Microsatellites help in flood detection

CYGNSS’s principal investigator at the University of Michigan in Ann Arbor. “We had known beforehand that there would be some instances of coherent scattering possible. That’s the phenomenon that creates such high-resolution images. It rarely happens over the ocean and we hadn’t really considered how often it might happen over land. It turns out that it happens quite frequently, and almost always when observing small inland water bodies. This promises to open up entirely new areas of scientific investigation.”

CYGNSS’s advantage over other space-based sensors for flood detection is its ability to see through clouds, rain and vegetation that may otherwise obscure floodwaters. Currently, flood detection is generally done by optical sensors on the U.S. Geological Survey-NASA Landsat satellites, which can’t see through clouds, and the microwave sensors on the European Space Agency’s Sentinel 1 and 2, which can’t see through vegetation. Capturing data from eight satellites instead of one is another advantage because it decreases the time between observations for locations, meaning more coverage, more rapidly, of flooding in the tropics. Together this means CYGNSS could bridge gaps in current coverage.

“Flooding from hurricanes can happen really quickly,” Chew said. “You can go from dry to a complete flood within a matter of hours. So even with satellites that observe Earth every two to three days you can miss a lot of information such as how quickly an area flooded and the maximum extent of flooding. But if you have more samples, like what CYGNSS gives you, then you can start to really pinpoint these types of things.”

However, this type of detection is still in its early days of development, and Chew and others are exploring how to infer the amount of water present and other parameters to complement soil moisture and flood data from other satellites. In addition, CYGNSS data currently takes two days to go from observation to data users.

“It’s very fitting that one of the new things that CYGNSS is unexpectedly good at determining, the extent of flood inundation, is very often a direct consequence of the thing it was designed to measure, namely hurricanes,” Ruf said. “So now, not only will we be able to observe the hurricanes while they are over the ocean, we will now also be able to map much of the damage they cause from flooding after landfall.”