Report of the 68th meeting of the CFHT SAC
Waimea, 9-11 November 2005

NOTE: Recommendation #3 includes the result of the Board of Directors' deliberation.

Recommendation #1 MegaPrime - Image Quality
Recommendation #2 MegaCam Operations
Recommendation #3 MegaCam runs
  Board of Directors' Response
Recommendation #4 WIRCam - Commissioning and data reduction
Recommendation #5 ESPaDOnS
Recommendation #6 FlyEyes, Pueo Hou and 'Ohana
Recommendation #7 CFHTLS - Follow-up to Mid-Term report
Recommendation #8 CFHTLS - Data release
Recommendation #9 CFHTLS - Observing strategy
Recommendation #10 Telescope Use and Scheduling
Recommendation #11 CFHT Future
Recommendation #12 CFHT Future II

The meeting was attended by SAC members D. Bohlender, C. Ftaclas, J. F. Gonzalez, H. Hoekstra, G. Mitchell, P. Petitjean (chair), N. Saint-Louis (vice-chair) and B. Tully. C. Veillet, J.-C. Cuillandre, P. Martin, D. Salmon, K. Ho, T. Forveille and G. Barrick participated in presentations and discussions.

1. Technical Activities Report

Derrick Salmon reported on the technical activities of this semester, including the integration of WIRCam and the MegaCam image quality.

Different maintenance and development activities of the building and telescope were described: air compressor and dryer systems, telescope hydraulics, oil leaks (epoxy-cement berms installed on 1st floor), soil erosion issues, time jumps in the TCS master clock and the WIRCam interface.

The summit is under continuing safety scrutiny at the moment and this represents a heavy load for many of the staff.

2. Instrument and Project Reports


The number of technical failures of the camera has decreased substantially after constructive discussions with CEA took place. A meeting was held between CEA and CFHT engineers in July and discussions took place between CFHT and CEA managements. The report on these different contacts between CEA and CFHT is not yet available. The final report, when ready, should be made available to SAC.

Major operational problems are due to cooling issues related to the rotating valve, CCD electronics, the lifting arm for the fiber rails and to continuing problems with fiber optic connectors. However, the global situation is improving. The availability of spares is less critical than a few months ago. Problems with the rotating valve have been investigated in detail and are now mostly understood.

Contacts between CEA and CFHT should, however, be maintained. MegaCam is a complex and fragile instrument and, although SAC is happy to see that the efficiency of the camera has increased, all reasonable efforts should be made to avert a major failure.

The Image Quality in the central half of the field is much better since L3 has been flipped. The image quality has been further improved by an increase of the primary mirror-to-corrector spacing in July 2005 and removal of a residual detector plane tilt in September 2005. Image-to-image image quality variability remains and is still not understood.

A model of the focus is in place and substantially decreases the amount of overheads related to focusing 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 microns.

New improved recipes for the pre-reduction of the images within Elixir are being prepared and should be available by 2006A. New master fringe patterns based on two years of data will be generated for different times of the night. The variations of the zero point by about 2 to 3 % from one run to the other is being investigated in collaboration with the SN team.

Based on this report SAC makes the following recommendations:

SAC Recommendation #1: MegaPrime - Image Quality

SAC is very pleased that the image quality has been further improved to reach specifications. The improvement is very impressive and SAC would like to congratulate the MegaCam team for this achievement. Attempts to make further improvements are encouraged but should be considered a low priority.

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SAC Recommendation #2: MegaCam Operations

SAC is pleased that the efficiency of the MegaCam Queue observations has substantially improved and that the reasons for some failures have been explained. SAC encourages CEA and CFHT to continue their fruitful collaboration on this matter. In particular a procedure could be defined in case of a major failure. SAC would like the report concerning the July 2005 meeting to be made available to them.

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SAC Recommendation #3: MegaCam runs

SAC still strongly suggests that the length of MegaCam runs be kept longer than 14 nights, and not be interrupted by use of another instrument during dark time.

After considering SAC's recommendation related to the length of MegaCam runs, it is the sense of the Board that in order to maintain flexibility in scheduling, SAC's recommendation be considered as a guidance to TAC but not be viewed as a rule or policy.

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Much progress has been made since the last SAC meeting and the instrument should be ready for its first scientific run in November. In particular, the four science detectors have been mounted into the detector module by Gerry Luppino of GL Scientific and integrated into the cryovessel. A new controller has been implemented; RON is of the order of 30-40 e. A lot of work on the software has been done and a number of problems have been addressed and solved. At the end of the October engineering run, a stable software and hardware environment had been established. The image quality of the instrument is excellent and images of 0.5 arcsecond over the field-of-view have been obtained (note that the pixel size is 0.3 arcsec).

