At some point after your first encounter with a typhon nightmare, January will call you. We say "at some point," because, like a lot of things in Prey, there are multiple triggers for this optional objective. You might get the call right after your first encounter. Or you might just get it a number of hours later, if you wander back into the Hardware Labs and open the Moon Door.
Regardless, January will tell you about a satellite orbiting Talos 1 that it thinks you can use to either attract or repel nightmares. But you’ll have to repair it first. There’s a bit of backtracking to get the part you need, but the ability to send a nightmare away with your TranScribe is pretty useful.
Find a satellite communication device
There’s a broken satellite you can harvest for parts in the Hardware Labs. All the way in the back of the Machine Shop is a broken computer console. Repairing it will allow you to bring in a satellite through the moon door. Grab the Satellite Psychotronic Transistor off of the satellite. This is what you’ll use to fix the other satellite.
Place the device on the satellite in the Exterior
You can use the airlock right there in the Machine Shop (or any airlock if you’ve wandered) to get outside. Follow your HUD to the satellite. It’s a little tricky to maneuver yourself alongside it, since it’s, you know, orbiting. It might take a couple tries, but just keep chasing the satellite until you get the part replaced.
Satellite uses remaining
All that’s left is to use your TranScribe to access the two audio logs from January. You can use the files four times immediately, while you’re still outside of the station, to just knock out the optional objective’s requirements without endangering yourself. But don’t forget you have the option. Any time you encounter a nightmare from now on, you can play an audio clip to make it disappear. You can also call a nightmare to fight, if you’re into that.
Also, playing the signal will get you Prey’s"You Rang" achievement/trophy.