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PLATO - TOU Thermal analyses

PLATO - TOU Thermal analyses. Summary of previous thermal analyses performed in 2010-2011 S.Basso – F. Borsa (I.N.A.F. – Osservatorio Astronomico di Brera ) . FE Model description : elements description. 3 element types are used, SOLID70 and LINK33 ( Ansys software). 3 Bipods

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PLATO - TOU Thermal analyses

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  1. PLATO - TOU Thermal analyses Summary of previous thermal analyses performed in 2010-2011 S.Basso – F. Borsa (I.N.A.F. – OsservatorioAstronomico di Brera) S.Basso - INAF OABrera

  2. FE Modeldescription:elementsdescription • 3 element types are used, SOLID70 and LINK33 (Ansys software) 3 Bipods (link element) • 12 points • metallic ring • 3 points • ~10000 nodes • ~8000 elements S.Basso - INAF OABrera

  3. PLATO - TOU Baffleheight Configuration 1&4 Configuration 2&3 The height of the baffle for configuration 2&3 is set to obtain the sameavarage temperature for the twoconfiguration Conf.1&4: Minimum possibleheight S.Basso - INAF OABrera

  4. FE Model results:Conf. 1&4 Heaters OFF, insulating links Baffle/tube (0.0296 W/K) , no IR coating on the Window and baffle emiss.=0.94 Verycloseto the -90°C (goal) S.Basso - INAF OABrera

  5. FE Model results:Conf. 2&3 Heaters OFF, no IR coating on the Window and baffle emiss.=0.94 Verycloseto the -90°C (goal) S.Basso - INAF OABrera

  6. FE Modelresults:Fast TOU Heaters OFF, no IR coating on the Window and baffle emiss.=0.94 The Titaniumbaffleisnotnecessarytoreach the goal (-90°C) S.Basso - INAF OABrera

  7. Washers FE Model results:Baffle-tube connection Baffle-tube connection S.Basso - INAF OABrera

  8. FE Model results:Last change The intermediate value of 0.0071 W/K per bipod corresponds to the value computed with the mechanical design proposed in PLATO.LAM.SYS.SPE.1065 - Issue 2 S.Basso - INAF OABrera

  9. FE Model results:termo-elastic analyses Evaluation of thermo-elasticdeformations of telescopes Thermalanalysis Structuralanalysis Model from 20°C to low temperature S.Basso - INAF OABrera

  10. FE Model results:termo-elastic analyses • Compression of lenses L1 • Compression of tube & baffle ~ -106°C • Vertical displacement temperature ~ -102°C L6 S.Basso - INAF OABrera

  11. FE Modelresults:Thermo-elasticforconf. 1&4 The presence of the baffle creates an asimmetry window: 10.140 arcsec L1: 0.058 arcsec Check for tilt of lenses S.Basso - INAF OABrera

  12. FE Modelresults:Thermo-elasticforconf. 1&4 • The thermo-elastic model is OK Tilt up to 25 arcsec do notinfluence High dependencefrom the baffle material S.Basso - INAF OABrera

  13. FE Model results:Conclusion • The new analyses show that the latest change in the I/F parameter move away from the goal to reach -90°C in the TRP (Temperature Reference Point) with the heaters off. The greater effect is the decrease of the CSS temperature from -10°C to -63°C. • In order to increase again the TRP Temperature to the goal the possibility are: • Increase the heaters power adding 1W for the normal TOU and 0.2W for the fast TOU. That means that the total heater power would increase of 32*1+2*0.2= 32.4W • Reducing the decoupling between the Camera I/F plane building bipods more conductive. This solution would increase the uncertainty in the mean temperature of the telescopes because the temperature of the Camera I/F plane is less known. • Adopt not conventional approaches like: • titanium baffle, • thermal filters • coating or layer on the internal surface of the baffle to reduce the internal emissivity S.Basso - INAF OABrera

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