Real-time analysis of the data is already working and the Terapix center is now involved in the implementation of the data reduction procedures. However, SAC is still concerned about the Elixir environment for WIRCam and would like a detailed report for the next SAC meeting. CFHT has more filters available than the number of filter-slots in the cryovessel. All filters should be offered to the community. The change of filters should however be minimized and if choices have to be made they should be made by the TACs and SAC.

SAC Recommendation #4: WIRCam - Commissioning and data reduction

SAC is very pleased with the progress of WIRCam commissioning and congratulates the teams involved. However, SAC is still concerned about resources for data reduction.

CFHT is encouraged to finish the development of the Elixir-IR pipeline and to enlarge its collaboration with Terapix to provide advanced WIRCam data products (stacked images and catalogs).

Although only 8 filters can be mounted in the filter wheels, the complete list of filters should be made available to the community in the call for proposal. The final selection of filters for each semester will be decided by the SAC-TAC. Changes of filters should be done not more than once a semester.

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The observations with ESPaDOnS have been proceeding very smoothly and have already been very successful scientifically. Observers are pleased by how easy it is to use the instrument and by the pre-reduction software package.
The guiding camera is limited to objects of magnitude brighter than 15 and the offset guiding mode has stopped working for an unknown reason. Although the camera was advertised as able to reach fainter magnitudes, this does not seem to be a major problem for the moment. The cross-talk between the linear and circular modes has been reduced by installing a new triplet lens. It should be further reduced and hopefully eliminated when another lens arrives before 2006.

In January 2005, the fibre bundle was damaged with a loss of a factor 2 in the transmitted flux. The first spare was damaged as well and the second spare has a loss of 0.4 mag. New fiber bundles will be provided by the Toulouse group, with a new design for the connectors. They should arrive early 2006.

Another problem is that there is a shift of the spectrum on the detector that amounts to about 0.1 pix/night (or 0.3 km/s) that is not yet understood. Finally, the spectral resolution is not as high as expected (it is at present 80000 in the spectroscopic mode “star only” and 68000 in the other modes).

For 2006A, ESPaDOnS was allocated 19 nights in total (3 for Canada, Hawaii and Taiwan and 10 for France) compared to 31 nights in 2005B. This just reflects WIRCam being made available for the first time. The question of installing a fiber into either WIRCam or MegaCam to feed ESPaDOnS will be investigated. It seems that this could be easier to install in WIRCam. This could be however a nice complement for MegaCam when the moon is up.

SAC Recommendation #5: ESPaDOnS

SAC is pleased with the ESPaDOnS performance and the scientific results already obtained. The origin of the wavelength shift noted over the course of the night and the not quite optimal spectral resolution and throughput should be investigated further.

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FlyEyes, Pueo Hou and ‘Ohana

FlyEyes is a demonstration project to estimate the performances of low-noise detectors for AO. Work started again in October and a schedule has been presented for a completion in February 2006.

Two nights are foreseen in April for testing with Pueo. At the end of July, the staff should know if it is interesting to use this cheap and efficient wavefront sensing system.

The project is linked to the Golden Age plan. The idea is to refurbish Pueo and to add a laser guide star (VASAO for Visible All Sky Adaptive Optics). The feasibility study of a new instrumental development was accepted by Board to be pursued in 2006.

The Phase II of ‘Ohana is under way. The delay lines have not been installed yet contrary to what was planned.

SAC Recommendation #6: FlyEyes, Pueo Hou and 'Ohana

SAC is happy to see that the FlyEyes project is progressing well. They encourage CFHT to pursue this project as future technology for adaptive optics. The goal of an all sky visible AO system is certainly of scientific merit and SAC encourages study of its feasibility. Community involvement should be expanded regarding the possible development of this system.

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The repartition of the Wide observations may be a problem in the near future. Indeed, observations in W3 will soon be completed and most of the remaining Wide observations will target W1. This will most certainly create difficulties in preparing the observing schedule. The primary reason for this situation is the larger area of W1 compared to other Wide fields. This larger area was supported by (i) the existence of a program with a PI at CEA to image a large field with XMM; (ii) the fact that there are very few interesting fields around D4 in terms of follow-up by other surveys. SAC considers that it is worthwhile to engage a discussion amongst the community concerning the possibility of decreasing the area of W1 and introducing a new W4 field.

SG has asked advice about the first world release. SG suggests using a subset of T004 expected in June 2006 to be released world-wide in January 2007. SAC is concerned about the availability of T004 for the Canadian-French community. It seems reasonable to release only data that have been available to this community for at least one year, as originally planned. Therefore SAC asks SG to consider releasing world-wide data from T003 one year after T003. The second release could happen six months after the first one, based on data part of T004 and so on. This issue could be settled during the next SAC meeting.

