Juno (spacecraft)

Juno ( Jupiter Polar Orbiter ) is a NASA spacecraft that will study the giant planet Jupiter from a polar orbit at least one year and has started on August 5, 2011. She is the second to New Horizons space probe of the New Frontiers Program of NASA, and thus may cost more than 700 million U.S. dollars. Unlike previous spacecraft to the planet Jupiter Juno has no nuclear energy, but generates the current required by new, more efficient and more resistant solar radiation. However, the use of solar cells is only possible because Juno on its polar orbit always has view to the sun. In addition, the probe is on this track always outside the strong radiation belts of Jupiter. A mission to the inner Galilean moons that are in the strong radiation belts of Jupiter, would be because of the high radiation would destroy the solar cells remain dependent on a nuclear power and especially radiation-resistant electronics.

• 2.1 instruments
• 2.2 Drive

Mission

The launch of the probe was performed on August 5, 2011 at 16:25 UTC ( originally scheduled for June 2010, and then for 7th August 2011) aboard an Atlas V ( 551 ) from Cape Canaveral. The probe was first placed on an orbit around the sun outside the Earth's orbit. About a year later, August and September 2012, there were two trajectory correction maneuvers. The first was held on 30 August 2012. The Leros -1b engine was ignited for 29 min 39 s, the speed s changed to 344 m / and 376 kg of fuel were consumed. On September 14, 2012, the engine was fired again for 30 minutes, resulting in the consumption of another 376 kg of fuel, the speed of 388 m / s changed. Thus, the probe approached on October 9, 2013, the earth up to 560 km and was of her accelerated by a so-called swing-by maneuver around 7.3 km / s in order to reach the Jupiter can.

Flight time to Jupiter is expected to be five years, so that the probe on July 4 2016Vorlage: / in 2 years achieved their goal future. Once there, Juno will enter into an elliptical polar orbit with an orbital period of eleven days. Juno is thus never be in the shadow of Jupiter, which is crucial for a permanent energy supply by solar cells. However, there is the maximum energy consumption only during the six-hour, in which measurements are performed when the layer of cloud Juno up to 5000 km approaches. The primary mission of the probe is applied to one year and will include 32 Jupiterumkreisungen.

Orbit

Juno is the first probe in this great distance from the Sun, which relies only on solar cells for power generation. Therefore, a very complex scenario for several weeks each lasting orbit has been selected. It had to be met among others the following conditions:

• Bypassing the strongest radiation belts, the radiation could damage the probe.
• So that the solar cells can provide the necessary current avoidance of entry into the shadow of Jupiter constant.
• Short distance to Jupiter at closest approach ( periapsis ) during the highly elliptical orbits.

The images clearly show that it will not be possible to extend the mission to a longer period.

Research objectives

Juno with the following tasks to devote:

• Verification of the existence of a solid core of Jupiter
• Determining the proportion of water, ammonia and methane in the atmosphere
• Studies of convection and production of wind profiles in the atmosphere
• Determining the source of Jupiter 's magnetic field
• Investigation of the polar magnetosphere

Technical Description

Junos main body is a six- sided prism. Each side has about 2 m edge length. Three of the six sides fourfold collapsible solar panels are fixed at 8.9 m in length that extend into space. Two of these modules are completely covered with solar cells, the third on only three fields, the fourth field is a carrier for magnetometer. In all three of the innermost solar panels covered with solar panel is about 2 m wide. However, the outer covered with solar fields are wider than the innermost of 2.65 m and so have a greater light collecting surface, a total of about 60 m². This is necessary because the solar radiation is less than 4 % of the corresponding Jupiter in the earth. The solar panels generate the mission end yet 435 watts of electrical energy.

At the center of the main body of Juno a parabolic antenna for communication in the X-band is attached to the earth. This will be covered with a permeable radio waves sun protection film. Due to the parabolic antenna through the axis of rotation of Juno, rotates around the spacecraft to spin stabilization 2-5 times per minute runs. Junos rotation circle with folded solar modules have a diameter greater than 20 m and launch weight of 3625 kg. As radiation protection for the on-board electronics a box from a centimeter thick titanium plates used with a total weight of about 200 kg.

Instruments

Juno is equipped with seven instruments:

Drive

Junos primary drive for the deep-space maneuver and for pivoting into the orbit of Jupiter is a Leros -1b engine with a thrust of 645 N. The fuels are hydrazine and nitrogen tetroxide. The position control system is provided with 12 nozzles monergol and mounted at four places of the main body.

Special

In memory of the discoverer of the large moons of Jupiter Juno wears an aluminum badge with the portrait as well as a handwritten note by Galileo Galilei and three Lego figures, Galileo, Jupiter and his wife Juno represent.

Amateur radio reception during the swing - bys

During the swing - bys on October 9, 2013 radio amateurs were invited to synchronously send Morse code to Juno that should be received by the Waves instrument. The message should consist of the letter "H " and "I" in Morse code ( "Hi" stands for " Hello "). It was sent extremely slowly, with each point Morse persists 30 seconds, because this corresponds to the period of rotation of the probe. NASA scientists could determine in this way, whether it comes to modulation effects due to the rotation. The message " Hi" is thereby extended to 10 minutes. The hams should be as evenly as possible distributed according to the final letters of their call sign, at frequencies from 28.000 to 28.450 MHz in the 10 meter band to achieve a broadband signal. Although the instrument would be able to receive waves of lower frequencies, however, this transmit signals would have been reflected on the ionosphere, and would not enter the space of the earth. The action began at 18:00 UTC, when Juno was over South America. The closest approach took place at 19:21 at an altitude of 559 km over South Africa, the action ended at 20:40 UTC, when Juno was on Central Asia and away from the earth. Thus, the word " HI" was sent 16 times from Earth to Juno and received on board from the Waves instrument.