Report of the 69th meeting of the CFHT SAC
Montréal, 11-12 May 2006

Recommendation #1 MegaPrime; CEA and CFHT
Recommendation #2 CFHTLS: LS observations
Recommendation #3 CFHTLS; Current allocation
Recommendation #4
CFHTLS: Extension of observations
Recommendation #5
CFHTLS: Reinstatement of the Very Wide component
Recommendation #6
WIRCam: Second call for large programs
Recommendation #7
Telescope statistics
Recommendation #8
Joint Canada-France proposals
Recommendation #9
Decommissioning of MOS and Gecko
Recommendation #10
Second round of large surveys

The meeting was attended by SAC members Pierre-Alain Duc (Vice-chair), L. Ferrarese, C. Ftaclas, J. F. Gonzalez, C. Gry, H. Hoekstra, R. Jedicke, G. Mitchell, P. Petitjean, N. St-Louis (Chair). The CFHT Director C. Veillet as well as P. Martin and D. Salmon, participated in presentations and discussions.

"Following discussions by the CFHT Board of Directors, Recommendation #6, WIRCam Large Programs - Next call for proposals", has been endorsed by the Board, effective immediately. The remaining recommendations, in particular Recommendation #5: Re-instatement of the CFHTLS Very Wide component; Recommendation #8 Joint Canada-France proposals; and Recommendation #9: Decommissioning of MOS and Gecko, have been deferred to the Board of Directors' regular meeting in December 2006."

1. Technical Activities Report

Derrick Salmon reported on the technical activities of this semester. The new air dryer system has been successfully re-installed and is working well since March 2006. The departmental permit for grounding grid repair has been received but it has not yet been sent to the Office of Mauna Kea Management because a request to add a new OHANA fiber optic conduit under the roadway will be added to the document. Another above ground conduit for OHANA is planned on CFHT and Gemini subleases. Work on the observatory’s building air handler is continuing and an investigation of the facility’s electrical power consumption has been conducted in an effort to identify the largest contributors and eventually save energy.

SAC was informed that CADC has agreed to continue providing the Poopsy software for proposal submission. Also, the mirror will not be re-aluminized next summer as planned; there is only a small amount of degradation, which has a very small impact on image quality. The mirror will thus be re-aluminized during the summer 2007.

2. Instrument and Project Reports


Technical failures of the camera are still occurring regularly but the staff is becoming increasingly knowledgeable about them and the time spent on repairs is decreasing. The pulse tube/rotating valve cryogenic system is the most troublesome. The fibre optic connectors are very unstable and the staff always has to be extremely careful when manipulating them. Improved technology is being looked into. There have also been some small problems with the SLINK communication system and with the jukebox/filter changer.

Following the July 2005 meeting between CEA and CFHT, it was agreed that both parties would evaluate in detail the potential repairs or re-design of some systems in the camera and decide on a course of actions. Possible re-designs include the cryostat flanges (there is only one spare available at the moment) and the rotating valve/pulse tube assembly. This evaluation is still pending.

SAC Recommendation #1

The proposed plan for modifications as discussed during the July 2006 meeting between CEA and CFHT has not yet been finalized. In view of the fact that the timescale for such re-designs is expected to be long, SAC recommends that actions be taken to accelerate the process.

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· WIRCam

Since the last SAC meeting, WIRCam has become part of the normal CFHT operations. Very few problems have occurred, but the weather has been so bad that not many observations have been carried out. A press release for the first results from WIRCam is being prepared.

Changes in readout and reset procedures have led to improved guiding. Problems with high noise levels (30-40 ADU) in some amplifiers were solved leading to a noise level below 15 ADU but in consequence a single frame readout time is likely to be limited to 1.4 secs. Furthermore, to avoid a problem with a gradient appearing on the science readout, it was decided that the arrays would be read twice, with the first read discarded. This provides more than the necessary settling time but is an easy fix for the moment. Therefore the times between integrations cannot be smaller than 2.8 secs at the moment.

Excellent image quality continues to be achieved but there have been some problems with the focus of one array with respect to the others. This problem is probably due to a varying thickness of the substrate on the arrays through which the light has to go through as the arrays are back illuminated. This is presently being investigated but the most likely solution will be a tilt of the entire mosaic. SAC notes that the new Bracket Gamma filter has arrived. The full set of filters is now being offered to observers. This semester, 9 filters were requested (there are only 8 slots available). After discussions between SAC and the members of the executive that were present, it was decided that by opening the instrument at a strategic moment (not at the beginning of the semester) to change one filter, the problem would be solved.

