The meeting was attended
by SAC members Pierre-Alain Duc (vice-chair), L. Ferrarese, C. Ftaclas, J. F. Gonzalez,
C.
Gry, H. Hoekstra, R., P.
Petitjean and N. St-Louis (chair). Jeremy
Lim, from the
Academia Sinica Institute of Astronomy and Astrophysics in Taiwan also
attended
the meeting. The CFHT director C.
Veillet, D. Salmon, Kevin
Ho, Loic Albert, Jean-Charles Cuillandre, Olivier Lai, Hervé Haussel
(for the
LS steering group) and P. Martin, participated in presentations and
discussions.
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LS will not
be completed by the end of 2008A |
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Terapix request to modify
the current data release agreement |
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Terapix request to stop
processing Very Wide data |
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Derrick Salmon reported on the
technical activities of this semester. The effects of the earthquake
that
occurred on 15 October 2006 were described. Although some damage did
arise at
headquarters and at the summit facility, these were relatively minor.
The dome
and its bogies move laterally by 2 cm and had to be put back in place.
The
precision HA incremental encoder track was damaged; its mechanical
interface
with the horseshoe and its drive roller were destroyed.
SAC congratulates the staff for their quick
and efficient work, which resulted in very little observing time being
lost.
The office of Mauna
Kea Management has given its
approval for the grounding grid repair work and for the OHANA
fibre-optic
conduit to be built under the roadway.
A contractor will be selected in November.
Although the number of failures continues to decrease, some problems remain. Since our last meeting, problems in 3 main areas have arisen:
Rotating valve of the cryogenic system: The source of the problems with this system has still not been identified. The motor torque has been eliminated; contamination of the buffer volumes attached to the rotating valve assembly is being investigated. A test cryostat has been fabricated to provide a test facility for this system without being attached to the camera.
CEA has offered to supply a new version of rotating valve. This is presently being considered by CFHT but no decision has been taken yet. The test cryostat mentioned above could be used to test this new rotating valve assembly but a pulse tube would be required to do so.
CEA has proposed to visit CFHT and carry out a complete maintenance procedure of the instrument. This was not specifically requested by CFHT but the offer is being considered. Over the years, the staff has gained a considerable amount of knowledge about the instrument, which has changed substantially since it was first delivered. An in-house maintenance program has already been established and is regularly being carried-out by the staff and it evolves as a better understanding of the failures is acquired. It is not clear if some additional procedures are needed.
| SAC
Recommendation #1 SAC acknowledges
the
renewed
technical collaboration between CFHT and CEA. It is now clear that
MegaCam will
be used at CFHT after the completion of the Legacy survey and that it
has
become an important component of CFHT instrumentation. We therefore
suggest
that lifetime and maintenance issues be clarified with regards to
recommendations from CEA and experience gained at CFHT. |
Jukebox: The jukebox was found to be misaligned by 2 mm with respect to the slide rails. It was realigned and gauge blocks as well as a new brass guide for the top right slide rail, were fabricated. This seems to have reduced the amount of wear. No problems with the jukebox have been encountered since these modifications were made last July.
Guider: In May there were problems with the guider readouts, which stopped several times a night. The problem has disappeared but its source has not been identified and is still being investigated. Writing a better error-handling program seems to have alleviated the problem.
Concerning data reduction, SAC is pleased that better recipes have now been incorporated into the Elixir package and that the flats are now really consistent from one chip to the other (at the 0.5% level).
·
WIRCam
Hardware:
Efforts have been made to make the instrument
more robust as a whole. Major improvements have been achieved in the
detector
read-out speed and a saturation map has been secured. The cross-talk
pattern
induced on scientific images by the on-chip guider has been
substantially
reduced; only a faint vertical line remains when many images are
stacked. Randomising the choice of the
guide star to
further reduce this effect has been implemented since 2006B.
One of the chips is slightly off the plane of the three others, leading to a difference in focus on that chip. The whole detector could been tilted to reduce the problem, which is thought to be caused by different thickness levels of the substrate. Removing the chips and shimming is considered risky. No decision has been taken yet on what to do. The focus sequence has been considerably shortened as it has been realised that two points are sufficient instead of a full focus curve.
