From European Space Agency: “Juice cast in gold”

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From European Space Agency


ESA JUICE Schematic

ESA/Juice spacecraft depiction

G. Fischer/IWF Graz

This model of Juice was built by the Technical University of Dresden, Germany, and the tests were performed by the Austrian Academy of Sciences’ Space Research Institute in Graz, Austria, as part of a project financed by the Austrian Research Promotion Agency (FFG). The lead scientist for the calibration effort was Georg Fischer of the Space Research Institute, also using computer simulations performed by Mykhaylo Panchenko.

In a decade’s time, an exciting new visitor will enter the Jovian system: ESA’s Jupiter Icy Moons Explorer, or Juice. As its name suggests, the mission will explore Jupiter and three of its largest moons – Ganymede, Callisto and Europa – to investigate the giant planet’s cosmic family and gas giant planets in general.

Juice is planned for launch in 2022, and its instruments are currently being perfected and calibrated so they are ready to start work once in space. This image shows one of the many elements involved in this calibration process: a miniature gold-plated metallic model of Juice used to test the spacecraft’s antennas.

Juice will carry multiple antennas to detect radio waves in the Jupiter system. These antennas will measure the characteristics of the incoming waves, including the direction in which they are moving and their degree of polarisation, and then use this information to trace the waves back to their sources. In order to do this, the antennas must work well regardless of their orientation to any incoming waves – and so scientists must figure out and correct for the antennas’ so-called ‘directional dependence’.

This shiny model was used to perform a set of tests on Juice’s Radio and Plasma Wave Instrument (RPWI) last year. It was submerged in a tank filled with water; an even electric field was then applied to the tank, and the model was moved and rotated with respect to this field. The results revealed how the antennas will receive radio waves that stream in from different directions and orientations with respect to the spacecraft, and will enable the instrument to be calibrated to be as effective as possible in its measurements of Jupiter and its moons.

Similar tests, which are technically referred to as rheometry, were conducted in the past for spacecraft including the NASA/ESA/ASI Cassini-Huygens mission to Saturn (which operated at Saturn between 2004 and 2017), NASA’s Juno spacecraft (currently in orbit around Jupiter), and ESA’s Solar Orbiter (scheduled for launch in early 2020 to investigate the Sun up close).

NASA/ESA/ASI Cassini-Huygens Spacecraft schematic

NASA/ESA/ASI Cassini-Huygens Spacecraft


ESA/NASA Solar Orbiter depiction

The test performed for Juice posed a few additional hurdles – the model’s antennas were especially small and needed to be fixed accurately onto the model’s boom, which required scientists to create a special device to adjust not only the antennas, but also the boom itself.

The model was produced at a 1:40 scale, making each antenna 62.5 millimetres long from tip to tip; scaled up, the antennas will be 2.5 metres long on Juice. The main spacecraft parts modelled here include the body of the probe itself, its solar panels, and its antennas and booms. The model has an overall ‘wingspan’ of 75 centimetres across its solar panels. The photo also shows a spacecraft stand, which extends out of the bottom of the frame. The gold coating ensured that the model had excellent electric conducting properties, and reacted minimally with the surrounding water and air during the measurements.

Meanwhile, the assembly of the Juice flight model has started in September, with the delivery of the spacecraft’s primary structure, followed by integration of the propulsion system.

From ESA 23 October 2019

JUICE begins to take shape

The assembly of the flight model of ESA’s JUICE spacecraft began in September, with the delivery of the spacecraft’s primary structure, followed by integration of the propulsion system that will enable the mission to reach and study Jupiter and its moons.

Unpacking of JUICE primary structure in Lampoldshausen. Credit: Courtesy of Airbus and ArianeGroup

On 2 September, the main skeleton of JUICE was delivered to the Arianegroup facility in Lampoldshausen, Germany.

The primary structure of the spacecraft features a central tube – the main load bearing element – with vertical shear panels located radially around the tube, and horizontal floor panels. This will be completed later with the optical bench and external closing panels that will form the outer walls and will be added when all the internal equipment has been integrated.

