The hatch is a nuclear missile silo.
Why:
It is protected by a thick concrete barrier.
There are blast doors to protect the crew.
There are weapons for site protection.
The computers banks are used as telemetry controls.
The satellite (108 minutes) is a launch window. Plus did you know that 4+8+15+16+23+42=108?
The sound of blast doors opening when the countdown was reached. (Locke shut it down before the main ignition)
The symbols -- bird (represents a flying projectile); fire (represents launch); arrow (represents a nuclear missile).
The "incident" most likely involves the launching of an earlier missile from the silo that we saw being used by the "tailies" and is now abandoned.
Someone else thinks its Egyptian hyroglyphs
http://i39.photobucket.com/albums/e1...ieroglyphs.jpg