Research and Development towards a Detector for a High Energy Electron-Positron Linear Collider

This exposition provides a detailed picture of ongoing and planned activities towards the development of a detector for a high-energy Linear Collider. Cases for which research and development activity does not exist, or needs to be bolstered, are identified for the various subsystems. The case is made that the full exploitation of the potential of a high-energy Linear Collider will require the augmentation of existing detector technology and simulation capability, and that this program should become a major focus of the worldwide particle physics community should the construction of a Linear Collider become likely.