This one is tricky, so I'm putting my solution from TA up.
For this achievement, it is crucial that you start early, capture one every non-defense mission, and win every defense mission. You can NOT capture all of them at the end. At least one of the desert planet's (Caldis?) points will never be available in the endgame. I waited 75 extra in-game days before giving up and restarting. It's likely that there are others. This can be done on any difficulty. Here's some hints;
--On Angel Gate's map, the foundries don't count to the total and you can't capture them anyway. I think you can reinforce at them, however.
--During "Into the Hive," there's a side path that leads to a shrine. It is a ways away from the efficient path, and you will receive NO objective concerning it. You MUST take the shrine during this mission, you will not have another chance. If you receive the Dreadnaught without capturing it, EXIT OUT immediately.
--There are a few other missions where you are ordered or advised to capture a shrine, most notably, the one where you first encounter the Elder (space elves). Always do so. It is sometimes possible to complete the mission without it, but it is harder, and you may not have another chance.
--The Force Commander can use an item called "Iron Halo" (or similar) to create a shield around himself that converts damage to energy loss. On the lower difficulties, careful micromanagement of this item can make him invulnerable, and still able to capture the asset.
--I was never able to capture the other asset during a defense mission, but I know of no reason it would be impossible. Your best bets are to send either Thaddeus (jetpack) or Cyrus (stealth). If you manage this, please post a comment. EDIT: NEO CRIMS0N was able to do so in the first one. I never tried until later missions, so maybe it's easier on the first ones?
--Bring the Dreadnaught into defense missions, he's average or weak in most missions, but his slow movement doesn't matter in defense, and his area attacks are great protection. Upgrade him to stun enemies for easy kills.