| Recommendation #1 | Review of systems |
| Recommendation #2 | WIRCam edge crosstalk |
| Recommendation #3 | Data distribution |
| Recommendation #4 | Data Assessment in future Large Programs |
| Recommendation #5 | Material change in strategy of a Large Program |
| Recommendation #6 | Extra observing time for recovery from failure for CFHTLS |
| Recommendation #7 | Photometric calibration of the Wide component of the CFHTLS |
| Recommendation #8 | Time allocation for future Large Programs |
| Recommendation #9 | New instrumentation beyond 2012 |
SAC suggests
the following development priorities:
A Elixir
WIRCam/WIRCam*
A MegaPrime*
A ESPaDOnS*
A Elixir –
ESPaDOnS / Queue ESPaDOnS
B DIMM
B
VASAO/FlyEyes
C Observatory
Automation
C ESPaDOnS
from Prime
Derrick
Salmon reported on the
technical activities of this semester.
Sarah Gajadhar
described the two major failures suffered by MegaCam last spring and
how they were addressed jointly by CFHT staff and a team from CEA.
First, she
explained why the shutter and jukebox came to collide.
Basically, to prevent interaction between
these two entities, which share a common volume, a pair of switches had
been
installed. In the early days of MegaPrime, one of the switches failed
(the
‘shutter-init’ switch) and was hard wired since extensive disassembly
would
have been required to reach it. The incident occurred when the other
switch
failed (the ‘shutter-closed’ switch). Essentially, the staff thought
that the
shutter was in a closed position and that is was thus safe to move the
jukebox
up, which was not the case. A full camera re- initialization was done
which
drove the jukebox up in the shutter.
The shutter
was replaced by a spare and this constituted the bulk of the recovery
work,
essentially because of the flatness requirement and the delicate nature
of the
material out of which it is made.
Naturally, both switches were put back into service but also
more robust
redundancy was implemented in the camera controller logic to prevent
similar
failures in the future.
Then, she
described how the i’ filter was destroyed when the MegaCam filter
clamping
latch system failed. The jukebox and filter slide rails were also
damaged in
the incident. The culprit was identified as the filter ID tag system
(or
software) which mistakenly reported 8 filters in the jukebox when in
fact only
7 filters were in the jukebox and one (the i’ filter) was still in the
beam.
When the initialisation was started after a failure, the jukebox moved
down and
the filter arm moved to its out-of beam position (ready for loading).
This
caused the i’ filter to be pulled out of the beam and released in a
position
partly in the camera filter slide, above the jukebox. When the jukebox
moved up
during the next initialisation step, it collided with the protruding
filter.
The filter
and jukebox slide rails were machined in house or refurbished and
installed in
the camera. A new i’ filter was ordered and put back into service in
October. The reliability of the ID
tag/reader system was improved but an improved radio-frequency filter
ID tag
system is being sought.
As the
recovery from these two major failures involved a major disassembly and
inspection of the camera, CFHT staff, with the agreement of CEA staff
itself,
decided not to carry out the annual maintenance disassembly planned for
September. SAC agrees that this was a reasonable decision.
During
these events, the collaboration between CFHT
and CEA staff was reported as effective and constructive. SAC is
pleased with this
situation and encourages a continued effort in this direction. We were also relieved to hear that the
rotating valve problem seems to be solved with the manufacturing of a
new
version by CEA and delivery in October.
SAC congratulates CFHT
and CEA for their excellent
work during the recovery from these two major MegaCam failures.
Work
continues on the SNDICE (SuperNova Direct Illumination Calibration
Experiment) project, which is aimed at improving the photometric
accuracy of
MegaPrime data. CFHT staff are working together with the SNDICE team to
install
the calibrated photodiode on the camembert in from of the dewar window.
·
WIRCam
Loic Albert
presented the many improvements that have been achieved this
semester for WIRCam.
