The $2.2 billion spacecraft will join NASA’s Parker Solar Probe, launched 18 months ago, in coming perilously close to the Sun to unveil its secrets.
Project manager for the European Space Agency Cesar Garcia Marirrodriga said it was a “fantastic moment”.
“We’re on the way to the Sun. Go Solar Orbiter,” he said.
Solar Orbiter performs in ‘symphony’ with Parker probe
Unlike the Parker probe, Solar Orbiter will not venture close enough to penetrate the Sun’s corona, or crown-like outer atmosphere.
But it will manoeuvre into a unique out-of-plane orbit that will take it over both poles, never photographed before.
European Space Agency’s science director Gunther Hasinger said the Sun-staring space duo would be like an “orchestra”.
Solar Orbiter was made in Europe, along with nine science instruments.
NASA provided the 10tth instrument and arranged the late-night launch from Cape Canaveral in the United States.
Nearly 1,000 scientists and engineers from across Europe gathered with their US colleagues under a full moon as United Launch Alliance’s Atlas V rocket blasted off, illuminating the sky for miles around. Crowds also jammed nearby roads and beaches.
The rocket was visible for four minutes after lift-off.
Europe’s project scientist Daniel Mueller was thrilled, calling it “picture perfect”. His NASA counterpart, scientist Holly Gilbert, said: “One word: Wow.”
NASA declared success 90 minutes later, once the Solar Orbiter’s solar wings were unfurled.
The boxy 1,800-kilogram spacecraft with spindly instrument booms and antennas will swing past Venus in December 2020 and again in 2021, and then past Earth, using the planets’ gravity to alter its path.
Full science operations will begin in late 2021, with the first close solar encounter in 2022 and more every six months.
Solar Orbiter to capture never-before-seen pole snaps
At its closest approach, Solar Orbiter will come within 42 million kilometres of the Sun, well within the orbit of Mercury.
The Parker Solar Probe, by contrast, has already passed within 18.6 million km of the Sun, an all-time record, and is shooting for a slim gap of 6 million km by 2025.
But it’s flying nowhere near the poles. That is where Solar Orbiter will shine.
The Sun’s poles are pockmarked with dark, constantly shifting coronal holes. They’re hubs for the Sun’s magnetic field, flipping polarity every 11 years.
Solar Orbiter’s head-on views should finally yield a full 3D view of the Sun, 150 million km from our home planet.
Director of NASA’s heliophysics division Nicola Fox said Solar Orbiter would offer a new perspective on the Sun.
“With Solar Observatory looking right down at the poles, we’ll be able to see these huge coronal hole structures,” she said
“That’s where all the fast solar wind comes from.
To protect the sensitive instruments from the Sun’s blistering heat, engineers have devised a heat shield with an outer black coating made of burned bone charcoal similar to what was used in prehistoric cave paintings.
The 3×2.4m heat shield is just 38cm thick, and made of titanium foil with gaps in between to shed heat.
It can withstand temperatures up to nearly 530 degrees Celsius.
Embedded in the heat shield are five peepholes of varying sizes that will stay open just long enough for the science instruments to take measurements in X-ray, ultraviolet, visible and other wavelengths.
Probes to help forecast space weather
The observations will shed light on other stars, providing clues as to the potential habitability of worlds in other solar systems.
Closer to home, the findings will help scientists better predict space weather, which can disrupt communications.
Ian Walters, project manager for Airbus Defence and Space, which designed and built the spacecraft, said predicting space’s weather was important for several reasons.
“We need to know how the Sun affects the local environment here on Earth, and also Mars and the Moon when we move there,” he said.
“We’ve been lucky so far the last 150 years [since a colossal solar storm last hit].
“We need to predict that. We just can’t wait for it to happen.”
The US-European Ulysses spacecraft, launched in 1990, flew over the Sun’s poles, but from farther afield and with no cameras on board. It’s been silent for more than a decade.
Europe and NASA’s Soho spacecraft, launched in 1995, is still sending back valuable solar data.
Altogether, more than a dozen spacecraft have focused on the Sun over the past 30 years.
It took until now, however, for technology to allow elaborate spacecraft like Parker and Solar Orbiter to get close without being fried.