Recon

Test Chamber 13: Place portals as shown in the image. Use a portal to move the laser sideways and a time portal to send it into the future. Travel through the time portal, taking some damage if necessary. In the future, rearrange portals so the laser hits the target. Head through the door.

Test Chamber 14: Travel to the present via a time portal. Summon a reflector cube and position it in the present as shown. Use a portal to direct a laser through the first node, then use this to reflect the laser into the next two nodes. Travel to the future. Use portals to bring a laser into the present through the time portal, ensuring it passes through the node. Retrieve the reflector cube from the future and bring it to the present. Position the present reflector cube to hit all three nodes. If needed, return to the future to retrieve the future reflector cube and bring it to the present again. Finally, position the future reflector cube to reflect the laser into the receiver to complete the chamber.

Test Chamber 15: Go through the particle field to the left. Place a portal where the laser hits the wall and a time portal on the opposite wall. Travel through the time portal to the future to bypass the particle field. Go to the other side of the room and use another time portal to return to the present, now on the other side of the particle field. Place a portal on the upper wall above the laser room to direct the laser to the first receiver. Travel to the future and place a portal on the small wall in the laser room to shoot the receiver. Return to the present. The laser should still be hitting the first receiver, powering an elevating platform. Stand on the platform and place a time portal behind the node to raise the platform further, allowing you to summon a reflector cube. Place this reflector cube on the lip above the second receiver. Travel to the future. Retrieve the future reflector cube and enter the laser room. Place a time portal in the laser room to bring the future reflector cube to the present. Position it to reflect the laser into the second receiver through the node. To reach the other side of the particle field without going through it, use an existing portal or a time portal. You need to be in the present on the other side. Climb the stairs and place a portal on the upper wall to hit the third receiver. Move the reflector cube onto the switch to complete the chamber.