The meeting was attended by SAC members John Hutchings (chair), Jean-GabrielCuby (vice chair), Thierry Forveille, Paul Hickson, Gilles Joncas, Pierre-Olivier Lagage, Alain Mazure, John Tonry (May 17 only). Michael West and Richard Wainscoat were unable to attend. A written report was submitted by Wainscoat on the material circulated before the meeting. Claude Catala attended as emeritus member, and CFHT personnel Pierre Couturier, Dennis Crabtree, and Derrick Salmon (May 17). The meetings ran for about half the normal 2.5 days and all sessions were open.
The agenda for the meeting was as follows:
This was an abbreviated 1 day meeting: technical reports from CFHT and the document on queue scheduling sent by Crabtree and Abbott, were distributed before the meeting and not presented in detail. In addition, the committee received advance reports on observing statistics, adaptive scheduling, and a memo on the CFHT12K headers from CADC.
a) Megaprime project: CCDs, schedule, WFC progress
b) 1K IR camera status
c) Instrument plan update
d) Megacam survey time
2. Operations issues
a) TAC coordination issues
b) Adaptive Telescope scheduling
c) Queue scheduling
d) Service observing
e) Data headers for CFHT archive
a) Users meeting preparation
b) Instrument decommissioning
c) Any Other Business
d) Initial listing of SAC resolutions
The CFHT reports:
are available on the CFHT web site and are not reproduced here. Many items were presented in detail during the users meeting and will be published in the proceedings of that meeting.
The committee met again on May 21 from 0830 to 1100 to formulate resolutions and discuss issues arising from the users meeting. The date for the next meeting was not settled but will be in the October 22-27 timeframe, in Hawaii.
The SAC has formulated statements on 7 hardware issues and 9 operational
issues as detailed below.
#1 Megacam focal plane stability
#2 CFH12K:Number of CCDs
#3 Wide-field NIR camera
#4 Optical fibre link to Coude
#5 Proprietary period
#6 Allocation of telescope time
#7 Joint proposals
#8 Queue Scheduling
#9 Megacam observing time
#10 Seeing monitor
#11 CFH12k Archive
The project status is updated
regularly on the CFHT website by project manager C. Veillet. We note here
a few issues that were discussed by SAC.
a) SAC noted that simulations of ghosting by bright stars may be of value in estimating their scientific impact and also in planning the data pipeline
b) It is understood that Terapix will request PI's permission for access to CFHT12K data during next semester to help develop the Megacam data pipeline.
c) SAC notes that the details of the wide field corrector will be available by the time of the next meeting.
d) If desired SAC can provide details of coloured glass filters.
e) In order to avoid unnecessary effort and expense on mechanical stability in the CCD mosaic, SAC has the following statement:
As the astrometric `overlapping plate' technique can calibrate the lateral geometry of the Megacam focal plane assembly, SAC recommends that the stability of this geometry between observing runs should not drive the design of Megacam. This design should on the other hand aim at a stability within an observing run of at least 1/50 of a pixel, and preferably 1/100.
SAC was informed of the schedule and current CCD performance tests
which continue to be of concern. The slow repeat time of the shutter is
also a source of observing inefficiency. It was suggested that the light
leaks in the shutter require a dark bag to enable daytime darks. The possibility
that there may be less than 8 CCDs in operation by the time of scheduled
observing time led to the following recommendation.
SAC advises that the CFHT12K camera be put into operation in semester
1998 II even with only 4 CCDs in place. This should not unduly impact commissioning
the full array during 1999.
The subject of a large-field NIR camera was raised again at the SAC
meeting and also at the users meeting. This emerges as a major new instrument
to follow Megacam with very strong support from the users meeting participants.
design by Hodapp was presented to the SAC. The design, performance, and field size need careful consideration, to be as competitive as possible, and several ssues were discussed. SAC would like to see an initiative on this as soon as possible, and make the following statement.
The realisation of a wide field NIR imaging camera as a major instrument
to follow Megacam is strongly urged by SAC and supported by the CFHT users.
