While you begin your missions equipped with a headlight, the infrared goggles are an in-game acquisition. They'll allow you to see in dim or lightless spaces just as well as you could in full brightness, though they do tint everything with that classic nightvision green. There's no light fall-off like what you experience with the headlight, which is great, but also makes it difficult to tell when you've exited the dark and can safely turn off the goggles. And that means you might end up consuming a lot more battery than you intended, so toggle those goggles every so often to see if you still need them on.