Report of 65th meeting of the CFHT SAC
Victoria, Canada, 17-18 May 2004


Recommendation #1 -GRIF
Recommendation #2 and #3 - MegaPrime
Recommendation #4 - WIRCam
Recommendation #5 - Espadons
Recommendation #6 - Pueo Nui / Fly Eyes
Recommendation #7, #8 and #9 - CFHTLS


The meeting was attended by SAC members J.-L. Beuzit, D. Bohlender, D. Elbaz, E. Emsellem, C. Ftaclas, G. Mitchell, P. Petitjean (chair), C. Pritchet, and B.Tully. KAO representative H. Kim was present as an observer. C. Veillet, D. Salmon, J.-C. Cuillandre, G. Barrick, W. Rambold, and P. Martin participated in presentations and discussions.


65th SAC Meeting Agenda: 17-18 May 2004

  1. Technical activities report (D. Salmon)
    1. DEC oscillations
    2. GRIF
  2. Instrument and Project reports
    1. MegaPrime (W. Rambold/J.-C. Cuillandre)
    2. WIRCam (P. Puget/T. Forveille)
    3. ESPaDOns (G. Barrick/N. Manset)
      1. Project status and schedule
      2. Commissioning
      3. Prime focus fiber feed
    4. Pueo Nui (D. Salmon/O. Lai/J.-C. Cuillandre)
      1. Project team, plan, and schedule
      2. Flyeyes
    5. Ohana Update (O. Lai)
    6. CFHT environmental data
      1. Second skyprobe (J.-C. Cuillandre)
      2. DIMM (O. Lai)
      3. Site testing (D. Salmon)
    1. CFHTLS report (Y. Mellier)
      1. Members at large; CDS member
    2. DOG report (J.-C. Cuillandre)
    3. External review (P. Petitjean)
    4. Observing strategy
  4. WIRCam SG (/P. Petitjean/J.-L. Beuzit)
    1. Filters
    2. Call for Proposals
    3. Large Programs
  5. Telescope use and scheduling
    1. 2004B schedule (C. Veillet)
    2. Trends in instrument use (C. Veillet)
    3. QSO report (P. Martin)
  6. 2004 Users’ Meeting
    1. Report (P. Petitjean)
  7. CFHT Future (Veillet)
  8. Other items
    1. CFH12K disposition – status report (C. Veillet)
    2. Scientific staff (P. Martin)
    3. SAC membership; Vice-Chairmanship
    4. TAC membership (P. Petitjean)
    5. Next meeting (P. Petitjean)

Back to top


1. Technical Activities Report

Derrick Salmon reported on technical activities.

A preliminary scope of work for an expanded Building Air Handler project has been reviewed. A custom clean-room humidifier was added to the Summit Clean Room Facility. Remote monitoring and control of the cooling system chillers is nearing completion.

The new declination axis encoder is not operational yet. The declination oscillations have been greatly reduced already but should be reduced further by implementation of this element. SAC continues to view a full solution of this long-term problem as a high priority.

One of the four locking segments that secure the upper-end to the telescope jammed during an upper end exchange in March. The problem was solved rapidly. Two segments have been serviced to during a subsequent engineering night. The two remaining segments will be serviced without a telescope shutdown.

Following the December/January runs, the GRIF wheel mechanism was returned to Meudon for rework. Both Meudon and CFHT efforts to repair GRIF are constrained due to limited manpower and it is unclear that a satisfactory solution can be found. It is unlikely that GRIF will be ready for July.

SAC Recommendation #1

Difficulties with the GRIF wheel mechanism remain and the instrument has not been fixed yet. In view of the continued slow progress and competition with other facilities, SAC recommends that GRIF no longer be considered as a priority by CFHT. If a solution is found by the GRIF French team on a short time scale, CFHT could consider re-evaluating the priority of the project and the availability of the instrument for 2005A.

Back to top

2. Instrument and Project Reports

· MegaPrime

The intermittent behavior of CCD#3 was fixed. CEA provided technical assistance with the repair and training for the CFHT staff. All 40 CCDs are operating normally once again.

The filter changing system continues to cause trouble. Concurrent with the CCD#3 repair, the filter change components were inspected. The filter slide rails were found to be manufactured of aluminum instead of stainless steel as designed. As a temporary measure, the slide rails were machined to allow the insertion of brass inserts at the filter contact points. A new slide rail mechanism will be fabricated from stainless steel by CFHT but the current fix is working well. The motor drive assembly continues to jam under cold weather conditions. It is planned to implement temperature control for the drive gearbox to prevent its temperature from going below 0 C.

