Welcome to Gaia! ::

Oh geez, this one was definitely one of the hardest missions. Fortunately, it's only really the beginning that is really difficult... once you're past that, you get a lot of powerful weapons, and only need to proceed the rest of the way cautiously.
In the beginning, you need to be *perfect*, you really can't screw up... you should know where your enemies are gonna be up until the hanger battle (also a tough spot, you gotta play really-really defensively).
After that, the only two other spots that pose a challenge is
1) blowing up that the engine system
2) gaining control of the ship at the end
With the first one, I recommend using your AR to shoot from a distance. Snipe 'em one at a time from the hallways.
With the latter, you just gotta play carefully... you should remember to take cover to the right, immediately as soon as you enter the room from the elevator. The fight that goes on afterward, you gotta be 100% aware, and ready to shoot 'em down as they come up.
I recommend using more of your Mauler's one-hit kill and AR (than the Callisto), actually. Try to figure out the best time to switch between those weapons (they're both more advantageous in certain quarters), take advantage of the AR's zoom function in long hallways and such.

If you want, I also recommend checking Youtube for both walkthroughs and speed runs too (I've found speed run strategies in particular areas can be helpful moving your a** in tight spots!).

Thanks, this thread's helped me out considerably.