BBC Future

Space Station

Enter the satellite Swarm

About the author

Richard is a science journalist and presenter of the Space Boffins podcast. He edits Space:UK magazine for the UK Space Agency, commentates on launches for the European Space Agency and is a science presenter for BBC radio. You can also follow him on Twitter or Facebook.

  • Satellite swarm
    Swarm, a constellation of three satellites, is designed to accurately measure the Earth’s magnetic field from an altitude of more than 400km (250 miles). (Copyright: IABG)
  • Sensitive load
    The delicate satellites have been built in an environment free from magnetic interference to ensure they only measure the Earth’s magnetic field. (Copyright: IABG)
  • Long tail
    The booms are designed to hold Swarm's sensitive magnetometers away from the electronic "noise" inside the main body of the spacecraft. (Copyright: Esa)
  • Blast off
    Once complete, the three satellites will launch atop a converted SS19 intercontinental ballistic missile later this year. (Copyright: Esa)
  • Eye in the sky
    The multi-satellite mission allows measurements to be taken over different regions simultaneously, building a 3D picture of the planet’s magnetic field. (Copyright: Esa)
  • Magnetic storm
    Its measurements will further our understanding of space weather and radiation hazards caused by particles from the Sun interacting with our magnetic field. (Copyright Esa)
Richard Hollingham visits Germany for a private viewing of Swarm, a mission designed to investigate the Earth’s magnetic field. But first he needs to surrender his wallet.

“You need to give me your phone, wallet and watch,” says the man behind the desk. ”You also need to take off your belt”. Not phrases you would normally want to hear from someone in uniform.

Stripped of valuables and dressed seemingly for surgery – in overshoes, a hat and gown – I am told to stand in front of a sensor for testing. I wait as the man studies the numbers on his computer screen. Satisfied, he lets me through the door.

Inside is a vast hall, around the size of a football pitch. This brightly-lit, three-story high “clean room” at Munich-based space company IABG is mostly empty; except for a cordoned-off area in the centre. Here, displayed like a unique piece of sculpture, are three of the most precise, delicate and fragile-looking satellites I have ever seen. They resemble giant, mechanical insects with glinting angular bodies attached to long extending arms. Together, these satellites make up Swarm – a European Space Agency (Esa) mission designed to map the Earth’s magnetic field with unprecedented accuracy.

To ensure the magnetometers on the three Swarm satellites measure only the Earth’s magnetic field, the spacecraft have been built in an environment free from all magnetic interference. Even the slightest source of magnetism – like a stray metal spanner or slightly magnetised bolt – could damage the instruments. Every magnetic field the satellites themselves generate, as a result of electronic components, has been precisely calibrated.

“We have been as careful as you can imagine,” says my guide, project manager Albert Zaglauer. “Even the glue that holds them together had to be tested.”

Disappearing act

So, if you forget to leave your slightly magnetic smartphone or credit cards at the door, you could set back years of work. And it is important work. Despite the arrival of new technologies, a surprising number of people – and businesses – still rely on a magnetic compass for navigation.

“Back in the 1700s it was the thing you would use,” says Richard Holme, Professor of Geophysics at the University of Liverpool. “In the 1930s, navigating by the Earth’s magnetic field was still important, now it’s become a less important part of things because of GPS. But if you get something that messes up GPS or you get really bad weather so you cannot pick up the GPS signal, then the magnetic field is the only game in town and is still used in ships and planes to determine the heading.”

Our magnetic field is constantly shifting. Keeping track of these changes is vital to ensure compasses in ships or aircraft are accurately calibrated. But in the last 150 years the field has also weakened by 10%. This weakening is particularly prevalent in an area of the southern hemisphere, known as the South Atlantic Anomaly. If this process continues, then the field could reverse. North will become south and south become north. There is evidence that this has happened many times in the past, so it could happen again.

However, there is another reason why we should care about a weakening of the Earth’s magnetic field and it goes to the heart of the existence of all life on our small blue-green planet. The Sun continuously spews out a stream of charged particles, known as the solar wind, and the occasional more violent burps that we have been enjoying recently from solar flares. Without the protection of the magnetic bubble around the Earth – the magnetosphere – our atmosphere would be at the mercy of these particles. It is extremely unlikely it could be torn away completely, but it makes our understanding of the magnetic field and how it’s changing even more important.

Back in the clean room, technicians check that the satellites fit together for launch. They wear gloves, treating the three spacecraft like precious artefacts. Such is their care that I wonder how they are going to feel when they strap the Swarm constellation to the top of a converted Russian Intercontinental Ballistic Missile and blast it into space. Probably a little nervous.

But Zaglauer says it is all part of the job. “If you don’t like to see the launch you shouldn’t work in the space business,” he says matter-of-factly.  

However, he admits the best bit is when it is over and the satellites you worked on for more than five years are in orbit and sending back signals. “We are more excited when we see data on the screens…then we celebrate.”

Swarm is due for launch on a Rockot launcher (a converted SS19 intercontinental ballistic missile) in July from the Plesetsk Cosmodrome in northern Russia. The satellites will end up in three different orbits to give scientists a 3D view of the Earth’s magnetic field and how it is changing. But having seen Swarm up close, it pains me to think that once they’re packed away in the nosecone of the rocket, these beautiful machines will never be seen again.

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