During the Where's Juno job, after talking to Janus, talk to Rikter to start this one. You'll have to repair the Radio Tower to the Northeast.
Once you get to the Radio Tower, flip the switch and head down to the zipline. Head to Riktor to finish the job.
Collector Card: Riktor - In the room past Juno's body with the ladder, it's on a ledge to the left.