Role of the Space Platform Requirements Working Group (SPRWG) in the NSOSA Satellite Architecture Planning Study

The National Environmental Satellite Data and Information Service (NESDIS) is conducting the NOAA Satellite Observing System Architecture (NSOSA) study in order to determine the most cost effective space architectures for NOAA’s weather, space weather, and environmental remote sensing missions. As a part of this study, in late 2015 NESDIS initiated the Space Platform Requirements Working Group (SPRWG) to determine the future needs and relative priorities for NOAA’s operational space-based observations for the 2030 time frame and beyond. For the NSOSA study, and thus for the SPRWG process, operational NOAA functions are considered the highest priority, and are defined as those which result in government actions that affect public safety or economic livelihood. SPRWG is purely advisory in nature; the responsibility for selecting and implementing the final architecture rests with NOAA senior leadership.

The membership of SPRWG, which I chaired, consisted of representatives from the user and research community and included NOAA and non-NOAA subject matter experts. Members were selected so that their collective expertise would span the spectrum of NOAA observational needs. The SPRWG used its members’ expert knowledge of the types of measurement data needed to develop operational products (e.g. forecasts, watches, and warnings) from space-based observations of phenomena related to weather, climate, space weather, and the general Earth environment. SPRWG completed its final report in May 2017.

A key element of the NSOSA study process is the Environmental Data Record (EDR) Value Model (EVM), which provides the most important objectives for meeting NOAA’s observations from space, the objectives' performance attributes at different levels of capability, and their priorities for improving the performance of the objectives from the Study Threshold Level (a level below which the objective has little or no value) to the Maximum Effective Level (the level above which further improvements are not useful or not cost effective). The EVM plays a central role in assessing the value of different space architecture alternatives. The most important part of the SPRWG charge is to assist NSOSA with the development of the EVM.

The SPRWG’s approach to developing the EVM is based on Multi-Attribute Utility Theory (MAUT) as used in decision analysis. Specifically, the goal is to develop a utility function, which takes as input all of the performance attributes of an architecture alternative and returns a real number that is referred to as the “utility” of the alternative. The utility is intended to have the property such that if decision makers (in this case NOAA leadership) are presented with two alternatives, the preference for one over the other will map directly with the larger computed utility. The objective is to produce what is called an efficient frontier plot, in which utility of an architecture is plotted as a function of cost of the architecture.

The final EVM included two groups containing functional objectives. Group A consisted of 19 objectives to deliver specific data records of importance to users in the NOAA service areas of weather, oceans, and fisheries. The objectives in Group A are mostly aligned with particular sensor types. They are particularly focused on sensor data types that support medium- and short-range weather forecasting and nowcasting, but also include data types relevant to operational ocean, fisheries, and long-term forecasting needs. The second group (Group B) also consisted, coincidently, of 19 objectives that support space weather. After defining all 38 of the objectives, it was necessary to define the performance attributes of each objective (e.g. accuracy, horizontal resolution, latency), and the performance values of the attributes at three levels - the Study Threshold (ST), Expected (EXP) and Maximum Effective (ME) levels. There were three design cycles in the NSOSA study; each cycle improved upon the previous EVM and resulted in a refined set of objectives, attributes, and justifications. The SPRWG found this iterative process to be extremely important, in fact essential, in developing a consensus EVM and associated report that could be used in the NSOSA process.

The final objectives and priorities for improvement over the ST level of performance for Groups A and B were determined through discussions among SPRWG members and users of NOAA satellite observations, including forecasters and numerical weather prediction experts. In developing the objectives, performance attributes, rank order and swing weights, SPRWG used many documents from the WMO, the NOAA Consolidated Observational User Requirements List (COURL), observational impact studies that have appeared in the scientific peer-reviewed literature, and results from Observing System Simulation Experiments (OSSEs) and Observing System Experiments (OSEs) to inform its judgment. The final result was derived from a synthesis of many sources of information.

This talk summarizes the SPRWG process, which was new to SPRWG members, and the results from the EVM.

This presentation represents the personal views from the Chairman of SPRWG and is not an official NOAA presentation, nor does it necessarily reflect NOAA’s positions.