Juno will use the Microwave Radiometer (MWR) instrument to be the first spacecraft to probe inside Jupiter, learning about its structure and chemical composition. To see what’s under the cloud tops, the MWR will measure the radiation emitted from inside the planet. The clouds radiate in all frequencies of the radio, microwave and infrared ranges. But only microwave frequencies can make it out through the thick clouds. The depth from which the radiation can escape depends on frequency, so by measuring different frequencies of microwave radiation, the MWR can study different layers of Jupiter’s interior. The MWR consists of six radiometers designed to measure the microwaves coming from six cloud levels. The levels range from the cloud tops, where the pressure is the same as that on Earth, down to a depth of hundreds of miles, where the pressure is a thousand times greater. The deepest layers will reveal Jupiter’s water content, which is key to understanding how Jupiter formed. The MWR will also allow us to determine how far down atmospheric features, such as the cloud bands and the Great Red Spot, extend. Each of the six radiometers has an antenna, and all six antennas are located on two sides of Juno’s hexagonal body. Each antenna is connected by a cable to a receiver, which sits in the instrument vault on top of the spacecraft. Dr. Michael Janssen of the Jet Propulsion Laboratory (JPL) leads the MWR instrument team. JPL provided the MWR sub-system components, including the antennas and receivers.