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Liftoff for Solar Orbiter

(10 February 2020 - ESA) ESA’s Solar Orbiter mission lifted off on an Atlas V 411 from Cape Canaveral, Florida, at 05:03 CET on 10 February on its mission to study the Sun from new perspectives.

Signals from the spacecraft were received at New Norcia ground station at 06:00 CET, following separation from the launcher upper stage in low Earth orbit.

Facing the Sun

Solar Orbiter, an ESA-led mission with strong NASA participation, will provide the first views of the Sun’s uncharted polar regions, giving unprecedented insight into how our parent star works.

It will also investigate how intense radiation and energetic particles being blasted out from the Sun and carried by the solar wind through the Solar System impact our home planet, to better understand and predict periods of stormy ‘space weather’. Solar storms have the potential to knock out power grids, disrupt air traffic and telecommunications, and endanger space-walking astronauts, for example.

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Solar Orbiter (courtesy: ESA/ATG medialab)

“As humans, we have always been familiar with the importance of the Sun to life on Earth, observing it and investigating how it works in detail, but we have also long known it has the potential to disrupt everyday life should we be in the firing line of a powerful solar storm,” says Günther Hasinger, ESA Director of Science.

“By the end of our Solar Orbiter mission, we will know more about the hidden force responsible for the Sun’s changing behaviour and its influence on our home planet than ever before.”

“Solar Orbiter is going to do amazing things. Combined with the other recently launched NASA missions to study the Sun, we are gaining unprecedented new knowledge about our star,” said Thomas Zurbuchen, NASA’s associate administrator for Science at the agency’s headquarters in Washington.

“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 program missions to the Moon.”

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Solar Orbiter at IABG (courtesy: ESA – S. Corvaja)

At its closest, Solar Orbiter will face the Sun from within the orbit of Mercury, approximately 42 million kilometres from the solar surface. Cutting-edge heatshield technology will ensure the spacecraft’s scientific instruments are protected as the heatshield will endure temperatures of up to 500ºC – up to 13 times the heat experienced by satellites in Earth orbit.

“After some twenty years since inception, six years of construction, and more than a year of testing, together with our industrial partners we have established new high-temperature technologies and completed the challenge of building a spacecraft that is ready to face the Sun and study it up close,” adds César García Marirrodriga, ESA’s Solar Orbiter project manager.

New perspectives on our parent star

Solar Orbiter will take just under two years to reach its initial operational orbit, making use of gravity-assist flybys of Earth and Venus to enter a highly elliptical orbit around the Sun. The spacecraft will use the gravity of Venus to slingshot itself out of the ecliptic plane of the Solar System, which is home to the planetary orbits, and raise its orbit’s inclination to give us new views of the uncharted polar regions of our parent star.

The poles are out of view from Earth and to other spacecraft but scientists think they are key to understanding the Sun’s activity. Over the course of its planned five-year mission, Solar Orbiter will reach an inclination of 17º above and below the solar equator. The proposed extended mission would see it reach up to 33º inclination.

Solar Orbiter's journey to the Sun (courtesy: ESA)

“Operating a spacecraft in close proximity of the Sun is an enormous challenge,” says Sylvain Lodiot, ESA’s Solar Orbiter spacecraft operations manager.

“Our team will have to ensure the continuous and accurate pointing of the heatshield to avoid the potential damage from the Sun’s radiation and thermal flux. At the same time, we will have to ensure a rapid and flexible response to the requests of the scientists to adapt their instruments’ operations according to the most recent observations of the Sun surface.”

Solar Orbiter will use a combination of 10 in situ and remote-sensing instruments to observe the turbulent solar surface, the Sun’s hot outer atmosphere and changes in the solar wind. Remote-sensing payloads will perform high-resolution imaging of the Sun's atmosphere – the corona – as well as the solar disc. In situ instruments will measure the solar wind and the solar magnetic field in the vicinity of the orbiter.

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Solar Orbiter instruments (courtesy: ESA/ATG media lab)

The above diagram shows a cutaway of Solar Orbiter's suite of ten science instruments that will study the Sun. There are two types: in situ and remote sensing. The in situ instruments measure the conditions around the spacecraft itself. The remote-sensing instruments measure what is happening at large distances away. Together, both sets of data can be used to piece together a more complete picture of what is happening in the Sun’s corona and the solar wind.

The in situ instruments:

  • EPD: Energetic Particle Detector
    EPD will measure the energetic particles that flow past the spacecraft. It will look at their composition and variation in time. The data will help scientists investigate the sources, acceleration mechanisms, and transport processes of these particles.
    Principal Investigator: Javier Rodríguez-Pacheco, University of Alcalá, Spain
  • MAG: Magnetometer
    MAG will measure the magnetic field around the spacecraft with high precision. It will help determine how the Sun’s magnetic field links to the rest of the Solar System and changes with time. This will help us understand how the corona is heated and how energy is transported in the solar wind.
    Principal Investigator: Tim Horbury, Imperial College London, United Kingdom
  • RPW: Radio and Plasma Waves
    RPW will measure the variation in magnetic and electric fields using a number of sensors and antennas. This will help to determine the characteristics of electromagnetic waves and fields in the solar wind. RPW is the only instrument on Solar Orbiter that makes both in situ and remote sensing measurements.
    Principal Investigator: Milan Maksimovic, LESIA, Observatoire de Paris, France
  • SWA: Solar Wind Plasma Analyser
    SWA consists of a suite of sensors that will measure the solar wind’s bulk properties, such as density, velocity and temperature. It will also measure the composition of the solar wind.
    Principal Investigator: Christopher Owen, Mullard Space Science Laboratory, United Kingdom