SAC applauds the fact the Elixir pipeline is now ready. This pipeline is for the time being based on the IDL software package to provide flexibility but requires a few manual procedures. Some of the 2005B data have been reduced using this pipeline and distributed to users. The automation of the astrometry and of image de-trending remains to be done and is planned for the end of 2006. What is the best type of flat field to use also remains to be decided upon.


The new fibre bundles have been received by CFHT. It was determined that they had a very similar throughput as the old ones before they were damaged. The original 50% throughput shortfall of the entire instrument (0.3 mag) is still not understood and is currently being investigated. No progress has been made yet on the problem of the wavelength shift occurring during a night. The resolution, which is not quite as high as previously announced, is probably the best that can be expected. This is still being looked into.

The problem of polarization cross-talk has mostly been solved by replacing the collimator triplet lens. The problem was due to birefringence of the lens due to thermal stressing. The original lens as well as the first replacement suffered this problem but the second replacement lens did not.

Queue observing with ESPaDOnS has still to be looked into since the bad weather has barely left sufficient time to fully test the 2-instrument (MegaPrime and WIRCam) queue mode. However, we note that at the present time, the observers are invited to share the allocated nights in order to improve the observing efficiency. This effective ²mini-queue² is organised by the observers and has been working well up to now.


SAC notes that the semester observing plan of the LS and its impact on PI programs was sent, as requested, by the SG to the TACs but re-emphasize that it should be sent early enough to give the TACs time to evaluate its impact. Therefore the schedule should be sent no later than 1-2 weeks after the proposal deadline.

The LS progress report documents sent to the SAC before each meeting are extremely useful to evaluate the status of the survey. Therefore these documents should be made available to SAC members in good time in order for SAC to be able to give them proper consideration before and at the meeting.

SAC finds the way in which the SG has consulted the LS community on the issue of opening a new field for the Wide component extremely satisfactory. SAC is happy that this will provide the necessary flexibility to help insure that the core program of the Wide component be completed on time.

SAC acknowledges that the first World Wide Release of the LS has now been defined as T0003 and that a date has been set for its release (16 February 2007).

SAC Recommendation #2

In their report to SAC, the SG states that the Wide component core program (u/2, g, r/2, i, z/2) will be completed by the end of 2007B and that the SNLS may be ramping down at that time. This satisfies the SAC recommendations made during the mid-term review of the LS. SAC requests a plan for LS observations up to the expected end-date of the survey, at the end of 2008A.

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SAC Recommendation #3

SAC recognises that within the current allocation, not all the planned observations will be completed. The SG states that at least three more semesters are necessary to complete the survey as originally planned. SAC recommends that a review of the state of the survey take place in one year from now at the time of the next user’s meeting.

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SAC Recommendation #4

In particular, to fully understand the impact if an extension were not granted, SAC would like to see presented during this review a quantitative analysis of what scientific goals of the original project will be compromised as a consequence.

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Letter from the Canada-France Ecliptic Plane Survey team

SAC discussed the letter sent by the CFEPS team to the agency’s representatives, the chair of the Board and of the SAC concerning a possible re-introduction in the LS of some parts of the Very Wide component.

SAC Recommendation #5

SAC notes that the bad weather on Mauna Kea is persisting and that in consequence the average number of validated hours per night has not been increasing. Therefore the previous arguments (see recommendation number 9 in the mid-term review) remain valid and therefore SAC recommends that the VW-component or part of it not be re-introduced.

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4. WIRCam large programs next call for proposals

SAC extensively discussed WIRCam Large programs, taking into account input from members of the committee that are also members of the TAC. Discussions included making more specific the nature of large programs as well as a possible delay for the next call for proposals.

SAC Recommendation #6

SAC recommends that a second call for WIRCam large programs go forward as planned next August for semester 2007A. SAC re-emphasizes that TACs should commit, at the time of acceptance, observing time for the number of semesters required to complete the program.

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5. Telescope Use, Scheduling and DDT

SAC discussed the evaluation process of joint Canada-France proposals, including the effect of the pressure on the various instruments that is different in each country. TAC members also explained that the procedures that had been derived to evaluate joint WIRCam Large Programs which involved ranking of the proposals by each TAC and then a telephone communication between both chairs to discuss the WIRCam Large programs did not work in practice because of the difficulty in finding common dates for the TAC meetings.

SAC Recommendation #7

SAC requests that CFHT make the statistics on the pressure on different instruments publicly available.

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SAC Recommendation #8

SAC proposes that joint Canada-France proposals should be re-discussed by the TAC members who are also SAC members and that they should reach a final ranking at the time of the SAC meeting.

