Report
of 67th meeting of the CFHT SAC
Paris, 30-31 May 2005
SAC Report
The
meeting was attended by SAC members D. Bohlender, J. L. Beuzit, D.
Elbaz, C.
Ftaclas, J. F. Gonzalez, H. Hoekstra, G. Mitchell, P. Petitjean
(chair), N. Saint-Louis (vice-chair) and B. Tully. Jim Hesser for
the
Board and Korean representative Dr. Ho-Il Kim were present as
observers.
C. Veillet, J.-C. Cuillandre, P. Martin, P. Puget and D. Salmon,
participated
in presentations and discussions. L Simard from CADC was invited.
1.
Technical Activities Report
Derrick
Salmon reported
on the technical activities of this semester, including the
commissioning of
Espadons and the integration of WIRCam. Recent developments of the
Wircam
detectors and their controllers were also presented.
Different
maintenance
and development activities of the building and telescope were
described: building
air handling progressing slowly, soil erosion issues, the telescope
runaways
occurrences, the “drop into manual” problem, time jumps in the TCS
master clock.
In
anticipation of
WIRCam data, the online storage capacity has been increased to about 32
Terabytes.
Problems
with the
telescope associated with the DIMM have interrupted the project. It
should be
pursued on a manpower-availability basis.
2.
Instrument and Project Reports
MegaPrime
The
number of technical
failures of the camera has decreased substantially after an engineer
from CEA
came to CFHT and provided some sense of where CFHT needs to pay more
attention.
Some problems with the CCD controller electronics, the shutter, the
guide probe
and the fiber connectors have been investigated.
A
teleconference
between the CEA hierarchy and CFHT resulted in the clarification of
some issues
of concern. This has helped to solve the cooling problem and CEA will
be
providing electronic spares. Two people, including the former project
engineer
will spend one week at CFHT in July to help find a solution to the
problem with
the flanges. It should be understood that the camera is a complex
instrument and is fragile.
The
Image Quality in
the central half of the field is much better now that L3 is flipped.
Given the
mean seeing, 85% of the surface is within specification and the
remaining
problems are limited to two corners of the image only. SAC believes it
is worth
trying to understand the origin of the image quality problems. Models
have been
used to investigate possible answers to this question. The wavefront of
the
primary mirror does not seem to be involved. However, something is
affecting
the power of lens L1.
A
model of the focus is
in place and substantially decreases the amount of overheads related to
focussing the camera. The residuals from the model are approximately 73
microns
while in the best seeing the accuracy of the focus position is about 50
micron.
Based
on this report
SAC makes the following recommendations:
SAC Recommendation #1:
Although
the improvement of the IQ has been clearly demonstrated, it is very
worrying
that the optical performance of the system was improved by accidentally
installing a component upside-down. Therefore SAC recommends that
efforts
to understand the origin of the degraded IQ of Megacam should be
continued but
with a lower priority than WIRCam.
SAC
Recommendation #2: Length of Megacam runs
(Recommendation has
been removed - deferred to recommendation #3 contained in the
CFHTLS
Mid-term Review report, attached to this report.)
SAC is
worried about the low efficiency of the Megacam Queue observations and
the
remaining technical problems that may impact further this efficiency. A
visit
by CEA engineers is scheduled in July 2005 at CFHT. SAC requests a
written
report on the results of this visit based on input by both parties.
This should
be discussed at the next SAC meeting.
Depending
on the outcome of this visit and the report, SAC recommends that the
Board be
prepared to appoint an independent technical committee to review
difficulties
with the instrument and to help CFHT to implement the appropriate
actions.
WIRCam
All
science
detectors have been delivered by Rockwell. Their efficiency is
better
than specifications (70-80%) but the readout noise is slightly higher
than
specifications; overall they are therefore considered better than
expected.
ASICs are still not available but controllers are being developed by
CFHT. The integration of the optics in the cryovessel was done in
March
2005 and engineering runs take place every month since March. The image
quality
is excellent (~0.55² over the whole
field) and no major problem has been found so far. The
camera should be ready to be offered to the community in 2005B as
expected. 15
nights of PI programs plus 8 nights of engineering time as well as 2
nights of
DDT are foreseen.
All
observations should
be performed in Queue mode. CFHT has devoted an important effort to
develop a
pipeline for the pre-reduction of the data.
SAC Recommendation #4
SAC is
very pleased with the progress of the commissioning of WIRCam and
congratulates
the teams involved. However, SAC is still concerned about resources for
data
reduction.
