10:00 P.M.-11:00 P.M. - S1-E23
Visible crew/equipment: When the Drazens hug and turn the TV off, the camera crew is reflected in the TV. (00:27:40)
11:00 P.M.-12:00 Midnight - S1-E24
Visible crew/equipment: At around 11:30pm, just when Jack is preparing to take his first shots at the Drazens as they are running towards the speedboat, you can see a cameraman/technician (wearing a face shield), and a TV monitor behind Jack's head.
Answer: According to Jack in season 5, Nina was "deep cover" before the pair ever met, so it's safe to assume she was recruited before she joined CTU. As for what her primary mission was, who knows? Perhaps it was to gather sensitive intel and pass it on to her superiors. Given that she worked for an intelligence agency, it's not a stretch. Or perhaps we may find out in season seven.
Cubs Fan ★