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The 8-night rule

Christian Veillet presented to SAC an analysis of the 8-night rule, the history of its implementation, its observance and impact in the past ten semesters. SAC was pleased to learn that in order to achieve the best scientific use of the telescope and respect the TACs ranking as much as possible, the Director took measures, such as allocating D-time to increase the length of a run, to insure that not many programs had to be excluded because of this rule. Only 10 nights in the past 10 semesters had to be excluded. Many of the concerns at the origin of the 8-night rule are still valid today.

SAC Recommendation #9

SAC believes that in the immediate future, CFHT should take full advantage of the three main instruments (MegaPrime, WIRCam and ESPaDOnS) and should simplify as much as possible its operations for the sake of a higher efficiency. Therefore, in view of the small demand from users for MOS and Gecko, SAC restates its recommendation that these two instruments be de-commissioned in one year. The 8-night rule has no effect on this recommendation.

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DDT time

Following a request by SAC one year ago, Christian Veillet has prepared and presented to the Board last fall a report of the usage of the Directors Discretionary Time (DDT) at CFHT. This was presented to SAC. The origin of the DDT as well as its usefulness in general was described and an account for 2005 was provided. There are 10 DDT nights in total each semester and 3 of those have been given to the CFHTLS. Furthermore, some of these nights are used to prepare the scientific case for the future instruments or to solve tricky problems with the night allocations of the agencies. The general impression is that this is a positive measure and that the numbers of DDT nights is not excessively high even though the pressure on the telescope is quite strong. Therefore, SAC thinks that this measure should continue and that an account of the usage of DDT should be provided to SAC each year at the fall meeting.

Pierre Martin presented the QSO report. Queue observations are proceeding very well and the validation rate is now above 88% for A+B programs on MegaPrime. For WIRCam, the rate is still low in this early stage but most of the time was lost to commissioning and engineering.

SAC is pleased to hear that a new queue observer has been hired to help carry out the observations, which are intensive now that 2 instruments are being extensively used in queue. This has greatly helped to reduce the pressure on the staff.

6. CFHT’s Golden age

Christian Veillet presented an update on the goals and the metrics the observatory is using to keep track of failures. The percentage of clear sky time lost to failure per run is close to 4%, which is the present goal set by the management. This represents a very small amount of failures and SAC congratulates the staff for this achievement. SAC was informed that the plan is to attempt to decrease this to eventually reach 2% by 2010.

7. Long-term options for CFHT

Large surveys in the future

SAC discussed a possible second round of large surveys for MegaPrime and WIRCam after the completion of the Legacy Survey and found that it was premature to make a recommendation at this stage. Committee members would like to seek input from the CFHT users’ community on this issue.

SAC Recommendation #10

SAC recommends that, at the next CFHT users meeting, an agenda item be included to discuss a second round of large surveys.

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Other instruments in 2008-2010

SAC discussed the possibility of issuing a call for proposals to the community for the possible usage of outside instruments as Guest Instruments in the 2008-2010 time period. SAC does not believe that it is wise at this point to issue a call for ideas for the use of outside instruments in that period. SAC believes that the pressure will still be high on the three main instruments and therefore sees no need to complicate further the operations and add more duties for the staff.


Work on Fly-Eyes has been progressing smoothly. We note that the integration with PUEO should start in May and that on-sky tests should take place during the second semester.

VASAO is currently undergoing a feasibility study and results should be presented to SAC at the next meeting. Performance modelling of the expected Strehl ratios, field size and laser guide-star flux have been carried out and the necessary modification to the AO Bonnette and to the telescope are being made.

Christian Veillet presented a brief update of the recent developments of VASAO. Also, in early January 2006, a VASAO mailing list was created and a call for scientific input from the CFHT community was made and many ideas were received. SAC would like a summary to be presented at the next SAC meeting. A feasibility study for VASAO is now underway and SAC would also like to be informed on the outcome of this study at the next meeting.

8. Other items


Christian Veillet informed SAC that no buyers have been found for CFHT12K but that the detector (or part of it) can perhaps be used as a test detector for VASAO.


Pierre-Alain Duc has been designated by INSU as Vice-Chair of the SAC for a term effective immediately and ending on 31 December 2007.

CFHT Users meeting

The next users meeting should take place in France next spring. It was proposed to organise it in Marseille or in the surroundings and SAC approves this. The most probable dates for this meeting are 9, 10, 11 May 2007 and the SAC meeting should be held on the 12-13 May in Cassis.

Next meeting

The next SAC meeting will be held in Waimea on the 9-10 November 2006 with the summit visit on the 8 November.

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