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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.