Solar Orbiter is on its way
A rocket carrying Solar Orbiter, a probe that will take pictures of the top and bottom of the sun, launched Sunday night. The Atlas 5 rocket launched on time, just as the final Oscar statues were being handed out for the 2020 Academy Awards. It illuminated the night sky over Florida’s Atlantic coast as it headed away from Earth to place thespacecraft into an orbit around the sun.
It was a successful beginning to a mission that is a collaboration between NASA and the European Space Agency. In the day ahead, Solar Orbiter will test its instruments and prepare to initiate the complex maneuvers it needs to set course for what scientists hope is a decade of solar discoveries.
A new view of the sun
With Solar Orbiter, scientists will for the first time get a good view of the top and bottom of the sun. Until now, almost all of the solar-watching spacecraft have orbited in the ecliptic, or the same plane that the planets travel around the sun.
That change of view could help solve mysteries about how the sun spews high-velocity charged particles that fly outward through the solar system and buffet the planets, including Earth. The magnetic fields that accelerate those particles flow into and out of the sun’s poles. The data from Solar Orbiter could help explain the sunspot cycle — Why does the cycle last 11 years? Why are some quiet and others roar violently? — and help models to predict solar storms that could disrupt Earth’s power grids and satellites in orbit.
Ulysses, an earlier collaboration between NASA and the European Space Agency launched in 1990, also passed over the sun’s poles, but at much farther distances, and it did not carry a camera.
A long and winding journey
The launch trajectory will take Solar Orbiter away from Earth into an orbit around the sun. A flyby of Venus on the day after Christmas will sap some of its energy and let it spiral closer toward the sun.
Additional flybys — one of Earth, two more of Venus — will further adjust the orbit, which will still be in the ecliptic, the plane of the orbits.
A flyby of Venus in 2025 will swing Solar Orbiter out of the ecliptic to an angle of 17 degrees. That is enough to get a good glimpse of the polar regions. Additional Venus flybys will increase the angle to 33 degrees.
The mission is expected to complete 22 orbits of the sun in 10 years.
Solar Orbiter’s instruments
The spacecraft’s 10 scientific instruments are a mix. Some measure what is happening directly around the spacecraft, like the magnetic fields and particles of the solar wind. Others take pictures of what is occurring on the sun.
Remember the caution that you should not look directly at the sun? Solar Orbiter’s cameras have to do just that, and at a distance where the sunlight is 13 times as intense. Three peepholes in the heat shield will open for 10 days at a time to allow the instruments to collect data. The assorted cameras also have heat-resistant windows (think of them as scientific sunglasses) as protection.
The cameras will look at a range of wavelengths of light, including ultraviolet and X-rays. Some of the cameras break the light into separate wavelengths to identify specific molecules. The coronagraph includes a disk to block out most of the light to look at what is going on in the sun’s outer atmosphere.
Magnetic fields and solar storms
Occasionally, the sun erupts giant amounts of particles known as coronal mass ejections. When such an eruption slams into Earth’s magnetic field, it generates surges of electrical current.
Solar scientists do not have reliable ways to predict such an eruption. The largest one known to hit Earth was the Carrington event in 1859, named after one of the people who observed an intensely bright spot on the sun where the eruption occurred. The surge caused some telegraph wires to catch fire.
When Nicola J. Fox, director of NASA’s heliophysics division, talks about solar science to children at schools she introduces the Carrington event and how it knocked out the telegraph system in the U.S. for four days.
“The kids just kind of look at me like, ‘So what?’,” she said. “And then I say, ‘Imagine you didn’t have your iPad for four days.’ Panic ensues in the classroom.”
A similar event today could potentially cause not only continentwide blackouts, but also destroy giant transformers on the electric grid — damage that might take months or years to repair.
A smaller solar storm in March 1989 knocked out power in Quebec for nine hours.
Just a few years ago, Earth was lucky.
