Re: orbit
An orbit syncronized like this is typically used in Earth-observation satellites designed to compare observations under identical light conditions. I know of no public experiment on the Shuttle requiring such an orbit. I don't have enough data to know if this is really unusual or not.
The experiments are detailed in a large Acrobat document here. There is one Air Force experiment to detect radio emissions from the Earth. There are also rats, student experiments, and many other cool things.