All of the jobs for this employer, that I know of, require security clearances so most of the questions for your interview will be about that. My personal experience is when I asked about the job they gave me a PDF document that told a story. Totally obscure and didn't explain my job at all. It could be that details can't be shared until your clearance is approved - a process that may take 4 months. Prepare questions ahead of time. Decide what is important to you and be sure to ASK those questions.