Where did Spock go?

Hint 1 of 5:

With the bridge disabled, you're going to have to use another set of sensors
to track him down.

Hint 2 of 5:

Go down to Auxiliary Control and use the sensors there.

Hint 3 of 5:

Getting rid of that alien is a whole new problem.  See other questions in the
section if you need help on that puzzle.

Hint 4 of 5:

Then, once the alien is gone, just use the sensor controls (the right panel
of the three below the viewscreen).