A light baffle was added to the front entrance of the Wide Field Corrector and has significantly reduced scattered light coming from telescope structures.

Image quality :
Two effects have been noted :

The image FWHM degrades considerably faster from the center to the edge of the field of view than what was anticipated. There is a strong sense that this is due to the optics of the wide field corrector (WFC). It is not an alignment problem and must either be internal to the corrector or a flaw in the design. The WFC is currently believed to be at its best mechanical adjustment and L1 is the prime suspect. CFHT will attempt to re-characterize the lens at its normal operating temperature. It is very important to assess the impact of the degraded image quality (compared to expectations) on MegaPrime science, and especially the CFHTLS.

Detailed investigation of successive 30s long exposures separated by 1mn show erratic variations with time of the image quality as a function of distance from field center. This will be investigated further to decide if it is an instrumental or atmospheric effect.

Autofocus of the camera is still under development but considerable progress has been made. It is hoped that this automation will be concluded in a few months. In any case overheads for guide star acquisition and focusing have been greatly reduced to just a few 10’s of seconds on all areas of the sky.

Based on this report SAC makes the following recommendations:

SAC Recommendation #2 :

SAC recognizes the important work already done by CFHT to implement the autofocus system on MegaPrime. This system will reduce overheads by about 0.5 hour per night and will also have a positive impact on the overall image quality of the instrument. In view of these very important consequences SAC recommends that CFHT make the completion of the system the top priority for next semester.

Back to top

SAC Recommendation #3 :

Two areas of concern about the image quality have been discussed.

- It has been noted that the image quality changes with time on a time scale of minutes. SAC recommends that this effect be studied as soon as possible to understand the origin of these variations.

- The image quality decreases from the center to the edges of the camera by an amount larger than what was expected. This could have important consequences on the scientific outputs of MegaPrime. SAC strongly supports the idea that an engineering working group be created to investigate this technical problem very quickly and SAC should be kept informed on a regular basis.

Investigation and correction of these problems should be given a high priority.

Back to top


The WIRCam project has progressed well, but final manufacturing and sub-system integration is not as expected in terms of delivery date.

Two Rockwell detectors have been proposed: the first one was out of specification in the J-band; the second one had too many bad pixels. As a result they have not been accepted. Plans currently assume that Rockwell will be able to deliver 4 detectors by December 2004. The science controller should be chosen by the end of the summer. Optical components have been delivered and within the specifications. Manufacturing of the barrels and cells is proceeding more slowly than expected at the University of Montréal. CFHT is very pleased about the cooling system developed in Grenoble. Final delivery to CFHT is planned for September. Software for instrumental control is developed. Filters have been chosen by the WIRCam Steering Group.

The previous plan of having WIRCam available to observers in 2005A has been significantly changed. The camera could be fully integrated at the end of 2004 allowing a test on the telescope in early 2005. This schedule is mostly driven by the delivery of the optics and the detectors. The camera might be on the telescope for science validation in the spring of 2005.

SAC Recommendation #4 :

Given the new schedule provided by CFHT for the completion of WIRCam, SAC expects the instrument to be available to the community for semester 2005B. SAC reiterates their view that Large Programmes (LP) are important to get the best science out of WIRCam. It will publicize the upcoming Call for Proposals for LP by publishing the TAC guidelines for such programs as soon as possible. The first Call for Proposals will be issued after the next SAC meeting, if the current WIRCam development schedule is maintained. In order to boost the emergence of collaborative LP proposals, a meeting will be organized in October 2004 in Paris. Some financial support is expected from the agencies and CFHT.

Back to top


The final pieces of hardware for the instrument have arrived in Toulouse and have been integrated into the instrument. Optical image quality is excellent, mechanical subsystems function well and system electronic systems are robust and reliable. The OMP team now feels they are at a stage where final acceptance with CFHT participation can take place.

National TACs have received proposals for 2004B as well as letters from the community suggesting Espadons could be used in shared risks as a visitor instrument during 2004B. SAC acknowledge the large interest from the community. However, the recommendation from SAC at the November 2003 meeting was to not have Espadons available for 2004B in order to ensure that the instrument was fully tested and had full capabilities available before the first science programs were carried out.

SAC feels they cannot override their previous recommendation based on the current schedule for commissioning.

Most of SAC members believe that it is better to follow the schedule as previously planned. The science verification phase should produce data available for the community as soon as November. All efforts should be made to ensure that Espadons is available for the community at the beginning of semester 2005A.

