Weather affects us everyday. And really big storms like hurricanes can be very violent. Each year they cause billions of dollars of damage, and put people’s lives in danger. We depend on weather forecasts to help us be prepared and stay safe when bad weather hits. Satellites orbiting in space around Earth help scientists forecast when and where storms will happen. In 2006, a new group of satellites called COSMIC was launched by the United States and Taiwan. COSMIC looks across Earth’s atmosphere to provide important information to help with weather forecasting. And now, a new more advanced system called COSMIC-2 provides even more information, which will improve storm forecasting especially in warm, tropical areas near the equator. (Forecaster voice:) Just beautiful structure on this storm as it’s swirling across the central part of the country…. To make accurate weather forecasts, meteorologists and other scientists first need to know three things about the atmosphere: the temperature, how warm the air is, the air pressure, how compressed the air is at any one spot, and the humidity, how much water or moisture is in the air. They need to know how these three things vary at different altitudes, or heights from Earth’s surface and for as many locations on the globe as possible because what happens in one place affects the weather in other places. How can COSMIC-2 see these things? Well, It turns out COSMIC-2 satellites make use of some other satellites ones that were intended for a completely different purpose! GPS satellites circle Earth from very far away…… many times as far away as the COSMIC-2 satellites. These satellites constantly send out the radio signals that your smartphone uses to know exactly where you’re located and how to get where you need to go. But these radio waves can be used in a very different way. Scientists noticed that when the GPS radio waves enter the atmosphere, they bend slightly….. very much like how light bends when it enters water. This is called refraction. It turns out that by looking at exactly how much the radio waves bend, scientists can get a picture of the temperature, air pressure, and humidity in the atmosphere. This is called radio occultation. Data from COSMIC radio occultation helps create more accurate weather forecasts. (Forecaster voice:) Big cyclone right across the central part….. This information is also used by scientists to create weather models that run on computers. To forecast future weather, these models need to start with detailed measurements of current weather conditions. With more accurate information going in, the models can make more accurate predictions of the future weather. It turns out that since the measurements from COSMIC satellites are so accurate and are available everywhere, even over oceans this information can be used by other weather satellites to help make sure the data they contribute to weather models is accurate. Since we have been collecting this very accurate data about the atmosphere for close to 20 years now, COSMIC-2 will be a valuable tool for understanding our changing climate. COSMIC-2 is also very helpful in telling us about what is going on in the highest levels of our atmosphere, called the ionosphere. The ionosphere is home to some wild events, which are caused by radiation and particles from the Sun hitting our atmosphere, often called space weather. One example of this is the aurora. Space weather can interfere with sensitive electronics, like those used to keep airlines safely on their routes and high-speed trains on track. By measuring how radio waves bend in the atmosphere, COSMIC-2 provides weather, space weather, and climate data to help us prepare and be safe!