84th meeting of the Canada-France-Hawaii Telescope

Scientific Advisory Council

Waimea, Hawaii, September 27-28, 2013

Note: The report presented below is the public version of the SAC report as amended by the CFHT Board of Directors in accordance with the CFHT Communications Policy.

After deliberation at a special Board Meeting convened on 17 October 2013, the CFHT Board of Directors endorsed SAC’s recommendation No. 1, option (b) New instrumentation capabilities proposals.

The remaining recommendation will be further discussed at the Board’s next regular meeting, December 2013.

Recommendation 1 New instrumentation capabilities proposals
Recommendation 2 ngCFHT Project Office proposal

The 84th CFHT Scientific Advisory Council meeting was held at the CFHT headquarters in Waimea, Hawaii on September 27th and 28th 2013. The meeting date was moved up by a month and a half from its usual mid-November date to provide a prompt evaluation of the instrument proposals submitted in response to the Announcement of Opportunity for new CFHT instrumentation.

SAC members Hervé Aussel, John Blakeslee, Thierry Contini, Thierry Forveille (chair), Andrew Howard, Rodrigo Ibata, David Sanders, Marcin Sawicki (vice-chair), Gregg Wade and Jon Willis attended the meeting. Narae Hwang, from the Korea Astronomy & Space Science Institute, Eder Martioli, from the Brazilian Laboratorio Nacional de Astrofisica, and Wei-Hao Wang, from the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan, attended the meeting as invitees. The CFHT Executive Director Doug Simons, the CFHT Director of Science Operations Daniel Devost, the CFHT Director of engineering Derrick Salmon, and the CFHT Director of administration Deedee Warren participated in presentations and discussions. CFHT staff attended the open part of the meeting.

1. IQ improvement project

The SAC received an update on the progress of the dome venting improvements. The test venting unit installed on the telescope in late spring can be operated manually, as could be witnessed by the SAC members who participated in the September 26th summit visit. The remaining units are being delivered and will be installed within the next two months, in parallel with the hardware and software needed for their remote operation. Remote vent operation is expected to become possible by the end of 2013. SAC commends CFHT and its contractor for the very smooth progress of the project, and eagerly awaits the first results of the dome venting on the image quality delivered by the telescope.


The SAC received a detailed update on the progress of the construction of SITELLE. The project has made good progress, but integration and end-to-end testing have, unsurprisingly for such a challenging technical development, identified a number of problems. All but one of those are well under control, and are expected to affect the schedule to completion by only one or two months. The last problem, instabilities in the metrology laser signal, affects a proprietary ABB technology. CFHT consequently has limited information on the issue and we can only rely on the (good) record of that company.

3. Operations and Upgrade report

SAC received a presentation of the technical activities report by Derrick Salmon.

SAC again extends its acknowledgement to the CFHT staff for achieving significant progress on several projects, including the TCS upgrade project and the refurbishing of the dome shutter. The SAC members witnessed a demonstration of the shutter opening and closing during the summit visit, and were impressed at how smooth and silent that movement has become.

4. Evaluation of the instrument proposals

As part of the recent instrumentation Announcement of Opportunity, the SAC evaluated the five instrumentation proposals that were received by the CFHT. The proposals were reviewed individually by each of the SAC members, then extensively discussed over the course of two days of face-to-face meetings. Following these deliberations, the SAC has reached the following conclusions.

The SAC recognizes the high scientific potential of the new SITELLE instrument and feels that expanding the filter set with the ten proposed additional filters will help maximize the scientific return and community engagement for a very modest investment. The SAC recommends the SITELLE filters proposal be funded as requested. Should the cost of the filters exceed the estimate provided in the proposal, the SAC recommends that prioritizing within the list be the responsibility of the SITELLE team but is willing to advise if needed.

SAC felt that the two most compelling instrument proposals were the SPIRou and the MegaCam Upgrade proposals. These two projects were financially mutually exclusive, with the MegaCam Upgrade proposal requesting >90% of the available funds and SPIRou ~65%. The MegaCam Upgrade consists of several related but independent components with a range of merits and costs, of which the CCD upgrade component was the most expensive by far (~$2M). Given the modular nature of the proposal, the SAC chose to evaluate the MegaCam Upgrade proposal as a set of related components. The SAC also notes that to be truly effective, the SPIRou and the Upgraded MegaCam instruments will have to be matched by very large observing time commitments by the community, equaling or surpassing those allocated to the CFHTLS.

The SPIRou proposal was regarded as potentially delivering the most exciting science among all the proposals (provided the instrument is delivered on spec and in a reasonable time); SPIRou is also likely to be a unique instrument with no equivalent currently planned for any telescope. The drawbacks of the SPIRou proposal generally have to do with risk, which is substantial and not fully quantified.

