Find the third coordinate sphere is a mission in The Lost Frontier. After getting two coordinate spheres, Keira reveals they were masking the signal of a third sphere located at an old ship graveyard called Sector Zero, to which Jak promptly sets sail.
The first part of the mission, after entering the vortex, consists of a rather long and linear flight that involves dodging large space junk and ghost pirates, as well as shooting down aerial mines and said pirates' planes. Straight firepower and maneuverability is useful here, both to shoot down anything in your way and to dodge anything you cannot shoot down. You will automatically exit the vortex once you pick up the sphere at the bottom, after which the mission takes an unexpected turn.
With the ACS Behemoth actively attacking the Phantom Blade, your first order of business will be to destroy the dark eco-charged debris that float toward it. After the floating bombs you must attack the Behemoth by destroying power nodes on the ship's hull, a difficult task as the ship is heavily guarded by automated turrets. Consider picking them off one by one by using the size of the ship to your advantage, by using its bulk to avoid being targeted by all the turrets at once. After the three power nodes it will once again being infusing ship wrecks with dark eco, so proceed to take them down.
The Behemoth will now launch a pair of Aeropan bombers, which you will want to shoot down as they will attack the defenseless pirate galleon. After that, concentrate on taking out the targets in the hangar, after which the mission objective shifts to destroying more power nodes on the exterior of the ship. Aeropan fighter squadrons will also appear now, so proceed to take them down as needed. Skyheed will now release a new weapon, which simultaneously prevents you from attacking the ship.
Eight laser drones will now fly above the Behemoth, blasting the Blade with powerful eco lasers from time to time. They will also focus at you if you are attacking them, in which case they will fly in front of you, assuming a diamond-shaped formation and start firing their lasers at you one by one. Destroy each drone until all of them are down, then proceed to destroy the last remaining power nodes and cause the Behemoth to retreat. You can now safely enter the Phantom Blade and finish the mission.