Microwave Radiometer (Juno)

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In this view several white squares of different sizes can be seen on the side of the spacecraft;this side has five of the six MWR antennas. The triangular boom on the right is the Magnetometer (MAG) instrument
The white square is the biggest MWR antenna, and takes up another side of the spacecraft. This antenna is for 600 MHz.[1]
This visualization released by NASA depicts the layers that MWR will observe below the top visible cloud layer

Microwave Radiometer (MWR) is an instrument on the Juno orbiter sent to planet Jupiter.[2] MWR is a multi-wavelength microwave radiometer for making observations of Jupiter's deep atmosphere.[3] MWR can observe from 1.37 to 50 cm when describing light by a wavelength, and from 600 MHz to 22 GHz when describing light by frequencies.[3][4] This supports its goal of observing the previously un-seen atmospheric features and chemical abundances hundreds of miles/km into Jupiter's atmosphere.[3] MWR is designed to detect six different frequencies in that range using separate antennas.[5] Determining the features and abundances of oxygen, nitrogen, and sulfur at up to 100 Bars of pressure will shed light on the origins and nature of Jupiter.[3] It is also designed to detect the amount water and ammonia deep inside Jupiter.[5] It should also be able to provide a temperature profile of atmosphere down to 200 bar.[5] Overall MWR is designed to look down as deep as 1,000 atmospheres which is about 342 miles (550 kilometers) on Jupiter.[6]

MWR views Jupiter in microwave light wavelengths so it can see up to hundreds of miles deep into the planet.[2] In August 2016, as Juno swung closely by the planet MWR achieved a penetration of 200 to 250 miles (350 to 400 kilometers) below the surface cloud layer.[2] MWR is designed to make observations below the cloud-tops, especially detecting the abundances of certain chemicals and determine dynamic features. [3] The region has not been observed like this previously.[3]

MWR was launched aboard the Juno spacecraft on August 5, 2011 (UTC) from Cape Canaveral, USA, as part of the New Frontiers program,[7] and after an interplanetary journey that including a swingby of Earth, entered a polar orbit of Jupiter on July 5, 2016 (UTC),[8][9]

The electronics for MWR are located inside the Juno Radiation Vault, which uses titanium to protect it and other spacecraft electronics.[4][10][11] The antennas and transmission lines are designed to handle the radiation environment at Jupiter so the instrument can function.[4]

At the time of its use in the 2010s, it was one of only four microwave radiometers to have been flown on interplanetary spacecraft.[3] 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.[5][3] There is also radiometer type instruments on Rosetta comet probe, and Cassini-Huygens.[3] 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.[5] However, MWR is designed to look down as deep as 1000 bar of pressure.[3]

MWR used six separate antennas of different size that are mounted to the sides of the Juno spacecraft body.[6] As the spacecraft turns (it is a spin-stabilzed spacecraft) each antenna takes a "swath" of observations of the giant.[6] Five of the six antennas are all on one side of the spacecraft.[6] The sixth and biggest antenna fills the whole side of another side the Juno body.[6]

Antennas

MWR antennas:[1][6] MWR has six antennas on two different sides (it has six sides total) of Juno[6] There are two patch array antennas, 3 slot arrays, and 1 horn antenna.[6]

  • 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 5 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.[6]

See also Reflective array antenna and Slot antenna

See also

References

  1. ↑ 1.0 1.1 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 2.2 Spacecom - Jupiter's Stripes Go Deep, and Other Surprises from Juno Probe - October 2016
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ 4.0 4.1 4.2 Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Key and Driving Requirements for the Juno Payload Suite of Instruments
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

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