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d-ISVR Recommendations Introduction and Close-out

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Title: d-ISVR Recommendations Introduction and Close-out


1
d-ISVR RecommendationsIntroduction and Close-out
  • A. Poglitsch

2
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

3
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.

4
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.

5
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)

6
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

7
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

8
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.

9
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.

10
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.

11
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.

12
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)

13
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.

14
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.

15
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.

16
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.

17
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.

18
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.

19
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.

20
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.
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