Weather Pattern Predictions

Deep in space, eight satellites orbit the Earth as part of NASA’s cyclone global navigation system. NASA hopes the data from these satellites will help predict weather patterns and potentially save lives.


Deep in space, eight satellites orbit the Earth as part of NASA's Cyclone Global Navigation System.

NASA hopes the data from these satellites will help predict weather patterns and potentially save lives.

Here is the story.

CYGNSS, Cyclone Global Navigation Satellite System, constellation of eight microsatellite-class spacecraft, they're 29 kilograms, about the size of a lunch tray.

You could fit them on the desk.

We launched all eight of them on a single launch vehicle.

They're in a 35-degree inclination, about 550-kilometer-altitude orbit.

That means that they are flying over the tropics mostly, between plus and minus 35 degrees latitude.

There's a single instrument, single science instrument, on the spacecraft.

It's a GPS receiver, very sensitive.

We have antennas on both the top and the bottom of the spacecraft.

We're able to measure the directly received signal from the GPS satellites, as well as the GPS signal that reflects off of the ocean's surface, and by comparing those signals, we're able to measure the ocean-surface roughness, and from the ocean-surface roughness, we're able to infer the surface wind speed.

We've made a lot of advancements compared to previous platforms to do similar research.

We can revisit the same place on the Earth quite quickly.

We've got great coverage over the tropics, and we're able to see through dense precipitation in the core of a hurricane and make wind-speed retrievals in places where other aircraft-based instruments and other satellites that have similar instrumentation weren't able to do this in the past.

It's not a direct measurement of the wind speed, but it's a measure of the ocean-surface roughness.

So, if you can imagine a very still pond or a lake, very glassy surface, and you can, say, see the moon reflecting in that surface, you're going to get a very sharp reflection.

You're able to see the moon very easily, you know, specular reflection on the surface.

If it's windy and there's a little bit of a roughness on the surface of the ocean, you'll see that reflection of the moon is kind of scattered out, and you don't have that clear reflection of the moon.

The light is scattering off the surface, and so that's a similar thing that happens with the GPS signal when it hits the ocean, so the more that signal is scattered and less of a specular, sharp reflection, that indicates a higher wind speed at the surface that causes that surface roughness, and so there's wind-retrieval algorithms that the scientists have developed to be able to correlate surface roughness into actual wind speeds anywhere in the range from a few meters per second all the way up to 70 meters per second, which is category-5 hurricane, 150-mile-per-hour-plus winds.

Really what motivated the whole mission is that, in the past, oh, at least 30 years, since about 1990, there's been a great improvement in forecasting the track of a storm, where is it going to make landfall, several days out.

So, we've gotten a lot better at that, about 50% improvement in being able to forecast the track of a storm.

Where we haven't made any improvement is being able to forecast how strong the storm is going to be when it makes landfall and how fast it's going to intensify.

So, we fly hurricane-hunter aircraft through the storm to make measurements, but you can only do that so often and really when the storm gets closer to land, and with CYGNSS, we're able to make similar measurements 24/7 from multiple spacecraft and measure these wind speeds in places that have never been measured before in the hurricane with a hope that we will improve the models that scientists use to forecast rapid intensification of these storms.

So, ultimately, what it's going to mean to, you know, people on the ground that live in coastal areas is better indication of, is this storm going to be strong when it makes landfall?

Do you need to evacuate early?

Is it more likely that the storm is going to degrade and not be so intense such that evacuation isn't necessary?

Ultimately, you know, saving lives and, you know, advanced warning for when strong storms are going to hit is what CYGNSS is going to provide in the future.

So this is a tool that we can use to visualize where our satellites are located right now in orbit, and so if I switch to this view, you can see, as they're going around the orbit, they're not all perfectly evenly spaced right now.

One of our goals is to space them more evenly, but as long as they're about 5 to 10 degrees apart in the plane of the orbit, we can get unique measurements from all the spacecraft.

So, this is a very useful tool.

At any point in time, I can quickly jump to see, you know, where over the Earth are the spacecraft transiting.

I give you a world map, or maybe I prefer to look at the ground tracks of the spacecraft as they fly over.

So, here you can kind of see an example of how if there was a hurricane in the Caribbean here, you know, our spacecraft are flying over ground tracks.

One after another, our spacecraft flying over the storm.

So, you can imagine as over the course of the day, all these ground tracks, they fill in and just cover the entire tropics.

So, we're able to make measurements over the entire region between plus and minus 35 degrees latitude.

I think really what we've been trying to do all along is design and operate a mission that's going to save lives by allowing people an opportunity to evacuate coastal areas, you know, well in advance of the storm.

You know, we can't stop the brute force of a hurricane itself, but, you know, just like, you know, a tornado warning gives someone the opportunity to evacuate the area, you know, these hurricanes that span hundreds of miles and cause all the devastation that they do, people really need as good of an indication of whether to evacuate or not, and CYGNSS will be able to provide the improvement to the models that allow this to happen.