The radiometer’s six channels span 0.6 to 22 gigahertz. Its lowest-frequency channels can sense emissions from roughly 6 to 20 feet beneath Io’s crust, while higher frequencies probe shallower material.[2]
The instrument does not directly place thermometers at those depths. Researchers derive the temperature profile from microwave brightness measurements and modeled electrical properties of Io’s surface material. The two flybys, on December 30, 2023, and February 3, 2024, sampled overlapping tracks mainly across the hemisphere that always faces Jupiter, so the results do not constitute a uniform global survey.[3][5]