SAC Recommendation #5

SAC is pleased to see that collaboration between the Espadons team and CFHT is, despite occasional communication difficulties, excellent and positive. It acknowledges the fact that the acceptance process will be started by the end of May 2004 with a CFHT team being sent to Toulouse. SAC strongly recommends that CFHT consider the acceptance and commissioning of Espadons as a very high priority. Every effort should be made so that Espadons can be announced as being available to the community for semester 2005A. SAC recognizes the strong interest of the community for the use of Espadons and encourages the community to submit proposals in September 2004.

Back to top

Pueo Nui

Pueo-Nui and FlyEyes development continues on a best-effort basis. Most work in the past six months has concentrated on FlyEyes. CFHT is about to receive the cryostat for FlyEyes. The project is not the highest priority but it is anticipated that it should be ready by the end of the year. A team of three engineers visited AO development laboratories in Meudon and ESO in April to become familiar with current technologies and development issues. Discussions were extremely useful. The technical feasibility report requested at the last SAC meeting has only been the focus of very recent efforts.

The Pueo-Nui system is an obvious test bench for larger telescopes. However, several projects have been started recently on 8m-class telescope. As emphasized by the Workshop held in Grenoble in the Spring of 2004, scientific targets for CFHT will be limited.

SAC Recommendation #6

SAC is pleased to see that the development of Fly-Eyes is progressing very well and encourages CFHT to proceed with this project as resources permit.

The adaptive optics environment has dramatically changed over the past year with several new projects being started on 8m telescopes. Therefore PUEO-NUI is no longer considered as a priority. SAC recommends that CFHT consider OHANA as its major development project.

Back to top

· Ohana

The Ohana project is progressing well. Injection tests show that the average injection efficiency is around 20% at CFHT. Phase II of the project should start soon. It includes the technical demonstration of interferometry between different telescopes and a demonstration of the scientific impact. This includes obtaining fringes from two telescopes (CFHT-Gemini experiment) and the assembly of components tested elsewhere (injection modules, coherent transport fibers, delay lines, beam combiner). One delay line should be installed in the Coudé room. Some room could be found at CFHT for a Ohana laboratory.

· CFHT Environmental Data

A steel pedestal mount for the DIMM telescope was installed at the foot of the dome shutter between the windscreen and the shutter. Tests have been undertaken and data have been acquired but a full automation of the system is not yet in place. Considerable development delays have resulted from the departure of Eugene Magnier and from bad weather. Development continues.


SAC acknowledges the work by the Steering Group and its efforts to involve the participating communities in the analysis of CFHTLS data. SAC discussed in length the report by the Steering Group.

There are very serious concerns about the survey efficiency. CFHTLS time was allocated assuming 6.5 hrs per night while the present efficiency is only about 5.5 hrs per night. This is due to a combination of technical problems, overheads and bad weather.

As the instrument matures, time lost to technical problems and overheads should decrease over the next semester. The recent very bad weather is a real problem: on average the queue observing system anticipates 20% of the time to be lost to weather while about 50% has been lost during the last six months.

The past inefficiency of the survey had a particularly bad impact on the Very Wide survey component and any additional delay will make its scientific competitiveness questionable. Time constraints for this part of the survey are very important and the concern is that some time sequences are not finished once they are started resulting in the loss of an entire discovery/recovery sequence.

The SNIa time sequenced program should still have a high priority however.

The time fraction within the survey has been adjusted, keeping the SN search at the highest priority and favoring the Very Wide part of the survey compared to the Wide.

Although changes are understandable, this implies some concerns about the low fraction allocated to the Wide. Indeed important science goals are attached to this part of the survey. Therefore, a general assessment of the efficiency of the survey and its implications on the science to be achieved should take place in the next year or so. After this is done, a general discussion of the survey should take place to refine the goals of the survey and to define priorities to be applied during the second half of the survey.

From the discussions within SAC there is a strong feeling that very high quality science is being carried out by PI MegaPrime programs positioned at the top of the observing queue and that, at least for these highest-ranked PI programs, the same priority should be given to these PI programs as for the CFHLS.

Some discussions are going on as what should be the official starting date of the survey.

The presurvey is part of the survey and given the stabilization of the system, 1st of June 2004 seems to be an appropriate date. SAC feels, however, that given the length of the survey this is not a big issue. Indeed, as the problems with the present low efficiency of the survey show, the problem is not about this possible one month of observing time but more what is the science that will be achieved in 5 years including all data taken during the survey and the presurvey. This should be discussed by SAC within the two coming years or so in the light of what has been (or has not been) achieved by the survey.

