marked red on mini map not show on normal map.) Medium EDF controlled areas. ( Blue Hexagon on mini map and map.) and High EDF Controlled areas (have blue hexagon with arrow on top on mini map and map).