CFHT should begin planning for this now, for implementation by 2002. A
field size of 20 arcmin or larger is highly desirable. We recommend a working
group be set up by CFHT
The delays in the OSIR IR 1K camera had been discussed by SAC by email before the meeting. The interest in getting the camera operational as soon as possible was emphasised by both SAC and the participants in the users meeting. There was considerable discussion over the optimum plate scale, which appears to be larger than that in the present design. Eventually it was established that minor changes in the scale which do not impact the cost or schedule are to be pursued immediately.
The commissioning and performance of the OASIS instrument were discussed, and presented at the users meeting. It appears that the instrument works well, is user-friendly, and that the data processing software is in good shape.
Several proposed new instruments were described in various levels of detail and documentation. While many of these are of interest, CFHT have indicated that they wish SAC to comment on them on the basis of submitted proposals. SAC WILL LOOK FOR SUCH PROPOSALS AT ITS NEXT MEETING IN LATE OCTOBER. Nevertheless it should be noted that both instrumentation and operations are signficantly limited by budgetary constraints, and few new instruments will be possible within the CFHT instrumentation plan.
7. Instrument changes
There was considerable discussion of operations limitations and scheduling efficiency at the SAC and users meetings. In view of this, SAC wishes to make the following recommendation.
SAC approves the implementation of fibre links to the coude that will
a) enable quick changes from PF or f/8; and b) allow high throughput
of both visible and UV light, including light from the AOB. SAC also
urges that plans be pursued to enable rapid change between PF and
f/8 to improve observing and scheduling efficiency. In this regard the
installation of extra dome openings (such as in the Gemini domes) may also
improve dome seeing and thus observing efficiency."
SAC realizes that CFHT operations are about to undergo significant and unprecedented changes as 8M class telescopes become available to the CFH community, and the CFHT budget becomes tighter. Observing efficiency and simplification of the instrument complement are of increasing importance. The following paragraphs summarize the discussions and recommendations on these issues.
The length of proprietary time for various types of science and
instrument were discussed at both meetings. There is a consensus that 1
year is an appropriate time, but that the issue needs revisiting as times
and instruments change. The application form already notes that the 1 year
time is proposed. Thus:
SAC reiterates its recommendation
#7 from Oct 1997, and still looks forward to its endorsement
from the Board of Directors.
The improving of observing and scheduling efficiency was discussed in
a number of contexts. SAC makes the following recommendation regarding
the accounting of nights among the agencies.
In order to facilitate and optimize the scheduling of the CFHT, the
SAC recommends that departures from the strict allocation of nights to
the individual agencies be allowed in any individual semester. Such departures
would accumulate to no more than 5% of the share per agency per semester,
and would be made in such a way that such imbalances do not last more than
The matter of joint proposals sent to more than one agency was discussed at length in both SAC and users meetings. It is clear that there is a strong general desire that the individual TACs find a way to support such proposals equally in the case of the CTAC and CFGT. This has not been achieved in the 1998 semesters, in spite of advertised willingness to do so. SAC has formulated the following recommendation, and has the agreement of the CTAC and CFGT chairs to try to make this work. SAC regards this as an important issue particularly in using large format imagers efficiently, as well as encouraging scientific collaborations between CFHT communities. In connection with the final part of the recommendation, SAC suggests that proposals requesting more than 20 nights for completion be allowed one extra page of text in their initial proposal.
In order to enable proper agreement between individual agency TACs on
joint proposals, each committee will direct a subgroup to exchange
reactions and preliminary rankings on such proposals before their meetings.
It is strongly desired that the committees will achieve equal support of
joint proposals by each side. SAC also proposes more extensive review
(e.g. by referees) of large or long-term proposals initially, as well as
continued review each semester.
