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The spacecraft carries 10 separate instruments, including both remote sensing instruments for observing the Sun and in situ instruments which sample the fields and particles in the solar wind.
Credit: ESA
28 October 2024
Solar Orbiter was selected as the first element in the European Space Agency (ESA) Cosmic Vision 2015-2025 programme in October 2011. Following the launch, in February 2020, the Solar Orbiter spacecraft has orbited the Sun once every ~6 months. A series of gravitational assist manouevres at the Earth and Venus (EGAM/VGAM) have lowered the closest approach to the Sun to 0.28 AU (1 AU – an astronomical unit – is the distance of the Earth from the Sun). In February 2025 a VGAM will occur which will start to raise the plane of the orbit out of the ecliptic, such that the spacecraft will reach higher and higher heliocentric latitudes (~34° by the end of the mission). The near-Sun distances allow the spacecraft to orbit the Sun with a reduced angular speed relative to the solar rotation (~25.5 days), such that individual active regions on the surface, will remain beneath the spacecraft and visible to the remote sensing instruments for an extended period of time. The tilted plane of the orbit will allow a more detailed view of the poles of the Sun and enhanced sampling of the solar wind emitted from these regions.
The spacecraft carries a payload comprising 10 separate instruments, or suites of instruments. These can be divided into two groups: (i) The remote sensing instruments, which are tasked to observed the dynamics of the Sun and its surface layers in a variety of different wavelengths and through a variety of techniques; (ii) the in situ instruments which will study the particles, fields and waves fields in the solar wind immediately above those source regions on the Sun which are monitored by the remote sensing instruments.
A vital element in the Solar Orbiter in situ payload is the SWA suite of sensors. Made up of 3 separate sensors and a central DPU, the SWA suite has the key task of characterizing the vast majority of the electron, proton and α-particle populations, which comprise the solar wind, together with measurement of the abundant heavy ions, such as O6+ and low iron charge states such as Fe9+ or Fe10+. These measurements provide the means by which plasma processes observed remotely on the Sun can be linked to their output exhausts in the solar wind.
The SWA investigation is a major international hardware collaboration, led by UCL/MSSL (Principal Investigator: Prof. Christopher J. Owen). In addition to the overall leadership of the suite, UCL/MSSL will provide the bulk of the hardware for the Electron Analyser System, one of the 3 sensor systems within the suite. The Proton-Alpha Sensor and the Heavy Ion Sensor are led by partners in France and the USA respectively. The central data processing unit, built in Italy, serves all 3 sensors and completes the suite.
A complete description of the SWA suite can be found in the instrument paper:
Owen, C.J., et al., The Solar Orbiter Solar Wind Analyser (SWA) Suite, doi:10.1051/0004-6361/201937259, A&A, 642, A16, 2020.
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More details and news can be found on the ESA Solar Orbiter website.
