d-ISVR Recommendations Introduction and Close-out

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d-ISVR RecommendationsIntroduction and Close-out

• A. Poglitsch

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Board Findings and PACS Response (1)

• The Board is satisfied to note that significant
  progress has been made in the PACS FPU design
  since the ISVR and the implementation of the
  bolometers as shown by the amount and quality of
  the documentation provided to the reviewers.
• J

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Board Findings and PACS Response (2)

• The Board notes that the draft instrument
  specification has been updated in line with the
  recommendation given at the ISVR. The
  specification, however, at present concentrates
  on the optical definition of PACS, and the Board
  expects that the draft specification will be
  further extended to cover explicitly further
  engineering requirements on PACS.
• The scope of the PACS Instrument Requirements
  Document (PIRD) is a compilation of high-level
  requirements on implementation and performance of
  the instrument to meet the scientific
  requirements. With the exceptions described in
  the PIRD, all derived or additional requirements
  are addressed in separate documents, a list of
  which has been added to the PIRD in response to
  the Boards request.

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Board Findings and PACS Response (3)

• The Board was impressed by the work performed on
  the optical design of the focal plane unit, i.e.
  a complete redesign of the FPU in 6 months. The
  implementation of the bolometer arrays greatly
  simplifies the instrument and also allows for an
  improved straylight rejection/baffling. The Board
  considered the optical design to be completed,
  however, to be accompanied by a detailed
  alignment plan and an instrument straylight
  analysis that is to be completed by the time of
  IIDR.
• A straylight analysis has been performed of the
  "entrance optics" subunit for straylight sources
  placed on the rear of the primary mirror, near
  the central hole (KT-AN-004). Already at the end
  of the entrance optics the straylight fulfills
  the requirements at the detector level.A
  detailed alignment plan has been prepared
  (KT-PL-007) which describes the tasks for FPU
  subunit internal alignment, subunit-subunit
  alignment, and also a proposal for FPU-Telescope
  alignment.

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Board Findings and PACS Response (4)

• The Board takes note that the Cryogenic Readout
  Electronics (CREs) for the GeGa detectors has
  made real progress.It appears that the
  managerial problems have been resolved since the
  ISVR, while the technical problems, i.e.
  demonstration of feasibility, have not been
  solved yet. The development remains technically
  extremely critical and is in addition also
  becoming schedule critical. The Board asks PACS
  to identify possible ways forward for the GeGa
  detector arrays in case the CRE technology will
  not be demonstrated in time and thus not be
  available when needed.
• The technical feasibility of the CREs has been
  demonstrated in the meantime, i.e., all
  functional blocks of the CRE have been
  implemented and tested separately, and either
  already meet the requirements, or the
  modifications necessary to make them meet the
  requirements have been identified.(See IIDR
  presentation by IMEC)

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Board Findings and PACS Response (5/1)

• The Board notes little progress in the
  development of the grating mechanism. Although it
  does not appear to be on the critical path yet,
  the Board would clearly like PACS to accelerate
  the activities. The Board notes with concern
  little exchange of information between PACS
  system engineering and the grating responsibles
  and would like PACS to improve on communication
  exchange. The Board asks PACS to already now
  consider means of recovery for the case that the
  design does not mature in time as needed.
• On CM 12 CSL presented the current AIV schedule
  and confirmed the delivery dates for the AVM and
  CQM
• First functional tests at 4K on the cryogenic
  prototype will take place in March 2001.
  Selection of lubricants / lifetime tests
  (bearings) are foreseen for April and May 2001.
  Launch-lock breadboard is available, a grating
  sample will be available in April-Mai 2001

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Board Findings and PACS Response (5/2)

• Actuator EM available, CQM/PFM procurement will
  be released in March 2001, Position Sensor
  procurement for the CQM/PFM will be released in
  March 2001
• Drive mechanism ITT for CQM/PFM on EMITS since
  23-Jan-01
• Diffraction Grating procurement for CQM/PFM will
  be released in June 2001
• The ICD with respect to FPU has been issued

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Board Findings and PACS Response (6)

• The option of a parallel mode of PACS and SPIRE
  was not fully addressed in the presentation, and
  the Board would like PACS to perform a critical
  trade-off for the IIDR, taking due consideration
  of the lifetime impact of the parallel operation
  of the 3He sorption coolers for PACS and SPIRE
  and the scientific benefit of such mode.
• The full impact (lifetime resulting level 1 and
  2 temperatures, including dynamics) can only be
  answered by detailed thermal modeling at system
  level (PACS SPIRE Herschel cryostat).A
  trade-off of scientific benefits vs. side
  effects, therefore, has to be delayed until the
  latter ones have been quantified.The development
  of PACS is not affected by this issue being left
  open.

