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Solar Orbiter Payload Working Group Kick-off Meeting ESTEC, May 16/17 2002 Environmental Issues Solar Orbiter Payload Working Group XY-plane trajectory plot including extended mission Environmental Issues - Thermal 1.5 Nominal mission - 149 day cycle = 2,142 to 34,275 W/m2 (0.8 to 0.2 AU). 0.5 Sa Y [AU] Need to address thermal balance for high load values and for variation of thermal input. 1 We must validate the design concepts by recommending extensive modelling and tests. What facilities can be used for such testing? Alan Gabriel expresses great concern about the primary mirror temperatures - for VIM, EUS and EUI (in order). The feasibility of operating such systems must be addressed urgently. Ear 0 -1.5 -1 -0.5 0 0.5 1 1.5 thr Ve -0.5 -1 -1.5 X [AU] Solar Orbiter Payload Working Group Environmental Issues - Thermal In the proposal, few instruments have more than a ‘hand-waving’ approach to the thermal modelling. Some are more detailed, but all need a thorough thermal analysis to demonstrate feasibility. Very little has been said about the variability question - despite the variation of thermal input of a factor of 17. Large/many radiators are foreseen. Only one or two instrument teams have estimated sizes. Can we accommodate them all?! Some instruments need a light rejection path to space (VIM, UVC) - we need to accommodate this. Some further, specific issues need investigation, such as the performance and integrity of multilayers at high temperature. Solar Orbiter Payload Working Group Environmental Issues - Particles We need to consider exposure to the particle environment, including, • The 0.2 AU solar wind • Exposure to flare/CME particles, in particular at 0.2 AU • Cosmic rays • Including a consideration of solar neutrons at 0.2 AU. Solar Orbiter Payload Working Group Environmental Issues - Particles Must demonstrate that the different detector systems can cope with the particle environment. This is for the working groups. If ‘standard’ solar wind flux is 25x that at 1 AU, can we expect values of order 250 p/cm3? At 400 km/s, this is 106 hits/cm2.s. Is this a worry? Perhaps not if the detectors are ‘buried’ (i.e. do not see Sun directly) and if energies are low enough (plenty at 100 keV and less), but we must be sure. Is the chance of being hit by a stream of flare-generated energetic particles the same as at 1 AU? What about CME-shock accelerated particles? Difficult to estimate, but could be greater? Solar Orbiter Payload Working Group Environmental Issues - Particles Cosmic ray flux should be similar to 1 AU but will probably vary more with the cycle and with coronal evolution? What about neutrons? 15 min half-life means that we might expect to see some at 0.2 AU. Only from flares? Need to investigate potential effects on, e.g. our detector systems. In addition to the detectors, there is concern over optical coating - e.g. CDS study of hydrogen bubbles forming under gold-coated mirrors due to impact of solar wind on mirror surfaces. Was OK at 1 AU, but needs study to assess the effects at 0.2 AU.