Longer satellite altimetry cycles could offer broader insights into inland waters

Longer satellite altimetry cycles could offer broader insights into inland waters
by Simon Mansfield
Sydney, Australia (SPX) Sep 30, 2024

Satellite observations have long been recognized for their efficiency in monitoring Earth's surface, especially in remote regions like rivers and lakes. Now, a group of international researchers suggests that longer orbital repeats of satellite altimetry - where satellites take less-frequent measurements over a wider area - may provide more valuable data than missions with more frequent, but localized, observations.

These findings were published on Aug. 27 in the 'Journal of Remote Sensing'.

Satellite altimetry involves measuring the time it takes for a signal to return after bouncing off a point on Earth. This data can reveal water levels, surface composition, and other details. Observing how these measurements change over time can offer insights into environmental factors, including climate change.

The study focuses on two types of satellite altimetry missions: geodetic missions (GMs) and exact repeat missions (ERMs). GM missions typically take longer to return to the same location, often over a year, and sample at dense intervals of a few kilometers. ERM missions, on the other hand, offer more frequent measurements - from ten days to a month - but sample at wider intervals, sometimes spanning tens to hundreds of kilometers.

"This paper specifically highlights the advantages of GM data over ERM data in various applications," said Liguang Jiang, assistant professor at Southern University of Science and Technology in China. "In the realm of lake studies, GM data offer the potential to reveal the bigger picture of lake variations across entire regions. This broader perspective becomes invaluable in furthering our understanding of hydrological cycles at continental and even global scales."

The research compared data from four satellites - Jason-1, Jason-2, CryoSat-2, and AltiKa DF - which operated between October 2010 and November 2023, alternating between GM and ERM cycles. The team found that GM cycles offered a more comprehensive understanding of hydrology, sampling many more lakes compared to ERM cycles. GM data also provided better insights into larger hydrological patterns and the local factors influencing water levels.

Jiang noted that GM data can help reveal features of large water bodies, such as river levels and elevation profiles, offering a broader and more detailed perspective.

"The findings presented in this paper serve as a springboard, demonstrating the exciting possibilities that GM data holds for advancing research on inland water bodies," Jiang added. "By leveraging this rich data source, future studies may unlock the full potential of GM data and make contributions to a deeper understanding of our planet's freshwater systems."

The next steps for the researchers include developing computational tools to better process GM data for hydrological research.

Jiang is also affiliated with the Changjiang River of Scientific Research Institute (CRSRI), and the study was co-authored by Karina Nielsen and Ole B. Andersen of the National Space Institute at the Technical University of Denmark. The research was supported by the CRSRI Open Research Program, the Shenzhen Key Laboratory, and the Southern University of Science and Technology.

Research Report:Beyond Exact Repeat Missions: Embracing Geodetic Altimetry for Inland Water Monitoring and Modeling