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) Catania, 11/Jun./2014 S.Basso - INAF OABrera FE Model description: elements description 3 element types are used, SOLID70 and LINK33 (Ansys software) • • • 12 points metallic ring 3 points ~10000 nodes ~8000 elements 3 Bipods (link element) Catania, 11/Jun./2014 S.Basso - INAF OABrera PLATO - TOU Baffle height Configuration 1&4 Configuration 2&3 The height of the baffle for configuration 2&3 is set to obtain the same avarage temperature for the two configuration Conf.1&4: Minimum possible height Baffle height [mm] Catania, 11/Jun./2014 Fast 1&4 2&3 100 117 92 S.Basso - INAF OABrera 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 -80 tube baffle L6 L5 L4 L3 L2 L1 Window TRP tube baffle Thermal gradient inside each component L6 L5 L4 L3 L2 L1 Window Temperature 50 45 -90 40 35 -100 30 -110 -120 25 Very close to the -90°C (goal) 20 15 10 -130 5 -140 0 Al Catania, 11/Jun./2014 Ti Al Ti S.Basso - INAF OABrera FE Model results: Conf. 2&3 tube baffle L6 L5 L4 L3 L2 Temperature L1 Window Heaters OFF, no IR coating on the Window and baffle emiss.=0.94 Thermal gradient inside each component 30 -80 25 -90 20 -100 15 -110 Very close to the -90°C (goal) 10 -120 5 -130 Al baffle and coupling=0.0290 Al baffle and coupling=0.0148 Al baffle and coupling=0.0074 Ti baffle and coupling=0.0293 Catania, 11/Jun./2014 Al baffle and coupling=0.0290 Al baffle and coupling=0.0148 Al baffle and coupling=0.0074 Ti baffle and coupling=0.0293 tube L6 L5 L4 L3 L2 baffle -140 L1 Window 0 S.Basso - INAF OABrera FE Model results: Fast TOU Heaters OFF, no IR coating on the Window and baffle emiss.=0.94 tube baffle L6 L5 L4 L3 L2 Window TRP tube baffle L6 L5 L4 L3 L2 L1 Window -80 L1 Thermal gradient inside each component Temperature 40 35 -90 30 -100 -110 -120 25 The Titanium baffle is not necessary to reach the goal (-90°C) 20 15 10 -130 5 -140 0 Baffle AL Catania, 11/Jun./2014 Baffle Ti Baffle AL Baffle Ti S.Basso - INAF OABrera FE Model results: Baffle-tube connection Conductance baffle/tube N° joining points Joining material 0.0074 0.0148 0.0296 0.0296 2.9558 4 6 12 6 12 Ti Ti Al Ti Al Catania, 11/Jun./2014 Flexure size [mm] (length/height/minimu m thickness) 23/7/0.7 23/10/0.7 23/10/0.7 23/10/0.7 18/10/0.7 (current mechanical design) Washer - Size [mm] (ext.diameter/int.diameter /height) Yes (ceramic) – 10/6/10 Yes (ceramic) – 10/6/8 Yes (ceramic) – 8/4/12 No No Baffle-tube connection Washers S.Basso - INAF OABrera FE Model results: Last change Heat from CCD [W] (cold case) Heat from CCD [W] (hot case) 0.94 (normal TOUs) 1.73 (FAST) 1.46 (normal TOUs) 2.63 (FAST) OB Temperature [°C] -63 Bipod conductance [W/K] 3*0.012=0.036 Lenses emissivity Outer emissivity (tube, baffle and CCD) Inner emissivity (tube and CCD) 0.9 0.005 0.94 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 Catania, 11/Jun./2014 S.Basso - INAF OABrera FE Model results: termo-elastic analyses Evaluation of thermo-elastic deformations of telescopes Model Thermal analysis Structural analysis from 20°C to low temperature Catania, 11/Jun./2014 S.Basso - INAF OABrera FE Model results: termo-elastic analyses Compression of lenses L1 Compression of tube & baffle ~ -106°C temperature ~ -102°C Vertical displacement L6 Catania, 11/Jun./2014 S.Basso - INAF OABrera FE Model results: Thermo-elastic for conf. 1&4 The presence of the baffle creates an asimmetry window: 10.140 arcsec L1: 0.058 arcsec Check for tilt of lenses Catania, 11/Jun./2014 S.Basso - INAF OABrera FE Model results: Thermo-elastic for conf. 1&4 The thermo-elastic model is OK D Z [mm] Tilt [arcsec] Window -589 10.140 L1 -507 0.058 L2 -450 0.029 L3 -334 0.018 L4 -225 0.016 L5 -200 0 L6 0 0 Catania, 11/Jun./2014 Tilt up to 25 arcsec do not influence High dependence from the baffle material S.Basso - INAF OABrera 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: 1. 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 2. 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. 3. Adopt not conventional approaches like: • titanium baffle, • thermal filters • coating or layer on the internal surface of the baffle to reduce the internal emissivity Catania, 11/Jun./2014 S.Basso - INAF OABrera