Around five years ago, a team led by a physicist from Kiel University, Professor Robert Wimmer-Schweingruber, won the coveted tender for providing instruments to be placed on board the “Solar Orbiter” space probe. This joint mission of the European Space Agency (ESA) and the US space agency NASA is expected to launch in October 2018, and will go closer to the sun than has ever been done before. Now, exactly on schedule, the preparations in Kiel for this mission are entering their final phase. On Monday 21 November the flight instruments from Kiel will be handed over to the space probe installation team in England.
Instruments on board a space probe must be able to withstand large temperature variations, intense vibrations during the launch of the rocket or voltage surges, without their functionality being affected. In order to ensure this, scientists at the Institute of Experimental and Applied Physics subjected their instruments to extensive tests. Representatives of ESA assessed the results just over two weeks ago, and after a few subsequent improvements, finally certified the solar particle sensors from Kiel for use in space. “Our sensors have passed the tests with flying colours!” said a delighted Wimmer-Schweingruber. “The instruments have been approved. On Monday, our team will personally deliver them to England. It is especially thanks to our excellent team that we have successfully met the tight deadline!”
A total of four instruments will be installed in the “Energetic Particle Detector” (EPD) on board the space probe. The sensors measure electrons, protons and ions of all the particles in space, from helium nuclei right through to iron nuclei. They must cover a particularly wide energy range, from approximately 2 kiloelectronvolts up to 200 megaelectronvolts. The results of these measurements will help to better understand sun particle radiation and its effect on the earth.
In addition to a team of engineers, there are also scientists, doctoral candidates and students from Kiel University involved in the EPD projects. They work together in an international team, with members from Spain, Germany and the USA. Among the total of four instruments in the “Energetic Particle Detector” (EPD) are an Instrument Control Unit (ICU) and the SupraThermal Ion Spectrograph (SIS). This SIS will undertake particle measurements during the voyage to the sun, in an energy range from around 100 kiloelectronvolts to 10 megaelectronvolts. The sensor was developed at the Johns Hopkins University Applied Physics Laboratory (APL) under the leadership of Professor Wimmer-Schweingruber.
Three sensors were developed in the Kiel physics cleanroom:
The STEP (Supra Thermal Electrons and Protons) sensor measures in the energy range from 2.5 to 65 kiloelectronvolts. If there is an influx of particles in this range, electrons are deflected by means of a magnetic field on the one side of the instrument. Only protons and ions are measured here. On the other side of the instrument, without a magnetic field, the entire flow of particles in the relevant energy range is measured. The difference between the two sides allows determination of the electrons present.
The EPT-HET1 and 2 instruments are identical, and each contain two sensors: EPT (Electron and Proton Telescope) and HET (High-Energy Telescope) sensors. Together they measure electrons in the energy range from 20 kiloelectronvolts to 20 megaelectronvolts, as well as protons from 20 kiloelectronvolts to 100 megaelectronvolts. The HET also measures heavy ions up to 200 megaelectronvolts. The EPT-HET1 and EPT-HET2 instruments can each measure in two directions (sun-facing side / dark side or alternatively prograde / retrograde relative to orbit).
The Kiel projects are funded by the DLR Space Agency, and the SIS is funded by the ESA.
Prof. Robert Wimmer-Schweingruber
Institute of Experimental and Applied Physics
mobile phone: +49 173 951 3332