Canada France Hawaii Telescope
96th Meeting of the Canada-France-Hawaii Telescope
Scientific Advisory Council
20-21 November, 2019, Waimea, Hawaii
After deliberation during its December 2019 meeting, the CFHT Board of Directors, in consultation with the Executive Director, endorse the following SAC recommendations:
| Recommendation 1 | Improvements to RV Precision for SPIRou |
| Recommendation 2 | Delay Sale of H4RG Detector |
| Recommendation 3 | DRS Team's Request for SPIRou Data |
| Recommendation 4 | SITELLE Modulation Efficiency Variations |
| Recommendation 5 | Improvements to Dome Vents |
| Recommendation 6 | Validation Ratio of Large Programs |
Report of the 96th meeting of the CFHT Scientific Advisory Council,
November, 2019
The 96th Scientific Advisory Council meeting was held at CFHT Headquarters on Nov 20-21 2019. SAC members Anthony Boccaletti, Sylvie Cabrit, Stéphane Courteau, Emanuele Daddi (vice-chair), David Lafrenière, Eugene Magnier, Nicolas Martin, Roberto Mendez, Tracy Webb and Chris Willott (chair) attended the meeting. Associate partner representatives Sophia Dai (NAOC) and Li-Hwai Lin (ASIAA) also attended. The CFHT Executive Director Doug Simons and many CFHT staff gave presentations and participated in discussions during the meeting.
Maunakea Spectroscopic Explorer (MSE)
The MSE Project Office has had a very productive year. Overall efforts have included a clear emphasis on outreach within Hawaii and the global astronomy community to increase awareness and participation, and converting the detailed science case into a design reference survey. The growth of the science team (now up to 409 members from 36 countries) is an encouraging sign of the community awareness and interest. The outreach to the communities has also paid off in terms of the high ranking of the project within the French Prospective. Also critical are the submitted support requests to the Australian Research Council and US NSF. SAC applauds the ongoing effort of the MSE project office to drum up support for the project.
SPIRou
Several technical interventions have recently affected SPIRou. The cold head motor failed in August, which required using a spare as a replacement. The compressor also had to be changed at the same time for compatibility reasons. In total this operation entailed 1 week of warm up and 3 weeks of cooling. The RV signal oscillates intermittently in some of the orders with periodicity of a few hours and PTV amplitudes of 0.5 to 2m/s. The source of this problem is not yet identified. In addition, the temperature also shows oscillations at the milli-K level. This however has very little impact on the velocity precision. The polarization crosstalk has been measured to be ~1.2%, below the technical specification of 2%.
To perform a better determination of the field mirror hole positioning which sets the fraction of the light going to the guider and to the spectrograph, the fiber-fed source has been replaced by a larger beam source to illuminate the full mirror aperture.
The K-band background continues to exceed the instrument technical specifications. A cooling system was installed in the slit room which reduced the temperature to the initial value prior to the installation of SPIRou, but the temperature in the Coudé room did not change significantly. The power dissipated by the Laser Frequency Comb (LFC) unit is a major contributor to the high Coudé room temperature. Another system to cool the Coudé room is under consideration. The Cassegrain unit and fiber interface are also major contributors to the high background. Some tests were made and are being analyzed.
A number of other more minor operations/issues have been conducted or identified: improvement of Fabry-Pérot insulation, new linux-based detector readout system, instability of the fiber to field mirror alignment, RV jumps due to telescope movement, developing agitator sensing, regular pumping of the cryostat, regular filling of the helium compressor. There has been no recent work on the double scrambler, and the LFC is not yet in regular use.
A loss of transmission that occurred in the last semester was traced back to the molecular adhesion in one of the rhombs. New rhombs, made by a different company (Winlight) with more experience in molecular bonding, are being procured. These new rhombs will be housed in a titanium mount to reduce the thermal stress on the optics. Because of the higher quality ZnSe material procured by Winlight, it is expected that the new rhombs will provide higher transmission in the Y and J bands. Single rhomb operation was considered to increase transmission, but SPIRou would lose its unique capability to measure all four Stokes parameters, so this option will not be pursued further.
