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Observing
at WMKO |
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Instruments
Available for Semester 2027A
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For detailed information about the instruments, please check the Instruments Home Page
For information about which instruments can be used on the same night, please check Instrument Sharing
For a Resolving Power vs. Wavelength comparison of Keck
instruments, please check this Instrument Comparison graph.
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Keck I Instruments are:
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HIRESb
(blue x-disperser) scheduled for hibernation no earlier than the conclusion of semster 27B
HIRESr
(red x-disperser) scheduled for hibernation no earlier than the conclusion of semster 27B
KPF unavailable in 27A, see below
KPF-CC unavailable in 27A, see below
LRIS-ADC (red and blue, with ADC)
LRISp-ADC
(polarimeter, with ADC)
MOSFIRE
OSIRIS-NGS
OSIRIS-LGS
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Keck II Instruments are:
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DEIMOS - limited availability, see below
ESI - hibernated after 26A
ESIi (ESI
with the Integral Field Unit) - hibernated after 26A
KCWI
NIRSPEC (without AO) - limited availability, see below
NIRC2-NGS
NIRC2-LGS
NIRC2p-NGS/LGS non-facility visitor mode, see below
SCALES-NGS/LGS - limited availability, see below
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Subaru Time Exchange Instruments are: |
FOCAS, HDS, Hyper Suprime-Cam, IRCS, MOIRCS, PFS, CHARIS, VAMPIRES, REACH, Fast PDI, NsIR, NIR-WFS, FIRST-PL, and IRD. See below for
limitations.
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Telescope Limits |
Please note that Keck I and Keck II have different eastern and western telescope limits. This affects the times objects will be available for observing. Objects can be acquired earlier on Keck II and followed later on Keck I.
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Special Notes for Semester 2027A:
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Keck II facility: There will be one 5 night shutdown period on Keck 2 during bright time in the 27A semester to complete dome, shutter, and high priority infrastructure work. The work is intended to take place during May bright time, but dates will be finalized during the telescope scheduling process, taking into account scientific demand and the requirements of the infrastructure projects.
Keck I and Keck II bottom shutters: If not completed in 26B, there may be a period of 2 weeks on each of Keck 1 and Keck 2 where the bottom shutter will be fixed at 25 degrees elevation in order to replace wire ropes on the bottom shutters. Targets below 40 degrees elevation would experience vignetting. Please note on your coversheet if this restriction would be a significant impact to your science..
KPF and KPF-cc: KPF will not be available in 27A. KPF had an operations review in January 2026 that identified reduced detector thermal control and increased detector noise as key stability issues. In 27A, the team will begin work to address the hardware causes of these issues with an expectation of completion by the end of 27A.
Keck I AO: The following AO modes will be available throughout the 27A semester:
- NGS and single star LGS
- KAPA in LTAO mode with STRAP or TRICK
Keck II AO: Keck 2 AO with the new HAKA DM will be available in NGS mode with guide stars brighter than R=15, and in LGSAO mode with no restrictions.
SCALES: Arrival of SCALES has been delayed, and the instrument is currently expected to arrive at the Observatory in November. Pending a successful pre-ship review in October, SCALES is anticipated to install and begin commissioning at the end of the 26B semester and continue commissioning through the first few months of 27A. Routine science is expected to begin in April 2027. The imaging channel and low-resolution IFS are expected to be commissioned during the first few nights on sky, with the medium-resolution IFS commissioned next, followed by coronagraphy. Note that SCALES can still do high-contrast imaging and low-res spectra at performance no worse than NIRC2 without the coronagraph modes. Due to remaining schedule uncertainty, SCALES proposers should have a backup observing program, with a preference for NIRC2 observations. For more information on SCALES, see the SCALES homepage
DEIMOS: DEIMOS will be unavailable February - April for commissioning of a new science detector. DEIMOS is expected to be available for science beginning in May. The Flexure Compensation System (FCS) for DEIMOS is currently non-functional. PIs should be aware that troubleshooting is ongoing but there is a potential that FCS will not be restored to service until after the detector upgrade is completed.
NIRSPEC: Nirspec will be unavailable for 5 weeks beginning in late April for routine service.
Nirc2-polarimeter: NIRC2 in polarmetric imaging mode, in both NGS and LGS AO, will be offered in a non-facility visitor mode for 27A. NIRC2 has an internal Wollaston prism and the K2AO system has two external half waveplates (HWPs) that are optimized for JHK- or L-band science. To swap between the JHK-HWP and L-HWP is a daytime task such that we cannot support both modes on a single night. NIRC2 polarimetry and non-polarimetry are supportable on a single night. In polarimetry mode, LGS tip/tilt stars must be within 30-arcseconds of the science object
We ask observers interested in proposing for NIRC2p to reach out to nirc2_info@keck.hawaii.edu and we will put you in touch with the polarimetry team.
ZWFS, CRED2 and ORKID: ORKID will be available for use throughout the semester. ZWFS and CRED2 will be available until HISPEC FEI installation, expected around April/May. PIs who wish to use these technology demonstrators 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.
Instrument Hibernation: : 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 was hibernated in May 2026. Unless a compelling scientific or strategic need emerges, NIRES will be decommissioned at the end of the 27A semester.
- ESI: ESI was hibernated in July 2026. Unless a compelling scientific or strategic need emerges, ESI will be decommissioned at the end of the 27A semester.