The remote-sensing instruments:

  • EUI: Extreme Ultraviolet Imager
    EUI will take images of the solar chromosphere, transition region and corona. This will allow scientists to investigate the mysterious heating processes that take effect in this region and will allow connecting in situ measurements of the solar wind back to their source regions on the Sun.
    Principal Investigator: David Berghmans, Royal Observatory Belgium.
  • Metis: Coronagraph
    Metis will take simultaneous images of the corona in visible and ultraviolet wavelengths. This will show the structure and dynamics of the solar atmosphere in unprecedented detail, stretching out from 1.7 to 4.1 solar radii. This will allow scientists to look for the link between the behaviour of these regions and space weather in the inner Solar System.
    Principal Investigator: Marco Romoli, INAF – University of Florence, Italy
  • PHI: Polarimetric and Helioseismic Imager
    PHI will provide high-resolution measurements of the magnetic field across the photosphere, and maps of its brightness at visible wavelengths. It will also produce velocity maps of the movement of the photosphere that will allow helioseismic investigations of the solar interior, in particular the convective zone.
    Principal Investigator: Sami Solanki, Max-Planck-Institut für Sonnensystemforschung, Germany
  • SoloHI: Heliospheric Imager
    SoloHI will take images of the solar wind by capturing the light scattered by electrons particles in the wind. This will allow the identification of transient disturbances in the solar wind, such as the type that can trigger a coronal mass ejection, in which a billion tons of coronal gas can be ejected outwards into space.
    Principal Investigator: Russell A. Howard, US Naval Research Laboratory, Washington, D.C., USA
  • SPICE: Spectral Imaging of the Coronal Environment
    SPICE will reveal the properties of the solar transition region and corona by measuring the extreme ultraviolet wavelengths given off by the plasma. This data will be matched to the solar wind properties that are subsequently detected by the spacecraft’s in situ instruments. European-led facility instrument.
    Principal Investigator for Operations Phase: Frédéric Auchère, IAS, Orsay, France
  • STIX: X-ray Spectrometer/Telescope
    STIX will detect X-ray emission coming from the Sun. This could be from hot plasma, often related to explosive magnetic activity such as solar flares. STIX will provide the timing, location, intensity, and energy data for these events so that their effects on the solar wind can be better understood.
    Principal Investigator: Säm Krucker, FHNW, Windisch, Switzerland

“The combination of remote-sensing instruments, which look at the Sun, and in situ measurements, which feel its power, will allow us to join the dots between what we see at the Sun and what we experience while soaking up the solar wind,” says Daniel Müller, ESA’s Solar Orbiter project scientist.

“This will provide unprecedented insight into how our parent star works in terms of its 11-year solar activity cycle, and how the Sun creates and controls the magnetic bubble – the heliosphere – in which our planet resides.”

We are all Solar Orbiters

Solar Orbiter will be one of two complementary spacecraft studying the Sun at close proximity: it will join NASA’s Parker Solar Probe, which is already engaged in its mission.

Solar Orbiter and Parker Solar Probe have each been designed and placed into a unique orbit to accomplish their different, if complementary, goals. Parker Solar Probe ‘touches’ our star at much closer distances than Solar Orbiter, to study how the solar wind originates – but does not have cameras to view the Sun directly. Solar Orbiter flies at an ideal distance to achieve a comprehensive perspective of our star, including both remote images and in situ measurements, and will view the Sun’s polar regions for the first time.

Beyond accomplishing its own science goals, Solar Orbiter will provide contextual information to improve the understanding of Parker Solar Probe’s measurements. By working together in this way, the two spacecraft will collect complementary data sets that will allow more science to be distilled from the two missions than either could manage on its own.

“Solar Orbiter is the newest addition to the NASA Heliophysics System Observatory, joining Parker Solar Probe in an extraordinary adventure to unlock the biggest mysteries of the Sun and its extended atmosphere,” says Holly Gilbert, NASA Solar Orbiter Project Scientist.

“The powerful combination of these two missions and their awe-inspiring technology advancements will thrust our understanding to new heights.”

Solar Orbiter is set to build on the legacy of missions such as the joint ESA/NASA Ulysses and Solar and Heliophysics Observatory (SOHO), to give us the most advanced look yet at our star, and its influence on Earth.

About Solar Orbiter

Solar Orbiter is an ESA-led mission with strong NASA participation. The prime contractor is Airbus Defence and Space in Stevenage, UK. Solar Orbiter is the first ‘medium’-class mission implemented in the Cosmic Vision 2015-25 programme, the current planning cycle for ESA’s space science missions.