Closeout of IBDR Recommendations

1
Close-out of IBDR Recommendations

• A. Poglitsch

2
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

3
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

4
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

5
Board Recommendations

• 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)

6
Board Recommendations

• 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!

7
Board Recommendations

• 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)

8
Board Recommendations

• 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)

9
Board Recommendations

• 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 well
  try again for FM

10
Board Recommendations

• 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)

11
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

12
Board Recommendations

• 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

13
Board Recommendations

• 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

14
Board Recommendations

• 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

15
Board Recommendations

• 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

16
Board Recommendations

• 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

17
Board Recommendations

• 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)

18
Board Recommendations

• 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