The Gravity Science experiment will enable Juno to measure Jupiter’s gravitational field and reveal the planet’s internal structure. Juno will see how the material inside Jupiter churns and flows and determine whether the planet harbors a dense core at the center. Variations in Jupiter’s inner structure will have tiny effects on its gravitational field, which ever so slightly alters Juno’s orbit. The closer Juno gets to Jupiter, the more pronounced the displacements are. These subtle shifts in Juno’s motion cause equally subtle shifts in the frequency of a radio signal received from and sent back to Earth. Known as the Doppler effect, it’s the same type of frequency shift that happens when the pitch of an ambulance’s siren increases when speeding toward you and decreases when speeding away from you. To measure these tiny shifts, Juno’s telecommunication system is equipped with a radio transponder that operates in the X band, which are radio signals with a wavelength of three centimeters. The transponder detects signals sent from NASA’s Deep Space Network on Earth and immediately sends a signal in return. The small changes in the signal’s frequency tell us how much Juno has shifted due to variations in Jupiter’s gravity. For added accuracy, the telecommunication system also has a Ka-band translator system, which does a similar job but at radio wavelengths of one centimeter. One of the Deep Space Network’s antennas, located in Goldstone, California, has been fitted to send and receive signals at both radio bands. An instrument called the Advanced Water Vapor Radio- meter helps to isolate the signal from interference caused by Earth’s atmosphere. Dr. John Anderson of the Jet Propulsion Laboratory (JPL) leads the Gravity Science team. Mr. Anthony Mittskus leads the Telecom Subsystem, which is produced by JPL. The Italian Space Agency contributed the Ka-band translator system.