The MegaCam Upgrade proposal presents good potential science cases and the proposed set of instrument upgrades is straightforward and presents little risk with regards to schedule, cost, or performance. Additionally, for some of the partner communities the MegaCam upgrade (if fully executed and matched with a very significant time allocation) offers the potential to engage in exciting projects that they currently do not have access to (e.g., Euclid). On the negative side we note that the upgraded MegaCam is not as unique as MegaCam was a decade ago, with substantial competition now either already in or entering the field in the area of wide-field imaging; on the other hand, MegaCam remains highly competitive in the u-band, particularly so with some relatively inexpensive enhancements. The SAC felt that significant gains could be achieved at relatively low cost even without the most expensive component of the proposal (the CCD upgrade), specifically in the areas of new filters, readout time and telescope overheads improvements, and taking advantage of the ongoing dome venting project.

Ultimately, given the defined $3M budget, the two options that the SAC considered were:

  1. The full $2.8M MegaCam Upgrade proposal
  2. The full $2M SPIRou contribution along with a MegaCam upgrade that involves readout time and telescope overheads improvements, new filters (as prioritized further below, and to be funded to the extend allowed by the
    3 M$ overall envelope).

Recommendation 1 - Evaluation of the instrument proposals

SAC recommends that CFHT proceed with option (b) as its top priority, as well as fund the SITELLE filter purchase. In the event that option (b) is chosen by the Board, we encourage the MegaCam Upgrade proposal team to pursue other sources of funding for the CCD upgrade. All SAC members would be thrilled to see the CCD upgrade realized.

We note that for maximum scientific return, either of the two options will require observing time commitments of the order of 1000 nights to realize the full potential of these instruments. We recommend that CFHT carry out future very large, proposal-driven, community-based collaborative surveys in the spirit of CFHTLS.

The SAC regards upgrading and extending the MegaCam filter set as a high priority that should lead to excellent scientific returns. We feel that this filter upgrade should be considered as part of a broader MegaCam upgrade that also involves read-out time and telescope overheads improvements, as well as the seeing improvements expected from the ongoing dome venting project. We recommend that the following filters be acquired for MegaCam as soon as possible, in the following order of priority:

    Priority 1:    u, Ca-II
    Priority 2:    g, r, i
    Priority 3:    OIII, DDO51
    Priority 4:    z, H-alpha

Provided the cost is not very significantly higher, we recommend that all these filters be of the larger format that can take advantage of the four currently unilluminated MegaCam CCDs. We recommend that CFHT handle the procurement of the new filters and the associated work, in scientific consultation with the proposers of the MegaCam Upgrade and Expanding the Filter Suite proposals (Cuillandre et al. and McConnachie et al., respectively).

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The SAC recognizes the long-term potential of the promising new MKID technology in the ANUENUE instrument but feels that the scientific return of the proposed instrument at present is not as broad as can be expected from some of the other proposals. The time-domain science outlined in the proposal, while exciting, is of interest to a fairly narrow segment of the CFHT user community. The spectrally resolved spatial imaging applications, with the currently envisaged MKID detector size, are not yet competitive with narrowband CCD imaging. There are also concerns regarding the risks associated with the technology development that is still needed to bring the MKID detector technology to the level envisaged for the proposed instrument. Consequently, the SAC regards this proposal as more of a technology development project than one that provides a facility instrument in a relatively short time. Nevertheless, we regard the MKID technology as potentially game-changing in the longer term; we encourage the ANUENUE team to continue work on this exciting technology and hope to see it taken to a more mature level.

5. Project office for the ngCFHT project

In the May 2013 SAC meeting the SAC received a request from the ngCFHT project team to support a project office. At that time SAC chose not to recommend support for the proposal yet noted that the idea of a project office represented an important and necessary step to move the project forward. However, the level of detail in the proposal left several important questions unanswered and specific feedback was provided to the team.

In response to this communication from the SAC the ngCFHT project team - now under the leadership of the CFHT - have returned to the SAC with a more detailed proposal that is credible in terms of aims, structure, funding and duration.

The SAC has already noted on previous occasions that the scientific aims of the ngCFHT project are of the highest standard and represent a bold yet technically achievable evolution of the CFHT facility.

The SAC notes that the decision to fund a ngCFHT project office from CFHT resources carries an element of risk. The chances of long term success are uncertain and the funds concerned could be used to promote shorter term observatory development.

The SAC notes that some of this risk would be offset if the CFHT contribution to the budget were reduced by in-kind contributions from potential ngCFHT partners.

However, overall the SAC recognizes that the CFHT will potentially benefit from defining a long term plan that is both scientifically and technically credible at the highest level of scrutiny.

It is worth noting that, during its discussions, the SAC focused as much as possible on the scientific implications associated with establishing a ngCFHT project office. Broader political considerations remain a Board issue.

Recommendation 2 - ngCFHT Project Office proposal

The SAC recommends that the Board support the proposal to create a ngCFHT project office.

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6. Next Meeting

The next CFHT SAC meeting will be held in or near Strasbourg, France, on May 27-28, 2014.