Earthscientists require timely, coordinated access to remote sensing resources, either directly by requesting that the resource be targeted at a specific location, or indirectly through access to data that has been, or will be acquired and stored in data archives. The information infrastructure for effective coordinated observing does not currently exist. This paper describes a set of capabilities for enabling model-based observing, the idea of linking scheduling observation resources more directly to science goals. Model-based observing is realized in this paper by an approach based on concepts of distributed planning and scheduling. The problem raises challenging issues related to planning under uncertainty, monitoring and repair of plans, and reasoning about human objectives and preferences.