So yea ive found this out the other day and pretty much got it all down. to find this location, when you start off on the free explore, just go left and keep going through all teh tunnels and such and youll eventually make it to Skywatch. enjoy the grind my friends.
I just go to the area I call the War Zone. It's pretty big & has both Fallen & Hive fighting each-other. It's just a little before you get to the place with the big array.