Next stop: Jupiter

Is anybody out there? Answering the question about where life in our solar system does – or could – exist is one of science’s biggest questions. But sometimes the answers to big questions come in the most unexpected places. It might look like something you could piece together in the kitchen, yet the fluxgate magnetometer has been behind some of the most astonishing discoveries of the space age.

Data recovered from magnetometers has revolutionised our ideas about where life might exist elsewhere in the solar system and beyond, revealed the structure of the Earth’s magnetic field, and helped us understand how the solar wind – the charged particles that stream from the Sun – can have such a devastating effect on life on Earth.

“What makes magnetometers so fundamental is that most of outer space has a magnetic field linked to it,” says Professor Michele Dougherty, Professor of Space Physics.

“To have a chance of understanding the environment there, you need to understand its magnetic field – it’s a fundamental quantity. If you don’t understand the magnetic field, then you can’t understand how the different processes that take place in the atmosphere and environment around other planets work.”

Developed during the 1930s, fluxgate magnetometers were widely used during the Second World War to protect ships from submarine attack. Nearly 90 years later, the essential principles remain the same.

Made from a doughnut-shaped magnetic core wrapped in two lengths of copper wire, an electrical current pushes the core into magnetic saturation – first one way, then the other – thus revealing the size and direction of a magnetic field.

But, instead of hunting for the magnetic signatures of submarines, today’s magnetometers are routinely launched into space in search of more interesting quarry.

Professor David Southwood (PhD Physics 1969), Senior Research Investigator and former President of the Royal Astronomical Society, explains: “Most objects – from the Sun to many of the planets – have either their own magnetic field, or interact with the solar environment in such a way that you get a lot of magnetic disturbances around them. So, a magnetometer is going to be required for almost any mission leaving Earth.”

And some of the most high-profile missions in recent times have been heavily influenced by Imperial scientists such as Professor Southwood and, earlier, Professor Andre Balogh. Described as the “godfather of the instrumentation side of the group”, Professor Balogh helped establish the College’s stellar reputation for magnetometer science – he founded Imperial’s Space Magnetometer Laboratory in the 1980s and paved the way for all future work, including the very latest mission, the Solar Orbiter.

In February, Senior Instrument Manager Helen O’Brien and her team oversaw the launch of the Solar Orbiter magnetometer, which blasted off from Cape Canaveral and is heading to the Sun to investigate the development of planets and how life begins.

“Although the technology has been around for a long time, the big difference now is the performance we’re trying to squeeze out of them,” says O’Brien.

“We’re working at temperatures and in high radiation environments that are breaking new ground. The fields we want to measure with Solar Orbiter, for example, are 50,000 times the equivalent we measure on the surface of the Earth. So, we’re getting much better at extracting small resolution from the instruments we have.”

Making major discoveries, including the unexpected, is in the Space Magnetometer Laboratory’s DNA. The ESA Cluster mission – a quartet of spacecraft launched in 2000 to study the Sun’s impact on the Earth’s space environment – was the first to study the Earth’s magnetosphere (the region of space surrounding an astronomical object dominated by its own magnetic field) in 3D.

Cluster provided the first 3D measurements of the structure and motion of the ‘magnetic boundaries’, which separate the magnetosphere from the impacting solar wind. This is important because the solar wind causes what’s known as ‘space weather’, the climatic conditions that can have an effect on Earth by knocking out satellites and power grids, for example.

And, in 2005, another Imperial-built magnetometer, this time on the Cassini mission to Saturn, made its greatest discovery so far. Less than a year after launch, Cassini’s magnetometer picked up strange signals from one of Saturn’s moons. The data seemed to suggest that icy plumes were issuing from Enceladus, so Professor Dougherty, who was the Principal Investigator for the magnetometer, flew out to NASA to argue the case for a closer fly-by.

“After they agreed I was so excited. Then as the fly-by approached I was terrified,” Professor Dougherty recalls. “If we hadn’t found anything, no-one would ever have believed me again. The team took a chance. It was based on the science, but we weren’t certain of what we were seeing. We were brave and it paid off.”

The fly-by revealed that beneath Enceladus’s icy crust lay a liquid ocean, a discovery that has revolutionised our understanding of where else life might be able to form. Until 30 years ago, scientists assumed the only place in our solar system that you’d find water was closer to the Sun. Hence the hunt for life, or evidence that it once existed, on Mars.

But the fact that Cassini’s magnetometer discovered liquid water on Enceladus – the moon of an outer planet – means life could form in lots of other places further from our Sun, and other suns.

Today, Professor Dougherty and a small team of engineers in the Space Magnetometer Laboratory are working on their biggest challenge yet – making the magnetometer for a new mission to Jupiter. Due for launch in 2022, the JUpiter ICy moons Explorer (JUICE) will explore the giant planet and three of its moons: Europa, Callisto and Ganymede.

JUICE will be the first spacecraft to go into orbit around an outer planetary moon and, although it will take more than eight years to get there, the prospect is tantalising. “I’m not renowned for my patience,” she admits, “but it’s essential if we’re to understand whether life might be able to form in the outer solar system. For habitability, you need liquid water, a heat source and organic material, and for all three to have been stable for a long enough period. We think that could be happening on Ganymede.”

Patrick Brown, Senior Instrument Manager on the JUICE magnetometer, is the engineer responsible for making it happen. Over the past 23 years at Imperial, Brown has worked on magnetometers for six missions, tailoring each for different environments. For JUICE, the challenges are hair-raising. To deliver Professor Dougherty’s data, the magnetometer must be tough enough to withstand huge variations in temperature and massive doses of radiation, yet sensitive enough to detect tiny changes in magnetic field.

“Jupiter has the largest planetary magnetic field in the solar system, and it has these big moons, one of which is full of volcanoes spewing out material that gets accelerated and trapped in the magnetic field. That means an intense radiation environment – like going through a nuclear reactor,” says Brown.

While Brown is in the maelstrom of the design and build phase, O’Brien and Professor Tim Horbury (BSc Physics 1992, PhD 1995), Principal Investigator of the Solar Orbiter magnetometer, can only watch and wait as their instrument heads for the Sun, closer than any previous European mission. “We’re going closer to the Sun than Mercury, so we’ll be able to measure the solar wind when it’s young and fresh,” says Professor Horbury. “That will give us a better understanding of how it’s formed – as well as the damage that space weather can do to satellites and electricity grids on Earth.”

The list of scientific successes highlights what makes the Space Magnetometer Laboratory special. The small, close-knit team has championed magnetometers since the start of the space age. Its degree of specialisation – it typically only builds one flight instrument per mission – is unusual, and its experience unrivalled. And its combination of world-class engineering with world-class science sets it apart.

“Our unique success is down to the fact that, at Imperial, we’re good at exploiting both the science and the instruments,” says Chris Carr, now head of the lab. “It keeps us at the heart of missions and it lets us produce great science. It’s a truly virtuous circle.”