The
electronic gain was changed as it was realised that the full dynamic
range of
the detector was not being exploited. As a consequence, non-linearity
corrections close to 10% instead of 5% will be required but fortunately
the
non-linear curve is well behaved. The
maximum possible exposure time will therefore be increased which in
turn will
increase the observing efficiency.
Calibrations: The
best way to carry out flatfielding (dome, sky or twilight) is being
investigated.
Standard stars are being observed to carry out the photometric
calibrations.
For wideband filters, the 2MASS photometry is used while for
narrow-band
filters, empirical zero points are being determined using appropriate
2MASS
filters. The data for the absolute calibration of the Y filter are now
in hand
and should be implemented within the next month.
The global
throughput of the instrument was estimated and found to be very high
(52% in H
and K and 41% in J). Also, the
exposure-time calculator was found to be fairly accurate when the
COSMOS team
evaluated their limiting magnitude on a very deep 10-hour integration
and
compared it with the value predicted by the calculator.
Pipeline: The
data reduction scheme has been determined
after exchanges with Terapix. It was decided that CFHT provides two
datasets to
Terapix, one with basic sky subtraction and one without (both have full
detrending). Terapix uses the first to mask faint sources on the second
set in
order to carry out a more accurate sky subtraction. Data reduction
procedures
for the two more challenging observing modes, Wide Dithering Pattern
and
Nodding Pattern, are still being worked on. In future months, efforts
will be
concentrated on automating the pipeline and improving the image
processing
recipes.
Up until
now, no pre-processed data has been sent to CADC. The data has been distributed on a
PI-request basis. This will be improved once the pipeline becomes more
automated.
·
ESPaDOnS
Since the
new fibre bundles have been installed, better fibre routings have been
found
and protections have been installed. Tests have been devised to monitor
their
throughput. A temperature-based focus model has been created and will
be
implemented during next runs.
Testing of the new
triplet lens has been carried-out and
the cross-talk from circular to linear (and vice-versa) polarisation
has been
confirmed to be at the 2-3% level (rather than 7% before).
| SAC Recommendation
#2 SAC
is
pleased
with the greatly reduced cross-talk of the ESPaDOnS Spectropolarimeter.
We recommend
that CFHT contact the user community to establish if there is a
scientific need
for further reduction. |
Return to top
FlyEyes is
progressing well and is in the final stages of integration with the
AOB. The
fibres from the lenslet array still need to be connected to the
cryostat, the
membrane mirror needs to be synchronised with the CCD controller before
the
closing of the AO loop is attempted.
SAC was
informed on the first fringes that were secured in June 2005 between
the two
Keck telescopes (a world first!). In that experiment, the star 107
Herculis was
observed and both telescopes fed their common interferometric focus
with 300
metres of single-mode fibres. Since then, bad weather has delayed
efforts. SAC
was informed that the OHANA team did however get another full night on
both
Kecks during which no interference fringes were found although
expected. The
reason for this is not well understood but clearly needs to be resolved
before
more progress can be achieved. More observing nights will be requested.
The
next step will be to link CFHT and Gemini and subsequently Keck and
Subaru. As
mentioned above, the office of
Mauna Kea Management has
given its approval for the fibre-optic conduit for OHANA to be built
under the
roadway and a contractor will be selected this month (November).
·
TCS
Last July,
the Remote Buss Monitor card caused the TCS to crash by overwhelming
the CPU,
The problem most likely caused by degraded electronics was temporarily
solved
by enabling staff to disable the interrupt when required. A new RBM
card is
being designed.
The computer handset
function was disabled since this
option was thought to be the origin of the infamous "phantom handset"
problem (unexplained commands to the TCS from the handset causing
random
telescope jumps). The problem has not re-occurred since.
The worn bearing on
the incremental encoder mount on
the HA axis which caused telescope jumps has been replaced.
Finally, non-sidereal
tracking was implemented to
facilitate observations of Mercury and of the SMART-1 collision on the
moon.