CFHT should
finish
the development of the Elixir-IR pipeline. Terapix is encouraged
to
provide advanced WIRCam data products (stacked images and catalogs) but
this
work should have a lower priority than the CFHTLS releases. In any case
proposals for Large Programs should provide a clear plan for data
reduction.
ESPaDOnS
The
introduction of the
instrument into CFHT observing has been proceeding very smoothly. The
Cross-talk between the linear and circular modes that has been
discovered will
be investigated next semester. The observing runs on the sky were very
successful scientifically. Observers were pleased by how easy it is to
use the
instrument and the pre-reduction package. Queue observing is foreseen
but not
before two years from now.
SAC Recommendation #5
SAC is
pleased with the instrument performance but is concerned by the
proprietary
status of the Libre-Esprit package. CFHT should offer remote data
reduction
capabilities if requested by users.
Fly-eyes,
Pueo-Hou and `Ohana
No
work has been done
on Fly-eyes this semester.
In
order to stimulate
instrumental developments at CFHT, a concept for an adaptive optics
system with
a laser guide star that would provide diffraction limited imaging in
the
optical is being investigated. The so-called Pueo-Hou instrument could
possibly
provide CFHT with a unique capability on the 2010 horizon.
The
Phase II of `Ohana
is under way. The goal is to demonstrate the potential of an 800-meter
fibered
interferometer with the 3 10-meter apertures existing on Mauna Kea. The
first
baseline to be used is the CFHT-Gemini baseline planned to be combined
by the
end of 2005. The corresponding delay lines will be shipped during the
summer
and installed in the first floor Coudé room. Discussions to
install a fiber
between CFHT and Gemini have begun. One night was spent with the Keck
interferometer to validate the fibered coherent transport using single
mode
fibers. It is suggested that an engineer from the instrumentation group
be
assigned to the project.
Other
instruments
SAC Recommendation #6
The
pressure on MOS is steadily decreasing. In addition, MOS is no longer a
unique
instrument and similar observing capabilities are accessible to all
communities. SAC therefore recommends MOS be decommissioned at the end
of
semester 2005B. Because of the availability of Espadons, SAC
recommends the decommissioning of Gecko at the same time.
3.
CADC
SAC
Recommendation #7
SAC is
impressed by the amount of data already retrieved by users from CADC
and
encourage CADC to pursue the development of tools to facilitate access
to the
data. SAC would like to monitor the impact of the CFHTLS in the
community and
therefore wishes to receive detailed statistics on the retrieval of
CFHTLS data
at the CADC every semester.
4.
CFHTLS
The
mid-term review of
CFHTLS took place just before the SAC meeting. Specific comments and
recommendations have been sent to Board as a separate document.
SAC
had a more general
discussion about how to improve the management of possible future
surveys.
Given that
the LS utilizes about
$1M/yr in telescope time and many times this amount in data reduction,
archiving and analysis resources it is believed that programs of this
magnitude
require a project coordinator who is not tied to any particular
component of
the science and can advocate to the SAC/Board, telescope and data
components to
see the project is completed with the best outcome for the corporation.
For
any future survey
or large program work, image quality and observing efficiency goals
should be
set as part of the survey definition and that survey work should not
begin
until these goals have been demonstrated. Survey commencement
should
require approval of the board based on recommendations from the SAC and
telescope director.
Given
that the
telescope currency used in execution of the LS is telescope hours and
that
observations are made in queue-mode the SAC believes it would be more
realistic
that all obligations, mandates and allocations associated with the LS
and all
future surveys be cast in terms of telescope hours rather than nights.
5. Telescope
Use and Scheduling and DDT
Queue
observations are
working very well and the validation rate is now above 85%.
Back-up
programmes to fill the queue in case of bad weather conditions (seeing
above 1
arcsec) are needed.
Ten nights per semester are put aside for
DDT. Note that at the moment, 3 nights are allocated to the CFHTLS. The
use of DDT should be reviewed by SAC. This has not been done
seriously so far. SAC has asked to the CFHT director to provide details
on how DDT is used at the end of each semester starting next semester.
About 15 nights of engineering time will also be spent next semester.
6. CFHT Future
Christian
Veillet
presented a plan for the next 5 years that has been discussed in house
with the
aim of maintaining the high level of motivation required for a
world-class
science facility in the 2005-2010 timeframe. R&D developments could
be
centered on the refurbishment of the AO system, a possible laser guide
star
system and the Ohana project.