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Board Findings and PACS Response (7)

• The Board notes that the selection for a black
  paint for straylight reduction in the FPU is not
  yet completed, however, supports the approach to
  consider this a commonality issue among the three
  FIRST instruments.
• BRDF measurements on test samples confirmed that
  NEXTEL Black Suede (Germany) and DeSoto Gunship
  (USA) paint with SiC grain layers are both
  suitable candidates. Results and a preliminary
  procedure are summarized in test report
  PACS-ME-MP-001. Further tests with larger SiC
  grains and glass micro-spheres are in
  preparation. Independent from these ongoing
  activities a detailed preliminary coating
  procedure was defined and procurement of the
  black paint has started. A qualification of the
  coating is required. For evaluation, PACS will
  provide a sample to ESA and ask Project to get
  support for the qualification program.

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Board Findings and PACS Response (8)

• The Board notes that the instruments development
  plan has been significantly improved since the
  ISVR. However, the delivery dates show little or
  no margins w.r.t. the need dates defined by ESA
  and agreed to by the instrument. The Board asks
  PACS to critically review the development plan
  and to optimise it in order to demonstrate
  adequate margin to the specified need
  dates.Further, the late qualification of the
  CQM, and in general the parallel activities of
  the CQM and the PFM plan should be addressed and
  potential conflicts be resolved.
• A more detailed break-down of the AIV phase for
  all PACS models in the development plan is
  defined in the PACS Test Plan, which was issued
  recently. In its present version, only during QM
  ILT a little margin could be identified, FM and
  FS test schedules and delivery dates remain not
  showing adequate margin.

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Board Findings and PACS Response (9)

• The Board is satisfied with the structure of the
  PACS system engineering team and the definition
  of responsibilities and reporting lines. However,
  the Board recognises room for improvement for the
  communication between the subsystem engineering
  managers and the subsystems. As one aspect of
  this, the role of Kayser-Threde, as industrial
  architect for the Focal Plane Unit, is not fully
  clear to the Board. The nominally large influence
  of Kayser-Threde in the system engineering
  decision making is not apparent in the system
  engineering team set-up and should be revisited
  by the PACS project.
• The FPU and the Optics System Engineers are in
  nearly daily contact with KT.In addition we have
  status meetings with KT every two to three weeks.

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Board Findings and PACS Response (10/1)

• The Board is concerned about the mass increase
  presented for the focal plane unit, and urges
  PACS to carry out the detailed design work and
  mechanical analysis and to find ways to reduce
  the mass. The Board is confident that PACS will
  be able to present at the time of the IIDR an
  instrument mass budget within the allocation and
  with adequate margins. One element in the design
  of the FPU is the structure support system. This
  is designed to minimise the head load onto the
  unit. However, since this is only a small
  fraction of the total heat load the board
  suggested to PACS the option of a less optimised,
  but simpler support system (similar to the
  concept used on SPIRE).
• In the IID-A, the maximum allocated mass for the
  three FPU instruments on the optical bench is 179
  kg.
• On the last technical FPU meeting with Project
  the following numbers where given by the
  instrument teams (without margins)

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Board Findings and PACS Response (10/2)

• HIFI 46kg
• SPIRE 45kg 7.2kg 3 kg 55.2kg
  (different from ESA minutes 51kg)
• PACS 71kg
• Total 172.2kg
• The mass of PACS is still TBC as long as the
  structural analysis is not completely finalized
  and as long as the detailed light weighting tasks
  on the main structure have not been performed.
  PACS will carefully look into all possibilities
  and make all efforts to reduce the mass of the
  FPU and to get adequate margins.
• In the new design of the PACS FPU structure also
  a modified structure support system is included.
  The suspension concept has been simplified, the
  thermal load increase to the FPU is acceptable.