First, the
1.0 version of the ‘I’iwi data-reduction pipeline has been
released and pre-processing of backlogged data from O6B and O7A has
been
executed and is continuing for the O5B and O6A semesters. The arrival
of new
manpower in the form of the recently-hired Canadian RA, Daniel Devost,
was a great
help in this regard. A lot of data has now been distributed to PIs and
Terapix
has now received images to be stacked, with a priority given to large
programs.
Included in
the new pipeline is the non-linearity correction, the
reference pixel correction (bias), dark-exposure subtraction, dome
flat-fielding, more robust bad-pixel masking, guide-window crosstalk
masking
and improved sky subtraction. In addition, the ‘I’iwi astrometry is
much more
robust as it uses the Terapix-produced ‘WIRCam.ahead’ file which
describes the
position of the WIRCam detectors based on actual observations. The
solution is
later tweaked detector by detector. Finally, the zero-point has been
determined
for all filters.
Another
improvement that was made this semester is that the WIRCam
cross-talk has been greatly reduced. The negative cross-talk was
eliminated
with a new wiring configuration of the detector controller and the
positive
cross-talk was eliminated with the replacement of specific video boards
in the
SDSU controllers. Only the edge
cross-talk (which is much smaller than the two mentioned above) remains
and is
still a mystery. It is not present on the engineering chip. A software
compensation has been implemented for now.
|
SAC Recommendation #2 -- WIRCam edge crosstalk SAC recommends that efforts be continued to identify a hardware solution to reduce the edge crosstalk in WIRCam. |
Nadine Manset
reported that this semester, most efforts were aimed at
the integration of ESPaDOnS within the QSO mode. The
entire chain of operation has been tested very successfully
on the sky in late September. Although improvements are still required,
all the
QSO tools (phase 2 tool, queue preparation tool, observing tool and the
electronic logbook) are functional. There should be no problem in using
ESPaDOnS in QSO starting in 2008A, as advertised. However, it is
expected that
observing in QSO with ESPaDOnS will require much more real-time
interaction
with the PI compared with MegaCam and WIRCam. For spectroscopy, there
are more
complicated issues that need to be addressed compared to imagery. Also,
the
observer has to make sure he or she understands well the overall
strategy that
the PI wishes to adopt.
Some work has
also been done on a new focus process and is reported as promising. Some minor work on improving the guiding
techniques has also been carried out.
A lot of
progress has also been achieved on the software side. First,
concerning the issue of making ESPaDOnS
work under the New Environment for Observing (NEO) framework, a
new command scheme has been developed that is compatible with the
software used
for MegaCam and WIRCam. These will be used instead of the scripts
already
provided to control the instrument.
For the data
reduction, in addition to the Libre-ESpRIT software, a
quick-look software based on ds9 has been prepared (ds9espadons). It
can be
used during the night to view raw images and spectra. It has been
tested by the
CFHT staff and is working well. For the final data reduction, a
software
package called Upena had been developed. Before data are reduced by
CFHT staff,
consultation with the PI will be made to insure that it is tailored to
his
needs.
These
routines are based on stable versions of the Libre-ESpRIT
components. If there is a need to introduce changes to the latter,
these will
be discussed with the CFHT staff so they are introduced correctly in
the entire
chain of observing and data reduction.
SAC is
satisfied that CFHT has gained sufficient control on the
Libre-ESpRIT software to guarantee smooth operation of ESPaDOnS in QSO
mode.
As for the
cross-talk reduction down to a level of ~1%, not much work
has been done on this issue this semester but the manufacturer of the
triplet
lens (which seems to be causing the cross-talk) are looking into the
problem.
Another possibility is to seek another manufacturer for the lens.
·
OHANA
Olivier Lai
presented an update on the status of the Ohana project. He
informed SAC that the team is getting ready for an observing run on the
Keck
telescopes. During this run, studies related to the vibrations of the
fibres
and to the rotation of the polarisation vectors as they move down the
fibres
will be carried out in addition to science observations of YSOs and
AGNs.
The next step
in the Ohana project is a link between the CFHT and Gemini
telescopes. Soon, all the conduits that will hold the fibres will be in
place
and the baseline will be measured next Spring. The Delay lines have
already
been laid in the CFHT Coudé room and soon flux and delay measurements
will be
made (in the IR) followed by auto- correlation and fringes. Once this
is
achieved, plans will be made to create a link with Gemini. On a much
longer
timescale, there are plans to link up with Subaru and UKIRT.