SAC was informed that the SPIRou team is considering the replacement of the spectrograph pupil slicer as this could improve mode scrambling and RV precision. This activity, which requires opening the SPIRou vessel, may increase the risk of damaging a part of the instrument, and its detector in particular.
CFHT has investigated the possibility of selling the engineering-grade detector obtained during the procurement of SPIRou’s science-grade detector. While SAC favours the sale of this e-grade detector given the low failure probability of the SPIRou detector, the prudent action in the event of an imminent upgrade of the instrument is to retain the e-grade detector until the upgrade has been completed.
There continues to be substantial development of the SPIRou Data Reduction System (DRS) by the SPIRou team. CFHT reprocesses and re-archives all SPIRou data when new versions of the DRS are released. Whilst great progress has been made, various ongoing improvements remain critical such as persistence correction, improved masks, telluric correction and background subtraction. The SPIRou team has requested access for a limited number of DRS developers to all SPIRou data (including that obtained by PIs) in order to continue to improve the software. Given the sensitive nature of SPIRou data, and in some cases metadata such as target name, pointing position, in this field of science, there is a concern that distributing these data to DRS development sites in Canada and France poses a risk to SPIRou PIs. The relevant SPIRou team members would sign a formal non-disclosure agreement.
SITELLE
SAC commends Marc Baril and his team for solving the field curvature problem on SITELLE and achieving a superb panchromatic image quality across the field. The plate scale and field-of-view have been reduced slightly (by 2.6%, now 10.2 arcmin on a side). The community should be informed about the plate scale changes and benefits of the improved image quality and field-uniformity, such as the ability to do mosaicking and observe larger targets. SITELLE continues to suffer from occasional variation in modulation efficiency with time and instrument flexure. CFHT has a detailed plan to upgrade the metrology receivers, providing increased reliability and robustness and reducing the burden on staff.
RECOMMENDATION #4: Address the variation of the SITELLE modulation efficiency by increased reliability of the metrology receivers. |
MegaCam
The development of the new GigE interface solution to replace the obsolete SLINK communication boards has progressed very well and is into the final phase of software testing. Results are very promising and everything indicates that this solution could be deployed soon with no impact on instrument performance. This transition will retire a significant liability for MegaCam, as new SLINK cards cannot be procured and very few spares remain. The failure of two more SLINK cards during the most recent semester illustrates the seriousness of the issue. Fortunately, spare cards were still available and were rapidly swapped in and, looking forward, further failures could be resolved by deploying the new GigE solution.
A failure of the MegaCam shutter prevented the instrument from being mounted on the telescope as planned for one run and resulted in the loss of one night. The problem, thought to be the result of normal aging, was fixed.
The MegaCam bi-annual cleaning was recently completed. A significant deposit was removed from the dewar window, which had impacted the photometric flat-field response by ~0.05 magnitudes in a small region of the array between 1 June 2019 and 10 September 2019. The community should be informed of the impact on data taken during this period.
Operations status
Technical issues with the crane used to exchange instruments have plagued the telescope this year, leading to the loss of 9 nights during which CFHT had no instrument available and the sub-optimal use of 7 bright nights in 2019A for which MegaCam had to remain on the telescope. Repairs have been made and are expected to hold until the crane is fully rejuvenated in 2020.
The dome-vent failure has been tracked to water freezing inside the vent slats. Temporary solutions have been put in place and all but 2 vents can now be two-thirds opened during normal operations. A lasting solution is in the works, which will be tested using a recently-built test platform. CFHT plans to deploy a turbulence monitoring system inside the dome. This should enable a characterization of the required seeing improvements beyond those already available when most vents are partially (two-thirds) open.