SAC has discussed the additional 4+4 nights from the C-F agencies. The general opinion is that major changes in the survey following the mid-term review have not had time to yield an acceleration of the survey and its prioritized goals. In particular, time is still spent to finish the VW observations. In addition, although the efficiency is increasing, some time is still needed for the community to be completely reassured that the instrument is stabilized. Finally, next semester will be the winter semester. To remain consistent with the idea that the survey should be accelerated, SAC therefore considers that it is too early to question these additional nights at least for next semester. The issue should be re-evaluated in six months from now.

For SAC it is clear that the 3-year observations of TNOs should be re-targeted compared to the original VW plan so that they provide TNO recovery. Complementary observations for stellar proper motions may be possibly considered at the very end of the survey or as PI programs.

Astrometry should not be consider a priority and such observations can be postponed to the end of the survey or to PI programs if need be.

SAC Recommendation #7: CFHTLS - Follow-up to Mid-Term report

SAC reiterates its view that SG should focus on the priorities as given in the mid-term report and recommendations. SAC is concerned about the present plan for u-band observations of W1; scheduling problems and tight data quality constraints make it impossible to complete before the end of 2008B. This should be investigated by the SG. u/2 and z/2 could be started now in other fields.

SG must include the constrains of Queue observations in its planning. Therefore SAC requests the semester observing plan be sent to the SAC, CTAC and FTAC chairs before TAC meetings.

SAC thinks that the delay between the mid-term review and now is not long enough to envisage a change in current allocation. Therefore it recommends that the 4+4 nights be allocated for the winter semester 2006A. If the upcoming semester supports CFHT estimates of 5 or more validated hours per night, then the extra time should no longer be allocated.

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SAC Recommendation #8: CFHTLS - Data release

A first World Wide release of scientific products should be clearly defined for the next SAC meeting. SAC recommends it is based on T0003 and should happen one year after T0003 has been released to the Canadian and French communities.

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SAC Recommendation #9: CFHTLS - Observing strategy

SAC is worried about the long-term plan as presented by SG in terms of telescope scheduling. It seems that the pressure on W1 is very high and W3 is well under way. It may be more efficient in terms of Q-scheduling to introduce a new field, W4 (of size about 25 square degrees), at about the same right-ascension as D4, and to decrease the size of W1 (by the same amount). SAC believes this change in the strategy will not affect the science goals and would result in only a tiny loss of observing time already invested.

SAC urges SG to investigate this possibility in collaboration with the community via the CFHTLS mailing list and direct contacts in particular with CEA. This will be discussed during next SAC meeting.

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4. Telescope Use and Scheduling and DDT

Two WIRCam Large Program proposals have been received. One proposal was on the French side only and the other one was Canadian-French. The French TAC would like the next LP deadline to be postponed in order for proposers to have time to get preliminary WIRCam data. This does not take into account that new proposers may be waiting for the second call for LPs and therefore SAC does not view this as necessary. The French TAC asks for ESPaDOnS to be proposed in Q-mode. This has already been discussed several times by CFHT and will be done when resources will permit. The Canadian and French TACs ask for the SG report to be available before the TAC meeting. SAC supports this request.

Queue observations are working very well and the validation rate is now above 85%. The working load is very high however and resources may be short at some stage.

SAC suggests that this be discussed by Board and in more detail during the next SAC meeting. Part of the solution may be found in-house.

A report is being prepared for the Board on the use of Director’s Discretionary Time. SAC considers that this report should be reviewed by SAC.

SAC Recommendation #10: Telescope Use and Scheduling

The community is pleased about the way Q-observations are performed. However, with two major instruments in Q-operation, CFHT resources may not be enough to ensure the highest efficiency of such an observing mode. Agencies should be aware that the added pressure on CFHT staff, which would only be increased if ESPaDOnS is operated in Q-mode, will most likely require more operational resources.

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5. CFHT Future

Christian Veillet presented an update of the plan for the future of CFHT. R&D could be centered on the refurbishment of the AO system, a possible laser guide-star system (VASAO) and the ‘Ohana project.

Christian Veillet has indicated that the long-term future of CFHT is partly linked to the possibility of other partners joining the corporation. About five nights a semester could be made available to the US community through a partnership with NOAO, bringing support for the operation of the Observatory.

SAC Recommendation #11: CFHT Future

SAC supports efforts 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 VASAO concept seems an interesting possibility to be investigated in more detail. SAC still thinks that any further plans should be based on a review of the present resources and how they could be adapted to the future.

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SAC Recommendation #12: CFHT Future II

The pressure for observing time from the Canadian and French communities is very high (larger than three). SAC therefore believes the funding from the agencies (either for operational purposes or instrumentation development) should be increased rather than selling observing time to other partners.

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6. Other items

SAC and TAC memberships

P.A. Duc and C. Gry have been nominated by INSU as members of the SAC to replace J.-L. Beuzit and D. Elbaz..

N. Saint-Louis will be the SAC-chair starting on January, 1st 2006. P. Petitjean will remain member of SAC through 2006.

Next meeting

The next SAC meeting will be held in Montreal on May 12-13, 2006.

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