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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)

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Presentation on theme: "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)"— Presentation transcript:

1 PLATO - TOU Thermal analyses Summary of previous thermal analyses performed in S.Basso – F. Borsa (I.N.A.F. – Osservatorio Astronomico di Brera) Catania, 11/Jun./2014S.Basso - INAF OABrera

2 FE Model description: elements description 3 Bipods (link element) Catania, 11/Jun./2014S.Basso - INAF OABrera 12 points metallic ring 3 points  3 element types are used, SOLID70 and LINK33 (Ansys software) ~10000 nodes ~8000 elements

3 PLATO - TOU Baffle height Configuration 1&4 Configuration 2&3 Conf.1&4: Minimum possible height Catania, 11/Jun./2014S.Basso - INAF OABrera Fast1&42&3 Baffle height [mm] The height of the baffle for configuration 2&3 is set to obtain the same avarage temperature for the two configuration

4 FE Model results: Conf. 1&4 Heaters OFF, insulating links Baffle/tube ( W/K), no IR coating on the Window and baffle emiss.=0.94 Very close to the -90°C (goal) Catania, 11/Jun./2014S.Basso - INAF OABrera

5 FE Model results: Conf. 2&3 Heaters OFF, no IR coating on the Window and baffle emiss.=0.94 Very close to the -90°C (goal) Catania, 11/Jun./2014S.Basso - INAF OABrera

6 FE Model results: Fast TOU Heaters OFF, no IR coating on the Window and baffle emiss.=0.94 The Titanium baffle is not necessary to reach the goal (-90°C) Catania, 11/Jun./2014S.Basso - INAF OABrera

7 FE Model results: Baffle-tube connection Baffle-tube connection Catania, 11/Jun./2014S.Basso - INAF OABrera Washers Conductance baffle/tube N° joining points Joining material Flexure size [mm] (length/height/minimu m thickness) Washer - Size [mm] (ext.diameter/int.diameter /height) Ti23/7/0.7Yes (ceramic) – 10/6/ Ti23/10/0.7Yes (ceramic) – 10/6/ Al23/10/0.7Yes (ceramic) – 8/4/ Ti23/10/0.7No Al18/10/0.7 (current mechanical design) No

8 FE Model results: Last change Catania, 11/Jun./2014S.Basso - INAF OABrera Heat from CCD [W] (cold case) 0.94 (normal TOUs) 1.73 (FAST) Heat from CCD [W] (hot case) 1.46 (normal TOUs) 2.63 (FAST) OB Temperature [°C]-63 Bipod conductance [W/K]3*0.012=0.036 Lenses emissivity0.9 Outer emissivity (tube, baffle and CCD)0.005 Inner emissivity (tube and CCD)0.94 The intermediate value of W/K per bipod corresponds to the value computed with the mechanical design proposed in PLATO.LAM.SYS.SPE Issue 2

9 FE Model results: termo-elastic analyses Evaluation of thermo-elastic deformations of telescopes from 20°C to low temperature Model Thermal analysis Structural analysis Catania, 11/Jun./2014S.Basso - INAF OABrera

10 FE Model results: termo-elastic analyses Catania, 11/Jun./2014S.Basso - INAF OABrera Vertical displacement L1 L6 temperature ~ -106°C ~ -102°C Compression of lenses Compression of tube & baffle

11 FE Model results: Thermo-elastic for conf. 1&4 Catania, 11/Jun./2014S.Basso - INAF OABrera Check for tilt of lenses The presence of the baffle creates an asimmetry window: arcsec L1: arcsec

12 FE Model results: Thermo-elastic for conf. 1&4  The thermo-elastic model is OK  Z [  m] Tilt [arcsec] Window L L L L L L600 Tilt up to 25 arcsec do not influence High dependence from the baffle material Catania, 11/Jun./2014S.Basso - INAF OABrera

13 FE Model results: Conclusion Catania, 11/Jun./2014S.Basso - INAF OABrera 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


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