Report of the 80th meeting

of the Canada-France-Hawaii Telescope

Scientific Advisory Council

CFHT Headquarters, Waimea, Hawaii, Nov 21-22/2011


NOTE: The report presented below is the public version of the SAC report as amended by the CFHT Board of Directors.

The 80th CFHT Science Advisory Council meeting was held at CFHT Headquarters in Waimea (Kamuela) Hawaii. SAC members John Blakeslee, Mark Chun, Thierry Contini, Pierre-Alain Duc, Thierry Forveille (vice-chair), Brett Gladman (chair), Coralie Neiner, David Sanders, Gregg Wade and Jon Willis attended the meeting. Invited visitors included: Bruno Castilho, LNA, Brazil; Youichi Oyama, Academia Sinica Institute of Astronomy and Astrophysics in Taiwan; Eric Peng, Peking University and Kavli Institute, China; and Doug Simons, Gemini North telescope.

The CFHT executive director Christian Veillet, and CFHT staff Derrick Salmon, Daniel Devost, and Jean-Charles Cuillandre made presentations. They and many members of the CFHT staff participated in discussions.

1. CFHT Legacy Survey.
SAC heard the steering group report on continued work on the CFHT-LS data. The target for the final release (T0007) is improved photometric consistency, but the metric of what criteria need to be satisfied before the work should stop remains elusive. SAC repeats the May 2011 recommendation:

Recommendation 1

Only the stacks and catalogues from the Deep and Wide survey components should form part of the Final CFHT-LS release (T0007), which should be made public as soon as possible. Additional data products after this final release should be considered 'value-added' products.

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2. Large program progress reports

SAC reviewed the status reports from the three original and still-active large programs (MaPP, MiMeS, and NGVS), and was satisfied with their progress. 100% completion for several of the LPs by end of 2012B now appears unlikely due to weather and their pressures on a limited RA range. The two most recent programs (TETRes and CFHQSIR) underwent their mid-term review and were declared to be making satisfactory progress and should thus finish their allocations. The TETRes LP flagged a possible systematic issue in WIRCam data products; SAC speculated that this may be related to other WIRCam photometry issues reported in the CFHT Technical Activities Report. The LP team is aware of the issue and will acquire their remaining observations in a way that minimizes the effect of this issue on their remaining data.

SAC will review progress reports again in May 2012. The currently-active LPs must provide CFHT with their requested RA and observing conditions (for inclusion in the 2012B call for proposals) by February 1st/2012. The 5 LPs must deliver their next status report to CFHT by April 15/2012, which CFHT will distribute to the national TACs before their meetings.

3. Future Large Programs

The Board approved Recommendation 2 of the May 2011 SAC meeting, permitting a new round of Large Programs to operate on the telescope beginning in semester 2013A. The call for proposals should be issued immediately, with proposals due by the end of February 2012. They will be reviewed by a Large-Program review committee in early May 2012, which will have access to comments from the national TACs of any community the proposers identify as potentially providing time to the LP. The large-program agency review committee (LPARC) will provide a ranking for subsequent approval by SAC at the May 2012 meeting, which will be forwarded to the allocating agencies for final approval. This round of Large Programs will include mechanisms whereby national TACs may optionally set priorities between later PI programs and existing LPs, although the balancing of the LP agency versus other agencies will continue to be the default way in which CFHT QSO prioritizes the telescope. In an attempt to maximize the probability of 100% data acquisition of future LPs, the risk inherent in requesting the majority of any resource (with examples being: available time on a certain RA or high-quality seeing time given typical past statistics) will form part of the evaluation process.

4. SPIRou

SAC heard a report about the progress during the beginning stages of SPIRou's Phase B study. SAC re-states (see Recommendation 3 of the November 2010 SAC report) that the phase B deliverables include a revised SPIRou Science Case for SAC review, based on the updated technical-capability estimates and arrival timeline relative to competing projects. SAC expects to receive these documents at least six weeks prior to a SAC meeting during which SAC would formulate a recommendation regarding future continuation of the project towards construction.


SAC reviewed a Phase A progress report from the 'IMAKA team. The team has presented a drastically- revised instrument development plan, which lengthens the overall plan (and probably total cost) but separates the progress towards a final full-capability instrument into a five-phase plan. The remainder of the already-funded phase A will confirm that the atmosphere permits in principle the full `IMAKA performance (roughly 0.3 arcseconds over a 1-degree field of view).

By the end of the Phase A, if the team wishes to continue down the multi-phase plan outlined in this progress report, SAC would want the final Phase A report to address:

  1. the science capabilities at each subsequent phase

  2. funding possibilities for each phase, especially the Phase 'B'

  3. Technical capabilities planned for each phase.

SAC additionally requests that the 'IMAKA team clarify (by May 2012) the number of engineering nights the Phase A activities are expected to require in 2012B and/or 2013A.


The progress towards SITELLE's arrival at CFHT was reported. CFHT will be defining its requirements for the acceptance testing of the guest instrument in roughly two years. No serious technical challenges have developed, and SAC advises that continued focus and efforts be maintained so that this next instrument arrives at CFHT as quickly as possible. SAC hopes the communities will prepare (by taking up offers made a year ago at the CFHT User's Meeting) for SITELLE's arrival by becoming familiar with the data from similar instruments.

7. Technical Activities report.

SAC reviewed the technical activities report delivered by Derrick Salmon. The last 6 months have been smooth from an operational point of view, with essentially no time lost due to technical issues.