Christian
Veillet
indicated that the long-term future of CFHT is partly linked to the
possibility
of other partners joining the corporation. The site itself could be of
interest
for specific projects.
SAC
Recommendation #8
SAC is
pleased of the efforts made by the CFHT director to prepare for the
future. The
substantial investments made recently to install unique new
instrumentation
(Megacam, Wircam, Espadons) will produce world class science at CFHT.
There is
a continuing need to support efficient operation and to bring these
instruments
to full functionality. It is also important that CFHT maintain a
healthy level
of technological development to attract and retain high-quality staff.
The Ohana project
is definitely to be pursued and the Pueo-Hou concept seems an
interesting
possibility to be investigated in more detail. SAC believes that any
further
plans should be based on a review of resources and how they could be
adapted to
the future.
7. Other items
Korean
cooperation
Korea will
end its collaboration
with CFHT soon. Korean and CFHT signed an MOU of cooperation in July
1, 2000. The first Korean paper based on CFHT data appeared in
2003. KASI
was very happy of the experience gained in the operation of a world
class
telescope and in the management of a multi-nation facility. They were
also
pleased to have participated in the development of state-of-the-art
instrumentation and to have given the opportunity to their young
astronomers to
gain useful experience. Now Korea is planning to build their own large
telescope by participating in Mexico’s plan for 2x6.5m telescopes on
San Pedro
Martir. They expect First Light by 2011. The funding provided by the
Koreans
has been used for the WIRCam project.
SAC and TAC memberships
Jean-François
Gonzales has been
appointed as a French SAC member. The next chair of the French
TAC will
be P.A. Duc.
Next meeting
The next SAC
meeting will be held in
Waimea on November 10-11, 2005.
CFHTLS Mid-Term
Review Report
Mid-term
review
process
- SAC asked the Steering
Group (SG) to prepare
an overview of the Legacy Survey. Each component was asked to submit a
separate report
- Each component of the survey and the
conduct of the
survey as a whole were reviewed by two external expert referees. 9 out
of 10 referees responded and provided very detailed reports.
- Members of the SAC were assigned to
prepare summaries of
the material for each component of the survey. These summaries were
made available to the SG.
- A workshop was held on 26-27 May 2005
at IAP with
approximately 100 registered participants. Status reports and
scientific results were presented. The workshop also featured several
active discussion periods.
- On the morning of the 28 May, SAC met
with the SG and
CFHT staff to review the major issues raised by the referees and during
the workshop.
- In the afternoon, SAC went into
executive session to
review all relevant information and formulate recommendations.
Overview
SAC
is generally impressed by the organization of the project as a whole
and the
effort and dedication of the different teams and CFHT staff to the
overall
goal. The SG report is well documented and comprehensive.
During
the workshop, discussions were very informative and clarified a number
of
technical and scientific issues.
The
results achieved by now are already impressive and SAC believes it
would not be
necessary to cut back the time needed to achieve the final goals if all
aspects
of the survey were proceeding according to the original plan. However,
the low
efficiency of the observations, partly due to weather conditions,
technical
problems and scheduling difficulties are presently jeopardizing the
expected
breakthrough results of all survey components.
In
view of the continuing high pressure by PI proposals and the
anticipated
pressure from WIRCam large programs, SAC judges that it is unrealistic
to
recommend a major increase in the amount of time currently being
allocated to
the survey each semester beyond the 4+4 additional nights already
allocated.
Given the highly competitive international environment, there is a need
to
guarantee the rapid completion of key components of the survey in order
to
optimise the return of the observing-time investment and to minimize
the risk
of instrument failure.
In
the view of the SAC, the recommendations below represent the most
reasonable
way to reconfigure the survey such that two of the original three
primary
science goals can be successfully completed in a timely fashion,
maximizing the
scientific return to the participating agencies and providing the
greatest
legacy value to the entire astronomical community.
SAC
Recommendations
Supernova
Survey
The
SNLS is presently
in an advantageous
position to have a major and long-lasting impact on the study of the
nature of
dark energy. This
survey has been very well thought out. It has clear scientific goals
that are
of the highest importance. The goal of 700 supernovae discoveries by
2008,
observed in 4 colours, if achieved, will make this survey the most
powerful
supernova survey to date and every effort should be made to guarantee
success.
