Field study
A field study was a period undergone by cadets at Starfleet Academy during their sophomore year which was in practice in 2373. Field study involved active duty aboard a Starfleet vessel, space station, or other installation during which the cadet was placed in a rotation of various posts, ostensibly to gain practical experience. It was similar to a training cruise, but more routinely involved active-duty situations among active-duty officers as opposed to environments and training ships meant primarily for education.

Captain Benjamin Sisko's field study was at Starbase 137. He was apprehensive when he was initially assigned there, but considered it to be one of the best experiences of his life. 

Nog's field study was performed on Deep Space 9 in 2373. Captain Sisko told him "The key to field study is simple. Keep your eyes and ears open, follow orders and try not to get in the way". ()
Starfleet Academy courses