SAC was
informed that FlyEyes saw its first light (loop closed on stars
as faint as m=14.8) at the end of April 2007 during a 3-night
engineering run.
Work is continuing on reducing the readout noise and on the software
communication interface between FlyEyes and the AOB.
·
VASAO
Work on the
seismometers and the
two-color experiment for VASAO is continuing.
The
seismometer was mounted on the
caisson centrale and preliminary vibration measurements of the
declination axis
while the hour-angle axis was held fixed were made last spring. They were found to be small.
The hardware
and software to carry
out the two-colour experiment that will take place in November is being
prepared and is nearly ready. In this experiment, two images of a
bright star
from the AO Bonnette are recorded on two CCDs (one operating at 400 nm
and the
other at 900 nm). This should allow
determining at which precision and under which conditions the atmospheric tip/tilt component of
the atmosphere can be obtained by measuring the separation of the two
colours.
·
DIMM,
Skyprobe and IR AllSky camera
SAC was
informed that the DIMM
software (acquisition and guiding) has been tested at headquarters.
This is
working well. Full automation remains to be completed. On the hardware
side,
the CCD will soon be replaced with one capable of millisecond exposure
times. The Skyprobe is now functional
and has been gathering data for a month. CFHT is keeping informed on
the
progress of the IR AllSky camera being developed for Large Synoptic
Survey
Telescope. There are also plans to have
a facility-wide seeing monitor, to be located on CFHT’s weather tower. This is still awaiting for approval from the
Office of Mauna Kea Management.
·
Telescope
automation
A report was
presented on potential gains and costs of the automation of
the telescope. The potential benefits to be gained were described.
These
include, among others, improved
reliability, reduced
observing costs and improved remote diagnostics. The
challenges to be met were also examined. These involve issues such as resources, implementation, changes in operation
and logistic and finally
safety. If, for example, at some point laser guide stars are in
operation at
the summit, the automation will become more difficult safety-wise. An
update on
the status of the project was also given. At the present time, in
addition to
the fact that the telescope is almost completely used in QSO mode, the staff has gathered
all the required information on the technical requirements and
have worked on generating high-level observing scenarios. They
understand the
scope of the project and have toured other facilities. The have now a
good
estimate of the overall effort that is needed in terms of resources,
cost and
time and have started the conceptual design process. It is estimated
that 2 years
will needed for implementation.
SAC is
satisfied that there are sufficient reasons for examining this
possibility in more detail. We
recognise that even without remote observations, there already have
been many
benefits to the automation process. SAC would like to continue to
receive a
report on the progress towards this goal once a year at its fall
meeting.
|
SAC Recommendation #3 –
Data
distribution Given the work and costs involved, SAC recommends that CFHT eliminate the option of distributing user data on DLT tapes.
|
·
Progress report
The steering
group
chair, Jean-Charles Cuillandre, presented the status report of the
Legacy
Survey including science highlights for each component of the survey.
Observations are continuing at a steady pace, thanks to favourable
weather. Following the destruction of
the i’ filter, the observing
strategies of the SNLS and Wide components were adapted which resulted
in no
lost time on the sky. However, for proper calibration of the supernovae
candidates to be observed in the new i’ filter,
new calibration data will be required.
·
Status
A detailed
plan of the 2008A and 2008B time allocation for the Legacy
Survey was presented by the Steering Group chair. A grand total of 228
hours in
2008A (below what is normally allocated) and 99 hours in 2008B are
requested.
In addition to normal, approved observations, this includes additional
requests
for the following elements.
SNLS-references
The steering
group is presently assessing the need for additional observing
time to recalibrate the new i’ filter
for the SNLS observations and are informing SAC that an additional 10
hours in
2008A (D1 field) and 30 hours in 2008B (D2, D3 and D4 fields) in good
seeing
may be needed to obtain references for calibration of the supernovae
candidates
observed with the new i' filter.