R1
SAC
considers that the supernovae
survey should be regarded as the first priority of the CFHTLS. In view
of its
importance, it should be given every chance to be completed as fast as
possible
and therefore should have the highest priority during queue observing.
The SAC
therefore recommends that the SNLS be ranked above Canadian and French
PI
programs at the same right ascension.
R2
The two data reduction
pipelines
are working very well and are a key element in the process, as they
provide photometry
that is checked
independently. Therefore they should
be maintained.
R3
MegaCam
queue-observing runs should
in no case be shorter than 14 consecutive nights in order to enable
adequate
sampling of the light-curves.
R4
Although
scientifically
interesting, the proposed additional
z-band
observations cannot be considered as a first priority in view of the
limited
time available to carry out the survey and should not be added to the
SNLS
observations.
R5 SAC
supports the plan of the SG to
re-introduce the two extra g’ epochs to better sample the light curves.
Deep
Survey
The
deep survey builds on the SNLS data with the addition of deep u-band
imaging of
the four SNLS fields. The referees note that the scientific case is not
as
compelling as for the SNLS and Wide Survey. However SAC recognizes the
importance of the u-band images for the legacy status of the SNLS
imaging data
and for all the science relying on multi-wavelength information.
Indeed, the
fields have been observed by XMM and Galex amongst other facilities and
a large
community is waiting for these data. Therefore, although not a
short-term
priority, the data must be obtained. SAC encourages the community to
organize
itself better around the science to be done with the deep fields.
R6 Deep
u-band
observations
of the D1, D3 and D4 SNLS fields should be completed but at a lower
priority
than the SNLS observations and the gr/2i Wide observations. u-band
observations
of D2 should be dropped to avoid duplication with the COSMOS survey.
Wide
Survey
The
multi-colour Wide survey is a very important part of the CFHLS with a
wealth of
science goals from cosmic shear to Galactic structure and clusters of
galaxies.
However, the main driver and justification of a high priority is the
study of
the cosmic shear. The particular strength of this survey compared with
its
competition is the large area coverage, which simultaneously gives
information
on structure up to 5 degrees scales and cosmic variance. SAC notes that
the
Wide Survey group clearly demonstrated that with the flip of L3, the
image
quality provided by MegaPrime no longer poses a risk to this component
of the
survey.
R7
Among the different parts of the
Wide survey, the cosmic shear has the most compelling scientific case.
It
should be given every possibility to achieve its goal as fast as
possible. It
should be considered as the second highest priority of the overall
survey and
should be given highest priority with respect to the other scientific
goals of
the wide. Its particular strength is the 170 square degree field which
should
not be reduced.
R8 g, r/2 and i imaging
should be done
first and finished
before the
end of 2007B. The u/2 and z/2 band observations are not
considered as
urgent, should be assigned equal secondary priority, and could be
completed
over a more extended time period. Given the reduced sensitivity of z’,
SAC
recommends obtaining z’ data with the proposed integration times but
the SG
should demonstrate the need for the second set of u/2
Very
Wide Survey
The
primary driver of
the CFHTLS Very Wide component is Kuiper Belt research. This
component
was originally approved as a survey of about 1300 square degrees of the
sky
within 2 degrees of the ecliptic plane, but avoiding the galactic
plane.
As summarized in the CFHTLS VW mid-term review document, the goals are
to
explore the stable zones of the solar system from 20 to 150 AU, measure
the size
distribution of the Kuiper Belt down to 100 km, provide a large sample
of
Kuiper Belt objects for modelling the underlying orbital distribution
of the
belt and enabling physical studies, and search for new orbital classes
as a
probe of planetary formation.
As
of 2004 December
only 250 square degrees have had Discovery/Nailing/Checkup (DNC)
observations
(800 degrees were expected at this point in time) and about 120 objects
have
been discovered. This already constitutes the largest sample of such
objects
available. However, at the current rate of observation, only half of
the
original proposed area would be completed during the 5-year CFHTLS
time-frame.
Because of this, the Very Wide survey is under the greatest threat of
not
meeting its goals. To overcome this shortfall, the SG suggested a
significant
acceleration of the discovery portion of the survey at the expense of
VW
observations in multiple filters. This strategy severely compromises
the legacy
value of the Very Wide component.
It
is difficult to argue
for a significant acceleration of the discovery phase since, as noted
by a
referee, there is no clear justification for how many objects are
needed and
what the sample will quantitatively constrain. This prevents an
accurate
estimate of the observing time really needed for a significant advance
in this
field.