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Board Findings and PACS Response (11)

• The Board takes note that the FPU thermal model
  has been established to a level of detail to
  allow for proper analysis and prediction of the
  static and dynamic thermal behaviour of PACS.
  This analysis should be pursued and completed.
• PACS thermal analyses, based on an upgraded PACS
  TMM and using the Simplified Thermal Model of the
  Herschel cryostat (Optical Bench) have been
  performed. Steady state temperatures and
  transients were predicted.
• During the last technical FPU Meeting at ESTEC
  (21 Feb 01) it was agreed that further detailed
  analyses should be performed with the PACS TMM
  based on the full ESATAN thermal model of the
  optical bench. PACS will deliver its thermal
  model to ESA for integration with the existing
  ESATAN cryostat model.

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Board Findings and PACS Response (12)

• The Board would like to emphasise the importance
  of EMC design and analysis, specifically for the
  bolometers and recommends to PACS to initiate
  related analysis and design work.
• Terry Bax who has a lot of experience from ISO
  will get a contract of one year to work on EMC
  matters, especially in the FPU area. This
  contract will be funded by DLR.

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Board Findings and PACS Response (13)

• The Board notes a potential mechanical problem of
  the Chopper w.r.t. the random vibration
  specification and asks PACS to provide a detailed
  assessment to the ESA project for consideration.
• The final modified design of the FPU structure
  has been achieved recently, and the SMM has been
  adapted correspondingly. A structural analysis
  is in progress, KT will provide vibration loads/
  resonance amplifications on the chopper until mid
  March 2001. PACS will provide a detailed
  assessment to the ESA Project for consideration
  right after the values were derived.

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Board Recommendations and PACS Response (1)

• The Board recommends to the PACS project team to
  implement improvements in the communication of
  the system engineering team with the subsystem
  responsibles.
• The PACS consortium has adopted this
  recommendation and introduced a regular exchange
  of information between the responsibles at system
  and subsystem level as well as a better
  co-ordination within the system engineering
  team.
• The Board requests that PACS completes the open
  analyses tasks for the instrument, specifically
  the straylight, alignment, mechanical and thermal
  analysis of the FPU.
• The status of these analyses is presented as part
  of the IIDR.

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Board Recommendations and PACS Response (2)

• The Board notes progress in all areas of concern
  identified during the last review. However, it is
  recommended that PACS places specific emphasis on
  the following identified critical areas
• Cryogenic Readout Electronics for the
  photoconductors
• The grating mechanism
• The bolometer arrays
• The PACS consortium fully agrees with this
  assessment and is making all possible efforts to
  achieve the necessary progress in these
  areas.The CRE development has made a qualitative
  step from uncertainty of technical feasibility to
  optimisation of circuit implementation.Concrete
  solutions for the grating drive bearings are in
  the process of evaluation.The first round of
  bolometer focal plane processing is near
  completion.

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Board Recommendations and PACS Response (3)

• The Board recommends to PACS to continue working
  on the development philosophy and plan in order
  to gain margins in the delivery dates and to
  reduce the parallel activities in CQM and PFM
  AIV.
• PACS is actively working, in co-ordination with
  Project (and in the future with the satellite
  Prime Contractor), on a development philosophy
  and schedule which will allow the delivery of a
  well-characterised instrument and be compatible
  with a launch in Feb 2007. This has been agreed
  upon during the Herschel-FPU Technical Meeting on
  Feb 21.

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Board Conclusions and PACS Response

• The Board is satisfied that PACS achieved all
  objectives of the Delta Instrument Science
  Verification Review set before the meeting.It
  is, however, also realised that PACS has a number
  of critical areas that need specific attention,
  and a significant amount of work has to be
  carried out in the time up to the IIDR.
• We can tell!!But we also appreciate the open,
  supportive atmosphere in which the PACS
  consortium, ESA and the funding agencies are
  working together towards a success of this
  project.