The structure is part of the so-called Structure, Shielding and Thermal Subsystem (SSTS), built under the responsibility of Airbus Defence & Space in Madrid, Spain, with participation by RUAG Space Switzerland and RUAG Space Austria.

One of the features of the JUICE SSTS is that the some of the vertical panels and parts of the closing walls of the structure are lined with a thin layer of lead, which provides shielding to protect the spacecraft’s electronic systems from damage by the severe radiation environment at Jupiter.

JUICE propulsion system integration. Credit: Courtesy of Airbus and ArianeGroup

Over the coming months, five companies will be working almost simultaneously on the STSS in order to ensure that JUICE can proceed to the assembly and integration phase that will take place in Airbus facilities in Friedrichshafen, Germany, so that it will be completed and ready for launch in 2022.

One of the main tasks at Lampoldshausen will be to integrate the propulsion system. This includes two identical propellant tanks that have been newly developed for EuroStar Neo, ESA’s new generation of platforms for geostationary telecommunications satellites. JUICE will be the first space mission to actually utilise them.

The first titanium tank, capable of holding 1600 litres of oxidant (mixed oxides of nitrogen, or MON), was carefully lowered inside the spacecraft’s central cylinder on 7 September. The second tank, which will contain monomethyl hydrazine (MMH) fuel, is scheduled for installation at the end of October.

“JUICE will need to carry more than 3000 kg of propellant in these tanks,” said Daniel Escolar, ESA’s Mechanical, Thermal & Propulsion System Engineer for the mission.

“Such a large load will be essential for JUICE to arrive in orbit around Jupiter and complete its scientific tour with multiple flybys of the Galilean moons, before eventually becoming the first spacecraft ever to enter orbit around Ganymede.”

JUICE propulsion system piping. Credit: Courtesy of ArianeGroup

The integration of the spacecraft’s propulsion system will, however, involve much more than installing two propellant tanks. Eventually, three fairly small tanks, each filled with helium pressurant, will be affixed around the exterior of the central cylinder, together with all the necessary plumbing. Some 130 metres of titanium piping will also have to be installed and welded in the STSS.

Other hardware to be added during installation of the propulsion system will include pressure regulators, valves, filters and thrusters. In addition to its single 400-newton main engine that will be used for the larger orbital manoeuvres, JUICE will carry eight 22-newton thrusters for smaller manoeuvres and as a backup system, along with twelve 10-newton thrusters for attitude control.

Meanwhile, engineers are busy carrying out other essential tasks that can only be completed whilst the external panels are not fitted, enabling easy access to the spacecraft’s interior. These include placing single layer insulation around the central cylinder, adding thermocouples to measure temperatures, and attaching support fixtures for the harness that will eventually be required to carry around 10 km of electrical cable.

According to the current schedule, the JUICE flight model will be moved to Friedrichshafen around March next year for integration and testing of its electrical systems.

Meanwhile, development of the JUICE scientific payload is continuing, and the magnetometer boom for the flight model has recently been delivered to ESA’s Space Research and Technology Centre in Noordwijk, the Netherlands, for three weeks of vibration and deployment tests.


JUICE – JUpiter ICy moons Explorer – is the first large-class mission in ESA’s Cosmic Vision 2015-2025 programme. It will complete a unique tour of the Jupiter system that will include in-depth studies of three potentially ocean-bearing satellites, Ganymede, Europa and Callisto.

The Jupiter tour includes several flybys of each planet-sized world, culminating with orbit insertion around Ganymede, the largest moon in the Solar System, followed by nine months of operations in its orbit.

JUICE will carry the most powerful scientific payload ever flown to the outer Solar System. It consists of 10 state-of-the-art instruments plus one experiment that uses the spacecraft telecommunication system with ground-based instruments.

JUICE’s instruments will enable scientists to compare each of these icy satellites and to investigate the potential for such bodies to harbour habitable environments such as subsurface oceans. They will also carry out observations of Jupiter, its atmosphere, magnetosphere, satellites and rings.

See the full article here .

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The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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