How do I open the doors of the base?

Hint 1 of 4:

You first have to visit the Welcome Building.  It's the only one you can
reach at first.

Hint 2 of 4:

The controls to open the doors are there.

Hint 3 of 4:

If you haven't done so already, walk into the closet to drop off your space
suit.  Doing so will open the door into the rest of the building, and picking
it up will open the door back outside.

Hint 4 of 4:

Use the controls below each of the symbols (square, circle, and triangle) to
unlock the doors.  The semicircles on the panels should change from red to
green.