The Hero's Journey (Side Mission)
You'll need the grapple to complete this mission. Speak to Larry Parker after freeing him in the Free Larry side mission to get started.
Your goal, easily visible from some distance, is the Purpletop Telecom Tower.
Shoot off the lock to gain access- there is some minor loot and a note inside.
Look up for the grapple points. Get in position for the lower one, and start your ascent.
Your goal is to destroy the small satellite dishes here. You won't encounter the first until you've completed your grapple ascent, then gone up two blue ladders.
Shoot the dish, then grapple up to the next platform for another.
The last three can't be climbed to, but Larry shows up to give you a hand. Climb up the last ladder, loot the backpack there, then use Larry's helicopter as a grapple point.
Swing yourself up to remaining three dishes, and destroy them all.
Your next objective is back at Parker Laboratories. You can make your own way there, but you can also save some time and complete an optional objective by grappling up and joining Larry in the helicopter.
When you get back, the lab is under attack. No bonuses for stealth here, so take out the roughly nine yokels here however you like. Watch out for a heavy mixed in with the chaff.
Destroying them all completes the mission.