MILANO 14-15/Dec.2010 S. Basso (INAF - Osservatorio Astronomico di Brera)

TOUs thermal analysesMILANO 14-15/Dec.2010

S. Basso (INAF - Osservatorio Astronomico di Brera)

Tasks

Milano, 14-15/Dec./2010 S.Basso - INAF OABrera

The goals of the thermal analysis are:

Dimensioning the baffle size for the three configurations in order to dissipate the heat from the ccd to the sky and to obtain a temperature of the TRP (Temperature Reference Point) of about -90°C

Understanding the temperature distribution in the TOUs (lens and structure)

FE Model description

The FEM model has been implemented according the following optical configuration (with 6lens+window)


Thickness Z quote material D/2 RcWindow 6 367.999

BK-795 inf

Window 2 361.999 95 infL1 23 359.999

S-FPL5189 177.907

L1 27.351 336.999 89 infL2 7 309.648

N-KZFS1171 794.743

L2 56.975 302.648 65 135.993L3 23 245.673

CaF257 151.934

L3 59.886 222.673 58 -225.28L4 17 162.787

S-FPL5365 -742.987

L4 16.24 145.787 65.5 -139.262L5 5 129.547

KZFSN564.8 -101.298

L5 115.547 124.547 67 -144.147L6 5 9

BK777 -103.275

L6 4 4 92 inf

FE Model description: geometrical parameters 3 cases are analyzed, two

normal TOUs and the fast TOU. The two normal TOUs have a different baffle shape and size according the position into the satellite.

Hbaffle

aincl

a


a aincl

2&3 40 24.31&4 40 37.03fast 40 30

FE Model description: thermal parameters

Emissivity of the first lens toward the sky (0.2; 0.9)

Emissivity of the last lens toward the ccd (0.3; 0.9)

Emissivity of the internal surface of the baffle (0.08; 0.3; 0.94)

Heaters (from 0 to 2 W) Heat source from the ccd (from 1.62 to

6 W) Bipod contuctance (from 3*0.00375 to

3*0.0056) Temperature of the Optical Bench (-

10°C; 0°C) Temperature of the ccd (-70°; no

constr.)

e=0.005 e =0.9

e =0.94


Heaters position

FE Model description:elements description

3 Bipods(link element)


• 12 points• metallic ring• 3 points

3 element types are used, SOLID70 and LINK33

~10000 nodes~8000 elements

FE Model description:results


Dimensioning of the baffle (middle November)configuration Normal 1&4 Normal 2&3 Fast

Qccd [W] 1.9 1.9 5bipod conductance

OB/TOU [W/K] 0.00375 0.00375 0.00375T OB [°C] -10 -10 -10

Heaters [W] 0 0 0emiss (window) 0.2 0.2 0.2

emiss (lenses) 0.9 0.9 0.9H baffle [mm] 120 160 150

angbaffleincl [deg] 37.03 24.3 30Tccd [°C] -70 -70 -70

Win

dow L1 L2 L3 L4 L5 L6

tube

+ba

ffle

-120

-115

-110

-105

-100

-95

-90

-85

-80

-113.8

-104.4

-94

-85.5

Mean temperature of each lens

Normal 2&3Normal 1&4Fast[°C]

With 5W for the Fast TOU from the CCD it is possible to dimension the heigth of the baffle

The heigth of the 2&3 TOU has been optimized to obtain the same temperature of the cases 1&4



Dimensioning of the baffle (middle November)

configuration Normal 1&4 Normal 2&3 FastQccd [W] 1.9 1.9 5

bipod conductance OB/TOU [W/K] 0.00375 0.00375 0.00375

T OB [°C] -10 -10 -10Heaters [W] 0 0 0

emiss (window) 0.2 0.2 0.2emiss (lenses) 0.9 0.9 0.9

H baffle [mm] 120 160 150angbaffleincl [deg] 37.03 24.3 30

Tccd [°C] -70 -70 -70

Win


tube

+ba

ffle

0

2

4

6

8

10

12

Thermal gradient inside each lens

Normal 2&3Normal 1&4Fast[°C]



The sensitivity has been performed on TOU 1&4 (middle November)

parameter

Value 1 Value 2 DT (TRP) [°C]

Qccd [W] 1.9 2.3 3.7

e Window 0.2 0.9 -1.5

T OB [°C] -10 0 1.6

Heaters [W] 0 2 15.1

e L6 0.9 0.2 -4.7

Note that the constrain of Tccd = -70°C overstimate the radial flux from the ccd to L6: for this reason the last row can be uncorrect.



