Integrated assessment of packaging architectures in Earth observing programs

When designing Earth observation missions, it is essential to take into account the programmatic context. Considering individual missions as part of a whole enables overall program optimization, which may bring important cost reductions and scientific and societal benefits. Several implementation trade-offs arise in the architecting process of an Earth Observation program such as NASA´s National Polar-orbiting Operational Environmental Satellite System (NPOESS) or ESA´s Earth Explorers. Such tradeoffs include choosing between large satellites and small satellites, standard buses and tailored buses, or centralized architectures versus clusters or trains of satellites. This work focuses on packaging problems, i.e. the assignment of instruments to satellites. More precisely, we study the tradeoff between multi-instrument platforms satellites that carry more than one instrument versus dedicated satellites carrying a single instrument. Our approach to the problem takes a systems engineering perspective and consists of three steps: first, a historical review of past Earth observation programs was done in order to gain insight into how decision makers have solved this trade-off in the past; second, we performed a qualitative analysis in which the most important issues of the trade-off were identified; third, a quantitative analysis was done based on an architecting model. The architecting model is multi-disciplinary because it takes a holistic view of the problem by considering at the same time scientific, engineering and programmatic issues. This exhaustive and multi-disciplinary exploration of the architectural tradespace can be very useful in the early steps of program architecting and could be a valuable tool to support decision making. The model is applied to ESA´s Envisat satellite as an example. Finally, some general insights on the architecture of an Earth Observation Program that we gained by developing and applying this methodology are provided.