Patching
of the Wide
In order to
insure that there are no holes in the coverage of the Wide,
The steering group is requesting additional 30 hours of observing time
for
patching (15 hours in 2008A and 15 hours in 2008B).
The
incomplete field coverage is
due to the recurring problem of data being rejected by Terapix for not
complying with the required seeing conditions, in spite of having been
validated by Elixir. In its spring report, the SAC asked the steering
group to
provide a justification of why the Terapix and Elixir seeing
measurements are
consistently and systematically different. At the meeting, the steering
group
chair informed the SAC that the metrics by which the image quality is
estimated
by Terapix and Elixir are different, but the SAC was still unclear as
to what
exactly causes the difference, which measurement is more reliable, and
how
seriously this impacts the analysis of the data. Although SAC was still
not
satisfied with the justification, a decision was made to take the
conservative
approach and grant the requested 15h for patching of the wide in 2008A,
rather
than incurring the risk of compromising the legacy value of the survey.
Photometric
calibration of the Wide
In order to
bring the Wide component of the LS to a similar calibration
level as the Deep, the steering group is requesting an additional 14
hours (10
hours in 2008A and 4 hours in 2008B) of observing time. They claim that
because
the observations have been obtained in a diversity of instrumental
setups over
the years, it is crucial to bring all data to a common reference. They
claim
that the data will allow a final optimisation of the overall
photometric
calibration of the wide and allow them to reach the 1% accuracy level.
Following
these various additional requests, SAC has the following
recommendations.
|
SAC Recommendation #7 –
Photometric calibration of the Wide component of the CFHTLS SAC recommends that this time be awarded. |
·
Terapix activities
SAC was
informed that since our last meeting, the T0004 dataset has been
released to the LS community with a slight delay compared the planned
date
(July instead of May). This release
includes all data for the Deep and Wide components from May 2004 to
October
2006. The next release, T0005, is planned for May 1st 2008
and will
contain CFHTLS data up to the end of 2007B. The Very Wide data (1st
official release) is planned to be released 2 months later as
recommended by
SAC one year ago (within one year of the release of T0004). SAC believes that these slight delays are
acceptable but encourages Terapix to attempt to comply with the planned
dates
as much as possible.
·
CADC
A report from
CADC
on the usage of CFHTLS data was presented.
Two modes of data retrieval are available. The first, the Query
mode, is
when a user fills in a form to query the archive dataset. And the
second is
when a user knows the identifier of the dataset and can access the file
directly without filling in a form (the API mode). The latter mode is
increasingly popular. The CFHTLS dataset constitutes about 50% of the
total
CFHT data served by CADC and more files are accessed every year. 90% of
the
retrieved data are for ‘Elixir’ processed data although request for
Terapix
Stacks are increasing every year. When the stacks become available to
the world
community, the number of request approximately doubles. CADC is also
providing
access to CFHTLS stacks developed by Stephen Gwyn, which are made of
all
publicly available CFHT MEGAPRIME images.
·
DDT time
Christian Veillet
prepared and presented a report on
the usage of the 10 nights of the Directors Discretionary Time (DDT) at
CFHT. Some 10 hours were
awarded for various targets of opportunities and urgent requests. Once again, a variety of dynamic research
programs are being carried out by the CFHT scientific staff. The
projects span
a wide variety of subjects from brown dwarfs to galaxy clusters and are
carried
out using all CFHT main
instrumentation. SAC finds this
report very interesting and would like
to see them continued to be prepared once a year.
·
QSO Report
Pierre Martin
presented the QSO report. The
weather during 2007A was better than usual for a winter semester, which
alleviated somewhat the time lost due to the two major failures with
MegaCam.
However, the flexibility of queue observing allowed to quickly change
to WIRCam
programs which resulted in more than excellent statistics for that
instruments:
100% of all programs (A+B+C) were completed. Some 2007B programs were
even
started. For MegaCam, 10 nights less than usual were available and the
loss of
thei’filter made the situation difficult due to the fact that after the
repair
the camera had to be used even though the moon was bright. In spite of
all this
about 85% of A+B programs with MegaCam were completed.
