CAPE CANAVERAL, Florida — Solar Orbiter, an international collaboration between the European Space Agency (ESA) and NASA, is scheduled to launch from here on Sunday (Feb. 9). Its goal: to study the sun up close.
To do so, the craft is outfitted with a suite of 10 instruments — four in-situ instruments and six imagers — that will make detailed observations, providing a comprehensive view of our star. The spacecraft will also capture the first images of the sun's polar regions. Liftoff is set for at 11:03 p.m. EST (0403 GMT on Feb. 10).
"Solar Orbiter will be the first time we send a satellite out to take images of the sun's poles, and we'll get the first-ever data of the sun's polar magnetic fields," Daniel Müller, the mission's ESA project scientist, said in a prelaunch science briefing on Feb. 7. "We believe this area holds the keys to unraveling the mysteries of the sun's activity cycle."
You can watch the launch live here and on Space.com's homepage, courtesy of NASA TV. NASA's launch webcast will begin at 10:30 p.m. EST (0330 GMT Feb. 19).
Müller added that Solar Orbiter will also gather data about the sun's far side, and the science team will use this data to create the first 3D view of our star.
The $672 million Solar Orbiter will act as a mobile laboratory in space, using its instruments to track the evolution of eruptions on the sun from the surface out into space, and all the way down to Earth.
"Our entire solar system is governed by the activity that comes from the sun," said Nicky Fox, director of NASA's Heliophysics Division. "There's a continually streaming kind of soup of energetic particles that moves away from the sun and bathes all the planets. We call that the solar wind."
The solar wind and the sun's magnetic field together create a huge bubble called the heliosphere, which protects our planet from powerful interstellar radiation called cosmic rays. According to Fox, very energetic eruptions of plasma called coronal mass ejections (CMEs) that originate on the sun also become embedded in the solar wind.
When a CME makes it way to Earth, the solar particles can interact with our planet's magnetic field to produce powerful electromagnetic fluctuations. These geomagnetic storms are troublesome because they can disrupt technologies here on Earth like communications systems and even power grids, and can also be dangerous to astronauts and satellites in space.
Solar Orbiter will link the sun to the heliosphere as never before, helping to establish a cause-and-effect relationship to what happens on the sun and what we observe in the near-Earth environment, mission team members have said.
"The majority of [the solar wind] comes from the polar regions we've never imaged," added Thomas Zurbuchen, Associate administrator of NASA's Science Mission Directorate. "We will see it for the first time with Solar Orbiter."
Müller said that one of the mission's goals is to understand how the solar magnetic field works and how it affects the solar cycle, a periodic change in the sun's activity.
"People have been observing the sun since telescopes were invented 400 years ago, but we don't really know what drives this 11-year cycle or the amplitude," said Müller. "We cannot predict how strong the next cycle will be."
The key to understanding it all may lie at the sun's poles. "We know the sun's magnetic field is transported a little like on a conveyor belt: from the equatorial regions of the sun, to the poles and presumably back — that part we don't know yet," Müller said.
In order to crack this solar mystery, a spacecraft needs to orbit at an angle out of plane with the sun's equator and stare down at the poles. And that's just what Solar Orbiter will do.
The spacecraft is equipped with three instruments that will measure the sun's magnetic field. With the data collected, the team will try to connect the dots between magnetic field observations on the sun's surface to the magnetic field measurements where the spacecraft flies.
But Solar Orbiter isn't the only spacecraft tasked with studying the sun. It will join a fleet of sun-observing probes that have been busy collecting data about our host star for decades, including NASA's record-setting Parker Solar Probe (PSP), which launched in 2018.
"It's a great time to be a heliophysicist," Fox said. "All of our spacecraft have their own specific science missions,but work together as a team."
Günter Hasinger, ESA's director of science, said that Solar Orbiter will stand on the shoulders of the sun-observing spacecraft that came before it, including two other joint ESA-NASA missions — Ulysses and the Solar and Heliospheric Observatory (SOHO).
Hasinger explained that Ulysses was the first spacecraft to actually fly over the poles of the sun. "Ulysses flew at a very large distance and with its eyes closed," he said, "so we didn't get the information that Solar Orbiter will get."
He compared the fleet of solar spacecraft to an orchestra: "Every instrument plays a different tune, but together they play the symphony of the sun."
Thanks to data collected by Ulysses, the Solar Orbiter team knows that the sun's poles are incredibly dynamic, and there are major differences in the sun's magnetic fields at the poles compared to the magnetic fields elsewhere.
"In general, the sun's poles look like the rest of the solar surface," said Müller. "The difference lies in the magnetic field." He and the rest of the science team think they will observe the early stages of the next solar cycle at the poles first, which is why Solar Orbiter's mission is so important: It will fill in major gaps in our understanding of how the sun works.
Every 11 years, Müller explained, the sun flips its global magnetic field — the north pole becomes the south pole and vice versa. By sending Solar Orbiter on a journey outside the ecliptic (the plane in which Earth and the other big planets orbit), scientists will capture unprecedented views of the region, shedding light on its processes.
Solar Orbiter is scheduled to launch on Sunday (Feb. 9) atop a United Launch Alliance Atlas V rocket. It is expected to make its first science measurements as early as May, with full science operations commencing in November 2021 when the craft's imagers come online.
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