Wow. I'm surprised anyone has that one remaining. Everyone I know has that done from when people used to do patrol for bounty completions. Just grab some bounties (I find earth to be the best for public events) and open destinypublicevents.com on your smart phone. It'll tell you where to be and when to get those knocked out. If you use that site you can pretty easily get at least 5-6 done per hour in the Cosmodrome.