Pre-Phase A Report - Lisa - Nasa

128 Chapter 5 Payload Design
Resulting temperatures are summarised in Table 5.3 .
Location T Location T
( ◦ C) ( ◦ C)
Optics bench 21.0 Support cylinder stiffening ring 4 (front) 2.2
Proof mass 20.4 Support cylinder middle 14.3
Sensor 20.4 USO box plate 24.7
Titanium housing 20.4 USO box 26.6
Primary mirror −19.7 End plate of Y-shaped tube 19.8
Secondary mirror −45.3 Y-tube apex (surrounding USO boxes) 19.8
Telescope thermal shield 4.4 Y-tube, from USO plate to electronic plate 23.0
Electronics plate 32.1 Y-tube, from electronics plate to primary mirror 11.8
Analogue electronics box on plate 33.6 Y-tube in front of primary mirror, aft end −33.2
Digital electronics box on plate 33.8 Y-tube in front of primary mirror, middle −49.0
Support cylinder stiffening ring 1 18.6 Y-tube in front of primary mirror, front end −65.4
Support cylinder stiffening ring 2 16.0 Laser electronics radiator 12.2
Support cylinder stiffening ring 3 9.7 Sunshield
Table 5.3 Nominal case temperature distribution.
When the results for the nominal steady state case are applied to the detailed optical bench
model the maximum temperature predicted, in the region of the EOM, is 22.9 ◦ Candthe
minimum temperature predicted is 20.1 ◦ C. For the housing the maximum temperature
difference between sides is 1.4 ◦ C. The temperature sensitivity of various components
compared with these nominal temperatures is given in Table 5.4 for various changes in
the thermal boundary conditions.
Item Proof Optics Payload Primary Support
Mass Bench Electron. Mirror Cylinder
Nominal case temperature ( ◦ C) 20.4 21.0 33.6 –19.7 14.3
SVM Base/Ring increased by 10 ◦ C +4.5 +4.5 +4.8 +4.2 +4.9
Solar Constant increased by 50 W/m 2 +0.5 +0.5 +0.5 +0.5 +0.6
Shield αs incr. by 0.052 W/m 2 (to EOL value) +3.1 +3.1 +3.2 +2.7 +3.4
Electronics power increased by 1 W +1.4 +1.4 +2.5 +0.9 +1.4
Optical bench power increased by 0.5 W +9.4 +10.0 +1.3 +2.8 +4.9
CFRP conductivity doubled –1.3 –1.3 –0.8 +4.2 –2.2
Table 5.4 Component temperature changes ( ◦ C) compared with nominal case.
The steady state results indicate that the optical bench should come to equilibrium within
the required temperature range of 20 ± 10 ◦ C under “nominal” conditions. However this
temperature is sensitive to the payload power dissipation and the spacecraft temperature
in particular, and to a lesser extent to a number of other parameters. If the spacecraft
temperature and payload power dissipation are kept constant then seasonal and sunshield
3-3-1999 9:33 Corrected version 2.08