In the early hours of Sunday, September 4, Solar Orbiter flew by Venus in a gravity-assisted maneuver that changed the spacecraft’s orbit and brought it closer to the sun. As if the orbiter was trying to get its attention as it approached another body in the solar system, just two days before their closest approach, the sun threw massive ‘coronal mass ejection’ directly at spacecraft and planets – data reveal at this point.
On August 30, a large coronal mass ejection shot from the sun in the direction of Venus. Shortly after, the storm reached the second planet from the sun. As data continues to stream from Solar Orbiter, the strike sheds light on why “in situ” monitoring of space weather and its impact on solar system objects and spacecraft is so important.
Fortunately, there’s no negative impact on the spacecraft, as the ESA-NASA Solar Observatory is designed to withstand and actually measure violent outbursts from our star — although Venus doesn’t always go away that easily. CMEs have a tendency to erode Venus’ atmosphere, stripping gas as they whizz by.
Fly higher with Venus
Solar Orbiter has completed a quarter of its decade-long mission to observe the Sun up close and learn about its mysterious poles. Its orbit was chosen to resonate closely with Venus, meaning it returns to Earth’s vicinity every few orbits, using its gravity to alter or tilt its orbit.
Venus’ third flyby occurred at 01:26 UTC on Sunday, when Solar Orbiter passed 12,500 kilometers from the center of Venus, about 6,000 kilometers from its gaseous “surface.” In other words, it traveled half the width of the Earth.
Its distance, approach angle, and velocity to Venus have all been carefully engineered to get the exact desired effect from Venus’ massive gravitational pull — bringing it closer to the sun than ever before.
“The close approach went exactly as planned, thanks to extensive planning by our colleagues in the flight dynamics department and diligent care from the flight control team,” explained Solar Orbiter Operations Manager Jose-Luis Pellon-Bailon.
“By exchanging ‘orbital energy’ with Venus, Solar Orbiter uses Venus’ gravity to change its orbit without the need for a lot of expensive fuel. When it returns to the sun, the spacecraft’s closest distance will be closer to 4.5 million kilometers than before.”
Learn about the particles that pose a radiation risk
Since Solar Orbiter encountered a solar storm, the data came home, showing how the local environment has changed as the large CME swept in. While some instruments had to be turned off when approaching Venus to protect them from stray sunlight reflecting off the planet’s surface, Solar Orbiter’s “in situ” instruments remained on, which recorded an increase in the sun’s energetic particles.
The sun is always emitting particles, mainly protons and electrons, and some ionized atoms like helium. When particularly large flares and plasma jets are shot from the sun, these particles are picked up and carried with them, accelerating to near-relativistic velocities. It is these particles that pose a radiation risk to astronauts and spacecraft.
Improving our understanding of CMEs and tracking their progress as they zip through the solar system with ease is an important part of the Solar Orbiter mission. By observing the CME, the solar wind and the sun’s magnetic field, the spacecraft’s ten science instruments are providing new insights into how the 11-year cycle of solar activity works. Ultimately, these findings will help us better predict periods of stormy space weather and protect Earth from the sun’s violent outbursts.
Recent CMEs illustrate the difficulties of space weather observations. As can be seen in this video from SOHO, the “full halo” is visible as the CME rushes directly towards Earth, or in this case directly off the “far side” of the Sun.
From Earth, it’s tricky to determine whether a coronal mass ejection is headed toward or away from Earth, because in both cases it appears to be expanding. One of the many benefits of the upcoming Vigil mission is that by combining images taken from Earth’s direction and Vigil’s position on the “side” of the sun (the fifth Lagrangian point), distinguishing between incoming or departing storms will made easy and reliable.
space weather gets darker
The sun exerts influence on all celestial bodies in the solar system. This is why no life can survive on the inner planets, the temperatures are too high and their atmospheres were stripped long ago.
Understanding how space weather affects the human body, robots, communication systems, and plants and animals is critical as we venture from Earth to the moon.
In addition to a range of tools for understanding the sun’s impact on Earth’s infrastructure, ESA’s Space Weather Service network currently issues extreme space weather alerts to teams on missions throughout the solar system, and provides free access to Mercury, Venus and Mars through a web portal forecast, and Jupiter on the way.
“Collecting data on such events is critical to understanding how they arise and improving our space weather models, predictions and warning systems,” explains Alexi Glover, ESA’s Space Weather Service Coordinator.
“Solar Orbiter provides us with an excellent opportunity to compare our predictions with actual observations and to test how well our models and tools perform in these regions”.