Hal has spawned on a planet which is completely full of enemies, with no free space at all. How do I go about landing on this planet? I die within 15 seconds even with full armour and lasers and atomic bombs. I high no issues wiping out bases of any size on my home planet, but here I'm dead. I've researched everything that can be researched as well.

Well thats very a hard military mission. =)
It happens... some planets are overcrowded in Space Exploration. After you reveal the surface, aliens will populate it very fast. In our game (multiplayer) we used about 5 or 6 tryes. While landing, we lanched lots of nukes, clearing the area, each try. We had shields and lasers, that gave us some time for lauching more nukes.
Good Luck.
Remember you can also cheat landing. If you want the code, just ask

managed to do it in the end after about 15 tries. tons of battle drones and 7 nukes allowed me to make a foothold. Cleared a large are, stored everything in boxes in the middle of a lake now spawned back to my home planet to get more supplies. Hopefully I won't lose all the progress in one hour...