Canada France Hawaii Telescope

Report of the 92nd meeting of the CFHT Scientific Advisory Council,
November 2017

The 92nd Science Advisory Council meeting was held in Waimea, Hawaii, on November 14-15. SAC members Hervé Aussel (chair), Stéphane Courteau, Magali Deleuil, Tristan Guillot, David Lafrenière, Nicolas Martin, Roberto Mendez, Kim Venn, Richard Wainscoat and Chris Willott (vice chair) attended the meeting. Keiichi Umetsu, from Academia Sinica attended the meeting as observer. CFHT Executive Director Doug Simons, CFHT Director of Science Operations Daniel Devost, CFHT Director of Engineering Andrew Sheinis, CFHT Optical Engineer Gregory Barrick and CFHT Software Manager Kanoa Withington participated in presentations and discussions, together with numerous observatory staff. SAC was very impressed by the high quality of all presentations and commend all CFHT staff for their dedication in offering to its users a world class facility.

SAC heard a presentation by CFHT executive director Doug Simons on the status of Maunakea Observatories and the TMT project. SAC learned about increasing threats on the future availability of UKIRT due to telescope decommissioning. SAC is very concerned about this and hopes that UKIRT will remain available to host SPIRou should MSE start construction. SAC was updated on the various programs put in place by CFHT to engage with the community and views the investment of nights offered to young high school students to conduct science projects as extremely valuable for the future of astronomy in Hawaii.

Maunakea Spectroscopic Explorer (MSE)

SAC heard about the enormous effort that the Project Office has put into the Conceptual Design Review of MSE in early to mid-2017. Conceptual designs were examined for all major systems of MSE, where most systems had designs submitted from more than one prospective partner agency. SAC was impressed by the new CAD rendering of the facility by IDOM, Spain. Feedback was given by the MSE project office and external experts, and specific designs selected as the most promising going into the preliminary design phase. MSE is now prepared for the next stages, e.g., the system design review and cost/performance trade studies. The CFHT Operations group leader also provided support to the MSE project by contributing to the observatory and building facilities design and development phase, and also in assisting with managing the external contract with M3 engineering for the inner pier and outer building structural analysis. The MSE project office have completed a Statement of Understanding between the prospective partner agencies. SAC thanks the MSE Management Group Chair Jean-Gabriel Cuby for his leadership, and welcomes Patrick Hall as the incoming Chair.

SAC agrees that the MSE science case remains impressive and relevant, but also recognizes that the project is reaching a level that is beyond the CFHT resources. MSE now requires the partner agencies to commit to the project, and provide leadership going into the preliminary design phase. SAC notes that progress on MSE now also depends on the renewal of the Master Lease.

Operations Status

CFHT staff performed a very successful primary mirror recoating in August 2017. Taking only 6 days, this was the fastest recoating to date, several days quicker than usual. Photometric zeropoints taken after the recoating show that the throughput is back at a similar level to after the last recoating. CFHT staff reported to SAC lessons learned and possible improvements for the future including replacing the filaments of the coating chamber with a magnetron for more reliable mirror coverage. SAC commends the full CFHT team that carried out this recoating work so efficiently.

CFHT staff reported on a previous SAC recommendation concerning washing the mirror before the latest recoating to determine whether regular washing would provide a reflectivity improvement. CFHT staff explained that washing is a complex process that adds risk and a prior study showed only marginal improvement post-washing, therefore this was not performed and will not be considered in the future. The primary mirror is cleaned bi-weekly using CO2 snow and one option is to test the effectiveness of increasing the frequency of this process.

A decision on whether to change from a 3-year to 2-year recoating schedule will need to be made in 2018. Next year, SAC will reconsider this issue using the excellent analysis provided at its May 2017 meeting and a resource cost estimate from CFHT.

ESPaDOnS

ESPaDOnS (and GRACES) continue to function reliably. There has been one minor incident apparently linked to water condensation on the surface of the detector. This contamination can be traced back to 21 May 2017, when ESPaDOnS suffered a loss of cooling power, resulting in the detector warming up in the middle of the night. Images of the detector showed unusual “splotches” between May 25 and August 29 when the problem was addressed at least partially by pumping. The effect on the data measured by the CFHT team is very subtle and does not appear to be a concern for science. However, the PIs of affected ESPaDOnS programs should be informed so that they can check for any sign of degradation of data quality.

