Might be the wrong group but a question about TERPS

Today there was a twin turbo-prop flying around (not traffic patterns)
Freeman Field, IN (SER). I was wondering if there is a set type of plane the
FAA uses to TERP the approaches. I do not think I've seen a plane like this
one.

For years they've had a few DC-3s setting out here, I thought it might have
been one of those. When I first heard it, I jumped up and ran outside to
look. A lot of good it did, left my glasses in the house.

Thanks,
Fred