Solar Orbiter

This article is about the European Space Agency heliophysics orbiter. For NASA's in-situ heliophysics orbiter, see Parker Solar Probe.

Solar Orbiter

ESA's Solar Orbiter An artist's impression of the Solar Orbiter.
Mission type	Solar heliophysics orbiter
Operator	ESA / NASA
COSPAR ID	2020-021A
SATCAT no.	45167
Website	sci.esa.int/solar-orbiter/
Mission duration	7 years (nominal) + 3 years (extended) ·
Spacecraft properties
Manufacturer	Airbus Defence and Space Ltd
Launch mass	1,800 kg
Payload mass	209 kg
Dimensions	2.5 x 3.1 x 2.7 m
Power	180 watts
Start of mission
Launch date	10 February 2020, 04:03 UTC
Rocket	Atlas V 411
Launch site	Cape Canaveral, SLC-41
Contractor	United Launch Alliance
Orbital parameters
Reference system	Heliocentric
Regime	Elliptic orbit
Perihelion altitude	0.28 au
Aphelion altitude	0.8-0.9 au
Inclination	24°-33°
Period	150 days
Epoch	Success
Main
Type	Ritchey-Chrétien reflector
Diameter	160 mm (6.3 in)
Focal length	2.5 m (8 ft 2 in)
Wavelengths	visible light, ultraviolet, X-rays
Instruments EPD Energetic Particle Detector EUI Extreme Ultraviolet Imager MAG Magnetometer METIS Coronagraph PHI Polarimetric and Helioseismic Imager RPW Radio and Plasma Waves SoloHI Heliospheric Imager SPICE Spectral Imaging of the Coronal Environment STIX X-ray Spectrometer/Telescope SWPA Solar Wind Plasma Analyser
File:Solar Orbiter insignia.png The insignia for the Solar Orbiter mission. Cosmic Vision

The Solar Orbiter (SolO) 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?"

SolO will make observations of the Sun from an eccentric orbit moving as close as ~60 solar radii (R_S), or 0.284 astronomical units (au), placing it inside Mercury's perihelion of 0.3075 au. During the planned 7-year mission the orbital inclination will be raised to about 25°.

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.

Scientific objectives

The spacecraft will make a close approach to the Sun every six months. 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?

Science payload

The science payload is composed of 10 instruments:

Heliospheric in-situ instruments (4)

• SWA - Solar Wind Plasma Analyser (United Kingdom): consists of a suite of sensors that will measure 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 will provide measurements of solar wind ion composition for key elements (e.g. the C, N, O group and Fe, Si or Mg).
• EPD - Energetic Particle Detector (Spain): To Measure 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.
• MAG - Magnetometer (United Kingdom): It will provide 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.
• RPW - Radio and Plasma Wavesalyzer (France): Unique amongst the Solar Orbiter instruments in that it makes both in situ and remote-sensing measurements. RPW will measure 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.

Solar remote-sensing instruments (6)

• PHI - Polarimetric and Helioseismic Imager (Germany): To provide high-resolution and full-disc 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 will 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
• EUI - Extreme Ultraviolet Imager (Belgium): To provide image sequences of 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, provide the first-ever UV images of the Sun from an out-of-ecliptic viewpoint (up to 34° of solar latitude during the extended mission phase)
• SPICE - Spectral Imaging of the Coronal Environment (France): To perform extreme ultraviolet imaging spectroscopy to remotely characterize plasma properties of the Sun's on-disc corona. This will enable matching in-situ composition signatures of solar wind streams to their source regions on the Sun's surface ··
• STIX - Spectrometer Telescope for Imaging X-rays (Switzerland): To provides imaging spectroscopy of solar thermal and non-thermal X-ray emission from 4 to 150 keV. STIX will provide 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
• METIS - Coronagraph (Italy): To simultaneously image the visible, ultraviolet and extreme ultraviolet emission of the solar corona and diagnose, 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
• SoloHI - Solar Orbiter Heliospheric Imager (United States): To image 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. It will provide unique measurements to pinpoint coronal mass ejections (CMEs). (NRL provided) ·

Timeline and status

• April 2012: €300 million contract to build orbiter awarded to Astrium UK.
• June 2014: Solar shield completes 2 week bake test.
• September 2018: Spacecraft is shipped to IABG in Germany to begin the environmental test campaign.
• February 2020: Successful launch

Launch delays

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

Trajectory

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 0.9 au. 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°.·

See also

• Advanced Composition Explorer – NASA satellite of the Explorer program
• Aditya-L1 – India's first solar observation mission
• Parker Solar Probe – NASA robotic space probe of the outer corona of the Sun
• Solar Dynamics Observatory – NASA mission, launched in 2010 to SE-L1
• Solar and Heliospheric Observatory – European space observatory
• Solar Sentinels – A 2006 concept for a series of missions to the Sun
• Space sunshade – Spacecraft shield to reduce starlight and irradiation
• STEREO – Solar observation mission (2006–present)
• TRACE – NASA satellite of the Explorer program
• Wind – NASA probe to study solar wind, at L1 since 1995Pages displaying short descriptions of redirect targets
• Ulysses – 1990 robotic space probe; studied the Sun from a near-polar orbit

External links

• Solar Orbiter homepage - ESA
• Solar Orbiter at eoPortal