On December the values are changed (see e-mail of Helene Pasquier 2/12/10)

1&4 Fast 1&4 FastQccd [W] 1.623 1.9776 Tmax (Window) -123.5 -114.1

bipod conductance OB/TOU [W/K] 0.0044 0.0044 Tmin (Window) -130.7 -122.8

T OB [°C] -10 -10 Tmax (L1) -121.5 -111.7Heaters [W] 0 0 Tmin (L1) -123.4 -114

emiss (Window) 0.9 0.9 Tmax (L2) -121 -111.1emiss (last lens) 0.9 0.9 Tmin (L2) -121.4 -111.6H baffle [mm] 110 95 Tmax (L3) -120.5 -110.5

angbaffle [deg] 40 40 Tmin (L3) -120.5 -110.5angbaffleincl [deg] 37.03 30 Tmax (L4) -120 -110

Tccd [°C] NA NA Tmin (L4) -120.3 -110.4cond. [W/mK] 210 210 Tmax (L5) -120.1 -110.1emiss baffle 0.94 0.94 Tmin (L5) -120.6 -110.7

TRP [°C] (~L2) -121.2 -112.55 Tmin (L6) -121.7 -112Area [m2] 0.1041 0.0789 Tmin (baffle) -124.3 -113.7

ellipt. Area [m2] 0.0897 0.0727



Temperature of 1&4 configuration with the new parametersW

indow

L1 L2 L3 L4 L5 L6 tube&

baffl

e

-130

-125

-120

-115

-110

-105

-100

-95

-90

-85

-80

K (baffle-tube) = 210 W/mK & baffle emiss. = 0.94 K (baffle-tube) = 6.7 W/mK & baffle emiss. = 0.94

K (baffle-tube) = 210 W/mK & baffle emiss. = 0.3 K (baffle-tube) = 210 W/mK & baffle emiss. = 0.08



Temperature gradient of 1&4 configuration with the new parameters

Win


tube&

baffl

e

0

2

4

6

8

10

12

14

16

K (baffle-tube) = 210 W/mK & baffle emiss. = 0.94K (baffle-tube) = 6.7 W/mK & baffle emiss. = 0.94K (baffle-tube) = 210 W/mK & baffle emiss. = 0.3



Window (fast TOU) L1 (fast TOU)



L2 (fast TOU) L3 (fast TOU)



L4 (fast TOU) L5 (fast TOU)



L6 (fast TOU) Tube + baffle (fast TOU)



Temperature at TRP (fast TOU)



Conclusion The baffle size could be as short as possible (also for the fast TOU with the new

reduced value of heat (2 W instead of 5 W) To obtain a TRP temperature of -90°C a very low value of emissivity of the baffle

must be used (14°C of thermal gradient in the window!) or insulating the baffle from the tube (problem in the convergence in the FE model)

The heaters increase the temperature in the TRP of 7,5°C/W (to be verified with the new value of the parameters). Their position must be on the top of the tube

The difference of the mean temperature of the lenses are less than 5 °C (not for the window)

Next steps Solving the problem of convergence using an insulating interface between baffle

and tube Better modeling the connections between the lens, the mechanical structure and

the ccd Implementing the thermo-elastic deformation to understand the optical behavior Improving the sensitivity analyses with the new parameters

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MILANO 14-15/Dec.2010 S. Basso (INAF - Osservatorio Astronomico di Brera)

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