Complex sentence: The NIMS instrument detected longer than one year activity in Zamama, therefore it is considered of the persistent type and it has been NIMS-detected five times but only NIMS-observed nine times.
Split into simpler sentences: The NIMS instrument detected activity on Zamama lasting longer than one year activity; therefore, it is considered persistent type. It has only been NIMS-detected five times, but NIMS-observed nine times.