SAC
was
informed of the efforts required to get the Gecko spectrograph ready
for an
observing run in 2006A.
| SAC Recommendation
#3 In view of the fact that 2 man-months were required to get GECKO operational for a 4-night observing run in 2006B and that no GECKO proposals have been received for 2007A, we re-iterate our recommendation to de-commission it. |
·
Progress report
The steering group
chair presented the progress report of the Legacy Survey for the past
year. Science highlights for each
components of the survey (SNLS, Deep, Wide and Very Wide) were also
presented.
The visibility of the science from the LS is more and more acknowledged
world-wide and the impact of the survey is expected to increase sharply
with
the first world data release which will take place in February 2007 and
consists of T0003 data.
Concerning
operations,
SAC
was informed that the introduction of the summer W4 field to alleviate
the
problem of securing data for the winter W2 field paid off grandly: in
just one
season, 66 integration hours of W4 were accumulated, almost catching up
the
total integration time on W2 up to now (73 hours). The validation rate
remains
low but this is due to very bad weather on Mauna Kea, mainly during the
winter
months. Although all components of the survey have suffered, the
steering group
points out that under unstable conditions, the Deep and Wide components
suffer
a lot with respect to the SNLS. Therefore, the loss of the 2+2
allocation from
the Canadian and French agencies has resulted in a net loss for these
two
components. The steering group therefore requested that the
additional 2+2
nights policy be re-instated.
| SAC Recommendation
#4 It has now become clear that the LS will not be completed by the end of 2008A. Even with the re-instatement of the 2+2 nights, an extension will very likely be required to complete the LS. SAC feels that allocating 2+2 additional nights to the LS would put unnecessary pressure on PI programs until 2008A and therefore does not support this request. |
SAC
was
informed of the progress made regarding the photometric calibration of
the
data. Previous versions of Elixir were
not able to calibrate the images to better than 2% but refinements to
recipes
used and realisation of the limitations of others now lead to a
calibration
accurate at the 0.5% level.
A report of Terapix
activities was also presented by the steering group chair. These mainly
consisted in (i) the production of MegaCam and WIRCam PI data
(including
CFHT-LS related ones), (ii) the production of the photo-z for the
CFHTLS deep
data using the T0003 release, (iii) the production of the T0003 data
release
and (iv) development and improvement of software.
Terapix has expressed
its
concerns about the increasing workload generated by PI programs and the
productions of the Very Wide stacks.
| SAC
Recommendation #5 Terapix has asked the LS steering group to modify the current data release agreement to make it yearly instead of once every semester, given that semi-annual releases have not been made so far. As we see no problem with such a change, we recommend this release schedule be implemented. |
| SAC Recommendation
#6 Terapix wishes to stop processing Very Wide data except when requested by PIs. SAC does not support this suggestion. Instead, to insure legacy value, SAC recommends that there be an official release of all first epoch data in stacked form within one year of the release of T0004. |
·
Observing Plan for the end
of the LS
The steering group chair presented a detailed plan for the end of the LS. The SNLS, Deep and Wide will continue to observe until the end of 2008A while the Very Wide component will finish observing in 2007B. In order to finish the survey as planned during the mid-term review, the Wide component will be requesting an extension in 2008B to complete observations of the W1 field and to secure pre-survey data for W4.
·
Joint
Canada-France
proposals
The members of the
SAC-TAC from Canada and France
met before
the beginning of the SAC meeting to discuss joint Canada-France
proposals. As
the possibility of giving the Canadian and French TAC chairs the
ability to
change the ranking of proposals has not yet discussed by the Board, no
changes
in the rankings took place. However, the informal
discussions went well and the SAC-TAC members found the
exercise extremely useful. Although we note that this time there were no main disagreements, we believe
that such a process could be efficient.
·
Large
WIRCam programs
SAC notes that the
call for WIRCam programs has
once again
led to a small number of proposals (one joint Canada-France proposal
and one
from France) which were in fact re-submission of the ones from last
year.
However the success rate was high, as all programs were accepted.
·
DDT Time
Following a request by
SAC, Christian Veillet prepared
and presented a report on the usage of the 10 nights of the Directors
Discretionary Time (DDT) at CFHT (3 of these are given to the LS).
The CFHT scientific
staff are carrying out a dynamic
research programs in various branches of astronomy and using all CFHT
main
instrumentation. Some of the DDT is also used to prepare the scientific
case
for the future instruments or to solve tricky problems with the night
allocations
of the agencies. SAC finds this report
very interesting and would like to see them continued to be prepared.
·
QSO Report
Pierre
Martin presented the QSO report. Two
instruments are now being fully offered in queue mode (MegaCam and
WIRCam).
Both instruments are working extremely well in this mode although they
have
been severely affected by bad weather.
The
observing efficiency of MegaCam was reported to have continued to
increase
mainly because of fast guiding acquisition and a reliable automated
focus
model. In spite of the un-cooperative weather (46% of QSO nights lost
in
2006A), the completion rate of A+B programs in 2006A is nearly 73%.
For WIRCam,
some nights have been used for engineering and commissioning. The 2006A
completion rate is lower than for MegaCam but is still acceptable at
61% in
view of the 48% of nights lost to weather.
In both
cases, the 2006A queue validation efficiency is extremely high at 92%.
General
remarks that can be made for queue observing with MegaCam and WIRCam
are: (i)
the entire chain of operation from the planning of the queue to the
commands
sent to the telescope is robust and efficient, (ii) the very concept of
queue
observing is sound and (iii) well adapted for those programs that have
time
constraints. Finally, (iv) when the
weather is bad, either because of non-photometric conditions or
variable
seeing, observing in queue is very difficult.
Operational
overheads for MegaCam are still very good at 10-15% of an observing
night. For
WIRCam, the overheads have decreased but are still relatively high at
25-30%. They are dominated by the focus
sequence, the guiding acquisition and pointing corrections and by
telescope
offsets.
QSO
staffing is improving following the hire of the 2 new service observers
at the
end of 2006A. The situation is still tight but acceptable.
Integrating
ESPaDOnS in QSO is starting to be discussed. One difficulty that could
arise is
the very different philosophy of the control software of ESPaDOnS
compared to
that of MegaCam and WIRCam. No specific schedule has been adopted yet
for the
implementation of ESPaDOnS in queue; the progress of this project will
depend
on the availability of resources.
For
logistics reasons, the TACs have requested to be informed of the
programs
ranked C that CFHT carries out.
Christian Veillet
presented an update on the goals and
the metrics the observatory is using as well as the means used to keep
track of
failures. The
pressure on the telescope remains high both in France and Canada
although there
is a definite decrease after the peaks at the end of 2005 caused by the
arrival
of WIRCam and ESPaDOnS. The number of publications per year based on
CFHT data
remains above the goal of 50 since mid 2002.
The effect of Legacy Survey is not yet included in these
statistics.
The percentage of
clear sky time lost to failure
per run is 4.7%, above the present goal of 4% set by the management. This still represents a very small amount
of failures
and SAC congratulates the staff for this achievement.
The first steps
towards the automation of the summit
have been taken. The overall increase
in the efficiency and a better maintenance program are the basis before
concrete actions can be undertaken. The
first stage that is being considered is to observe from headquarter in
Waimea.
The efforts remain modest for the moment but are slowly ramping up. It
is
important to define the project well.
Finally, the next
users meeting in May 2007 is viewed
as very important to prepare for the future of CFHT.
6. Long-term
options for CFHT
·
Large programs for MegaPrime and WIRCam beyond 2008
SAC discussed the
possibility that large programs be
extended to the other main instruments available at CFHT, Megaprime and
ESPaDOnS. The possibility of allowing
smaller programs to extend over several semesters was also discussed.
| SAC
Recommendation #7 SAC feels that there is a place at CFHT for large and multi-year programs with all major instruments and believes that the advisability of such programs and how they could be implemented needs to be explored. As this requires input from the community, SAC recommends that this should be on the agenda of the next User’s meeting. In light of the community’s views, this issue will be discussed further at the next SAC meeting. |
A
feasibility study for VASAO was presented to SAC by Christian
Veillet. Work on this project started one
year ago and has mainly been carried out by Olivier Lai,
Derrick Salmon and Christian Veillet. More staff are now getting
involved such
as Kevin Ho and Dan Sabin.
The ELP-OA project in
France is proceeding and there has been an agreement to share expertise. Both Jean-Paul Pique (Co-I of ELP-OA) and
Auguste le Van Suu (ELP-OA) visited CFHT, which was useful for them to
have in
mind a potential physical location for future implementation and for
CFHT to
gain knowledge on the one and two photon options for the laser.
CFHT wishes to test
some
key concepts of VASAO. A simple
prototype seismometer is now being studied to monitor the vibrations of
the
telescope. The launch of a 330nm beam
to get a clear photometric measurement of the flux provided is
considered as an
interesting experiment to be carried out at CFHT.
SAC has become aware
that a
disagreement concerning the flux efficiency of the two possible laser
options
(the single photon excitation with the UV 330nm line and the two photon
excitation) has arisen within the ELP-OA collaboration in France. A
review by
independent experts, requested by the INSU ASHRA program, raised doubts
on the feasibility
of the single photon excitation option (supported by Jean-Paul Pique).
SAC was impressed by
the
very interesting presentation made by Olivier Lai on the various
upcoming
challenges awaiting the VASAO project. Main issues include the
differential
tip-tilt sensing scheme, the Laser Guide Star launch telescope, the
determination and tracking of the focus, the Pueo Hou high-order AO
system and
slow guiding and the feedback from the seismometer. The VASAO error
budget was
also presented in great detail in the document presented to SAC and
prepared by
Derrick Salmon.
A report was recently
sent
to the external review committee of VASAO which consists of many
renowned
experts from around the world. Their reply should provide a valuable
independent evaluation of the project.
In the context of
VASAO,
SAC believes that Fly-Eyes is an important development, a new approach
to low
noise detectors and applauds the recent progress achieved.
We anticipate seeing on-sky testing.
SAC
Recommendation #8
VASAO remains an interesting concept and we support continued development of the idea to bring it to a sufficient level of maturity where cost and schedule estimates can be generated. However the technical issues that have been raised on the use of one or two lasers should be addressed before major manpower and/or funds are committed. |
Christian Veillet
briefly
described the various responses that have been received
since he issued a call for new ideas in
January 2006. Among the suggestions are a large field-of-view IR
camera, an IR
ESPaDOnS and a very high-resolution spectrograph for asteroseismology. These will be discussed at the next users
meeting in May 2007. At the next SAC meeting, we intend to prepare a
summary of
these discussions and devise a mechanism that will allow us to estimate
the
various scientific benefits of the various options and how they fit in
the
present context at CFHT.
Preparations for the
next Users meeting are well
underway. The agenda is available on the CFHT Web site. The booking of
a
conference room in Marseille is being looked into. The room at l’Agora
des
Sciences has been pre-booked but it can only contain 80 people. SAC
believes
that with the various important issues that will be discussed,
attendance might
very well be higher than this. Another conference room is being
searched for.
To stimulate
discussion, CFHT is planning to make a
Web-based enquiry within the user community about their satisfaction
with the
use of the telescope and desires for future projects.
An
invitation has been made by Dr Jeremy Lim to hold the CFHT 9th
users
meeting in Taiwan.
·
CFHT12K
Christian Veillet
informed the SAC that he has been
contacted by UH for the possible purchase of CFHT12K.
CFHT is presently looking into putting the camera back into
working order.
·
SAC membership
The SAC chair informed
the committee that Dae-Sik Moon of the
University of Toronto has been
nominated for Canadian SAC membership.
No further appointments have been made.
Regarding
SAC membership, some SAC members
have stated that they prefer that
the TAC chair from France and Canada be appointed to the SAC.
·
Video conferencing of SAC meetings
SAC briefly discussed
whether attendance of SAC
meetings be allowed by a conference interface.
The committee agreed that this is not a good idea but that if a
member
cannot attend, the committee can seek his opinion by telephone if he is
available.
·
Next meeting
The next SAC meeting
will be held on the12-13 May in
Cassis, France.