NASA's Juno Probe Reveals Glass-Like Surface of Io's Giant Lava Lake
Juno has an instrument called the Microwave Radiometer (MWR), which consists of antennas spread around the spacecraft. It operates between 600MHz and 22GHz, allowing it to penetrate the murky Jovian atmosphere. It can also relay important information about the surface of Io, like the presence of almost perfectly smooth volcanic lakes.