Complex sentence: The name of the comet is simply C/2012 S1, with the addition "(ISON)" merely identifying the organization where the discovery was made, the Russia-based International Scientific Optical Network.
Split into simpler sentences: The name of the comet is simply, C/2012 S1. The addition of "(ISON)" after its name, merely identifies the organization where its discovery was made, the Russia-based International Scientific Optical Network.