RECOMMENDATION #5: Assess the significance of potential further improvements to the dome vents before committing significant engineering effort. |
The combined mounting of ESPaDOnS and SPIRou at the Cassegrain focus was investigated further. For simultaneous observations, it would require a dichroic to separate the visible and IR beams and a symmetrical reflecting surface (same dichroic) to cancel out the induced instrumental polarization. This would enable the gathering of full optical+NIR spectra and a more flexible scheduling of the two instruments at the cost of a 10 to 20% throughput reduction. Further investigation is needed before a decision can be made and the scientific community should help build the science case behind the need for the combined instrumentation.
The safety-compliant Bridge Crane Access platform is almost ready for installation and should be implemented by early 2020.
Work is continuing on lightening the Dec wrap to ensure the cabling does not suffer tension as the telescope moves. This effort should also be concluded in early 2020.
We commend CFHT for installing a new astrometric camera on the telescope to optimize the telescope pointing. It is anticipated that this camera will save a significant amount of time during SPIRou and ESPaDOnS runs. It will eventually also be used to derive photometric zero points.
An effort to clean the mirror with a polymer was successful. It led to a marked improvement of the mirror reflectivity, which is back to the level expected 2 years after re-coating. The procedure was performed in daytime and did not impact the telescope's regular operations. SAC is supportive of the planned experiment to determine whether regular application of this product will maintain primary mirror reflectivity.
Upgrade work on the mirror aluminizing chamber has continued. It is expected that this effort will be completed before the next mirror re-coating some time between March and May 2020.
Large Programs
CFIS
CFIS continues to progress at a slower than expected rate due to weather and technical problems, as well as competition with PI projects at similar RAs. The Large Program completion review sub-committee recommended the allocation of 43 extra nights to CFIS, which have now been allocated by CFHT in 2021A and 2022A. SAC is aware that the validated to allocated ratio for CFIS (and indeed the Large Programs in general) is significantly lower than for the PI programs in 19A (and has been the case in previous semesters) and has resulted in a much lower LP fraction of time than the planned 60 and 70% by Canada and France, respectively. SAC discussed several remedies to this problem, including those outlined in the CFIS report. In spite of the slow observing progress, SAC is pleased to see peer-reviewed science coming out of the survey.
VESTIGE
VESTIGE was heavily impacted by bad weather and technical problems during 2019A and its completion rate remains low. The Large Program completion review sub-committee recommended the allocation of 18 extra nights to VESTIGE, which were recently awarded by CFHT in coming semesters 2020A and 2021A. This should provide a reasonably high chance that the LP will reach at least 80% completion by the end of 2021A. SAC will closely monitor the evolution of the completion rate in coming semesters and continues to be pleased with the steady rate of publications coming from the team despite the low completion rate.
CIPP
CIPP is finishing in 2019B. The time sampling of the 2019A allocation was affected by bad weather and bridge crane problems. Regular UH time has been requested in 2020A to continue the parallax measurements. Final epochs are still needed for some targets. If supported through 2021B with additional small regular UH time allocations on WIRCam, most of the science goals will be accomplished. The group has started publishing results concerning unusual or otherwise interesting individual objects. Analysis of a volume-limited sample of brown dwarfs and low-mass stars has begun, comprising hundreds of objects from WIRCam, Gaia and Spitzer.
SIGNALS
The SIGNALS team has published four refereed papers so far and continues to demonstrate the scientific value of this large program. Data collection is proceeding at a satisfactory rate. We wish the SIGNALS team continued success.
SLS
SAC is pleased to receive a report on the start of the SPIRou Legacy Survey. The instrument is performing well and the team is collecting data. Due to many issues that affected CFHT during the 19A semester, SLS obtained significantly less data than planned. It is hoped that the data collection rate will be closer to the expected rate in future. The PI notes that fewer SPIRou nights have been scheduled in 19B than required for the allocated science+engineering activities. This is unfortunately due to the loss of ~10 nights at the start of 19B when access to the summit was prevented. SAC was concerned at the apparent low SLS validated to observed rate of 78% in the report. CFHT staff informed SAC that this is partly due to optimistic S/N expectations in 19A (that have now been corrected) and partly due to a difference in the S/N threshold for validation adopted by CFHT. It is anticipated that the validated rate will soon reach the ~90% achieved by other instruments. SAC notes the issue of apparent prioritization of time-constrained transit observations and suggests the QSO team ensures equal opportunity for execution of time-constrained and regular observations. SAC looks forward to the publication of papers that are listed as in preparation.
