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Subaru/Keck Time Exchange Program

(August 5th, 2025) Keck's information has been delayed and will be announced later on this page. Below is the information up to S25B.

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

Keck I telescope will be unavailable for use from August 31 - October 16 for a second planned shutdown to conduct repairs of the telescope pier.

5. Available Instruments

Keck I telescope:

Keck II telescope:

  • Keck II AO: Keck II AO (Nirc2 and NIRSPAO) will be unavailable for 3weeks beginning in mid-August.
  • DEIMOS: Deimos will be unavailable from October 1 through the end of January for the installation of a new science detector.
  • ESI
  • KCWI
  • NIRES
  • NIRSPEC/NIRSPAO
  • NIRC2
  • Adaptive Optics with LGS / NGS
  • Nirspao and KPIC: Nirspao and KPIC will be available through the end of November. NIRSPAO and KPIC will no longer be available for use once SCALES arrives at the Observatory. PIs may apply and be scheduled for Nirspao and KPIC time in the December-January timeframe, but must be willing to switch to a backup instrument (Nirspec, Nires, Nirc2-NGS) if SCALES installation is ready to commence during these months. For more information on SCALES, see https://arxiv.org/pdf/2208.10721
  • KPIC: KPIC Phase I capabilities continue to be offered as a facility instrument in 25B, during the timeframe that KPIC is available. More information on KPIC Phase I can be found at https://nexsci.caltech.edu/missions/KeckSolicitation/KPIC_PhaseI_Facilitization_Proposal_Instruction.pdf.

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. For NIRSPEC+LGS-AO applicants, NIRSPEC with NGS-AO or 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: NIRES will be hibernated at the conclusion of the 2025B semester.
  • 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 is being considered for hibernation in 2027. A separate communication soliciting feedback will be sent to the community.

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.

  • NIRSPEC/NIRSPAO reconfigs: Please note that Nirspec and Nirspao/KPIC nights will be scheduled in campaign mode to limit the number of reconfigs into AO during the semester. This may impact the ability to schedule certain date critical observations.

  • Twilight Cadence Observing: In 2025B, 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.

  • Please be sure to refer to the Keck instruments webpages for more details.

6. Available Amount of Time

In S25B, 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 5, 2025