MegaCam

SAC was presented with the latest developments on the MegaCam Performance Improvements. An update to the dethost computer allows benefit from the full 7s improvement enabled by the MegaCam fast readout of the CCDs implemented last semester. SAC was very impressed that, through the whole process since 2015, the time gained amounts to 11.5 seconds for the full readout procedure (from 53.5 to 42s), or an impressive ~73h for the average 23k exposures per year. SAC was also pleased that the shutter timing has been much improved and is now accurate at the 10ms level.

SITELLE

The OPD tilt correction implemented in March 2016 and the addition of interferometer self-diagnostics, to detect problems as they occur in real time, has yielded a ~10% improvement in the modulation efficiency since the science verification phase and greatly diminished time losses at the telescope by allowing to continue a previously halted observation without having to restart it from the beginning. The CFHT and SITELLE teams are to be commended for such improvements. A remaining issue is the image degradation at the edges of the field. This may be caused by the last surface of the two cameras lens group which exhibits an abrupt surface drop at the very edge of the aperture. The collimator also shows higher aberrations than the Zeemax design, if the focus term is removed from measurements. Some field curvature is indeed present in the measured collimator wavefront error. However, this effect may be less significant than that from the camera itself. The need to continue assessing the overall camera and collimator effects of wavefront errors on the delivered science image quality and the impact on the science results remains. A possible option might be to include a stop on the problematic lens to reduce edge camera effects; the resulting throughput reduction would need to be calibrated. This should be investigated by the CFHT and SITELLE teams pending available manpower and relative importance against other SAC priorities. Fortunately, this problem affects only a few current SITELLE programs. Future PIs should be informed about the loss of image quality at the edges of the field.

WIRCam

The only issue with WIRCAM was a failure of one of its filter wheels on the night of 2017 September 3. Fortunately, this did not result in significant loss of observing time as observations continued without further filter changes for the rest of the night. The instrument was then taken off the telescope for investigation and the problem was quickly traced to broken sapphire balls in the wheel bearing, very likely the result of normal wear after 13 years of use. The sapphire balls were replaced by spares on both wheels. The steel races into which the balls roll were also replaced by spares as they showed some signs of degradation. After these repairs, both wheels functioned properly and the instrument has been back on the telescope and operating without problems since. SAC commends the CFHT staff for their efficient handling of the situation.

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SPIRou

SAC heard presentations by CFHT staff and the SPIRou team on the status of the Acceptance Tests conducted at IRAP, the ongoing work at CFHT to accommodate SPIRou, and the plans for the commissioning and science verification. SAC commends all the involved parties for their efforts to deliver a great instrument to the community. SAC was pleased to learn that the Acceptance Tests have not revealed any showstopper. With the delivery to UdM of H4RG detectors of excellent quality and cosmetics, one of the major source of concern about the project has been alleviated, and the goal of a 1 m/s RV accuracy seems reachable. SAC was made aware that some technical tests are likely not to be passed, and urges the SPIRou team to assess the impact of these on all the science cases that are to be addressed by the instrument. SAC looks forward to receiving the final report of the Acceptance Tests and be informed of the results of the review. SAC agrees with CFHT that it is very unfortunate to have a hard shipping deadline at the end of December 2017, so that final improvements to the instrument will have to take place at CFHT rather than at IRAP.

SAC emphasizes that the science verification data are to be made immediately public to the CFHT community. SAC stresses that the science requirements must be met using the official and open source Data Reduction Software (DRS).

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Telescope Use and Scheduling

A detailed report on telescope time allocation and observations scheduling was presented. A small fraction of the Director's Discretionary time was dedicated to high school programs and little engineering time was used in 2017A. For 2017B, a much lower number of nights were initially made available for the semester in order to spare time for the possible start of SPIRou commissioning. This time will come back in the pool for PI programs. The instruments demands in 2018A remain comparable to 2017 semesters with still ESPaDOnS and MegaCam being the most demanded but a much higher pressure on SITELLE from Canada.

