Thermal Analysis of Planck HFI - European Space Agency
Transcript of Thermal Analysis of Planck HFI - European Space Agency
16th Thermal and ECLS Workshop - ESTEC 1
Thermal Analysis of Planck HFI
16th European Workshop on Thermal and ECLS SoftwareESTEC, 22-23 October 2002
Jayne FeredayRuther ford Appleton Laboratory
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SUMMARY
• Planck mission overview
• Thermal design concept
• Systematic effects
• Global thermal model
• Radiative transfer model
• Thermal analysis issues
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3rd medium-sized mission of ESA’s Horizon 2000 scientific programmeTesting theories of the early universe and the origin of cosmic structure Measuring anisotropies in the Cosmic Microwave Background - ∆T/T ~ 2 x 10-6
PLANCK MISSION OVERVIEW
LFI (30 - 100GHz)
Tuned radio receiver array at 20K
HFI (100 - 850GHz)
Bolometer arrays at 100mK
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Passive cooling to 50/60K• 3 v-groove shields to maximise radiation to space
JPL sorption cooler to ~20K• cools LFI and HFI precooling stage• thermally sunk to v-groove shields
RAL 4K JT cooler• precooling at 18K
Dilution refr igerator to 100mK• precooling at 1.6K
THERMAL DESIGN CONCEPT (1)
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0.1K stage
1.6K stage
4K stage
18K plate
GFRP struts
THERMAL DESIGN CONCEPT (2)
LFI
HFI
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Work done as part of ESA’s Systematic Effects Working Group (SEWG)
Observations must be corrected for the effects of detector noise and layers of intervening material
Bolometer performance highly dependent on absolute temperature and temperature stability
SYSTEMATIC EFFECTS
⇒ Stringent stability requirements (e.g. bolometers < 19 nK.Hz-0.5)
⇒ System level analysis needed – detailedunderstanding of fluctuations
⇒ Interaction between instruments, spacecraft and coolers is complex
⇒ End to end modelling vital
⇒ Global thermal model created
⇒ Used to assess stability issues by providing full feedback loops to all spacecraft elements
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GLOBAL THERMAL MODEL
SVM (Alcatel)
LFI (LFI)
Waveguides and struts
HFI (RAL)
Harness
Solar array
Cooler interfaces
Shields
Space loads
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Operational environment• L2 position and orbit - scanning/spin
Coolers• Sorption cycling• JT instabilities• Effect of JT getter temperature being raised
General• Electronics switching • Influence of 3rd V-groove temperature on LFI• Influence of LFI temperature on HFI
Combined effects
Stability of sorption cooler identified as largest source
SOURCES OF INSTABILITY
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SORPTION SIMULATIONS RESULTS
17.48
17.5
17.52
17.54
17.56
17.58
17.6
10000 11000 12000 13000
Time, s
Tem
p, K
4.5882
4.58825
4.5883
4.58835
4.5884
4.58845
4.5885
10000 11000 12000 13000
Time, s
Tem
p H
FI,
K
50.3739
50.374
50.3741
50.3742
50.3743
50.3744
50.3745
Tem
p s
hie
ld, K
4.5882
4.58825
4.5883
4.58835
4.5884
4.58845
4.5885
10000 11000 12000 13000
Time, s
Tem
p H
FI,
K
50.3739
50.374
50.3741
50.3742
50.3743
50.3744
50.3745
Tem
p s
hie
ld, K
4K
Telescope
Sorption cooler cold end
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AIM: To produce a modelled detector output, including noise,to be used for the “ removal of systematic effects”
INPUTS: Simulated sky Time Ordered Data (TOD)TOD of the thermal variations of critical nodes in the HFI.
Model received showing bolometer performance against thermal behaviour• supplied in MathCAD format• produces bolometer output power, taking into account system noise• originally took constant temperature as an input• modified to accept arrays of thermal fluctuation data
Excel used originally• MathCAD add-in• macros used to feed thermal model output data into model• run time and file size became restrictive very quickly
MathCAD model re-written in C++C++ command line model now used that enables sky data and thermal data files to be input in batches
RADIATIVE TRANSFER MODEL
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TRANSFER MODEL OUTPUT
Detected Model Sky at 100GHz with Stable4K Power on Detector from Temp Fluctuationsand ‘Constant’ Sky
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Detected Model Sky at 100GHz with TemperatureFluctuations
TRANSFER MODEL OUTPUT
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Run time• Sorption cooler data sets 40,000s • 1/3s data output required• Convergence criteria must be high• Constants material properties used where possible• Nodes set to boundary temperatures where possible
Format compatibility• Thermal model in ESATAN – output to .csv files• Sky TOD in FITS format• Bolometer model in MathCAD
Configuration control• Several different models required – cooldown, cooler failure cases, stability cases• $INCLUDE function used whenever possible to ensure model update is easy – ‘plug in’ modules
THERMAL ANALYSIS ISSUES