Cluster turns the invisible into the visible

September 2, 2010, European Space Agency
An artist's impression of the Cluster quartet. Credits: ESA

( -- Cluster has spent a decade revealing previously hidden interactions between the Sun and Earth. Its studies have uncovered secrets of aurora, solar storms, and given us insight into fundamental processes that occur across the Universe. And there is more work to do.

The aurora, those dancing lights in the polar skies, are but the visible manifestation of an invisible battle taking place above our heads. Supersonic particles from the Sun collide with our planet’s magnetic field every day. Most are deflected away but some are trapped by Earth’s magnetism and accelerated to collide with the atmosphere, creating the aurora, the planet’s radiation belts and from time to time large magnetic storms worldwide.

In its decade studying this activity, Cluster has discovered giant magnetic whirlpools injecting new particles into Earth’s field, huge ‘holes’ in the uppermost atmosphere of Earth that create black regions in the visible aurora, and magnetic dead spots called nulls that form just as the magnetic landscape of space is about to snap into a new configuration.

“Cluster has shown us a previously hidden world of new details,” says Philippe Escoubet, ESA Cluster Mission Manager. As well as understanding the aurora, Cluster has a practical side: it unveils the environment that spacecraft such as navigation and are expected to work in. can damage spacecraft electronics, sometimes critically, so Cluster’s characterisation of this danger can lead to more robust satellite design.

There is a global science community working on Cluster. Every other day, a science team somewhere in the world has a paper accepted for publication that relies on Cluster data. The Cluster Active Archive already possesses more than 1000 users worldwide, ensuring that the science results will continue even after the mission itself comes to an end.

(Click 'Enlarge' for animated version) Auroral brightnening due to substorms over Canada. Cluster data has helped provide scientists with a new view of magnetospheric processes, challenging existing theories about magnetic substorms that cause aurorae and perturbations in GPS signals. Credits: Canadian Space Agency/ University of Calgary

Ten years is a long time in the severe condition of space. The four Cluster spacecraft are all showing their age and the operations team face a daily challenge to keep the fleet operational. Perhaps the biggest task is to make sure the power keep flowing.

The solar panels no longer generate as much electricity as they did, and the batteries onboard are gradually breaking down in a dramatic way: a series of minor explosions. The batteries are made of non-magnetic silver-cadmium to avoid interfering with Cluster’s instruments. But over time, such batteries generate oxyhydrogen, an explosive gas. To date seven batteries have cracked across the four spacecraft, two of which were more like small explosions. Ground controllers saw the spacecraft lurch each time this happened. From twenty batteries, just nine remain. Yet new, creative scenarios for operations mean the spacecraft remain almost fully functional despite the loss of battery power.

And there is a lot still to be done. Recently, Cluster’s approach to Earth was lowered from 19 000 km to just several hundred kilometres. This will sweep Cluster through the regions responsible for the final acceleration of auroral particles, giving scientists an unparalleled view of this behaviour.

Whilst Cluster is firmly in orbit around the Earth, its science is fundamental to our understanding of the most distant realms of the Universe.

“We are doing astrophysics close to home,” says David Southwood, ESA Director of Science and Robotic Exploration, “Beyond the solar system is an enormous Universe, filled with uncountable stars. The spaces in between them are full of magnetic fields. Other missions study the objects - the islands in the universal ocean - but Cluster studies the very ocean itself.”

is expected to operate until 2012. A mission extension is under review to extend its operations to 2014.

Explore further: Cluster spacecraft reach greatest separation at fifth anniversary

Related Stories

ESA’s Cluster flies through Earth’s electrical switch

May 19, 2006

ESA’s Cluster satellites have flown through regions of the Earth’s magnetic field that accelerate electrons to approximately one hundredth the speed of light. The observations present Cluster scientists with their first ...

Scientists weather a space storm to find its origin

August 2, 2005

A team of researchers from the UK and France used SOHO, ACE and the four Cluster spacecraft to study a huge eruption on the Sun, tracing its progress from birth to when it reached Earth.

A decade of studying the Earth's magnetic shield, in 3-D

August 31, 2010

Today (September 1), space scientists around the world are celebrating ten years of ground-breaking discoveries by 'Cluster', a mission that is illuminating the mysteries of the magnetosphere, the northern lights and the ...

Cluster's decade of discovery

July 16, 2010

( -- ESA's pioneering Cluster mission is celebrating its 10th anniversary. During the past decade, Cluster's four satellites have provided extraordinary insights into the largely invisible interaction between ...

Recommended for you

Neutron-star merger yields new puzzle for astrophysicists

January 18, 2018

The afterglow from the distant neutron-star merger detected last August has continued to brighten - much to the surprise of astrophysicists studying the aftermath of the massive collision that took place about 138 million ...

New technique for finding life on Mars

January 18, 2018

Researchers demonstrate for the first time the potential of existing technology to directly detect and characterize life on Mars and other planets. The study, published in Frontiers in Microbiology, used miniaturized scientific ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (1) Sep 04, 2010
Sub: Science-Next Dimensional Knowledge
Plasmas and Electromagnetic fields hold the keys for next century. ESA cluster mission is helping this perspective change to reality
The missions must continue to monitor and Esa hopes to go -Solar orbiter Phase as early as possible in view of Cosmic Alignment.
The scienceof Cosmology Vedas interlinks help in this direction.
Vidyardhi Nanduri

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.