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Subaru/Keck Time Exchange Program

Last Updated with S26A information on August 18, 2025

1. Definition

According to the agreement between Directors of Subaru Telescope and Keck Observatory, Subaru users can apply to Keck time through this Subaru-Keck time exchange program. This time exchange program is coordinated so that astronomers in each community can mutually access unique instruments of each telescope. Scientific merits of the proposals are reviewed and determined in each TAC independently (namely, proposals from the Subaru community using Keck are reviewed by Subaru TAC).

2. Eligibility

Only Japanese or Taiwanese researchers (i.e., those belonging to institutes in Japan or Taiwan, or those of Japanese nationality) or EACOA/EAO fellows are eligible for this Subaru -> Keck application.

3. Observing Mode

Observations with Keck Telescope will be executed in a 'classical' mode (except for KPF-CC; see below). Keck observations are always executed remotely, either from the Keck office at Waimea or approved remote sites. At-home observing will continue to be available to observers. Please see the Keck webpage for information about remote observing, including at-home observing.

We note that Keck observations from the Mitaka remote observing room is available for Subaru-Keck time exchange users. We have some experience of successful Keck observations from Mitaka remote observing room without fatal problems, but please be reminded that the support is provided only with a best-effort basis, and thus we cannot always guarantee safe/stable Keck observations.

Proposals requesting Target of Opportunity (ToO) observations and intensive programs are not accepted.

4. Telescope Downtime

No telescope downtime is planned in the S26A semester.

5. Available Instruments

Keck I telescope:

  • KPF & KPF-CC: The 26A coversheet will contain both the KPF and KPF-CC instrument options. The KPF Community Cadence (KPF-CC) program is operating a queue observation service in 2026A, which is an opt-in program. For PIs who wish to opt in, they must select the KPF-CC instrument on their coversheet. Additionally, PIs must submit all proposed observational requests to the queue prior to their TAC’s proposal deadline. Failure to do both of these steps may result in your program’s exclusion from the queue, even if time is awarded.
    Programs seeking multi-hour long observations of single targets on a single night (such as but not limited to Rossiter-McLaughlin observations, atmospheric studies in-transit, asteroseismology measurements, etc), should NOT opt in and should select the KPF instrument on the coversheet.
    Much more detail on the KPF-CC program, how/why to opt-in, and how to submit requests can be found at this link, please read carefully: https://docs.google.com/document/d/1-TfR6lNEtHO3muw_2Sc7l9Klveb3yovMUu28Jeq21t0/edit?usp=sharing

  • Keck I AO: NGS and LGS with OSIRIS will be available for the full semester. KAPA commissioning is expected to be completed at the end of the semester, and LGS proposals may benefit from KAPA performance improvements.

  • LRIS

  • MOSFIRE

  • OSIRIS

  • Adaptive Optics with LGS / NGS

Keck II telescope:

  • Keck II AO: Keck II AO (Nirc2) will be unavailable from February 1- May 17 for installation of both a new deformable mirror (HAKA) and new instrument SCALES. Starting 18 May, HAKA + NIRC2 will be available in NGS mode with guide stars brighter than R=12, and in LGSAO mode with no restrictions.

  • DEIMOS: Deimos will be unavailable from late May until the end of the semester for the installation of a new science detector. Please see https://www2.keck.hawaii.edu/inst/deimos/detector_issues.html for the latest on the current DEIMOS detector’s performance status.

  • NIRSPEC (without AO): NIRSPEC will be unavailable for 5 weeks beginning May 6th for routine service. NIRSPEC with LGS and NGS are no longer available.

  • NIRES: Due to both the extended 26a AO downtime and science losses resulting from the Keck II shutter failure in 25a/b, NIRES will remain available from February 1 – May 17. NIRES will be hibernated after May 17.

  • NIRSPAO and KPIC: Nirspao and KPIC are no longer available for use and have been removed from the coversheet.

  • ZWFS & CRED2 and ORKID: These technology demonstrators are available for use after May 17, when Keck II AO returns to service. PIs who wish to use these should consult with the Keck AO team before proposing and PIs should select NIRC2-NGS on their coversheet, with a clear description of what mode they will be using in their coversheet summary.

  • KCWI

  • NIRC2: NIRS2 will be unavailable from February 1- May 17. Please see above “Keck II AO”.

