In the early hours of Sunday, September 4, the Solar Orbiter flew close to Venus to perform a gravity-assisted maneuver that changed the spacecraft’s orbit, bringing it closer to the Sun. As if trying to get the orbiter’s attention because it’s bound to another object in the solar system, the sun unleashed a “massive coronal mass ejection” directly at the spacecraft and the planet just two days before its closest approach — and the data reveals.
On August 30, a large coronal mass ejected from the Sun in the direction of Venus. Soon, the storm reached the second planet from the Sun. As data from the Solar Orbiter continues to arrive, this hit reveals why “in situ” monitoring of space weather and its effects on spacecraft and objects in the Solar System is so important.
Fortunately, there were no negative effects on the spacecraft, as the ESA-NASA Solar Observatory is designed to withstand and measure violent outbursts from our star — although Venus doesn’t always set off so easily. Coronal mass ejections tend to erode Venus’s atmosphere, removing gases as they pass.
Fly high with Venus fly by
Solar Orbiter is a quarter of the way through its decade-long mission to observe the Sun up close and glimpse its mysterious poles. Its orbit was chosen to be in close resonance with Venus, meaning that it returns to the planet’s circumference every few orbits to use its gravity to alter or tilt its orbit.
This third flight of Venus took place on Sunday at 01:26 UTC, when the solar orbiter passed 12,500 kilometers from the center of the planet, which is nearly 6,000 kilometers from its gaseous “surface”. In other words, it traversed a distance half the width of the Earth.
The distance from Venus, the angle of approach and the speed were precisely mapped to get exactly the desired effect from the planet’s great gravity – bringing it closer to the sun than ever before.
“The close approach went perfectly to planning, thanks to a great deal of planning from our colleagues at Flight Dynamics and the diligent care of the flight control team,” explains Jose Luis Bellon Bellon, Director of Solar Vehicle Operations.
“By exchanging ‘orbital energy’ with Venus, Solar Orbiter has used the planet’s gravity to change its orbit without the need for expensive masses of fuel. When it returns to the Sun, the spacecraft’s closest approach will be about 4.5 million km closer than before.”
Understand the particles that pose a radiological hazard
Data brought home since the Solar Orbiter experienced the solar storm shows how its local environment has changed with the CME sweep. While some instruments had to be turned off as they approached Venus, in order to protect them from stray sunlight reflecting off the planet’s surface, the Solar Orbiter’s “on-site” instruments remained on, recording among other things an increase in solar-energy particles. . .
Particles, mostly protons and electrons, but also some ionized atoms like helium, emit from the sun all the time. When particularly large plasma flares and ejections are fired from the Sun, these particles are captured and carried with it, accelerating them to near-relativistic speeds. It is these particles that pose a radiological hazard to astronauts and spacecraft.
Improving our understanding of CMEs and tracking their progress as they pass through the Solar System is a big part of the Solar Orbiter’s mission. By observing CMEs, the solar wind and the Sun’s magnetic field, the spacecraft’s 10 science instruments provide new insight 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 planet Earth from violent sun eruptions.
This latest continuous medical system illustrates the difficulty of observing space weather. As shown in this footage from SOHO, a “full corona” appears when the CME is either coming straight to Earth, or in this case heading away, from the sun’s “far side.”
Determining whether coronal mass ejections are coming toward Earth or far away is difficult when viewed 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 the direction of the Earth and Vigil’s position on the ‘side’ of the sun, it will be easy and reliable to distinguish a storm that is coming or leaving.
Space weather gets deep
The sun exerts its influence on all the bodies of the solar system. This is the reason why life cannot survive on the inner planets, as their extremely high temperatures and atmospheres were stripped long ago.
As we venture from Earth to the Moon, it is crucial to understand how space weather can affect human bodies, robots, communication systems, plants and animals.
In addition to a suite of tools for understanding the Sun’s impact on Earth’s infrastructure, the European Space Agency’s Space Weather Services network is currently alerting flight teams throughout the Solar System to severe space weather, with forecasts for Mercury, Venus and Mars freely available via the network portal, and Jupiter at The Road.
“Collecting data on such events is critical to understanding how they arise, and to improve space weather models, forecasts and early warning systems,” explains Alexei Glover, Space Weather Service coordinator at the European Space Agency.
“Solar Orbiter provides us with an excellent opportunity to compare our predictions with real observations and test how well our models and tools are performing for these regions.”