Juno

Juno is a NASA New Frontiers mission to place a spacecraft in an elliptical polar orbit about Jupiter to study Jupiter's interior structure. Juno is due for launch on an Atlas V launch vehicle in 2011 and after an Earth flyby in 2013 should go into orbit about Jupiter in 2016.

The final polar orbit of Juno will have a period of about 11 days and will be highly elliptical with a perijove at 1.6 RJ above the North Pole and apojove at RJ. The nominal mission is planned to last for 32 orbits, or roughly 1 year, and Juno will communicate its data to Earth with a 2.5 m high gain antenna. Accurate observations of Juno's trajectory in this polar orbit will allow Jupiter's gravitational field to be determined to a very high degree of precision and constrain its higher order J-coefficients (Section 2.7.1). The Juno mission should thus be able to establish whether or not Jupiter has a core. The polar orbit also limits the damage done by Jupiter's powerful radiation belts and keeps the spacecraft continuously in sunlight throughout its mission. Through this, and also through designing the spacecraft to have very low power consumption, Juno will the first outer planets' mission not to be powered by radioisotope thermal generators (RTGs). Instead, it will be powered by three 2 x 9 m solar panels as can be seen in Figure 8.7. The spacecraft will be spin-stabilized, rather than three axis-stabilized to dispense with the need of power-hungry reaction wheels. The electronics are protected from radiation by placement in a shielded instrument electronics vault.

The polar regions are fascinating areas of the giant planet atmospheres, but the polar regions of Jupiter are relatively hard to see from the Earth due to Jupiter's low

JADĀ£ will measure the distribution of electrons sod the velocity distribution and composition of ions

Scalar Helium Magnetometer (SHM)

SHU will measure the magnitude of the magnetic field in Jupiter's environment with great accuracy.

Ultraviolet Spectrograph (UVS)

UVS is an imaging spectrograph that is sensitive to ultravielet emissions.

MWR is designed to sound deep into the atmosphere and measure thermal emission over a range of attitudes.

Fluxgate Magnetometer (FGM)

The two FGM sensors will measure the magnitude and direction of the magnetic field in Jupiter's environment.

Plasma Waves Instrument (Waves)

JunoCam wrfl provide visible-color Hiiages of the Jovian cloud tops.

Jovian Infrared Auroral Mapper (JIRAM)

JIRAM will acquire infrared images and spectra of Jupiter. JIRAM is located en the bottom deck

Figure 8.7. Payload system of the Juno spacecraft. Courtesy of NASA.

Gravity Science (GS)

The June Gravity Science investigation wil probe the mass properties of .Jupiter by using the communication subsystem to perform Deppter tracking.

Microwave Radiometer (MWR)

Waves will measure plasma waves and radio waves In Jupiter's magnetosphere.

JADĀ£ will measure the distribution of electrons sod the velocity distribution and composition of ions

Jupiter Energetic-particle Detector Instrument (JEDI)

JEDI is a suite of detectors that will measure the energ: I and angular distribution of

JunoCam wrfl provide visible-color Hiiages of the Jovian cloud tops.

Microwave Radiometer (MWR)

MWR is designed to sound deep into the atmosphere and measure thermal emission over a range of attitudes.

Jovian Auroral Distributions Experiment (JADE)

Scalar Helium Magnetometer (SHM)

SHU will measure the magnitude of the magnetic field in Jupiter's environment with great accuracy.

Gravity Science (GS)

The June Gravity Science investigation wil probe the mass properties of .Jupiter by using the communication subsystem to perform Deppter tracking.

Fluxgate Magnetometer (FGM)

The two FGM sensors will measure the magnitude and direction of the magnetic field in Jupiter's environment.

Jovian Infrared Auroral Mapper (JIRAM)

JIRAM will acquire infrared images and spectra of Jupiter. JIRAM is located en the bottom deck

Ultraviolet Spectrograph (UVS)

UVS is an imaging spectrograph that is sensitive to ultravielet emissions.

Plasma Waves Instrument (Waves)

Waves will measure plasma waves and radio waves In Jupiter's magnetosphere.

Figure 8.7. Payload system of the Juno spacecraft. Courtesy of NASA.

obliquity and were not well observed by previous space missions such as Galileo and Cassini, which remained close to the equatorial plane. Juno's polar orbit allows its suite of remote-sensing instruments to look straight down at Jupiter's North Pole from a very close distance allowing it to map the polar region with unprecedented detail.

Juno will carry a number of remote-sensing instruments relevant to exploring Jupiter's atmosphere. For the most part these will concentrate on trying to determine conditions in Jupiter's deep atmosphere to complement the mission's main goal of determining the interior structure of the planet.

Microwave Radiometer (MWR)

The Microwave Radiometer will probe the deep atmosphere of Jupiter down to around 200 bar using six separate radiometers sounding from 1.3 cm to 50 cm that sweep across the planet as the spacecraft spins. These observations and their limb-darkening can then be used to determine the temperature profile of the deep atmosphere and also constrain the deep abundance of ammonia and water. The latitudinal dependence of the retrieved deep-temperature profiles will allow the circulation of Jupiter's deep atmosphere to be inferred to a much greater depth than was obtained by the Galileo probe.

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