Technological advances have enabled new types of distributed space missions (DSMs) that can improve the data resolution along many dimensions over monolithic, “flagship” spacecraft. Future DSMs will fuse data from a wide variety of sensors including other spacecraft and various ground- and air-based in situ platforms. The New Observing Strategies Testbed (NOS-T) is a new digital engineering environment based on systems engineering principles for simulating DSMs using a loosely coupled, event-driven architecture that manages communication between logically and geographically distributed user-developed applications. This paper demonstrates how NOS-T can evaluate new operational modes for satellite constellations using real-time stream gauge data from the U.S. Geological Survey (USGS) National Water Information System (NWIS) to decrease the latency of targeted spacecraft observations of flooded areas. The test case uses real-time data from NWIS stream gauges in the U.S., artificially triggers a flooding event, subsequently tasks satellite observations, and downlinks data to a ground station. It demonstrates how NOS-T enables the transfer of information between in situ and space-based sensors in a digital engineering environment to aid conceptual design of future DSMs across organizational boundaries.