Once you reach Level 16 you'll unlock "Ghost Ships", whose owner is listed as UNKNOWN on your Job Board. Some of these ships have a helmet somewhere inside, typically close to the cockpit but seemingly always in "crew areas" (as opposed to engineering spaces between inner walls and the hull). They are light blue in the scanner when you're in Objects mode.
When you collect these helmets, you'll get an Unidentified message in your Data Miner computer app. Recover the data to see what the message's title and owner is. The message you get from the helmet seems to randomized from a fairly short list. For this achievement, you need the message from The Machine God (the message is titled "The Machine God", its owner is "The Machine God", you get the idea). You specifically need to play the audio of the message from the Hab computer to get the achievement. You will not get the achievement by just reading the text of the message; it doesn't trigger until you play the audio.
You probably won't need more than a few helmets to get the right message. Make sure you decrypt all the message you get since it's hard to tell which scrambled message is which.
You can exit to the menu then re-enter Career mode to refresh the list of ships on your Job Board. Handy for if there are no UNKNOWN ships listed. Once you're in space, you can just grab the helmet and immediately head back to the Hab. On some ship designs with some helmet spawns you can spend as little as like 20 seconds from starting your shift to ending it with a new helmet recording.
Not a hard achievement, but easy to overlook since the audio that gets played (and which triggers the achievement) is just someone reading the text you can already see (and viewing the message's text doesn't trigger the achievement). Not very intuitive but that seems to be how it is.