Maunakea Spectroscopic Explorer (MSE) Update

By / par Pat Hall (MSE Management Group Member)
(Cassiopeia – Winter 2022)

A search was conducted this fall for a new MSE Project Scientist. Negotiations with the top candidate are expected to be concluded in time for the candidate to virtually attend the CFHT Board and MSE MG meetings in early December. A search for an MSE Project Manager is to begin imminently, with a goal of hiring as early as January 2023.

The overarching news at this time is an adjustment of the MSE project as a result of the newly legislated Mauna Kea Stewardship and Oversight Authority. MKSOA will be responsible for granting new leases on Maunakea. Because the transition to MKSOA will last until 2028, meaning that any site renewals for Maunakea will not come until at least 2028, MSE construction realistically cannot start until the early 2030s.

Given these facts, the Project Office has presented to the CFHT SAC and Board a two-component plan consisting of parallel work on development of the MSE proper and on an MSE-Pathfinder instrument for CFHT. The following two-component plan is still subject to change pending CFHT Board approval and MSE management group feedback, but it is appropriate to share a snapshot of it with the community at this time.

The proposed next step for MSE development is a trade study and down-select of telescope configurations (original MSE, 2-mirror with 2.75x more fibers, or 4-mirror with 4.27x more fibers), followed by establishment of a cost estimate and technically-paced schedule for the chosen configuration. All that can safely be said at this point is that the increased capabilities of the 2- or 4-mirror configurations (including larger collecting areas) will come with added costs.

The MSE-Pathfinder instrument is proposed to reduce technical risk by demonstrating on-sky the science capabilities of MSE’s primary subsystems and principal software platform while producing shared science data products for the community. It is envisioned as a scientific capability for timely spectroscopic follow-up on targets-of-opportunity (TOOs) detected by existing and upcoming high-profile facilities such as Vera C. Rubin Observatory’s LSST alerts for time domain and transient targets. In addition, MSE-Pathfinder will utilize MSE’s Program Execution System Architecture framework to validate the envisaged software platform to execute survey planning, scheduling, targeting and fiber allocation, data reduction pipelines, database management, science products archive, and “data-lab” science platform.

MSE-Pathfinder is proposed to use moderate-resolution optical spectrographs fed by fibers from one of two systems: 1) a prime-focus MOS of ~1000 fibers; 2) a large-format IFU sharing the Cass Bonnette with VISION (a common feed for SPIRou and ESPaDOnS), enabling rapid switching between those three instruments.

MSE-Pathfinder will explore analytical and design choices for MSE, such as:

  • Sky subtraction for fiber-fed spectroscopy at Maunakea site
  • Efficient scheduling software for combined survey programs
  • Waveband splitting and pupil splicing outside of the spectrographs with the goal of simplifying the spectrograph design and enable efficient industrialized spectrograph production
  • Validation of anti-reflective nano-coatings as an emerging technology for astronomical instrumentation

The proposed timeline for a call for participation in MSE-Pathfinder is early 2023.

Meanwhile, an NSF ATI funding proposal has been submitted to explore an innovative wavelength splitting and pupil slicing pre-optics module design developed by Sam Barden. Each module splits spectrograph input into separate wavelength channels (blue, green, red, J, H) feeding single-channel spectrographs, and slices the telescope pupil to decrease the input pupil size representative of a smaller telescope aperture. The pre-optics modules can be located near the telescope focus to shorten the fiber length of the blue sensitive spectrograph channels to optimize throughput. The wavelength splitting replaces large dichroics from the spectrographs with smaller ones in the pre-optics modules. The pupil slicing lessens technical risks with spectrograph design. Although more spectrographs are required, the pupil sliced instruments should take up less overall volume than the unsliced versions. The tradeoff is the need to operate many more detector systems. The pre-optics modules will enable modularization in design, manufacturing, assembly, alignment, and installation resulting in a cost-effective spectrograph system that is compact, space efficient, and compatible with the higher degree of multiplexing desired enabled by the 2- and 4-mirror telescope designs.

Last but not least, Canadian proponents of WFMOS (Wide-Field Multi-Object Spectroscopy) have submitted a CFI proposal to obtain funding for a targeted set of preliminary design needs widely applicable to all potential 10-meter-class WFMOS facilities, including but not limited to MSE. Proposal co-leads are Pat Hall (York) and Solomon Tesfamariam (UBC). Funding news is expected in early 3Q 2023.

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