1. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 1 MPE J. Schubert PACS IHDR

2. 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 2 Content Overview QM FPU, Status and Problem Areas Status PACS Mechanical I/F to S/C Status PACS Thermal I/F to S/C –Allowed Mechanical Loads to Ge:Ga Detector I/Fs –Design and Changes on Cooler L0 I/Fs –Allowed Mechanical Loads to Level 0 Cooler I/Fs –Temperatures of LO I/F to HERSCHEL S/C In Orbit On Ground (IMT, and EQM)

3. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 3 Overview PACS FPU FPU QM structural parts manufacturing and assembly completed –Housing compartments blackened with KT 70 –Top Optic mirrors integration and alignment started Thermal and Load/Structural Analysis finalized Mechanical, Thermal and Electrical I/Fs to the S/C and to Subunits frozen Warm and Cryo Vibration performed on STM structure with success Subunits delivered (Chopper) or within the end of the AIV phase Extremely tight schedule increases risk for all parties and possibly shifts problem to the FM

4. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 4 Overview (cont.) Open issues to be worked on Distribution board  qualification/testing of PCB board not finalised, delaminating problem observed, investigation ongoing Mirrors  Gold layer on 3 of 13 mirror batches did not pass the tape test, investigation ongoing Detector Array  Delta cold vibration tests to be performed on Detector Array Components PhFPU  Bolometer Kevlar suspension failed during cold vibration in STM FPU, cold delta vibration test in preparation PhFPU I/F to S/C  a) mechanical load from S/C cooling is critical, b) not enough clearance between back shells of S/C harness and PhFPU connector panel (TBC)

5. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 5 PACS Mechanical I/F to S/C PACS FPU ICD Drawing Issue 27 DRAFT distributed to ESA & Industry for comment, 04-July-03 Major design changes compared to issue 25 reworked+implemented –Level 0 S/C IF to Ge:Ga detectors, pin to flat I/F (compliant to IID-A) –Mechanical I/F to OB, pin diameter & position (compliant to IID-A) Further detailed information added –Cold/Warm configuration, Mounting & Handling Equipment and Non Flight Items etc., drawing split into ten separate drawings Final release after working in ASTRIUM comments (received 9-Oct-03) –PACS QM manufacturing finished, no further updates beyond Issue 27 foreseen –Further requests/changes beyond Issue 27 are only possible via formal CR to PACS Level 0 Sorption Cooler I/F not reflected in Issue 27 anymore (separate drawing needed by CEA) –Removing I/F-adapter (ECP#6) accepted by ESA and Industry

6. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 6 PACS Thermal I/Fs to SC GeGa Level 0 I/F (2x) Pin I/F changed to rectangular I/F soldered to pin; Conduct resistance at I/F can be tuned to minimize heating of blue detector Ge:Ga Level 0 GeGa Level 0 PhFPU Level 0 Level 1 Level 1 I/F (3x) Thread distance changed from 33 mm to 37 mm PhFPU/Cooler Level 0 I/F (2x)

7. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 7 Mechanical Loads to Level 0 Ge:Ga Detectors I/F Amendment to CR, H-P-PACS-ME- 008 issued 29.Oct03, includes also updated mechanical load values for the Ge:Ga Detectors L0 I/F to be in line with the changed mechanical I/F (pin to flat mounting I/F): –Torque, longitudinal bending moment to central copper cold pin. < 1.8 Nm –Torque, rotation moment to the central copper cold pin < 0.2 Nm –Axial force to the central copper cold pin < 500 N –Lateral force to the central copper cold pin < 100 N This IF loads regarded as uncritical For the fixation of the straps a mounting tool is foreseen

8. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 8 ECP PACS-ME-ECP 06, issued 27-July-03 agreed 16-Oct-03 –Reason for ECP: I/F temperature requirements of 1.85K at the end of the cooler recycling phase, acc. H-P-PACS-CR-0009, cannot be met -> 46h cooler hold time in question –Proposal (agreed): Remove I/F adapter; remaining contribution from PACS side to the overall thermal conductance (He-tank to Evaporator I/F) is now the contact resistance at the I/F to the cooler -> ~ 30% gained in thermal conductivity to the cooler I/F Engineering Change at PACS Thermal Cooler L0 I/F New DesignOld Design

9. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 9 Mechanical Design at L0 Cooler I/F after ECP Changed Mechanical I/F Design at PACS Cooler S/C strap routing/ integration location of S/C temperature sensors Necessary design change on PhFPU side rerouting PhFPU 2K strap shifting 2K feed through I/F baffle to reduce radiation environment performed already CQM Parts manufactured ! BUT: Mechanical loads from S/C ? S/C Cooling Strap to Pump (cut in drawing, shown partly only) PhFPU Cooling Strap to Bolometer S/C Cooling Strap Evaporator PhFPU Baffles PhFPU Feed Through S/C Temp. Sensors

10. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 10 Mechanical Loads to Level 0 Cooler I/F Change Request to PACS IID-B: H-P-PACS-ME- 008, Issued 26-Nov-2001, I/F Loads identified as Single point failure –The mechanical loads arising from the level 0 cooling straps to the fixation points of the cooling straps at the PACS FPU must be limited. Impact of no- change: Damage of the mechanically sensitive thermal I/Fs during mounting and/or during launch can happen. –Static load: 50 N –Dynamic load: 50 grams (20.8G rms assumed) CR was not processed further. Reason: missing final design of S/C level 0 cooling strap (under Industry responsibility) Current Design for the S/C cooling strap: –½ mass of cooling strap, pulling at the Level 0 I/F was 312 grams –New ½ mass acc. AIR LIQUIDE study could be 100-125 grams

11. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 11 Mechanical Loads to Level 0 Cooler I/F (cont.) First results from FEE on cooler switch I/F done by CEA-SBT (01-Oct-03): –dynamical response of the switch, (e.g. first eigenfrequency) depends on the additional mass fixed at the interface level: -50 grams, the first eigenfrequency is 194 Hz -100grams........................................ 180 Hz -300 grams......................................... 140 Hz –maximum admissible mass at I/F could be potentially increased to 100 grams. TN on FEE calculation in preparation. S/C cooling strap design needs to be balanced between conductance requirements (reduce cross section, change material TBC) and mechanical load requirements MPE proposes to perform a coupled FEE analysis, to take into account the dynamic behaviour of the S/C cooling strap and to perform a cold vibration test in "full" configuration (PhFPU/cooler/cooler switch + strap) representative to the flight configuration Amendment to CR, H-P-PACS-ME- 008 issued 29.Oct03, but 100 grams can not be guaranteed as long as no detailed FEE analysis is performed.

12. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 12 HERSCHEL L0 I/F Temperature to the Cooler Evaporator Agreement reached on HERSCHEL Open Tank Solution, HERSCHEL L0 I/F meeting 30-Oct-03 @ESTEC

13. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 13 Estimation of PACS Level 0 I/F Temperatures in Orbit HERSCHEL Tank Temperature:1.7K Material Pods: Al 1050 Open Pods:Open Tank Solution for the Evaporator I/F Conductance data taken from AIR LIQUIDE analysis HP-2-AIRL-AN-0004 I/FTotal Conductance [W/K] Max Heat Flux [mW] Calculated Temperature at IF [K] Max. Temperature allowed [K] OK Blue Detector0.039 *)0.8 -1.631.72-1.742Yes Red Detector0.0820.81.711.75Yes Cooler Pump Condensation End of Cond. Low Temp. 0.061  10 ~ 500  2 1.86 9.9 1.73 N/A 10 5 - Yes Cooler Evaporator Condensation End of Cond. Low Temp. 0.101 50  15  1 2.19 1.85 1.71 2.8 1.85 Yes *) Can be tuned at the I/F

14. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 14 Difference between Ground and Orbit Tilt of Cryostat –The temperature of the cooler evaporator I/F at the end of the recycling phase defines the condensation efficiency of the 3 He (hold time of the cooler) –The difference between on ground and in orbit is the convective effect. This only affects the recycling phase. Once the cooler is cold, orientation does not matter. -In orbit: We can assume the in-orbit case corresponds to a 60-90° tilting for the cryostat on ground. At the end of the recycling phase, the power flowing through the evaporator strap is 18 mW (measured 14 mW in the latest test). -On ground: If the cryostat can only be tilted 20°, the power flowing through the evaporator strap at the end of the recycling phase can extrapolate to be about 30-35 mW !!!

15. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 15 Difference between Ground and Orbit (cont.) Herschel Tank Temperature Orbit: 1.7K Ground (IMT): 1.7K to 1.8K –Temperature shift at cooler I/F up to 100mK due to warm up after days L1 Temperature (~PACS FPU temperature) Orbit: 3K to 3.5K Ground(IMT): 6.3K to 7.3K –Thermal load from L1 to L0 through switch base increased (0.45mW -> ~2mW) –Impact to hold time (needs further assessment using measured values) –Impact on the Net heat lift at 300mK (needs further assessment using measured values) Thermal Radiation Environment Orbit: 9K –10K Ground (IMT): 8K – 10K –5- 6 K, no impact expected, for 10 K we don't know (hard to calculate) –cooler is pretty much covered by protective baffles and caps (best we could do) It is assumed the heat sink to the cryostat drops back down to 1.8 K once the condensation phase is completed

16. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 16 Estimation of PACS Level 0 I/F Temperatures IMT Tank Temperature:1.75K Thermal radiation environment:8K-10K, not taken into account Level 1 temperature unknown: 6.3K to 7.3K, not taken into account Conductance data taken from AIR LIQUITE analysis HP-2-AIRL-AN-0004, Al 1050 I/FTotal Conductance [W/K] Max Heat Flux [mW] Calculated Temperature at IF [K] Max. Temperature allowed [K] OK Blue Detector0.27 *)0.8 -1.631.78-1.812Yes Red Detector0.0430.81.771.75(No) Cooler Pump Condensation End of Cond. Low Temp. 0.036  10  500  2 2.02 15.5 1.81 N/A 10 5 - No Yes Cooler Evaporator Condensation End of Cond. Low Temp. 0.03520 deg tilt 80 (TBC)  35 (TBC)  1 4.04 2.75 1.78 2.8 1.85 No Yes *) Can be tuned at the I/F

17. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 17 Estimation of PACS Level 0 I/F Temperatures EQM Tank Temperature:unknown, used also 1.65K Thermal radiation environment:unknown, should be  5K Level 1 temperature unknown: unknown, should be around 4K to 5K Conductance data taken from AIR LIQUITE analysis HP-2-AIRL-AN-0004 I/FTotal Conductance [W/K] Max Heat Flux [mW] Calculated Temperature at IF [K] Max. Temperature allowed [K] OK Blue Detector0.062 *)0.8 -1.631.66-1.682Yes Red Detector0.2120.81.651.75Yes Cooler Pump Condensation End of Cond. Low Temp. 0.106  10  1000  2 1.74 11.1 1.67 N/A 10 5 - No Yes Cooler Evaporator Condensation End of Cond. Low Temp. 0.09320 deg tilt 80 (TBC)  35 (TBC)  1 2.51 2.03 1.66 2.8 1.85 Yes No Yes *) Can be tuned at the I/F

18. PACS IHDR 12/13 Nov 2003 Overview and Mechanical/Thermal IFs to FPU 18 Summery on PACS Level 0 I/F Temperatures In Orbit –With the “Open Tank Solution” and with Al 1050 for the HERSCHEL tank pods, PACS Temperature requirements on the L0 I/Fs can by fulfilled. On Ground –It is not clear whether the PACS cooler can be recycled and/or run at 0.3mK with sufficient cooling power during IMT test. –With a cryostat tilt of more than 20 degree, the situation can be improved by a factor 2.3 (for recycling only) –IMT/EQM testing and testing conditions needs further assessments to be performed by all parties. –Lionel Duband (CEA) needs to perform further calculations (tests?) using new validated boundary temperatures for the Ground test.