Addressing common constraints to science data downlink

Science data is the sole or principal product of spaceflight missions funded by the NASA Science Mission Directorate. However, post-launch resource and technical constraints largely external to the project may limit continuous achievement of the expected science data downlink volume. This paper provides two examples of how flight projects may exploit the flexibility of the end-to-end mission data system to compensate for fluctuations in downlink supply and demand. The major downlink resource constraint is the finite supply of, and the very high demand for, the available Deep Space Network (DSN) assets after subtracting scheduled unscheduled DSN downtime. Given their minimal ability to mitigate DSN resource limitations, flight projects must consider mission operations improvements that may help to achieve Level 1 (i.e., mission success) requirements. Technical constraints to achieving the desired downlink include factors that cause data volumes to vary on a daily basis. For example, the difference between the predicted versus achieved data volume returned by the Mars Exploration Rover (MER) relay link impacted the daily planning of rover driving and science data collection. This problem can be alleviated by flight project action to refine the operations and science data return planning process.