WASHINGTON (National Academies PR) – A new report from the National Academies of Sciences, Engineering, and Medicine says that enhancements to the geodetic infrastructure are needed to answer important questions about sea level rise, water resources, geological hazards, and more over the next decade.
The report, Evolving the Geodetic Infrastructure to Meet New Scientific Needs, compares the current capabilities of the geodetic infrastructure with the requirements of high-priority science questions for 2017-2027. Many of these questions can be supported by the existing geodetic infrastructure, as long as it is maintained. However, other science questions will require enhancements.
The geodetic infrastructure is made up of measurement techniques used to determine Earth’s orientation in space, its gravitational field, the trajectories of satellites in orbit around Earth, and the positions of reference points on Earth.
Data from these reference points define the terrestrial reference frame, which in turn defines the locations of every point on Earth. Geodetic data underpin research in a wide variety of science disciplines and areas of study that require precise location data, from weather forecasting to geology.
“The international geodetic infrastructure is largely invisible, but it is the foundation of many areas of scientific research and their applications,” said David T. Sandwell, chair of the committee that wrote the report and professor at the Scripps Institution of Oceanography. “While the current infrastructure is serving science and society well, our ability to maintain and enhance the geodetic infrastructure will be critical to advancing science. For example, several of the NASA satellite missions planned for the next decade will be useless if their tracking systems, which rely on geodetic data, were to fail.”
The three main measurement systems of the geodetic infrastructure. Very Long Baseline Interferometry (VLBI) provides information on Earth orientation and scale. Satellite Laser Ranging (SLR) provides information of the center of mass of the Earth and scale, and also a backup for orbit determination.
Global Navigation Satellite System (GNSS) allows tens of thousands of GNSS receivers on spacecraft, aircraft, ships, and buoys, and in local geodetic arrays to access or connect to the International Terrestrial Reference Frame.
The report examines high-priority science questions about sea level change, terrestrial water cycles, earthquakes, tsunamis, volcanic eruptions, climate and weather forecasts, and terrestrial ecosystems, all of which rely on accurate data from the geodetic infrastructure, and were identified in a 2018 National Academies report, Thriving on Our Changing Planet: A Decadal Strategy for Earth Observation from Space. For example: How much will sea level rise, globally and regionally, over the next decade and beyond, and what will be the role of ice sheets and ocean heat storage?
Monitoring Sea Level Change
Sea level is a leading indicator of climate change, and monitoring sea level change, understanding the causes of these changes, and projecting how sea level might change in the future are critical for coastal infrastructure, ecosystems, and communities.
The report says a broad array of satellite observational systems, whose accuracy depends heavily on a precise geodetic infrastructure, are required to observe and understand sea level changes, to project future sea level changes, and to mitigate their impacts. According to the report, the international terrestrial reference frame may not have sufficient accuracy for sea level science in the future.
Geodetic Infrastructure Enhancements
The report identifies improvements in the geodetic infrastructure that would facilitate advances in answering the next decade of high-priority science questions. Among the most important are:
- Finalize testing of next generation Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) systems, and complete deployment of Global Navigation Satellite System (GNSS) receivers able to receive signals from multiple satellite systems to achieve a balance of geodetic measurement techniques between the Northern and Southern hemispheres, document the errors in the systems, and improve the ability to estimate their positions accurately and automatically.
- Work with the international community to implement a fully time-dependent terrestrial reference frame that will accommodate sudden, annual, and long-term changes in the locations of fundamental stations that include these three geodetic techniques.
- Increase the capabilities for measuring the center of mass motions expected over the next 100 years, due to the melting of the Greenland and Antarctic ice sheets.
Maintaining and enhancing the geodetic infrastructure will require collaboration among international partners and many U.S. federal agencies, including the National Aeronautics and Space Administration. Open data, accurate and open software, and a skilled workforce capable of developing and implementing improvements, also will be necessary, according to the report.
The study — undertaken by the Committee on Evolving the Geodetic Infrastructure to Meet New Scientific Needs — was sponsored by NASA and the National Academy of Sciences Arthur L. Day Fund. The National Academies are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine. They operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln.