Solar Orbiter

The Solar Orbiter (SolO)[8] is a Sun-observing satellite, developed by the European Space Agency (ESA). SolO is intended to perform detailed measurements of the inner heliosphere and nascent solar wind, and perform close observations of the polar regions of the Sun, which is difficult to do from Earth, both serving to answer the question "How does the Sun create and control the heliosphere?"

Solar Orbiter
ESA's Solar Orbiter
Artist's rendering of Solar Orbiter
Mission typeSolar heliophysics orbiter
OperatorESA / NASA
COSPAR ID2020-010A
SATCAT no.45167
Mission duration7 years (nominal)
+ 3 years (extended)[1][2]
Spacecraft properties
ManufacturerAirbus Defence and Space
Launch mass1,800 kg (4,000 lb)[3]
Payload mass209 kg (461 lb)[4]
Dimensions2.5 × 3.1 × 2.7 m (8 × 10 × 9 ft)[3]
Power180 watts[3]
Start of mission
Launch date10 February 2020, 04:03 UTC[5]
RocketAtlas V 411 (AV-087)[6][7]
Launch siteCape Canaveral, SLC-41
ContractorUnited Launch Alliance
Entered serviceNovember 2021
(start of main mission)
Orbital parameters
Reference systemHeliocentric
RegimeElliptic orbit
Perihelion altitude0.28 au[6]
Aphelion altitude0.91 au
Inclination24° (nominal mission)
33° (extended mission)
Period168 days
TypeRitchey-Chrétien reflector
Diameter160 mm
Focal length2.5 m
WavelengthsVisible light, ultraviolet, X-rays
Solar Orbiter insignia.png
Insignia for the Solar Orbiter mission.
Euclid →

SolO makes observations of the Sun from an eccentric orbit moving as close as ≈60 solar radii (RS), or 0.284 astronomical units (au), placing it inside Mercury's perihelion of 0.3075 au.[9] During the mission the orbital inclination will be raised to about 24°. The total mission cost is US$1.5 billion, counting both ESA and NASA contributions.[10]

SolO was launched on 10 February 2020. The mission is planned to last 7 years.

A comparison of the size of the Sun as seen from Earth (left, 1 au) and from the Solar Orbiter spacecraft (0.284 au, right).
The Solar Orbiter structural thermal model shortly before leaving the Airbus Defence and Space facility in Stevenage, UK.


The Solar Orbiter spacecraft is a Sun-pointed, three-axis stabilised platform with a dedicated heat shield to provide protection from the high levels of solar flux near perihelion. The spacecraft provides a stable platform to accommodate the combination of remote-sensing and in situ instrumentation in an electromagnetically clean environment. The 21 sensors were configured on the spacecraft to allow each to conduct its in situ or remote-sensing experiments with both access to and protection from the solar environment. Solar Orbiter has inherited technology from previous missions, such as the solar arrays from the BepiColombo Mercury Planetary Orbiter (MPO). The solar arrays can be rotated about their longitudinal axis to avoid overheating when close to the Sun. A battery pack provides supplementary power at other points in the mission such as eclipse periods encountered during planetary flybys.

The Telemetry, Tracking and Command Subsystem provides the communication link capability with the Earth in X-band. The subsystem supports telemetry, telecommand and ranging. Low-Gain Antennas are used for Launch and Early Orbit Phase (LEOP) and now function as a back-up during the mission phase when steerable Medium- and High-Gain Antennas are in use. The High-Temperature High-Gain Antenna needs to point to a wide range of positions to achieve a link with the ground station and to be able to downlink sufficient volumes of data. Its design was adapted from the BepiColombo mission. The antenna can be folded in to gain protection from Solar Orbiter's heat shield if necessary. Most data will therefore initially be stored in on-board memory and sent back to Earth at the earliest possible opportunity.

The ground station at Malargüe (Argentina), with a 35-m antenna, is used for 4 to 8 hours/day (effective). ESA's Malargüe ground station will be used for all operations throughout the mission with the ground stations in New Norcia, Australia, and Cebreros, Spain, acting as backup when necessary.[11]

Mission operationsEdit

Animation of Solar Orbiter's trajectory
Polar view. For more detailed animation, see this video
Equatorial view
   Solar Orbiter ‹See Tfd› ·   Mercury ‹See Tfd›  ·   Venus ‹See Tfd› ·   Earth ‹See Tfd› ·   Sun ‹See Tfd›

During nominal science operations, science data is downlinked for eight hours during each communication period with the ground station. Additional eight-hour downlink passes are scheduled as needed to reach the required total science data return of the mission. The Solar Orbiter ground segment makes maximum reuse of ESA's infrastructure for Deep Space missions:

  • The ground stations, which belong to ESA's space tracking station network (ESTRACK)
  • The Mission Operations Centre (MOC), located at ESOC, Darmstadt, Germany
  • The Science Operations Centre (SOC), located at ESAC, Villanueva de la Cañada, Spain
  • The communications network, linking the various remotely located centres and stations to support the operational data traffic

The Science Operations Centre was responsible for mission planning and the generation of payload operations requests to the MOC, as well as science data archiving. The SOC has been operational for the active science phase of the mission, i.e. from the beginning of the Cruise Phase onwards. The handover of payload operations from the MOC to the SOC is performed at the end of the Near-Earth Commissioning Phase (NECP). ESA's Malargüe Station in Argentina will be used for all operations throughout the mission, with the ground stations of New Norcia Station, Australia, and Cebreros Station, Spain, acting as backup when necessary.[12]

During the initial cruise phase, which lasts until November 2021, Solar Orbiter will perform two gravity-assist manoeuvres around Venus and one around Earth to alter the spacecraft's trajectory, guiding it towards the innermost regions of the Solar System. At the same time, Solar Orbiter will acquire in situ data and characterise and calibrate its remote-sensing instruments. The first close solar pass will take place in 2022 at around a third of Earth's distance from the Sun.[13]

The spacecraft's orbit has been chosen to be 'in resonance' with Venus, which means that it will return to the planet's vicinity every few orbits and can again use the planet's gravity to alter or tilt its orbit. Initially, Solar Orbiter will be confined to the same plane as the planets, but each encounter of Venus will increase its orbital inclination. For example, after the 2025 Venus encounter, it will make its first solar pass at 17° inclination, increasing to 33° during a proposed mission extension phase, bringing even more of the polar regions into direct view.[13]

Scientific objectivesEdit

The spacecraft makes a close approach to the Sun every six months.[14] The closest approach will be positioned to allow a repeated study of the same region of the solar atmosphere. Solar Orbiter will be able to observe the magnetic activity building up in the atmosphere that can lead to powerful solar flares or eruptions.

Researchers will also have the chance to coordinate observations with NASA's Parker Solar Probe mission (2018-2025) which is performing measurements of the Sun's extended corona.

The objective of the mission is to perform close-up, high-resolution studies of the Sun and its inner heliosphere. The new understanding will help answer these questions:

  • How and where do the solar wind plasma and magnetic field originate in the corona?
  • 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?


The science payload is composed of 10 instruments:[15]

Heliospheric in-situ instruments (4)
  • SWA - Solar Wind Plasma Analyser (United Kingdom): Consists of a suite of sensors that measures the ion and electron bulk properties (including density, velocity, and temperature) of the solar wind, thereby characterizing the solar wind between 0.28 and 1.4 au from the Sun. In addition to determining the bulk properties of the wind, SWA provides measurements of solar wind ion composition for key elements (e.g. the C, N, O group and Fe, Si or Mg)[16]
  • EPD - Energetic Particle Detector (Spain): Measures the composition, timing and distribution functions of suprathermal and energetic particles. Scientific topics to be addressed include the sources, acceleration mechanisms, and transport processes of these particles[17]
  • MAG - Magnetometer (United Kingdom): Provides in situ measurements of the heliospheric magnetic field with high precision. This will facilitate detailed studies into the way the Sun's magnetic field links into space and evolves over the solar cycle; how particles are accelerated and propagate around the Solar System, including to the Earth; how the corona and solar wind are heated and accelerated[16]
  • RPW - Radio and Plasma Waves (France): Unique amongst the Solar Orbiter instruments, RPW makes both in situ and remote-sensing measurements. RPW measures magnetic and electric fields at high time resolution using a number of sensors/antennas, to determine the characteristics of electromagnetic and electrostatic waves in the solar wind[16]
Solar remote-sensing instruments (6)
  • PHI - Polarimetric and Helioseismic Imager (Germany): Provides high-resolution and full-disk measurements of the photospheric vector magnetic field and line-of-sight (LOS) velocity as well as the continuum intensity in the visible wavelength range. The LOS velocity maps have the accuracy and stability to allow detailed helioseismic investigations of the solar interior, in particular of the solar convection zone high-resolution and full-disk measurements of the photospheric magnetic field[4]
  • EUI - Extreme Ultraviolet Imager (Belgium): Images the solar atmospheric layers above the photosphere, thereby providing an indispensable link between the solar surface and outer corona that ultimately shapes the characteristics of the interplanetary medium. Also, EUI provides the first-ever UV images of the Sun from an out-of-ecliptic viewpoint (up to 33° of solar latitude during the extended mission phase)[4]
  • SPICE - Spectral Imaging of the Coronal Environment (France): Performs extreme ultraviolet imaging spectroscopy to remotely characterize plasma properties of the Sun's on-disk corona. This will enable matching in situ composition signatures of solar wind streams to their source regions on the Sun's surface[4][18][19]
  • STIX - Spectrometer Telescope for Imaging X-rays (Switzerland): Provides imaging spectroscopy of solar thermal and non-thermal X-ray emission from 4 to 150 keV. STIX provides quantitative information on the timing, location, intensity, and spectra of accelerated electrons as well as of high-temperature thermal plasmas, mostly associated with flares and/or microflares[4]
  • Metis[20] - Coronagraph (Italy): Simultaneously images the visible and far ultraviolet emissions of the solar corona and diagnoses, with unprecedented temporal coverage and spatial resolution, the structure and dynamics of the full corona in the range from 1.4 to 3.0 (from 1.7 to 4.1) solar radii from Sun centre, at minimum (maximum) perihelion during the nominal mission. This is a region that is crucial in linking the solar atmospheric phenomena to their evolution in the inner heliosphere[4]
  • SoloHI - Solar Orbiter Heliospheric Imager (United States): Images both the quasi-steady flow and transient disturbances in the solar wind over a wide field of view by observing visible sunlight scattered by solar wind electrons. SoloHI provides unique measurements to pinpoint coronal mass ejections (CMEs). (NRL provided)[21][22]

Institutions involvedEdit

The following institutions operate each instrument:[23]

Timeline and statusEdit

  • April 2012: €300 million contract to build orbiter awarded to Astrium UK[25]
  • June 2014: Solar shield completes 2 week bake test[26]
  • September 2018: Spacecraft is shipped to IABG in Germany to begin the environmental test campaign[27]
  • February 2020: Successful launch[28]
  • May-June 2020: Encounter with the ion and dust tails of C/2019 Y4 (ATLAS)[29][30]

Launch delaysEdit

In April 2015, the launch was set back from July 2017 to October 2018.[31] In August 2017, Solar Orbiter was considered "on track" for a launch in February 2019.[32] The launch occurred on 10 February 2020[5] on an Atlas V 411.[7][33]

The launch of Solar Orbiter from Cape Canaveral at 11.03pm EST on 9th February 2020 (US date).


The Atlas V 411 (AV-087) lifted off from SLC-41 at Cape Canaveral, Florida, at 04:03 UTC. The Solar Orbiter spacecraft separated from the Centaur upper stage nearly 53 minutes later, and the European Space Agency acquired the first signals from the spacecraft a few minutes later.[10]


After launch, Solar Orbiter will take approximately 3.5 years, using repeated gravity assists from Earth and Venus, to reach its operational orbit, an elliptical orbit with perihelion 0.28 AU and aphelion 0.91 AU. The first flyby will be Venus in December 2020. Over the expected mission duration of 7 years, it will use additional gravity assists from Venus to raise its inclination from 0° to 24°, allowing it a better view of the Sun's poles. If an extended mission is approved, the inclination could rise further to 33°.[1][34]

