New NASA ocean-monitoring satellite blasts into space

Sentinel-6 Michael Freilich continues a nearly 30-year mission of measuring sea levels - allowing scientists to better understand the impacts of climate change.
Published: Nov. 21, 2020 at 4:23 PM CST
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VANDENBURG AFB, Calif. (WMTV) - Just before 9:30 a.m. local time, a joint U.S.-European satellite lifted off from Vandenburg Air Force base. The Sentinel-6 Michael Freilich satellite, about the size of a small pick-up truck, was carried into space atop a SpaceX Falcon 9 rocket. After several months of calibration, the satellite will continue a nearly 30-year mission of observing the height of Earth’s oceans. The onboard technology will conduct the most accurate measurements to-date of changing sea levels. Mission goals include enhancing weather forecasts and providing detailed information on large-scale ocean currents to aid ship navigation - especially near coastlines.

The step-forward comes in year when ten tropical systems were observed rapidly intensifying - taking advantage of warm ocean temperatures. Warmer ocean waters expand to accommodate heat content and, as a result, sit higher than colder ocean water. By measuring sea-level, Sentinel-6′s observations can tell scientists how much levels have expanded - a method that stands in for measuring heat content. That information can be mapped and included to enhance weather forecasts for hurricanes and other tropical systems.

The primary instrument, a radar altimeter, will bounce signals off the ocean surface. Much like a Doppler Weather Radar, the satellite will measure how much time it takes for a pulse to be sent out, bounce off its target (the ocean in this case), and return. This information will be used to determine the height of the ocean. An Advanced Microwave Radiometer will determine the amount of water vapor between the satellite and the ocean, which affects the speed of the radar pulses.

Sea-levels are rising, but according to NOAA scientists, they do not rise at the same rate everywhere. Sentinel-6 will be useful in mapping out sea-level changes and preparing for flooding in the years ahead.

Sentinel-6 onboard instruments go beyond just measuring ocean height. The spacecraft will also track changes in temperature and humidity in the atmosphere. A device called the Global Navigation Satellite System – Radio Occultation (GNSS-RO) has been installed to monitor changes in radio signals from navigation satellites. As one of the navigation satellites moves around Earth, its signal must pass through the atmosphere. By using a method called radio occultation, the GNSS-RO measures very small changes in the radio signal’s frequency, path, and speed. This refraction allows scientists to measure temperature, density, and moisture content - all elements which can be passed onto into weather models.

As of late Saturday morning, the satellite was in orbit and ground controllers say the spacecraft is in good health. Sentinel 6 will undergo a series of checks and calibrations before being entered into service in the next few months.

The satellite is named after the late Michael Freilich, the former director of NASA’s Earth Science Division. He was well-known in advancing the observations of Earth’s oceans from space. The mission is a joint-effort between NASA, the European Space Agency, the National Oceanic and Atmospheric Administration (NOAA), SpaceX, the European Commission, and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).

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