Satellite to study the sun like never before
The Sun has always fascinated mankind, so it is perhaps hardly surprising that the European Space Agency (ESA) in conjunction with NASA is to launch a scientific satellite to study it like never before. However, what might be surprising (but perhaps ought not be), is that the satellite is to be largely designed and built in the UK.
European space company, Astrium, has been selected as prime contractor for the £300million Solar Orbiter mission due to launch in 2017. Solar Orbiter will carry a number of highly sophisticated, lightweight instruments, weighing a total of just 180kg. The onboard sensors will measure everything from suprathermal and energetic particles, the Sun's magnetic field, visible and ultraviolet emissions, radio and plasma waves, coronal mass ejections, different wavelengths of light emitted, non-thermal X-ray emission; all in an effort to better understand and predict solar activity.
A high resolution imager and spectrometer will capture the short wavelength, ultraviolet emissions of the Sun's atmosphere. To examine the visible light projected by the surface, and measure local magnetic fields, Solar Orbiter will carry a high-resolution magnetograph.
A vital element in the Solar Orbiter is the development of the Solar Wind Analysis (DWA) suite of sensors lead by UCL and the Mullard Space Science Laboratory. Three separate sensors will characterise electron, proton and gamma particle populations which make up solar winds, and access the abundance of heavy ions.
As well as providing overall leadership, UCL will be responsible for the Electron Analyser System (EAS). The EAS will make measure the electron velocity distributions of solar winds, and derive properties such as density, temperature, bulk velocity and heat flux.
Another sensor being developed by the Max Planck Institute in Germany is the Extreme-Ultraviolet Imager (EUI). This is a suite of remote-sensing telescopes which will capture images in high resolution and show the structures in the solar atmosphere from the chromosphere to the corona.
The EUI will observe and analyse the global morphology and local dynamics of the solar atmosphere, in particular at the base of the corona. The full-Sun imager will show the gross structure of the whole Sun at coronal temperatures, while the high-resolution telescopes will show in selected wavelength bands the fine structures that become visible in the close-up views of the Sun during the Solar Orbiter's perihelion phase of the orbit.
The EUV reflectivity of the optical surfaces is obtained with specific EUV multilayer coatings. The spectral selection is complemented with filters that reject the visible and infrared radiation. Only the ultraviolet photons can reach the detectors where they are converted into an electrical signal.
At its closest point, the spacecraft will be closer to the Sun than any previous spacecraft, braving the fierce heat and will carry its telescopes to almost one-quarter of Earth's distance from our nearest star providing unique data and imagery. It will also be the first satellite to provide close up views of the Sun's polar regions, which are very difficult to see from Earth. It will be able to almost match the Sun's rotation around its axis for several days, and so it will be able for the first time to see solar storms building up over an extended period from the same viewpoint.
