During the 15-year GRACE mission, scientists "found significant changes in every part of the world," Michael Watkins, lead scientist for GRACE-FO and director of NASA's Jet Propulsion Laboratory in Pasadena, California, said during a briefing on April 30. One of the most significant findings was the extent to which the melting of Earth's polar ice caps has contributed to rising sea levels, Watkins said.
As that ice melts — whether the water becomes a part of the ocean or seeps into the soil — it changes how mass is distributed on our planet. And when Earth's mass distribution changes, so does its gravity field. By measuring those changes, the GRACE missions can track Earth's water cycle and how climate change affects oceans, glaciers, sea ice, groundwater, and even moisture in the atmosphere.
To detect these gravitational changes, the twin spacecraft will fly about 137 miles (220 km) apart and send microwave signals back and forth. When they pass over a region where gravity increases or decreases, the distance between the two spacecraft will change slightly, allowing the satellites to map Earth's gravity field. In other words, GRACE-FO will map Earth's water movements "by actually measuring the weight of the water," Watkins said.
Although the two GRACE-FO spacecraft are very similar to those used in the previous GRACE mission, they will carry one new piece of equipment: the experimental Laser Ranging Interferometer. If this new technology works as planned, it could provide measurements up to 10 times more accurate than the microwave measurements, NASA officials said.
Original article on Space.com.
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