This popped for me immediately after:
WARNING - the game will warn you but just in case you missed it:
You CANNOT backtrack after you accept the final mission from Anne after clearing all the antennas. This means you would have to replay the map again if you have not finished the other achievements!
From start to finish on easy this took me a bit over 5 hours after doing all achievements, all missions (including Clutch Nixon missions), and collecting all available power cores . Be prepared to add time on harder difficulties.