GRACES Time Exchange

SAC was made aware of difficulties encountered in trying to implement its recommendation #8 of the May 2017 SAC report concerning the folding of the France agency accepted proposals into the Gemini Canadian queue. As a result, French astronomers in 17B were allocated dedicated nights, losing the advantage of queue scheduling at Gemini. SAC notes that the Gemini support staff was very helpful and tried as much as possible to help these first-time users of this facility. There was no proposal submitted for the GRACES exchange time in 18A for France, and SAC is concerned that that situation is partly due to the inability to operate in queue mode, combined with the small amount of time offered. SAC urges CFHT and our Canadian colleagues to try to find a solution for the execution of France programs in queue mode.

SNR QSO

QSO operations have been reported to proceed efficiently and without any major issues. There was some discussion about how to proceed with time gained through the use of SNR mode. CFHT has revised the policy in the recent past, in connection with the Large Program CFIS, and the SAC agrees with this revision. Accordingly,

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Reporting of Exposure Metadata to CADC

CFHT is presently reporting metadata from instrument exposures to CADC in near real time, and this information is publicly accessible. The information reported (and public) includes pointing (RA, Dec), date and time, filter, exposure time, object name, and PI. Pixels are not available. The present protocol appears to derive from a 1991 Board directive to make the metadata immediately public. That directive predates the modern internet.

The SAC received several requests to limit public access to exposure metadata. The motivations included work on high-profile and competitive objects.

SAC further noted that access to metadata is useful for eliminating possible duplication of observations, and therefore recommends that all metadata be internally available to CFHT staff for the purposes of technical evaluation of proposals.

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ITAC

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Large Programs

CFIS

SAC is confident that the missing 38 hours in 17A will be returned by the CFHT scheduling team to the CFIS LP in 18A. Dark time PI programs from C and F were therefore reduced in 18A. SAC discussed the advantage of using SNR QSO in the u-band. In that process, private communication with Rodrigo Ibata revealed that the CFIS team would prefer to uphold the current observing strategy and avoid SNR QSO for this filter in order to (a) maintain a consistent depth for the various science goals over the survey (since several thousand square degrees have already been covered with the previous strategy), and (b) realizing that u-band exposure times are short, and therefore decreasing these in good seeing would only bring marginal speed gains because of the overheads. SAC appreciates these comments and supports status quo for the ongoing observing strategy.

CIPP

SAC was pleased to learn that the CIPP program has started well and that the team appreciates the support they received from the CFHT team for the scheduling of their observations. While recognizing that astrometry measurements require different epoch observations spread over years which indeed delays the publication of results, SAC encourages the CIPP team to take advantage of their previous observations to ensure some early publications.

VESTIGE

SAC was pleased to see that the acquisition of the VESTIGE LP data is advancing at a decent pace and that the team is able to handle the processes needed to extract science from the data. It is very encouraging that 6 papers are already close to circulation within the team or in preparation, based on LP data and data from the pilot program. SAC is looking forward to the publication of these results and the science enabled from the continued data acquisition.

Large Program call: 2018B-2022A

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The approximate timeline for the selection process would be the following:

• Feb 1, 2018: Large Program call opening
• Feb 15, 2018: non-binding letters of intent due
• Mar 31, 2018: Large Program proposal deadline
• June 15, 2018: LP ranking by national TACs
• June 21, 2018: LP TAC meeting
• June 30, 2018: SAC telecon for LP selection
• Mid July 2018: BoD time allocation.

Operational and development priorities

SAC acknowledges that the reception and commissioning of SPIRou will use substantial resources in 2018A, that is likely to slow down other activities. However, SAC felt that some other items are also important, albeit with a lower priority.

1. Normal operations
2. SPIRou
3. PH2 improvements
4. SITELLE image quality improvements
5. Mirror coating chamber refurbishment

Next SAC Meeting

The next SAC meeting will take place at the Observatoire Astronomique de Strasbourg (France) on May 17-18, 2018.