The centerpiece of the Solid-Earth Science Working Group strategic vision for NASA is the creation of a constellation of satellites that will provide continuous, global coverage of the continuously changing surface (and interior) of the earth. The title of the SESWG report, Living on a Restless Planet, emphasizes three underlying themes. “Living” refers to the need to gather the best possible information to help us anticipate and deal with the natural hazards of living on a dynamic planet. “Restless” conveys the idea that many of the geologic changes of greatest societal importance are rapid, even on human time scales. “Planet” emphasizes that the topics focus on spaceborne techniques that view the entire earth. Tackling these themes will require both basic and applied research.
We believe that the observational strategies outlined in the SESWG report provide a sound basis for guiding NASA’s solid-earth science program over the next few decades. The immediate goals (1–5 years) focus on launching an L-band InSAR satellite and continuing to collect, analyze, and distribute data from existing instruments. We endorse all of these goals, especially the InSAR satellite, which is identified as the top priority of the SESWG report.
Longer-term goals focus on new instruments that would capture information about solid-earth processes, and how they are changing over time, with sufficient spatial and temporal resolution to guide mechanistic models useful for making reliable natural hazard forecasts. Many of the new instruments (e.g., spaceborne LIDAR, thermal imaging spectroscopy, satellite-satellite interferometry for measuring time-variable gravity) would first be tested as technology demonstration missions over the next decade. We support this strategy as well as the goal of flying increasingly high-resolution instruments or constellations of instruments to measure surface deformation, topography, magnetic field, time-variable gravity, and land-surface characteristics. However, the specific technologies recommended at this early stage will not necessarily be the ones implemented in the long term (10–25 years). Although a long-term strategy is essential for planning, continued experience with new technologies at NASA and other space agencies will affect the optimal mission schedule and the choice of instrument to be flown. The goal should be to complement, not reproduce, instruments flown by other countries. Coordinating with other agencies (especially NSF) and with other parts of NASA might also help the Solid-Earth Division cope with the computational challenges that will arise from analyzing large volumes of data generated by the proposed observing program and from distributing some of the data in nearly real time. Without proper data analysis the instruments will be ineffective in meeting scientific objectives.