The CFHT proposal for queue scheduling was discussed by both SAC and the users. While there is a considerable range of opinion over the way it may be done, it is appreciated that this may lead to more efficent execution of approved programs, and SAC believes that it should be tried in practice. It is understood that a realistic study will be made during 1999 I for CFHT12K observations, and that detailed plans for the queue observing will be presented to SAC for discussion at the October meeting, particularly if a different type of time allocation is required from the TACs. We also wish to hear how time will be accounted among the agencies in this observing mode. We have the following recommendation.
As stated by the SAC in May 1997 in its recommendation
#5, queue scheduling will provide a substantial increase in observing
efficiency for many types of programme. Following this point, SAC recommends
adopting queue scheduling as the default for the CFHT12K camera. This new
operating mode will start in semester 1999 II and will apply to all accepted
proposals unless arguments have been explicitly given in the proposals
and approved by the TACs. CFHT staff may conversely decide that a
proposal cannot be executed in queue mode, if they lack particular in-house
CFHT proposals for adaptive scheduling were discussed by both SAC and the users.Continuous submission of proposals rather than the semester system was considered to bring more problems than it solved. However, some form of scheduling that deals with less than the whole semester was of more interest. The main ideas behind this were more responsive engineering time scheduling, and possibly reimbursing highly ranked programs that lost time, at the expense of lower ranked ones. SAC has suggested that CFHT present such ideas at a future time in more detail.
The Megacam project was proposed without explicit request for guaranteed time in exchange for the significant CEA contribution. Instead, a "guaranteed survey time" to be carried out during the lifetime of the project, at a rate of ~ 6 weeks of dark time per year was proposed. This is to be conducted by a consortium of observers from the whole CFHT community, with CEA as a legitimate part of this consortium.
SAC organised a workshop in Toronto in May 1997, to gather interested users from the CFHT community, and to start setting up the science drivers andthe strategy of the survey. This effort remains to be pursued.
As a first attempt to formalize these aspects, the letter of intent
signed between CEA and CFHT, in anticipation to the formal contract to
be signed later this year, was submitted to SAC, and a suggestion for its
implementation was presented to the users meeting by L. Vigroux. Many issues
remain to be clarified before a final contract between CFHT, CEA and the
signed. It is clear that a plan is required for the most effective use of Megacam that will satisfy both CEA and the scientific community. SAC will discuss this and propose such a plan at their next meeting. SAC has the following formal statement.
The organisation and implementation of reserved observing time for Megacam
large programs was discussed by SAC and the users meeting participants.
SAC will propose ways to ensure good science and participation in this,
by its next meeting. This represents a significant change in the way CFHT
observations will be run.
The need for a seeing monitor to aid with good queue observing was discussed
by SAC. It is clear that this is essential and would be of use to Gemini
and other observatories as well.
SAC recommends that CFHT participate in the setting up and running of
a mountain seeing monitor facility. In the meantime, SAC recommends that
alternatives such as monitoring the image quality on the guiding cameras
The CFHT archive
has not reached it full potential for scientific use because of the lack
of adequate header information. This was discussed at both meetings and
agreed that effort must be made to improve the current situation. It is
particularly timely to put this in place for the CFHT12K camera.
SAC approves the implementation of full header and observing log information
for the CFHT12K camera to enable proper archiving of data. This is essential
to realise the full potential of the CFHT archive.
Details of instrument decommissioning were not discussed, although the subject
was raised at both SAC and users meetings. SAC anticipates that CFHT will present
a more detailed decommissioning plan for discussion at a future meeting.
The CFHT users meeting was attended by more than 70 participants, approximately equally from Canada and France, and attendance of one from the University of Hawaii. The 2-day meeting included presentations on all of the issues in this report, as well as presentations by the NGC committee, and an extended open discussion on many of them. On day 3, invited CFHT science reviews were presented along with contributed papers, and the audience was enlarged by many more members of the Canadian Astronomical Society.
The users meeting program is on the CFHT web site, along with the web forum contributions, and the proceedings of the meeting will be published by CFHT, edited by P.Martin and S.Rucinski. This SAC report covers discussions from the users meeting as well as the SAC meetings.