pacs ihdr 12/13 nov 2003 ibdr close-out1 close-out of ibdr recommendations a. poglitsch

IBDR Close-out 1

PACS IHDR 12/13 Nov 2003

Close-out of IBDR Recommendations

A. Poglitsch

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IBDR Board Conclusions

• Instrument Design and Internal Interfaces– The Board considers the instrument design and

internal interfaces as consolidated and under basic configuration control for the FPU with the exception of the bolometer chain (in particular BOLA)

– The status of the Warm Boxes is less satisfactory (in particular DEC/MEC and OBSW documentation). EMC and grounding scheme need to be addressed with no delay. Reliability analyses are still missing

• External Interfaces– The Board does not consider the interfaces to the

spacecraft fully consolidated, however it sees these issues properly identified and expects industry to take the lead and to close out the pending issues with no delay

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IBDR Board Conclusions• AIV and GSE

– The model philosophy and verification approach need to be consolidated. Manufacturing flow charts need to be issued

• Schedule– The Schedule remains highly critical and PACS needs to

establish means to ensure close monitoring and follow-up with subsystems

• Summary– While the Board considers that formally not all objectives

of the IBDR have been fully met, it sees no need for a delta review

– The Board expects the issues raised in the recommendations in this report, as well as in the comments transmitted to PACS prior to the review, to be addressed and resolved in the timeframe given in the recommendations, and … well in advance of the next review

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Board Recommendations

• R1: To ensure a coherent system approach, an agreed set of documents and a documentation tree shall be established between PACS system and subsystems and with ESA and Industry in the timeframe of the spacecraft PDR.

• We did our best – but far away from perfect

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• R2: Ensure schedule stability and close monitoring of subsystem activities to retain, and possibly advance delivery dates. In particular, test sequences need to be optimised while still ensuring full characterisation. As much as possible overall logistics/transportation shall be optimised. Procurement of long lead and/or single supplier items shall be monitored carefully. This is regarded as ongoing work.

• Schedule stability hard to achieve (no margins allowed), advance of delivery dates impossible

• Duration of ILT cut to absolute minimum (6 months)

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• R3: Provide all means to close out open interface issues, and to freeze the interfaces with the spacecraft before the PDR.

• Requirements defined from PACS side. Frequent communication with S/C contractor, progress has been made

• Still some important I/F requirements not agreed at time when PACS QM hardware has already been built!

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• R4: Ensure that a Derating and Worst Case Analysis has been properly conducted prior to manufacturing.

• Input for some subunits available• Open – system approach not achieved; for

some subunits only foreseen for QM/FM (contract constraints)

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• R5: System analyses, FMECA and FDIR should be performed jointly by system engineering with PA

• Based on available FMECA (input from subsystems), first version of system FDIR available

• Input from some subsystems only after AVM (see R4)

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• R6: Ensure and closely monitor appropriate PA approach at subsystem level and close communications between system and subsystem PA. Investigate ways of optimising/(re)distributing the PA work between system and subsystems.

• Progress made with some subsystem suppliers• System-wide approach not yet achieved• Some partners still have to be convinced –

we’ll try again for FM

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• R7: Perform full signal detector (bolometer/ photoconductor + electronics) chain performance measurements as early as practically possible. This is considered normal work of highest priority

• Operation of photometer chain demonstrated– Bolometer focal plane array + multiplexer + buffer +

BOLC– No meaningful noise measurements due to contact

problem in 2K buffer unit

• Progress in spectrometer chain– Parallel operation of 7 photoconductor modules with

CREs and active shield drivers in lab electronics achieved

– Verification of full chain (including DECMEC) only at IL tests possible

– Noise of QM CREs above spec (at least for blue array)

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Board Recommendations• R8: Ensure early QM tests to feed back into FM

programme. Perform low temperature testing as earlier as possible. Investigate ways to test the 48-hour baseline autonomy and cooler recycling in view of the PACS cryostat hold time limitation of 10 hours. The planning should be completed in the timeframe of the spacecraft PDR

• Qualification at QM subunit level advanced– Operation/characterisation of detector chains– Cryo-qualification of mechanism, mechanism control

• Test cryostat design modified for extended operation

• Planning complete, but subject to shifts/delays due to highly success-oriented schedule

• Feedback for FM limited by schedule constraints

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• R9: Identify a clear model philosophy and FPU simulators to support coherently the development of the instrument from unit to system level, and ensure that all AVM units will be form fit and function for the AVM and EQM system level tests

• Closed – SPU, DECMEC, BOLC only fit and function (RFD). Simulation modes built into DECMEC and BOLC

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• R10: Ensure proper documentation of OBSW for DPU, SPU and DEC/MEC. In particular the Software Specification Document (SSD) shall be updated to reflect the actual status of development and testing. This should be completed in the timeframe of the relevant tests

• Closed– SSDs available– SVVPs available for SPU, DPU

• Open – DECMEC SVVP

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• R11: Assess the thermal impact of cooler recycling operations

• Closed – thermal model of photometer unit including cooler available, input provided to S/C thermal model

• Results of thermal modeling by S/C contractor alarming – not only L1 but also L0 show noticeable variability over days after recycling / instrument switching

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• R12: Define and include into the overall test plan a few sensible “degraded” modes of operations in order to provide some level of insurance in case of post-launch failure of a major unit/component

• Closed – integrated in Operational Modes Document– Chopper– Grating– Filter wheels

• Open – inclusion in test plan

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• R13: Define and plan OBSW (DPU, SPU, DEC/MEC) performance tests in order to supplement the functional tests currently carried out

• Ongoing work – all nominal data rate modes tested

• Final test of burst mode pending

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• R14: Assess impact of microvibrations on the grating assembly

• Progress – bearings show now degradation after cryovibration, in fact, friction torque reduced

• Impact of microvibrations on position accuracy still to be evaluated quantitatively. (Performance tests on lab bench without vibration isolation are within spec)

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• R15: Assess all the implications (instrument design, OBSW and ground processing) of the implementation of the PACS-SPIRE parallel mode; in particular a full assessment of the impact on autonomy and FDIR should be performed.

• PACS is operating as prime instrument and requires no service from S/C other than in regular prime mode

• No additional OBSW or ground processing capabilities needed

• FDIR of PACS as prime instrument fully applicable

pacs ihdr 12/13 nov 2003 ibdr close-out1 close-out of ibdr recommendations a. poglitsch

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