During its cruise phase to Venus, Solar Orbiter passed through the ion tail of Comet C/2019 Y4 (ATLAS) from 31 May to 1 June 2020. It will pass through the comet's dust tail on 6 June 2020.[29][30]

In June 2020, Solar Orbiter came within 77,000,000 km (48,000,000 mi) of the Sun, and captured the closest pictures of the Sun ever taken.[35]

The speed of the probe and distance from the Sun

See alsoEdit


  1. ^ a b Update: 1 September 2019 - 8 February 2020
  2. ^ "Solar Orbiter Mission". ESA eoPortal. Retrieved 17 March 2015.
  3. ^ a b c - 9 February 2020
  4. ^ a b c d e f - Last Update: 22 January 2020 - Retrieved 9 February 2020
  5. ^ a b - 8 February 2020
  6. ^ a b "NASA - NSSDCA - Spacecraft - Details".
  7. ^ a b "NASA Selects United Launch Alliance Atlas V Rocket to Launch Solar Orbiter Mission". United Launch Alliance. Digital Journal. 18 March 2014. Retrieved 19 March 2014.
  8. ^ Solar Orbiter (SolO). Leibniz-Institut für Astrophysik Potsdam (AIP). Accessed on 18 December 2019.
  9. ^ "Kiepenheuer-Institut fuer Sonnenphysik: SolarOrbiter PHI-ISS". Retrieved 9 August 2018.
  10. ^ a b - 11 February 2020
  11. ^ "ESA Science & Technology - Spacecraft".
  12. ^ "ESA Science & Technology - Mission Operations".
  13. ^ a b "GMS: Solar Orbiter's Orbit". 27 January 2020. Retrieved 14 February 2020.   This article incorporates text from this source, which is in the public domain.
  14. ^ - 10 February 2020
  15. ^ "Solar Orbiter". European Space Agency. Retrieved 2 August 2018.
  16. ^ a b c - 22 January 2020 - 10 February 2020
  17. ^ - Update 22 January 2020
  18. ^ "SPICE on Solar Orbiter official website". 12 November 2019. Retrieved 12 November 2019.
  19. ^}}
  20. ^ "MPS: SPICE: Spectral Imaging of the Coronal Environment". 11 May 2011. Archived from the original on 11 May 2011.
  21. ^ - Last Update: 22 January 2020 - Retrieved 8 February 2020
  22. ^ "Solar Orbiter Heliospheric Imager (SoloHI) – Space Science Division". Retrieved 9 August 2018.
  23. ^
  24. ^ Leibniz-Institut für Astrophysik Potsdam. "Solar Orbiter (SolO)". Webseite.
  25. ^ "ESA contracts Astrium UK to build Solar Orbiter". April 2012.
  26. ^ "Solar Orbiter's shield takes Sun's heat". June 2014.
  27. ^ Amos, Jonathan (18 September 2018). "Solar Orbiter: Spacecraft to leave UK bound for the Sun". BBC News.
  28. ^ Thompson, Amy. "Solar Orbiter launches on historic mission to study the sun's poles". Retrieved 10 February 2020.
  29. ^ a b "Solar Orbiter to pass through the tails of Comet ATLAS". 29 May 2020. Retrieved 1 June 2020.
  30. ^ a b Wood, Anthony (29 May 2020). "ESA'S Solar Orbiter set for unexpected rendezvous with Comet ATLAS". New Atlas. Retrieved 1 June 2020.
  31. ^ "ESA Science & Technology - Solar Orbiter launch moved to 2018".
  32. ^ "Europe's Solar Orbiter on track for 2019 launch". Air & Cosmos. 28 August 2017. Retrieved 19 September 2017.
  33. ^ "Solar Orbiter: Summary". ESA. 20 September 2018. Retrieved 19 December 2018.
  34. ^ "ESA Science & Technology: Summar". Sci.esa.inty. 28 February 2018. Retrieved 20 March 2018.
  35. ^

External linksEdit