Telescope Use and Scheduling
SAC was presented with a detailed report on telescope usage in 2019A (complete) and 2019B (ongoing), as well as statistics on telescope pressure and instrument demand for 2020A.
Planned runs were severely impacted by the crane failure in June/July 2019, which led to a very long MegaCam run, sub-optimally overlapping two bright-time periods. Only snapshot programs could be performed during those nights as bright time instruments could not be mounted on the telescope as scheduled. This particularly impacted SPIRou PI and LP programs. This was further compounded by the protests on the access road that led to the evacuation of the telescope before the crane could be repaired. Almost a month of observing was lost to the lack of summit access in July (19A) and August (19B).
Telescope pressure in 2019B from all agencies is at healthy levels. Instrument demand in 2019A shows that SPIRou, MegaCam and ESPaDOnS are the most requested instruments. The comparatively low demand for SITELLE is still a concern, even though it is mildly improving. WIRCam demand remains at a low but steady level. GRACES has seen continuous use by Gemini and CFHT is accumulating Gemini nights until enough nights are banked to redistribute them to the community over two consecutive semesters.
QSO and Phase 1
The QSO system continues to perform well. In 2019A, the QSO-SNR mode allowed to save 17h on MegaCam and about 3h on ESPaDOnS.
The intended 2019A QSO schedule had enough nights for each instrument to accommodate the accepted A&B programs, including LPs. However, 16 nights were lost during summit shutdown, and 9 to bridge crane failures (no instrument on telescope). In the end, MegaCam lost 27 nights of dark time (50/77) but got 7 nights of bright time (with some useful data), SPIRou lost 6 nights, WIRCam lost 4 nights, ESPaDOnS was spared, and SITELLE had 6 extra nights. In addition, weather losses were greater than typical.
Overall completion rate (validated / allocated) in 2019A was 70%-90% for WIRCam, ESPaDOnS, and SITELLE but only 40% for MegaCam (impacted by weather, crane issues and shutdown). The detailed statistics for SPIRou are not yet available due to SPIRou using the new Phase 2 system, but SPIRou also fared relatively poorly in 19A. The completion rate for LPs was well below that of PI programs: 45% for LPs compared to 79% for PI programs. Whilst this is partly due to a different instrument split for PIs and LPs, even for the same instrument the LPs have suffered a lower rate of validated / allocated in most semesters. This is due to a combination of factors including observing constraints and time-constrained PI observations having a high chance of being observed. Whilst CFHT attempts to balance the completion rate for all agencies (in which LPs are considered an agency) it is clear that the current procedures usually do not result in the expected balance, particularly in semesters particularly hard hit by weather or technical losses.
CFHT TAC Procedures
SAC was charged with a review of the existing CFHT time allocation process for PI proposals as this has not been documented recently. SAC was advised of the procedures in use by each agency to rank CFHT proposals. These ranked lists are brought to the ITAC (International TAC) meeting that normally occurs during a SAC meeting with participation from a subset of SAC. SAC discussed some ideas for improving upon the existing process. In the appendix we provide a full description of the current process and some of these suggestions for improvement.
Operational and Development Priorities:
- Normal operations
- SPIRou
- MSE
- Primary mirror reflectivity
- SITELLE
- Continue study to co-mount ESPaDOnS and SPIRou
Next SAC Meeting
The next SAC meeting will take place at Observatoire de Paris on 14-15 May 2020, hosted by Anthony Boccaletti. The MSE Science and Engineering Meeting will occur the following week on 18-20 May 2020 in Nice.