Delaying
the Very Wide
survey beyond 2008 is not a viable option because of the competition
with
Pan-Starrs.
The
other main
scientific drivers of the VW are the search for brown dwarfs, the
search for
high redshift quasars and the detection of GRBs. The latter cannot be
considered as a priority as only about one GRB per year (number
uncertain by a
factor of 3 to 5) is expected to be detected by the survey. The two
other
projects are mainly based on the i-band imaging which is not a priority
for the
Kuiper-belt survey. Well argued i-band observations could be considered
after
2008B in case the survey is extended.
R9
Given the higher priorities
put
on
cosmic shear and SN, difficulties with scheduling the time-constrained
observations, and the lower than expected efficiency of the survey, SAC
recommends that the DNC portion of the VW survey be terminated at the
end of
2005A. The determination of the orbital parameters of the
objects
already detected should be completed by executing the required recovery
and
3-year observations using the current multi-filter observing strategy.
Observing-time
requirements
The
amount of time
needed to achieve the reconfigured survey described above is 250 h of
validated
observations per semester till the end of 2008B (based on numbers
provided by
the SG). With a mean expected efficiency of 4.5 h per night this
corresponds to
~57 nights per semester. SAC wishes to ensure the success of the
reconfigured survey and does not consider it prudent to rely on the
possibility
of a significantly better QSO efficiency.
R10 In
order to obtain the required 250h, SAC
strongly recommends that the participating agencies continue to
allocate the
4+4 nights per semester. This additional allocation will be subject to
review
by SAC every year during the fall meetings. These reviews will be based
on the
SG progress reports and CFHT QSO statistics.
R11 The survey
end
date should be
moved from
2008A to 2008B. The need for a further extension of the survey after
this date
should be discussed by SAC two years from now.
Releases
R12 SAC
is pleased with the quality of
the work done at the Terapix center. However, the present delays in the
release
of advanced Terapix data products, especially stacked images, to CADC
are not
acceptable. The detrimental impact of these delays was noted by many
participants in the workshop. SAC urgently recommends that delays in
data
releases be greatly reduced. Intermediate data products including
stacked
images and catalogues must be made available to the community as
pre-releases
at most six months after the data have been received by Terapix.
The
content and data quality of these pre-releases should be defined by the
SG
together with Terapix.
R13 Terapix should cooperate
with the
SG to prepare a phased plan for the forthcoming releases of data.
Summary of
principal actions
taken by the Board of Directors
in response to the May
2005 SAC and
CFHTLS Mid-term Review reports
12
July 2005
In response to recommendations resulting from the
May 2005 SAC
and CFHTLS Mid-term Review meetings, the Board has taken the actions
listed
below. These actions were taken after
intensive discussions were conducted for several weeks on these
particular
items. The Board wishes to convey to
both, the CFHTLS Steering Group and the Scientific Advisory Council,
its
appreciation for the impressive amount of work and careful examination
reflected in the resulting recommendations.
1. SAC REPORT -
Recommendation
Recommendation
No. 6 – Decommissioning
of MOS and Gecko
Deferred further discussion of the decommissioning
until the
December 2005 meeting of the Board, and asked the Executive Director to
prepare
and issue an announcement to the community advising that these two
instruments
are being considered to be decommissioned within the next 12 months.
2. CFHTLS MID-TERM
REVIEW - Recommendations
Recommendation
No. 3 – Length of MegaCam
runs
Agreed not to establish a rigid policy for the
detailed
number of consecutive nights during each MegaCam run at this time.
The Time Allocation Committee should consider
this recommendation as additional guidance in the establishment of each
semester’s allocation.
Recommendation No.
9 – Terminating the
Very Wide component from the CFHTLS
Agreed to terminate the DNC portion of the Very
Wide
component at the end of semester 2005A.
Recommendation
No. 10 – Allocation of
4+4 nights per semester
Agreed to continue to view the addition by the
participating
agencies of these nights as extra, temporary allocations to the LS to
be done
on a semester basis and not as a permanent addition to the time
allocation to
the Survey.
The decision by the
participating Member Agencies on each semester beyond 2005B should be
made
early enough so that the TAC has advance notice of the allocations.
Recommendation
No. 11 – Extension of
survey end date by one semester
Deferred discussion to extend the end-date
of the survey observations to the Board’s December 2005 meeting.