  • Adaptive Optics with LGS / NGS

LGS-AO backup program:
Those who request LGS-AO time must prepare backup programs, because cloudy conditions may hinder propagation of laser. For OSIRIS + LGS-AO applicants, OSIRIS with NGS-AO is available as a backup instrument. For NIRC2 + LGS-AO applicants, NIRC2 with NGS-AO, and NIRSPEC without AO, are available.

Instrument Hibernations:
WMKO, in consultation with the Science Steering Committee after the receipt of the findings of the Instrument Suite Evolution task force (comprised of members of the WMKO community and WMKO science staff), is undergoing a process of hibernation and eventual decommissioning of instruments in the coming years as new capabilities arrive and to be responsive to pressures on WMKO resources. A hibernated instrument is not available for community use unless there is a significant emergent scientific and strategic need. After a year's hibernation, the hibernated instrument will be completely removed from service and decommissioned. The community should begin planning for the following:

  • NIRES: will be hibernated after May 17, 2026.

  • ESI: ESI will be hibernated at the end of the 2026A semester. ESI will continue to be scheduled in campaign mode to limit the number of reconfigs through each semester.

  • HIRES : HIRES will be hibernated after the conclusion of 2026B in order to provide Keck I Nasmyth location for future instrumentation, including the instrument ZShooter (PIs Kulkarni & Kasliwal, CIT) which will notionally arrive in 2029. A comparison of HIRES and KPF capabilities can be found here https://www2.keck.hawaii.edu/inst/kpf/KPFvsHIRES/. As per instrument evolution process, starting now and up to the start of the 27A semester, WMKO is soliciting feedback from the community regarding the HIRES planned hibernation. Please provide feedback through Keck Science Steering Committee members or address them to instrument_retirement@keck.hawaii.edu

  • Additional instruments are under consideration for hibernation and eventual decommissioning in later semesters, with a focus on those instruments whose capabilities are being significantly superseded by new instrumentation.

Twilight Cadence Observing:
In 2026A, institutions will continue to be able to allocate one twilight observing program per telescope, for a total of up to two programs. On Keck I, OSIRIS-NGS (imager only) will be available, and on Keck II, NIRC2-NGS will be available. Please note that due to ongoing AO upgrades, there will be times in the semester when AO is unavailable for cadence observations. Cadence program PIs are responsible for development of instrument scripts, providing documentation, and training of staff needed to make the cadence program a turnkey operation.

6. Available Amount of Time

In S26A, up to several Keck I nights and up to several Keck II nights are available to the Subaru community. The number of exchange nights will be determined based on the demand of each community.

7. Proposal Preparation for Programs using Keck Telescopes

Table 1. Guide for Applicants for Keck Time
Phase-I Subaru Submission Step 1. Applicants should submit their proposals via the webform by the deadline in Subaru Call for Proposals.


7-1. Step 1. Phase-I Submission to Subaru ProMS

Applicants intending to apply Keck observations via this Subaru Call for Proposals should access the ProMS 2.0 page to fill the webform. Proposals from the Subaru community to use Keck are treated as a part of Subaru Open Use Programs and are reviewed in the same way as other Subaru proposals.

How to complete the Application Form:

Please follow the instructions detailed in 'How to Submit'.

  • "1-12"(Observing Run):
    If your science goals can be achieved with any Subaru (or Gemini) instruments, please give the name(s) of your backup instrument(s) in the "2nd choice instruments" box. Please note that you need to contact the instrument PI in advance if your 2nd choice instrument includes a PI-type instrument of Subaru.
  • "1-15"(Observing Method and Technical Details):
    Describe by referring to Keck Instrument page.
    Please describe observing methods such as mode, grism, slit width etc. using the backup instruments, too.
    If you want to use FOCAS as the back up instrument, please check whether you need pre-image observations for your MOS masks. Please describe "I need preimage observations" in this section if you need pre-image observations.
    Please refer this page about the pre-image observations.

7-2. Step 2. Submission of Keck Coversheet (Approved Programs)

The PIs of approved proposals will be asked to submit the Keck Proposal Coversheet.

8. Phase-I Contact

Please contact cfp_consult_at_naoj.org.

updated on August 18, 2025