I have pinpointed the location of the second transportational Gate near the Sidon colony.  This site is dangerously close to the human refugee camps and must be quickly destroyed.
You will be dropped to the north of the Gate.  Carefully approach the site and watch for the formidable defenses that aliens have erected.  
From our scans it does not seem that the aliens have been actively using the Gate and thus you should have no concern about reinforcements.
However you should be concerned about the units already defending the gate.  There is a significant force present that you will have to deal with by yourself.  
Thus far you have not been stopped and we see no reason that you should be halted by this dangerous mission.