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Solar Orbiter Selected as ESA M-Class Mission

4 October 2011

Artists impression showing the location of the SWA sensors on the Solar Orbiter Spacecraft

UCL scientists/engineers are to provide instruments for a major space mission just selected by the European Space Agency (ESA).  The mission, called Solar Orbiter, will be sent into the inner solar system (as close as the orbit of Mercury) and will carry a set of telescopes to image the Sun and a complementary set of instruments to sample the outflowing solar wind. The mission will reveal how the Sun creates and controls the solar wind and thereby affects the environments of all the planets.  UCL has major roles in two of the ten instruments which will fly on the mission. 

On October 4th 2011, the Science Program Committee (SPC) of the European Space Agency (ESA) met to select which two of three candidate missions would be selected for the first and second (‘M1’ and ‘M2’) launch slots available for Medium class missions under its Cosmic Vision 2015-2025 Program.

The SPC selected and adopted the Solar Orbiter Mission as its M1 mission, with a scheduled launch in January 2017 from Cape Canaveral on a NASA-provided Atlas V 401 launch vehicle.  The spacecraft will undergo a number of gravity assist manoeuvres (GAM) at Earth and Venus which will act to both reduce the closest approach of the spacecraft to the Sun to 0.28 AU (1 AU is the distance from the Sun to the Earth) and to increase the orbital solar inclination angle to reach a maximum of ~34°.  

This mission scenario will enable the spacecraft to both view the Sun from close in and to view its polar regions.  In addition, a set of instruments on the spacecraft will also directly sample the electromagnetic fields and charged particles emitted from the solar surface and ejected out into interplanetary space.  Combining these measurements with the observations of activity on the solar surface will help Solar Orbiter scientists to discover how processes on the Sun create and control the interplanetary environment and ultimately affect the Earth and other planetary systems.

Cut-away diagram showing the structure of the 3 EUI telescopes

The spacecraft will carry 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.  UCL/MSSL has involvement in 2 of the key instruments on Solar Orbiter:

i) Prof. Chris Owen is Principal Investigator for the Solar Wind Analyser (SWA) Suite.  He leads an international consortium, with major partners in the USA, France and Italy.  SWA is a vital element in the Solar Orbiter in situ payload, comprising 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 streaming away from the Sun, together with measurement of 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.  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.  

Prof. Owen stated ‘We are really pleased to have successfully passed this critical milestone, as the team have been working hard towards getting this mission selected for a number of years’.

ii) Prof. Louise Harra is Co-PI and lead of the Science Working Group for the Extreme Ultra-violet Imagers (EUI) on Solar Orbiter.  This is also a multi-national collaboration, including members from UK, Belgium, France, Germany and Switzerland. The EUI instrument suite is composed of two high resolution imagers (HRI; one at Lyman-α, one at 174Å) and one dual band full-Sun imager (FSI) working alternatively at the 174 and 304 Å EUV pass-bands.  MSSL is responsible for the design, manufacture and delivery of the SO-EUI Common Electronics Box and on-board flight software. It is also responsible for the development of ground support equipment and its software.  

Prof. Harra commented ‘This will be the first time we have ever had a spacecraft in an orbit passing so close to the Sun, and carrying telescopes to image the solar atmosphere. The spatial resolution will be spectacular, and will allow us to understand what creates and accelerates the solar wind that the planets are all immersed in’.

Image of the Sun taken by the NASA SDO spacecraft on March 30, 2010, showing the highly structured and dynamic nature of the solar atmosphere, together with an prominence erupting out into interplanetary space (Credit: SDO/AIA).  Solar Orbiter will both image such activity at the Sun in multiple wavelengths, and directly sample the ejecta as they pass the spacecraft in interplanetary space.

The total cost of the mission, from designing and building the hardware through to the completion of the mission operations is capped at 499MEuros.

Contacts: Prof. Chris Owen (cjo [a t] mssl.ucl.ac.uk; Tel: 01483 204281)

Prof. Louise Harra (lkh [a t] mssl.ucl.ac.uk; Tel: 01483 204141)

Figure 1:  Artists impression showing the location of the SWA sensors on the Solar Orbiter Spacecraft

Figure 2: Cut-away diagram showing the structure of the 3 EUI telescopes

Figure 3:  Image of the Sun taken by the NASA SDO spacecraft on March 30, 2010, showing the highly structured and dynamic nature of the solar atmosphere, together with an prominence erupting out into interplanetary space (Credit: SDO/AIA).  Solar Orbiter will both image such activity at the Sun in multiple wavelengths, and directly sample the ejecta as they pass the spacecraft in interplanetary space.

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