Which requirement is necessary for aircraft operations to or from a satellite airport in Class C airspace?

For aircraft operations to or from a satellite airport in Class C airspace, it is necessary for the aircraft to be equipped with a transponder. This requirement is crucial because Class C airspace is designed to manage a higher volume of air traffic in a controlled environment. A transponder enhances situational awareness and safety by allowing Air Traffic Control (ATC) to identify and track aircraft on radar.

Having a transponder provides critical information such as the aircraft's altitude and its static position, which is essential for maintaining safe separation between aircraft, especially in busy airspace. The use of transponders significantly reduces the risk of mid-air collisions and helps facilitate more efficient air traffic management.

While the other options mention important aspects of flying, they are not specifically mandated for operations at satellite airports in Class C airspace. For example, a valid pilot certificate and ATC clearance are necessary for general aviation, but they do not uniquely apply to operations in Class C airspace or specifically to satellite airports within that airspace structure. Weather reporting by ATC is also not a prerequisite for operating at these airports. Therefore, having a transponder is the definitive requirement that enhances safety and compliance within this controlled airspace.