Search for light eco is a mission in The Lost Frontier. When Keira Hagai discovers that the eco seeker requires light eco to properly function, Phoenix recalls a location where they might find it, and they thus set out for the abandoned research rig.
Upon entering the facility you must first go through a short platforming exercise along suspended cages until you reach a large circular room. Look to the left for a Precursor idol, which will give you the eco teleport power (activated by pressing + on PlayStation 2, and on PlayStation Portable). Shortly after, a pair of franken apes will appear from the vents. These are more powerful than the ones you fought in Far Drop, but should nonetheless not be a problem. The eco teleport power does not function as an escape power, but rather as a utility one, as it can only be used to switch places with specific Precursor statues.
Use the new power while standing on a button in the center of the room to switch places with the statue, which will hold the following door open. Be careful of more mutants breaking free of the glass tanks lined along the walls until you encounter the next room. After the scene, go through another door to encounter a puzzle. To solve it you must use eco teleport and switch places with the statues behind the gates while standing on the second button followed by the first, so both statues hold down one button each and thus hold down both of the gates, allowing you to move to the next puzzle.
To solve this one, jump on the empty platform as it moves by and switch with the statue on the other one as it moves alongside the path at the other end, then quickly jump off your new platform. Now stand on the button nearby and wait until the statue on your first platform has moved past the barrier so it is on your side, then switch with it and jump off again next to the statue, which now holds down the last button and thus disables the gate that was blocking you.
From here continue through the facility, undergoing another platforming section involving the eco rocket jump and one with the use of the eco construct power, meanwhile periodically engaging franken apes and eventually ghoul spiders as well. You will have to solve another puzzle once you enter a larger cavern with three statues inside. Look for green crystals on the ground to use your construct power, one of these creates an accessible path to a small section behind you, from where you can create another path out of crystals to a larger ledge that overlooks the statues. Use eco teleport to switch with one of them, then use eco construct to create a third crystal path to the ledge on the other side of the gap in front of you, switch back with the first statue so you can actually access the crystals you just created.
Open the nearby chest here for the Sky Baron Uniform and keep going forwards until you reach a large room where you finally reunite with Keira. After a cutscene you must fight against several waves of spiders and apes before the mission is complete.