Microwave Radiometer (Juno)

Determining the features and abundances of oxygen, nitrogen, and sulfur at up to 100 bar of pressure (1451 psi) will shed light on the origins and nature of Jupiter. (1 bar is roughly the pressure at Earth sea level, 14.6 psi.) One of the molecules MWR is intended to look for inside Jupiter is water, which it is hoped will help explain the formation of the Solar System. By probing the interior, the insights may reveal how and where Jupiter formed, in turn shedding light on the formation of the Earth. At the time of its use in the 2010s, it was one of only four microwave radiometers to have been flown on interplanetary spacecraft. The first was Mariner 2, which used a microwave instrument to determine the high surface temperature of Venus was coming from the surface not higher up in the atmosphere. There were also radiometer-type instruments on the Rosetta comet probe, and Cassini-Huygens. Previously, the Galileo probe directly measured Jupiter's atmosphere in situ as it descended into the atmosphere, but only down to 22 bars of pressure. However, MWR is designed to look down as deep as 1000 bar of pressure. (1000 bar is about 14,500 psi, or 100000 kPa) ==Antennas==

MWR has six separate antennas of different size that are mounted to the sides of the Juno spacecraft body. As the spacecraft turns (it is a spin-stabilzed spacecraft) each antenna takes a "swath" of observations of the giant. Five of the six antennas are all on one side of the spacecraft. The sixth and biggest antenna entirely fills another side the Juno body. MWR antennas: There are two patch array antennas, three slot arrays, and one horn antenna. • 600 MHz/0.6 GHz frequency/50 cm wavelength (biggest antenna takes up one side of spacecraft body and is a patch array antenna) • 1.2 GHz (also a patch array antenna, but located with other five antennas on one side) • 2.4 GHz (waveguide slot array) • 4.8 GHz (waveguide slot array) • 9.6 GHz (waveguide slot array) • 22 GHz frequency/1.3 cm light wavelength (horn antenna on upper deck of Juno) As Juno turns the antennas sweep across Jupiter, each frequency/wavelength capable of seeing a certain distance below the visible cloud tops. See also Reflective array antenna and Slot antenna ==Results==

During a close pass in summer of 2017 when MWR was operated at Jupiter, it detected temperature changes deep within the Great Red Spot (GRS) storm. On Perijove 7, which was the sixth science orbit MWR took readings of Jupiter's great red storm down to dozens of kilometers/miles of depth below the surface layers. The distribution of ammonia gas was reported on in 2017, and analyzed. An ammonia rich layer was identified, as well as a belt of ammonia poor atmosphere from 5 to 20 degrees north. ==See also==