The requirements for a SS on this mission are as follows: 100% LEV survival, 100% Civilian Survival, 100% Building Integrity!!! To make matters worse in most difficulties if too many Spider units are left around the map the "friendly" LEV units will open fire on empty and manned structures!! This means you have to consider disabling your own ALLIES with Geyser trap every once in awhile just to have them NOT RUIN your other two score categories!!!
YEAH, the Space Force is that dumb-no wonder Mars wants to Rebel...
This AWESOME Map and strategy are brought to you courtesy of Faqsimile's GameFAQ guide for the Original Game; it has a GREAT spawn by spawn breakdown of this mission:
http://www.gamefaqs.com/ps2/561586-zone-of-the-enders-the-2n...It was honestly essential for me to use or I would've had a breakdown trying to get a Perfect SS on this mission!! But honestly Ranking for individual Rescue Missions is easier and more practical on lower difficulties so I would try these achievements on your 2nd play through when you unlock the more powerful versions of Jehuty and can bring back all of your sub=weapons like Comet/High Missile/ and even 0-Shift for quickly moving about the map!