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How did Seasat use radar altimetry to study the oceans?

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Launched in 1978, Seasat was the first satellite dedicated to mapping the ocean surface using radar altimetry. The satellite functioned by transmitting pulses of radio energy toward the sea surface and measuring the precise time required for the signal to reflect and return to the spacecraft.12

By combining these distance measurements—which were accurate to within a few centimeters—with precise data regarding the satellite's orbital position, researchers were able to reconstruct the topography of the ocean surface. These measurements revealed that the sea surface is not perfectly flat; instead, it is warped by the gravitational pull of seafloor features. For example, massive seamounts create bulges in the ocean surface, while deep-sea trenches cause localized downwarps.123

By analyzing these variations, scientists were able to compute the gravity field of the ocean basins, allowing them to identify and map previously uncharted features such as ridges and fracture zones with a level of comprehensive coverage that ship-based echo sounders could not achieve.13