The global validation rate is still
excellent at 92%.
The total
amount of time lost to weather and engineering this semester
was 35% for MegaCam and 23% for WIRCam.
Operational
overheads for MegaCam are
stable at a level of about 10-15%. This is not expected to become lower
as they
are limited by filter changes. In any case, this is the level that was
expected
before observations started with MegaCam.
For WIRCam, the overheads are still dominated by the two-step
focus
sequence, guiding acquisition, pointing corrections and dithering
patterns. The implementation of an
automated focus model saves about 30 minutes per night, which reduces
the
overheads to about 20% of a night. Efforts are still being made towards
reducing this number.
Following a
question from SAC, we were informed that, at the present
time, the length of a night is considered as follows: 6h-long for
MegaCam and
6.5h-long for WIRCam as the nights are longer in the IR and the
observing
overheads are shorter. For ESPaDOnS, a value of 7h is adopted for the 1st
semester of operation in QSO mode (2008A) but there it is hoped that
this can
be increased to 8h in the following semester.
·
CFHT’s
Golden age.
The CFHT
director informed SAC that he will be
presenting to the Board a new plan with an extension up to 2012 instead
of
2010. The present agreement with Taiwan, which is valid until 2010,
could be
renewed. In addition, SAC was informed that a total of 5 nights per
semester
for 4 semesters (20 nights in total) are to be opened to the US
community
starting in 2008B. The proposal will be submitted to the Telescope
System
Instrumentation Program (TSIP). The observing would then be attributed
to
observers via the regular NOAO time allocation process.
Finally, we were informed that options to
finance new instrumentation beyond 2012 are being looked in.
Some
observatory metrics were briefly mentioned.
As of early November, a total of 75 papers based on CFHT data have
already been
published. Due to the technical problems with MegaCam this semester, it
is
clear that the goal of 4% for clear sky time lost to failures per run
is not
going to be met. However, regarding staff turnover, the numbers are
very good,
since none of the 40 staff left this year.
·
Large programs in 2008B-2012B
A total of 15
Letters of Intent were submitted
for possible Large Programs to be carried out in the period 2008B-2012B
for a
total of 1571 hours. 9% of these are to use WIRCam, 19% for ESPaDOnS
observations and 72 % for MegaCam projects.
We note that the Letters of Intent are mandatory and that no
other Large
Programs can be submitted.
SAC is
pleased with this enthusiastic response. Following
our recommendation number 12 from
last spring’s 71st meeting and based on the proposed
science, a
suggested LPTAC membership has been submitted to the Board.
|
SAC Recommendation #8 –
Time
allocation for future Large Programs SAC recommends that time allocation for future Large
Programs be made in hours. |
Details of the proposal
We suggest
that the proposals to be submitted by 1st February
2008 should be about 12 pages long and should contain the following
elements:
External referees
In view of the proposed names for the LPTAC
listed above, we feel that external referees are no longer necessary. However, if the Board decides otherwise, we
suggest that referees should be requested for all proposals and PIs
should be
asked for a list of people they wish to exclude as referees.
·
New instrument feasibility studies for future
instrumentation
In response to the call
for feasibility studies for future CFHT instrumentation, a total of 4
proposals
were received. All appeared reasonable to SAC and could constitute
viable
options, some in the nearer future others on a longer timeframe.
The CFHT director has informed SAC that
sufficient funds are available to carry out these four feasibility
studies for
future instruments. We note that once
delivered, these feasibility studies will be the propriety of the CFHT
Corporation.
|
SAC Recommendation #9 –
New
instrumentation beyond 2012 SAC recommends that the four feasibility studies be
funded.
|
·
Next meeting
In order to
facilitate travel to the LPTAC meeting which should be held
just before the next SAC meeting, in a central location in order to
improves
chances to attract potential LPTAC members, we suggest that the next
SAC
meeting be held in Toronto, Canada on the 15 and 16 May 2008. We
suggest that
the LPTAC be held in the same location on the 13 and 14 May 2008.