Title: d-ISVR Recommendations Introduction and Close-out
1d-ISVR RecommendationsIntroduction and Close-out
2Board 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
3Board 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.
4Board 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.
5Board 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)
6Board 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
7Board 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
8Board 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.
9Board 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.
10Board 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.
11Board 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.
12Board 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)
13Board 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.
14Board 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.
15Board 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.
16Board 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.
17Board 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.
18Board 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.
19Board 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.
20Board 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.