Marajó, Brazil

The Copernicus Sentinel-2A satellite takes us over part of northern Brazil’s Marajó island in Pará state.

Sediments discharged by the nearby Amazon River mouth (not pictured) are visible in the waters of the Atlantic Ocean north of the island.

The land area pictured is dominated by a savannah landscape, with mangrove forests and palm swamps along the coast. The area is known for its large plantations – called fazendas – with animal husbandry. Although not native to the island, domesticated water buffalo outnumber Marajó’s human population.

‘Popcorn’ clouds are visible in the upper part of the image, formed by convection and condensed water vapour released by plants and trees during the sunny day. On the left side of the image we can see Lake Arari, the size of which fluctuates greatly between the rainy and dry seasons.

Sentinel-2 images Earth in 13 spectral channels. Scientists can select which wavelength combinations to process over a given area to help better understand targets on the ground.

The channel combination used to create this image, which was acquired on 20 July 2017, is particularly useful for identifying different vegetation types and helps us to distinguish it very clearly from inland water bodies: water appears dark blue, while vegetation appears in a variety of bright colours.

This image is featured on the Earth from Space video programme.

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Gaia avionics model

ESA’s Gaia observatory was launched in December 2013, and is now surveying our Milky Way, creating creating the most accurate-ever map of the stars in our home galaxy and helping to answer questions about its origin and evolution.

The spacecraft is operated by teams at ESA’s mission control in Darmstadt, Germany, who send commands, download data and status information and ensure the health and functioning of this marvellous explorer. They also plan and conduct the routine manoeuvres needed to keep it in its orbital position, 1.5 million km from Earth.

In this picture, operations engineers can be seen working around part of the Gaia Avionics Model.

Avionics are the devices, hardware and software on a spacecraft that enable it to be controlled from the ground, include propulsion, attitude control, communication, computers and navigation.

“This model contains engineering copies of some of Gaia’s onboard units,” says spacecraft operations manager Dave Milligan.

“It is used for high-fidelity simulations allowing our team to test procedures and software on the ground before they are executed on the real thing, 1.5 million km away.

“It is was recently used to test an automatic micropropulsion recovery process, now successfully used in flight.”

More information

Gaia operations

Gaia science

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Neukum Crater perspective view

Perspective view of Neukum Crater, in the Noachis Terra region of Mars. The view highlights the relatively flat crater floor with its two shallow depressions, and striking dark dune field in the southeast corner.

The oblique perspective view was generated using data from the HRSC stereo channels. The scene is part of the region imaged on 31 December 2005, 24 May 2007 and 27 May 2007. North is to the left.

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Large Space Simulator

This circular enclosure, made to appear larger still by an array of mirrors at its end, is ESA’s Large Space Simulator. Some 15 m high and 10 m in diameter, it is cavernous enough to accommodate an upended double decker bus. 

Europe’s largest vacuum chamber, it subjects entire satellites to space-like conditions ahead of launch. Lowered through a top hatch, satellites are placed on the motion system seen in the centre, which is able to simulate their movements in space.

Once the top and side hatches are sealed, high-performance pumps create a vacuum a billion times lower than standard sea level atmosphere, held for weeks at a time during test runs.

The mirror array seen in the image reflects simulated sunlight into the chamber, at the same time as the walls are pumped full of –190°C liquid nitrogen, together recreating the extreme thermal conditions prevailing in orbit.

Portuguese-born Edgar Martins collaborated closely with ESA to produce a comprehensive photographic survey of the Agency’s various facilities around the globe, together with those of its international partners.

The striking results were collected in a book and exhibition, The Rehearsal of Space and The Poetic Impossibility to Manage the Infinite.

Characteristically empty of people, Martins’ long-exposure photos – taken with analogue wide-film cameras – possess a stark, reverent style. They document the variety of specialised installations and equipment needed to prepare missions for space, or to recreate orbital conditions for testing down on Earth.

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Setting sail

The European Columbus module is packed up and loaded for transport to the US in this image from 2006. Built in Turin, Italy, and Bremen, Germany, the completed module was shipped to NASA’s facilities in Cape Canaveral, Florida ahead of its February 2008 launch aboard Space Shuttle Atlantis.

Columbus has been providing microgravity research facilities for the past decade. In honour of this milestone, this week’s image celebrates Columbus’ triumph over setbacks. Many events factored into its delayed launch: the bureaucratic challenge of planning and budgeting, construction delays and the tragic 2003 Columbia Shuttle disaster meant Columbus was five years behind schedule by the time it climbed into the sky.

So it was with joy and relief when Columbus inside its climate-controlled container was loaded into the Beluga aircraft, an Airbus A300 named after the whale it resembles.

Among the many who attended its farewell ceremony was German Chancellor Angela Merkel.

Once at Kennedy Space Center in Florida, the fully integrated module underwent final tests before being loaded into the Shuttle payload bay.

Since its launch in February 2008, the biggest European contribution to human spaceflight has provided a multi-disciplinary, multi-user platform for research in biology, fluidics and physics, and technology demonstrations – and continues to do so today. 

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Simulating turbulence in solar wind plasma

Maybe you’re reading this caption while drinking a coffee. As you stir your drink with a spoon, vortices are produced in the liquid that decay into smaller eddies until they disappear entirely. This can be described as a cascade of vortices from large to small scales. Furthermore, the motion of the spoon brings the hot liquid into contact with the cooler air and so the heat from the coffee can escape more efficiently into the atmosphere, cooling it down.

A similar effect occurs in space, in the electrically charged atomic particles – solar wind plasma – blown out by our Sun, but with one key difference: in space there is no air. Although the energy injected into the solar wind by the Sun is transferred to smaller scales in turbulent cascades, just like in your coffee, the temperature in the plasma is seen to increase because there is no cool air to stop it.

How exactly the solar wind plasma is heated is a hot topic in space physics, because it is hotter than expected for an expanding gas and almost no collisions are present. Scientists have suggested that the cause of this heating may be hidden in the turbulent character of the solar wind plasma.

Advanced supercomputer simulations are helping to understand these complex motions: the image shown here is from one such simulation. It represents the distribution of the current density in the turbulent solar wind plasma, where localised filaments and vortices have appeared as a consequence of the turbulent energy cascade. The blue and yellow colours show the most intense currents (blue for negative and yellow for positive values).  

These coherent structures are not static, but evolve in time and interact with each other. Moreover, between the islands, the current becomes very intense, creating high magnetic stress regions and sometimes a phenomenon known as magnetic reconnection. That is, when magnetic field lines of opposite direction get close together they can suddenly realign into new configurations, releasing vast amounts of energy that can cause localised heating.

Such events are observed in space, for example by ESA’s Cluster quartet of satellites in Earth orbit, in the solar wind. Cluster also found evidence for turbulent eddies down to a few tens of kilometres as the solar wind interacts with Earth’s magnetic field.

This cascade of energy may contribute to the overall heating of the solar wind, a topic that ESA’s future Solar Orbiter mission will also try to address.

In the meantime, enjoy studying turbulent cascades of vortices in your coffee!

More information: Perrone et al. (2013)Servidio et al. (2015) and Valentini et al. (2016).

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