A formal review of the survey was expected to take place in Fall 2004. However, the coordinators of the different parts of the survey indicate that given the slow starting pace of the survey it will be very difficult to address the very important issues that should be reviewed such as the overall efficiency of the survey and the real expectations compared to the original goals. SAC recognizes that a minimum of data is needed in order for the coordinators to define what will be achieved in the end. Two major concerns have already been identified, namely the image quality and bad weather, that may prevent the survey to achieve its original goals. It is therefore better to wait until about half of the data have been acquired before making, if needed, difficult decisions about a rescope of the survey, or even the termination of part of the survey. Indeed, SAC definitely wants the coordinators to address the difficult question of what is the scientific impact of the image quality problems on the survey.


SAC Recommendations on CFHTLS

SAC Recommendation #7

SAC reemphasizes that everything should be done to finish time sequences once they have been started. Should a conflict require a choice between a regular PI programme and finishing an LS time sequence, priority should be given to the LS observation.

National TACs are advised to take into account possible sources of conflict (time sequences, alpha position of targets, seeing requirements) when assigning time to PI proposals. LS coordinators should submit a short summary of the proposed observational strategy for the forthcoming semester to the national TAC chairs in advance of their meetings.

Back to top

SAC Recommendation #8

SAC strongly recommends that the different groups of the survey estimate the impact of the worse than expected image quality on the scientific output of the survey. SAC expects a detailed report on this matter as soon as possible, but not later than the first external review of the Legacy Survey.

In view of the very slow start of the survey, mostly due to bad weather, the participating agencies have allocated more time to the LS for semester 2004B and 2005A. For the same reasons, SAC recommends that the first external review be completed in the spring of 2005. Details on the organisation of this review will be defined during the next SAC meeting. Should the slow rate at which data are being acquired continue over the next year, a re-evaluation of the goals and strategy of the survey should take place after the external review.

Back to top

SAC Recommendation #9

SAC recommends that the Steering Group defines as soon as possible the structure of the data releases and include this in the report to the next SAC meeting.

SAC welcomes the CADC offer to create a password protected space where products created by LS community users can be made accessible to any registered LS user.

Back to top

4. Telescope Use and Scheduling

C. Veillet presented the preliminary 2004B schedule to SAC after the SAC TAC members had reviewed it, including the eight additional nights allocated to the CFHTLS this semester. PI programs are oversubscribed by a factor of about two.

5. 2004 User’s Meeting

The two and one-half day user’s meeting was held from 13-15 May at Painter’s Lodge, near Campbell River, British Columbia.

There were approximately 60 attendees at the meeting. Very important and lengthy discussions took place about all parts of the CFHTLS survey and the WIRCam Large Programmes. Most of the issues are reflected in this report and several SAC recommendations are based on the outputs of these discussions.

Liz Bryson gave a very interesting talk about the people who made the CFHT work over the year.

Organization was perfect. SAC thanks the organizers and especially David Bohlender for their dedicated work.

6. CFHT Future

C. Veillet gave a brief summary of the state of CFHT’s past, current, and (anticipated) future operating budget. Several potential buyers of the CFHT12K camera have indicated their interest. Most of the time however cash is missing and an exchange for observing time is not particularly appealing.

At the end of 2005, CFHT instrumentation should consist of MegaPrime, WIRCam, Espadons, Pueo, MOS, and Gecko. SAC will almost certainly have to revisit the issue of decommissioning MOS and Gecko at this time.

7. Other items

· Staff; Astronomy Group

Loic Albert from University of Montréal has accepted the vacant Canadian Resident Astronomer position. He will be in charge of the WIRCam data reduction pipeline and analysis. The UH Resident Astronomer position was advertised earlier this year. Interviews will take place soon. The candidate is expected to contribute to support of Elixir and QSO coordination. Sam Kim from Korea should arrive at the end of May 2004 for a 1-year period. He will work on the Pueo-Nui project. Chi-hung Yan, from Taiwan, will join the astronomy group later this year to help with WIRCam data analysis.

· SAC/TAC membership

The current SAC members welcome David Elbaz and Nicole Saint-Louis, the new French and Canadian SAC members respectively. Nicole will assume the role of SAC vice-chairperson. David is also member of the French TAC.

· Next meeting

The next SAC meeting will be held on 11-13 November at CFHT in Waimea. The summit visit will be on 12 November.

Back to top