CFHT reported finding more evidence of gradual degradation of the MegaCam filter slide rail. The CFHT technical staff indicated that if left unattended this would eventually cause a serious problem. SAC has thus recommended (Recommendation 2 below) that finding a long-term solution to this issue is a high operational priority.

CFHT investigation has revealed clear systematic patterns in the response in the WIRCam detectors that affect ability to correctly flat field at the 2-5% level. Users of WIRCam who wish to work at or better than this precision are urged to contact the CFHT technical staff to better understand this effect. SAC urges CFHT to continue to investigate this issue as resources permit.

Progress continues toward an open-source pipeline (OPERA) for the ESPaDOnS instrument, which can use the Olapa detector, but this may still require a year or more. In the mean time, in order to fully exploit the 2-amp readout capabilities of Olapa, SAC asks CFHT to investigate a short-term workaround to allow the two-amp readout of Olapa to be processed by Upena/Libre-Esprit. If this can be accomplished on a shorter (weeks-months) time line than the OPERA development, this would allow significant reduction in readout times (factor of 2) for the >1 year before OPERA becomes available.

Via a summit tour and the Image Quality Improvement Project (IQIP) report, SAC was familiarized with the progress towards dome venting (project completion target being mid- to late 2013). For cost and ease of installation reasons, a larger number of smaller vents have been selected (whose proposed positions are already taped on in the inside of the dome). Computational fluid dynamics studies have helped refine the choices of vent number and placement. Additional information was presented as appendices contributed by Rene Racine, which will clearly be verified by the coming activities in the 'IMAKA Phase A.

The mirror re-aluminization during the August 2011 shutdown, and to a minor level the MegaCam service, was reported to have resulted in a major improvement of the measured throughput (from +15% to +26%, uniformly increasing as the band wavelength drops). It is clear that this level of improvement (26% improvement in u band) indicates that the four-year spacing since the last aluminization was too long an interval. SAC believes that it would be straightforward for CFHT to routinely monitor the MegaCam throughput in each band. SAC would like to be presented with a plot at each SAC meeting (in either the QSO or technical activities report) showing the zero point change in each band (relative to some fixed arbitrary reference in each band), extending over a window of the previous 4 years; this monitoring will provide a continuous quantitative measurement of the usual gradually-degrading throughput, to judge when a re-aluminization will merit the downtime. CFHT staff asserted that they will perform a more frequent future CO2 cleanings of the primary to help slow the degradation.

A progress report on studies to acquire an improved u-band filter was given. The investigation has revealed that the current u-band filter already has an efficiency which is quite high relative to the state of the art. Even minor improvements towards the short-wavelength end or a wider bandpass involves trade-offs of those two aspects relative to each other, and any improvement in either will be extremely costly (of order $80,000) to obtain only a small improvement. Although an improved u-band has scientific attraction, SAC judged at this time the possible improvements do not to merit the cost. The Executive Director pointed out that the LSST project is financing work to construct a high throughput filter and CFHT may in future potentially benefit from those efforts should they succeed.

Based on the discussions at the SAC meeting, SAC discussed priorities.

Recommendation 2: The Operational Priorities should be revised to:

  1. Normal Operations

  2. MegaCam filter wear

  3. IQIP


  5. SPIRou

  6. 'IMAKA

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7. QSO report

This semester's Queued-Service Observing report documented that 2011A was a worse-than-average weather semester with major losses of 42%, 23%, and 14% of MegaPrime, WIRCam, and ESPaDOnS time, respectively. The first half of 2011B has also had serious weather interruption. Beyond that no problems occurred regarding queue operations or their remote operations.

A minor point arose regarding the scheme of OB validation and the way that constraints are treated. SAC intends to discuss this further during the May 2012 SAC meeting. Before that time, for each parameter used for validation (example: IQ, transparency), a normalized cumulative distribution for the frequency of each parameter should be assembled, based on several years of measurements. Nights which are lost should not be eliminated from this distribution (for example, nights which are closed should be assigned a large arbitrary seeing value), so that one can judge the true probability range for certain conditions.

Some SAC members re-raised the issue hat the Night Report and Program Status queries on the QSO pages function quite slowly; CFHT staff indicated they would continue to look into this issue.

8. CFHT future.

SAC heard an update from the Executive Director regarding the expected timeline for future instrumentation up to about 2020. The chief near-term uncertainties of interest to the communities are the availability dates of SITELLE, SPIRou, and the completion of the dome venting project.

Pat Cote (HIA, Canada) presented a summary of the current state of studies to replace the current telescope with a nominal 10-meter diameter telescope feeding a multi-object spectrograph. Efforts presented included a) preliminary reports of the international science working groups, b) further technical studies of the pier and enclosure, c) a critical valuation of current CFHT infrastructure and d) moves toward building international partnerships. An extensive discussion followed, with notable inquiries coming from the representatives of the smaller partner communities. In 2012 SAC is expecting to receive documents describing a plausible set of technical capabilities for such a facility, the detailed science case addressable by those capabilities, and a report on the serious partnership avenues which exist to acquire the roughly 200 million dollar estimated cost.

9. Next Meeting:

The next CFHT SAC meeting will be held in Kingston, Ontario, Canada on May 14-15/2012. The nominal rotation of having the 2013 User's Meeting in Canada was confirmed as the intention; this may result in the May 2013 SAC meeting again occurring in Canada (possibly in proximity to the same venue).