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SpaceX Launches Second Satellite in Billion-Dollar Sea Level Monitoring Project
Early Monday morning, SpaceX successfully launched a joint NASA-European environmental research satellite, marking the second in a billion-dollar initiative to track long-term changes in global sea levels. This ongoing project is crucial for understanding a key indicator of climate change.
The latest spacecraft, named Sentinel-6B, ascended into orbit from California aboard a Falcon 9 rocket at 12:21 a.m. EST. It joins its predecessor, Sentinel-6, which launched in November 2020 and was named in honor of NASA climate researcher Michael Freilich.
Both Sentinel-6 satellites are equipped with advanced, cloud-penetrating radar. By precisely timing how long it takes radar beams to reflect from the ocean surface 830 miles below, these satellites can measure sea levels with an accuracy of approximately one inch.
They also provide valuable data on wave height and wind speeds. This project builds upon a continuous stream of sea level data collected from earlier missions dating back to the early 1990s.
This extensive data set consistently indicates a gradual but steady rise in sea levels, which is widely interpreted as evidence of global warming, largely attributed to human industrial activity.
However, in line with recent Trump administration policies that have aimed to scale back climate research and its interpretation, NASA’s pre-launch briefing for Sentinel-6B on Saturday notably avoided direct references to “climate change” or “global warming.”
For context, the press kit released by NASA for the initial Sentinel-6 mission in 2020 explicitly stated that the satellite would “provide information that will help researchers understand how climate change is reshaping Earth’s coastlines – and how fast this is happening.” In contrast, the press kit for Monday’s Sentinel-6B mission simply stated that the satellite “will contribute to a multi-decade dataset that is … key to helping improve public safety, city planning and protecting commercial and defense interests.”
Karen St. Germain, director of NASA’s Earth Science Division, also focused on the practical applications of sea level monitoring during the Saturday briefing, rather than explicitly mentioning climate change.
“Sentinel 6B is the latest in a line of missions stretching over three decades, keeping an uninterrupted watch over our planet’s sea surface height, finding patterns and advancing our understanding of planet Earth,” St. Germain stated.
She emphasized that the data from the Sentinel-6 satellites “underpins navigation, search and rescue and industries like commercial fishing and shipping. These measurements form the basis for U.S. flood predictions for coastal infrastructure, real estate, energy storage sites and other assets along our shoreline.”
St. Germain further explained that the data would assist scientists in “understand[ing] and predict[ing] coastal erosion and salt water encroachment into inland supplies of water that are used for agriculture, irrigation as well as municipal drinking water.”
Despite the nuanced language surrounding its purpose, the launch of Sentinel-6B proceeded flawlessly.
Following its liftoff from launch complex 4E at the Vandenberg Space Force Base, the Falcon 9 rocket’s first stage propelled the vehicle through the dense lower atmosphere, then successfully separated and executed a precise return landing at the California launch site. The upper stage subsequently performed two engine firings before deploying the 2,600-pound Sentinel-6B into an 830-mile-high orbit, tilted 66 degrees to the equator. This is the same orbital path utilized by Sentinel-6A and previous sea level-monitoring spacecraft.
The solar-powered satellite will complete one orbit every 112 minutes, traversing locations between 66 degrees north and south latitude, effectively covering 90 percent of the world’s oceans. Beyond its primary mission of measuring sea levels, the new satellite will also monitor temperature and humidity in both the lower atmosphere and the higher-altitude stratosphere, using an instrument that measures atmospheric effects on navigation satellite signals.
However, the core focus remains on monitoring Earth’s evolving sea levels.
As Craig Donlon, a European Space Agency project scientist, remarked prior to the first Sentinel-6 launch in 2020, “The dynamic balance that persisted before the industrial revolution has been upset by the almost instantaneous combustion of huge reserves of carbon as our society has developed. We see evidence of this dramatic change in many different measurements … but they all point the same direction: the Earth is warming. And the greatest indicator of this Earth system imbalance is sea level rise.”
The Sentinel-6 satellites are a testament to international collaboration, resulting from a partnership between NASA, the European Space Agency, the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), and the National Oceanic and Atmospheric Administration (NOAA). NASA’s contribution to the cost of both Sentinel-6 satellites amounted to approximately $500 million, with European partners contributing a similar sum.