The Solar Orbiter, a European Space Agency mission, took to the skies Sunday evening to join ongoing efforts in understanding our host star.
A United Launch Alliance Atlas V rocket lit up the skies over Cape Canaveral Sunday night at 11:03 p.m. EST (4:03 UT on February 10th) with the first space science mission of 2020: the European Space Agency's Solar Orbiter.
Mission controllers from the European Space Operations Centre report that the spacecraft is healthy, and has already signaled home while deploying its solar panels. It's now en route to an orbit around the Sun.
The Solar Orbiter, nicknamed Solo, will join an armada of solar missions, including the Parker Solar Probe and the venerable Solar Heliospheric Observatory (SOHO). Next comes a three-month commissioning phase, during which engineers will put the spacecraft's instruments through their paces before the so-called "cruise phase" begins. During this phase, instruments will begin taking measurements as the spacecraft is en route to the Sun.
"Solar Orbiter is going to do some amazing things," says Thomas Zurbuchen, (NASA) in a recent press release. "Together with our European partners, we're entering a new era of heliophysics that will transform the study of the Sun and help make astronauts safer as they travel on Artemis missions to the Moon."
Solar Orbiter is notable as the first mission designed to image the Sun’s poles. (Ulysses, a joint ESA/NASA mission, launched in 1990 to study the Sun's polar regions, but it didn't carry imaging instruments.) From this vantage point, Solar Orbiter will study the origins of the Sun's atmosphere and the birthplace of the solar wind.
The Solar Orbiter’s full science operations will get underway in November 2021, kicking off a four-year primary mission. Solo will make one pass near Earth on November 26, 2020, and two passes near Venus; these gravity assists will place the spacecraft in a long, looping orbit inclined 17 degrees to the ecliptic plane. Further gravity assists will ultimately change the inclination to 33 degrees by the end of the extended mission, placing Solo in an orbit that goes as near as 26.4 million miles (42.5 million kilometers, or 0.284 astronomical units) to the Sun. The first perihelion pass occurs in October 2022.
Solo’s mission overlaps — and is complementary to — NASA’s Parker Solar Probe. While Parker studies the Sun from close-up, it can't image the Sun directly. By imaging the Sun directly from a greater distance, and from an inclination that allows study of the poles, Solo will offer a comprehensive view of the Sun’s activity. The Parker and Solo teams will provide data that will help understand the Sun's magnetic activity and the origins of the solar wind. Both missions also offer a view of the energetic particles that ultimately flow from the Sun to Earth.
Beating the Heat
To carry out this challenging mission, Solo carries a suite of 10 instruments to study the Sun — both in-situ instruments that study the bath of particles and electromagnetism they're bathed in, as well as remote-sensing instruments that, for example, image the Sun from afar.
Solo will take the first high-resolution images of the Sun from up close using NASA's Heliospheric Imager (SoloHI), as well as an X-ray spectrometer, an ultraviolet imager and a UV spectrometer, and the Polarimetric and Helioseismic Imager (PHI). Solo also carries a Sun-blocking coronagraph named Metis to make key observations of the inner solar corona.
But making observations this close to the Sun won’t be easy. To accomplish this feat, the instruments will peer through portals cut through a 15-inch thick heat shield. The titanium and aluminum baffles are sandwiched with alternating gaps to distribute and disperse the intense heat.
Ironically, such a technologically sophisticated spacecraft as Solo incorporates some old technology. The final coating on the sunward-facing side of its heat shield is of black calcium phosphate, a material similar to what humans used to render cave paintings thousands of years ago.
“It’s funny that something as technologically advanced as this is actually very old,” says Anne Parcos (ESA) in a recent press release. The powder coating not only resists breaking down under the Sun's intense ultraviolet radiation, but it's also effective in shedding heat back into space. With it, Solo can withstand temperatures up to 970°F.
Solo will be another interesting solar mission to follow as Solar Cycle 25 gets underway.
Editorial note (March 5, 2020): This article was corrected to note the first perihelion pass of the primary science mission will occur in October 2021.