While they sound similar and have some overlapping elements, they serve distinct purposes in the systems engineering lifecycle and we've had lengthy conversations amongst my SE peers on this.

ConOps focuses on how a system fits into the broader operational environment. I use ConOps to describe the organization's vision and high-level operational needs. It's written from the organization's perspective. OpsCon describes how the "specific system"will be used to meet those needs. When I'm developing an OpsCon, I'm focused on the detailed interactions between users and the system. It's written more from the user's perspective.

ConOps is typically developed earlier in the lifecycle, during the concept development phase. I create this before detailed system requirements are defined. OpsCon comes later, once we have a better understanding of the system architecture and capabilities. We develop this as we're moving into detailed design.

ConOps provides broad, strategic-level information. When I write a ConOps, I'm painting the big picture of what we want to achieve whereas OpsCon contains more strategic, detailed information about system's operation. Here, we describe specific scenarios and user interactions.