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:
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.