Where are the Data Packets for the Data Hound Achievement? And if I've missed one can I return to get it later?
From the Xbox360Achievements.org Guide:
- Do a sharp right and you will find a metal platform with two turrets. Destroy the two turrets and collect the packet on the platform. This area is marked by two giant stone pillars.
- Go straight ahead and you will see a waterfall to your right. Hover behind the waterfall and you will see the packet on a metal platform.
- Go straight ahead till you meet a fork and go to the right. You will find a metal platform guarded by two turrets. Destroy them and obtain the packet on the platform.
- Same as previous, but take the left of the fork instead. Follow the path till you see a metal platform with two turrets on them. By now, you know what to do with them. The packet is on the platform.
- Go left and you will see shadowed area with a waterfall. Fly down by the waterfall and you will find the packet guarded by two Geth Mechs. Missiles ahoy at them.
- Go left, heading towards Vulcan Station. You will find a metal platform by the cave entrance. The packet is there.
The site also has a video showing the locations.
Once you've left the planet, you can't return. So you must get the data packets while doing the mission. IIRC all packets are accessible as soon as you get into the vehicle, so it's a good idea to get the packets as soon as you can so you don't forget to get them later.
This playthrough, although not great in video quality, shows you where everything is. The playthrough starts after having left Prometheus Station.
Note that you can do the packets, Vulcan Station, and Prometheus Station in any order, but once you enter Atlas Station, that's it. You can't go back to Aite after that. Granted, you can't leave Aite until you finish what you've started, but if you don't have all the Data Packets before entering Atlas Station, you won't get a second chance.