On July 23, 2012, NASA’s Stereo-A spacecraft was hit by a gigantic coronal mass ejection. Analysis showed that this outburst was bigger than the Carrington eruption. If Earth had been where Stereo-A was — the spacecraft travels in the same orbit as Earth, but ahead of the planet — that would have been a very interesting day.
A partnership with Parker Solar Probe
In 2018, NASA launched the Parker Solar Probe, which is making closer and closer flybys of the sun as it reaches the fastest speeds ever achieved by a human-built spacecraft. That probe is flying into the sun’s outer atmosphere, known as the corona, and eventually coming within four million miles of its surface. By comparison, Earth is 93 million miles from the sun. Mercury, the closest planet, is 29 million miles from the sun.
The close distance allows the Parker Solar Probe to make direct measurements of those regions, but it has to be protected from temperatures of about 2 million degrees Fahrenheit.
Solar Orbiter will be passing farther from the sun. At the closest point along its elliptical orbit, it will be just three million miles inside of the orbit of Mercury, and experience much less extreme temperatures. Instead of millions of degrees, temperatures at Solar Orbiter will reach several hundred degrees. That allows Solar Orbiter to carry a wider range of instruments.
Coordinated observations between Parker and Solar Orbiter could identify phenomena on the surface with conditions in the corona.
“It’s really a perfect dream, a marriage in heaven,” said Guenther Hasinger, director of science at European Space Agency during a news conference on Friday.
A fleet of sun watchers
In addition to Solar Orbiter and Parker Solar Probe, nine other missions are currently keeping an eye on the sun and the solar wind. Each has been designed to add unique data to our understanding of what our star is doing.
Here is what else is out there:
Advanced Composition Explorer, or ACE — A NASA spacecraft that monitors the solar wind from a vantage point between Earth and the sun.
Cluster — Four European Space Agency Earth-orbiting spacecraft investigating the interactions of the solar wind with Earth’s magnetic field.
Hinode — A Japanese spacecraft measuring the sun’s magnetic fields.
Interface Region Imaging Spectrograph, or IRIS — A small NASA ultraviolet telescope in orbit around Earth that studies the movement of heat and energy in the lower parts of the sun’s atmosphere.
Proba-2 — Two instruments on this low-cost European Space Agency satellite observe the sun.
Solar Terrestrial Relations Observatory, or Stereo — A NASA mission of two nearly identical spacecraft traveling around the sun in the same orbit as Earth, with one ahead of Earth and one trailing.
Solar Dynamics Observatory, or S.D.O. — A NASA spacecraft in geosynchronous orbit that studies the influence of the sun and solar weather on Earth.
Solar and Heliospheric Observatory, or SOHO — An earlier European-NASA collaboration that has been taking pictures of the sun since 1995.
Wind — A NASA spacecraft observing heated gas of charged particles coming from the sun.
European spacecraft, American rocket
Many big space missions are international collaborations. For Solar Orbiter, the European Space Agency was in charge of developing the spacecraft and its instruments. NASA paid for the Atlas 5 rocket for the trip to space.
The James Webb Space Telescope, the successor to the Hubble Space Telescope, is the opposite. NASA is building the telescope, and the Europeans are providing the launch vehicle, an Ariane 5 rocket from French Guiana.
The Rosalind Franklin rover that is to launch to Mars this summer was originally another NASA-European Space Agency collaboration but NASA backed out in 2012, because of cuts in the NASA budget. The Europeans turned to Russia to provide the rocket and the system to land the rover on the surface.
A slightly less busy rocket day
Solar Orbiter was not the only spacecraft scheduled to be launched from the East Coast on Sunday. A crewless Antares cargo ship with supplies, equipment and experiments destined for International Space Station was to lift off at 5:39 p.m. Eastern time from the Mid-Atlantic Regional Spaceport in Virginia. However, after a short postponement, Sunday’s launch was called off.
Northrop Grumman, which manages the Antares and Cygnus flights, described a problem with a sensor on the ground. It said it will not be able to attempt a launch again until Thursday because of weather concerns as well as time needed to address the problem that caused the scrubbed launch.