As ESA resume activities of science instruments after a shutdown and a safe standby period due to the COVID-19 pandemic, ESA’s planetary missions are getting back, including the ESA-NASA’s Solar Probe, gathering science data from around the Solar System.

On February 9, 2020, the United Launch Alliance Atlas V 411 rocket departed Cape Canaveral carrying the Solar Orbiter. The next day, mission controllers at ESOC (Space Operations Center) in Germany, received a signal indicating that the solar panels had successfully deployed.

The mission is led by ESA (European Space Agency) in cooperation with NASA, and it had the spacecraft developed by Airbus. It aims to take a close approach in studying the sun, its outer atmosphere, and solar wind, providing the first images of the sun’s poles and its magnetic environment. That will help to understand the sun’s 11 years solar cycle and its periodic solar storms.

Since the 90s, ESA has missions (Ulysses, SOHO, and Cluster) investigating the sun and its impact on the earth. According to Günther Hasinger, ESA’s Director of Science, the importance of the sun to life on earth, has been observed and investigated, and the potential of a solar storm to disrupt life is also known. It is expected to know more about the forces responsible for the sun’s changing behavior and its effect on the earth by the end of the mission. And how the inner heliosphere works, the impact caused by solar activity on it, which are a significant breakthrough. It will examine the charged particles blown by the solar wind into the interstellar medium.

The solar orbiter was selected as the first medium-class mission of ESA’s Cosmic Vision 2015-2025 Programme. It counts with high spatial resolution telescopes to capture data in the orbiter’s environment, to help understand how the sun can affect the environment throughout our solar system. 

Solar Orbiter’s unique trajectory includes Mercury’s orbit and 22 close approaches to the sun, operating in and out of the ecliptic plane, and measuring solar wind plasma, fields, waves, and energetic particles close enough from the sun to ensure that they are still relatively pristine.

For that, the orbiter has ten instruments. ESA member states and ESA provided nine, and NASA provided one and an additional sensor. The scientific payload elements of Solar were selected through a competitive selection process. The Solar Orbiter payload has a set of in situ and a set of remote-sensing instruments and a total payload mass of 209 kg. 

The in situ instruments will always be operating, measuring the environment around the spacecraft, identifying the presence of particles, waves, and electric and magnetic fields. The remote sensing will be restricted to 30 days per orbit when the orbiter reaches its highest angles to the solar equator and its closest reach to the sun. And it will picture the sun, its atmosphere, and its flow of material. The data collected will help to understand the sun’s internal functioning. The solar poles view will help us understand how dynamo processes generate the sun’s magnetic field.  

The remote-sensing instruments:  

EUI: Extreme Ultraviolet Imager  

METIS: Coronagraph  

PHI: Polarimetric and Helioseismic Imager  

SoloHI: Heliospheric Imager  

SPICE: Spectral Imaging of the Coronal Environment  

STIX: X-ray Spectrometer/Telescope  

The in situ instruments:  

EPD: Energetic Particle Detector  

MAG: Magnetometer  

RPW: Radio and Plasma Waves  

SWA: Solar Wind Plasma Analyzer  

Science Questions

Each orbital will be dedicated to a top-level science question, considering that its characteristics will change during the mission’s course. The questions are:  

“What drives the solar wind, and where does the coronal magnetic field originate from? 

How do solar transients drive heliospheric variability? 

How do solar eruptions produce energetic particle radiation that fills the heliosphere? 

How does the solar dynamo work and drive connections between the sun and the heliosphere?”  

Researchers will be able to coordinate investigations with NASA’s Parker Solar Probe mission, which will make measurements in the sun’s extended corona.  

 Mission’s Duration and Infrastructure

The duration of the nominal mission would be six to seven years, and the total extended mission would be ten years, with the cruise phase lasting two to three and a half years, and the science phase for around four years. There will be checks to ensure the ten scientific instruments are working as expected during the three months of the commissioning stage. 

During the cruise phase, there will be three gravity assist maneuvers (two past Venus in December 2020 and August 2021, and one past Earth in November 2021), the spacecraft will use that to approach the sun. However, the mission will regularly use Venus gravity assists to get closer to the sun, lifting it out of the ecliptic plane.  

The ground segment will reuse ESA’s infrastructure for Deep Space Missions (ESTRACK, MOC, SOC, ESOC, and ESA’s communication network).  

The spacecraft has a three-axis stabilized platform with a shield to protect from high levels of solar flux near perihelion. And it uses technology from previous missions, such as the solar arrays and the High-Temperature High-Gain Antenna from the BepiColombo Mercury Planetary Orbiter. 

The arrays can rotate to avoid overheating when close to the sun. The antenna also needs to handle the high thermal load; for that, it can fold and use the orbiter shield to protect itself. To provide extra power in moments, such as eclipse, the spacecraft counts with a battery pack. 

The data collected by the mission will be stored onboard and sent back to earth at the earliest possibility.  

To know more about the mission, visit ESA and NASA’s websites.

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This article was written by Juliane Verissímo - Marketing Department of VisionSpace