The new NASA-JAXA precipitation satellite works! The spacecraft was launched in February as part of an effort to improve global rain and snowfall measurements. You can see its first images, which are of a cyclone east of Honshu Island, Japan.

The Global Precipitation Measurement (GPM) Core Observatory satellite has two primary instruments: one measures microwave radiation, and the other emits and measures radar.


The GPM Microwave Imager (GMI) measures energy radiated in microwave wavelengths split along 13 channels. This allows the detection of different types of precipitation, as liquid raindrops and ice particles affect microwaves differently. This is the first spacecraft that will be able to detect and differentiate everything from light rain to heavy snowfall.

The Dual-frequency Precipitation Radar (DPR) actively bounces radar signals off of raindrop and snowflakes, capturing distances between the storm and the satellite. This will image the 3D structure of an entire storm. With two frequency channels, this will even permit independently mapping two precipitation classes: moderate to heavy rainfall, and light rain or snowfall.


NASA Goddard scientist Bob Meneghini explains why this is such a powerful combination:

"Both return independent measurements of the size of raindrops or snowflakes and how they are distributed within the weather system. DPR allows scientists to see at what height different types of rain and snow or a mixture occur — details that show what is happening inside sometimes complicated storm systems."

The combination of GMI and DPR data will lead to more accurate calculations of how much rain or snow falls on the Earth, improving understanding of how water moves around within the Earth system.


The spacecraft will be collecting data with a huge increase in resolution compared to the 1997 Tropical Rainfall Measurement Mission. The instruments should resolve rain structures down to 3 to 9 miles (5 to 15 kilometers) in diameter.

The first images were captured by the GPM on March 10th. The images are of an extra-tropical cyclone in the northwest Pacific Ocean, about 1055 miles (1700 kilometers) east of Honshu Island, Japan. The colours map to rain rates: red is heavy rainfall, yellow is lighter rainfall, and the bright blue in the upper left is falling snow.


Cyclones form when warm air collides with cold air. The storms are a mix of rain, snow, ice, high winds, or other severe weather. All that shows up in the first images: a broad warm front with heavy rain, narrowing to trailing cold front with a mix of rain and snow.

Because the storm is utterly normal in formation and structure, it serves as a good calibration test for the freshly-launched satellite. All sensors appear to be functioning normally, but it will take some time to officially validate the data. Currently, NASA is estimating that the data will be confirmed and released to the public by September of this year. Until then, it's nice to know the satellite is up, running, and performing as expected.

All images credit NASA/JAXA. To read more about the satellite, check out The Vane. To read more about why precipitation monitoring is so important,read our Water Day article.