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The Role of Small Satellites in NASA and NOAA Earth Observation Programs
associated with streamlined management techniques. Several missions have been quite successful, but delayed sensors, spacecraft development problems, launch vehicle availability and failure, and inadequate mission operations plans have all led to delays, cost increases, cancellation, and/or total loss. We must learn from these successes and failures to attain the full promise of small satellites in the future.
A common theme from the cases studied is that the attempt to achieve faster and cheaper missions by streamlining operations and reducing non-value-added tasks must also include plans to maintain balance among all program elements. Imbalances among the sensor, spacecraft bus, launch vehicle, and ground system elements can lead to serious inefficiencies and risks. Risk must be carefully assessed for all program elements when defining the system, particularly for schedule-critical missions. For the greatest cost-effectiveness, risk should be continuously assessed, progress monitored, and plans adjusted to keep the total program in balance. There is also a need for well-defined, well-understood, and consistent roles for government and industry partners and regular communication between all parts of the team.
User tolerance of risk is a key consideration when planning research or operational Earth observation programs. Some Earth science missions require access to long-term, consistent data sets from a variety of sensors. Operational systems, such as meteorological satellites, have strict requirements for data availability from multiple sensors for short-term and long-term forecasting. Although the risks for the individual small satellite components may be higher, small satellites may allow the design of a resilient, robust system (e.g., constellation of satellites) where the total mission risk is smaller. Thus, management structures must not only allow the benefits of small satellites to be realized, but must also enable assessment and mitigation of the new set of risks posed by new mission architectures.
Traditional procedures to develop mission and sensor concepts and the associated peer review process need to be streamlined. First, there must be appropriate mechanisms to ensure the design and maintenance of a coherent observing strategy. For example, solicitations for new NASA science missions should be consistent with the overall science directions of the Earth Science Enterprise. Second, management must address the issues associated with maintaining dynamic continuity of long-term data sets where the specific sensors (and even measurement techniques) will change over time. A comprehensive plan for cross-sensor calibration, data validation, and pre-launch characterization is especially important for climate research. Third, the science community must be prepared to make quantitative evaluations of sampling issues versus measurement quality in regard to the overall quality of the data products. This includes an evaluation of the impacts of data gaps as well as of levels of temporal and spatial resolution. The science community should be involved throughout the system design and implementation process rather than be limited to providing measurement requirements at the initial design stages. Regular assessments of sensor and system design, data products, and algorithms are needed to provide science community insight into the process.
The committee finds that the maturation of remote sensing science and the development of new sensor, platform, and launcher technologies now allow a more flexible approach to both research and operational Earth remote sensing. Small satellite missions have provided and should continue to provide an important component of how Earth observations are conducted from space. However, their limitations—both evident and more subtle—suggest that they are not an appropriate substitute for all larger satellites. The committee recommends that, in planning for future NASA and NOAA missions, the choice of mission architecture should be driven by the mission requirements and success criteria, and an optimum solution should be sought, whether with large, mid-size, small, or a mixed fleet of platforms. The committee also recommends that both the research and operational communities perform a complete analysis of sampling strategies in the context of potential new mission architectures.