Imperial's Professor Tim Horbury and Helen O'Brien are celebrating the impact of the Solar Orbiter as they mark five years since it first launched.
Solar Orbiter is a European Space Agency decade-long mission sent to study the Sun and its effects on the solar system.
Tim and Helen are part of the Imperial College London team which designed and built the Orbiter's magnetometer instrument, one of ten instruments on board this complex laboratory. Tim, from the Department of Physics, is the Principal Investigator and Helen is an engineer and Senior Instrument Manager.
What do we understand now about the Sun that we didn't before Solar Orbiter?
Tim - "Solar Orbiter has four big jobs: to find out how the Sun makes the solar wind that flows out into deep space; to find out how it accelerates particles to very high speeds; to show us how the solar wind can affect our lives on Earth; and lastly, how the sunspot cycle works.
"We're making great progress on lots of these: I personally think that we're very close to answering the first question, with the discovery of really short jets called "switchbacks" that help to push the wind away from the Sun and make it so fast. We're also using some of the new instruments to show how shock waves in space accelerate the particles and answering questions that we've had for decades. And we're using Solar Orbiter's real-time measurements to give us more warning of big auroras than we've ever been able to do before. For the solar cycle, we need to wait until we get a good look at the Sun's poles and that's coming very soon – stay tuned!"
What impact has Solar Orbiter had on science since it launched?
Tim – "An enormous impact! The vast volume of data that Solar Orbiter has collected and sent back to Earth over the past five years has resulted in at least one scientific paper a week being published. In fact, there are so many being published that it's almost impossible for us to keep track of them all. I attend conferences where almost every paper being discussed has drawn on Solar Orbiter data in some way. It's particularly satisfying to see new science being generated from our data that investigates aspects of space science that I hadn't even thought about. I'm immensely proud that Solar Orbiter has become such a cornerstone of the international solar physics research community."
What have been some of your highlights from the past five years?
Helen – "Proving that we can design and produce an instrument this complicated that is still working perfectly after five years of continuous service is an incredible feat of engineering. I love being one of the first to know about our bit of the space environment.
The solar wind we measure at the spacecraft is on its way out into the wider solar system – at some points of the orbit, we measure the wind that is on a collision course with Earth. We can predict whether big events, such as those that caused the recent Aurora seen throughout the UK, are on the way. At other parts of the orbit, we are on the other side of the Sun to Earth, so we can see what is heading out to the other side of the solar system. As we send astronauts further away from Earth, we need to know what is going on further afield – there are times when we can predict the space weather on Mars, or the Moon.
"It's great to be part of a big team of Sun 'babysitters', Sun-sitters so to speak - seeing what sort of mood the Sun is in, and whether it is going to impact our systems here on Earth or other space assets in the wider solar system."
"It's great to be part of a big team of Sun 'babysitters', Sun-sitters so to speak - seeing what sort of mood the Sun is in, and whether it is going to impact our systems here on Earth or other space assets in the wider solar system." Helen O'Brien Department of Physics
Tim – "The times when Solar Orbiter and its companion, NASA's Parker Solar Probe, align with each other are very exciting because it gives us a unique opportunity to measure the same solar wind coming from the Sun at two different distances. This means that for the first time we can see how it evolves as it flows out into interplanetary space and then arrives at the Earth. This gives us a key insight into activity such as solar weather patterns. It's moments and achievements like these that mean we're getting closer than ever before to answering some of the biggest space physics questions."
What are the most challenging aspects of working on Solar Orbiter?
Helen – "The simple fact that Solar Orbiter is working 24 hours a day, every day, millions of miles away, exposed to intense cold and bombarded with energetic particles is challenging! It's a very different way of working compared to working with instruments in a lab here at Imperial that can be inspected with our own eyes and switched off and left every Friday afternoon. We can never forget that the Solar Orbiter is up there working hard for us, and there's a very strong emotional pull that makes us want to check in on it every day and often several times a day.
"Some of the most nerve-wracking times are instrument reboots or upgrades. At the end of last year, we updated our software to include a new data compression algorithm: this was done from 24 million km away. Change is always scary: have we thought of and tested every possible scenario? This one worked flawlessly, and we can now get three times as much data down as before – which is great for the science, but any problem would have lost a lot of data. Before you do anything, you must be sure it's going to work."
What contribution has Solar Orbiter made to the space science community?
Helen – "Five years is a long time for a project like this to run continuously, and this is after over a decade spent designing and building multiple prototypes before we were ready to launch. One of the benefits of such a long project timeline is that we've been able to recruit many scientists and engineers at the beginning of their career and give them a strong foundation in the skills and experience needed for this type of research. They've since gone back out into the wider space sector to pursue their next role building and operating space hardware, from Mars Rovers to communications satellites. Solar Orbiter has had a direct positive impact on the wider UK space industry and economy. I'm very proud of that."
What's next for the Solar Orbiter mission?
Helen – "2025 is a big year of engineering challenges for Solar Orbiter: we have our closest flyby of Venus, then we race towards the Sun for another close pass in March, within 30% of the Sun-Earth distance. Our orbit allows us to co-rotate with the Sun's surface at this close distance - so we get to look at a particular part of the Sun for several days, and measure the solar wind it produces from close up – the view from Earth is of the Sun rotating beneath us, so this is a unique part of the orbit.
"Later this year, the orbit takes us around the back of the Sun, which means we will not be able to communicate with the spacecraft for 24 days – this is by far the longest time we have let the spacecraft fend for itself. The onboard software has lots of fail-safe functions, so it knows what to do if anything happens, but it is still scary to know our instrument will be out there, so far away, bravely measuring the magnetic field without any input from us at all."
Tim – "In only a few days' time, on the 18th February 2025, Solar Orbiter will get closer to Venus than ever before, reaching only a few hundred kilometres from its surface. That's closer to Venus than the International Space Station is above Earth. This is known as a 'gravity assist manoeuvre' and the reason we do these flybys is because they allow us to adjust spacecraft's trajectory. This Venus flyby will increase the inclination of the spacecraft's orbit from the Earth's – about 7 degrees – to around 17 degrees meaning we will be able to see much more of the solar poles.
"Really quickly, before the end of March 2025, we will be able to take the highest latitude photo of a solar pole ever taken, which will be a fantastic achievement - it's like we're starting a whole new space mission! We'll keep doing more flybys, increasing our latitude coverage even more, over the next few years."
Image credits: ©ESA