- HIRES: HIRES will be decommissioned no earlier than the conclusion of 2027B. Due to the nature of the instrument and need to free the Keck I Nasmyth platform for future instrumentation, HIRES will not undergo a hibernation period and will instead transition directly to decommissioning. The final decommissioning timeline will depend on both the readiness of Zshooter, which is set to occupy HIRES's current Nasmyth location, as well as the stability of KPF. A comparison of HIRES and KPF capabilities can be found HERE . As per instrument evolution process, WMKO is soliciting feedback from the community regarding the HIRES planned decommissioning. 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.
At-Home (pajama mode) Observing: At-home observing will continue to be available to observers. Please see https://keckobservatory.atlassian.net/wiki/spaces/MOSD/overview for information about remote observing, including at-home observing.
Time Domain Astronomy: Observers will continue to have the ability to propose both cadence and ToO programs using the cover sheet. Policies related to Target of Opportunity or Cadence proposals can be found at Too Policies and Cadence Policies. These policies are not applicable to Subaru Exchange time. TAC-approved Cross-institutional ToO (TDA) projects will continue to be able to interrupt observers at any Institution, to increase the utility of the ToO process.
Twilight Cadence Observing: The twilight cadence program will continue this semester, with NIRC2-NGS and OSIRIS-NGS available for use. Each institution may allocate one twilight cadence program per telescope. Please note that due to ongoing AO upgrades, there will be times in the semester when AO is unavailable for cadence observations (see above). 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. More details can be found in the Cadence Policy.
FOCAS, HDS, Hyper Suprime-Cam, IRCS, MOIRCS, PFS, CHARIS+SCExAO, REACH, FastPDI, VAMPIRES, NsIR, NIR-WFS, FIRST-PL and IRD will be available at Subaru. Please check the Subaru web site http://www.subarutelescope.org/Observing/index.html for detailed descriptions of these instruments. Please visit https://subarutelescope.org/Observing/Proposals/call.html for instrument restrictions, particularly for visiting (PI-type) instruments SCExAO+CHARIS, IRD, VAMPIRES, Fast PDI, REACH, NIR-WFS, NsIR, FIRST-PL and for filter availability of HSC. The SUBARU-KECK exchange will continue to have flexibility with regard to the number of nights available for exchange with the number of nights exchanged determined based on the demand from each community. Subaru ToO observers will continue to be able to interrupt Keck observers on the Subaru Telescope, and Keck ToO observers will be able to interrupt Subaru observers on the Keck Telescope. Compensation will be according to the policy of each observatory.
Subaru observations are executed in "classical" observing mode, except for HSC and PFS observations. Queue observing is the default observing mode for HSC; applicants who desire classical mode with HSC must
justify their request. For all classical observations, Subaru may support half night allocations, but whole night allocations are preferred. Please check the HSC queue mode website https://subarutelescope.org/Observing/queue/index.html for more details on HSC observations.
Subaru facility/instrument related restrictions for the 2027A semester:
- Telescope Downtime: The telescope will be unavailable for maintenance during two periods: (1) from February 1 to mid-March for AZ/EL incremental encoder replacement, and (2) beginning in mid-July for primary mirror recoating.
- Limited Dark Night: Due to the expected major downtime and the ongoing PFS-SSP, only about 15 dark nights will be available for normal open-use observations in the S27A semester. In particular, PFS time available for normal open-use programs, including the time-exchange programs, is expected to be very limited. PIs requesting dark time should take this limited availability into account when preparing their proposals.
- Near-Infrared Wavefront Sensor (NIR WFS): A new L-band dichroic was installed in the NIRWFS and is available for open-use starting from S27A under shared-risk mode. For details, please see the AO3k-NIR WFS webpage(s).
- Notice for PFS Observation: The Prime Focus Spectrograph (PFS) will be operated in shared-risk mode in S27A. Please carefully review the PFS webpage. Basically, PIs are required to run the PFS Spectral Simulator (ETC) and the Target Uploader, then include the ETC output(s) and Upload ID in the observation plan of the proposals.
- Filler Proposals: Keck users can apply for the HSC Queue Filler and PFS Community Filler Program without a time exchange cost. All Filler proposals must be submitted through the Subaru proposal submission system PROMS by Subaru’s normal and intensive proposal deadline. The PFS Community Filler program is open for proposals only during "A" semesters. For further details, please refer to the PFS page .
- Available facility instruments: Adaptive Optics (AO188-mode/AO3k-mode), FOCAS, HDS, HSC, IRCS, MOIRCS, PFS
- Status of PI-type instruments/devices:
- SCExAO / FastPDI: The Triple-differential imaging mode of SCExAO/FastPDI using the FLC modulator will be decommissioned and unavailable starting S27A.
- CHARIS: NGS-AO188 or NIRWFS-AO3k mode with SCExAO (including spectro-polarimetric mode)
- VAMPIRES: NGS-AO188 or NIRWFS-AO3k mode with SCExAO (cameras have been upgraded for improved sensitivity, speed, and dynamic range. A new multi-band imaging mode is available.)
- Fast PDI: NGS-AO188 or NIRWFS-AO3k mode with SCExAO (under shared-risk mode)
- REACH: (combination of [SCExAO] and [IRD] for single-mode fiber spectroscopy)
- IRD: NGS-AO188 mode
- NsIR Wave Plate Unit: (a visiting device for IRCS/SCExAO polarimetry mode)
- NIR WFS: (a near-infrared wavefront sensor inside the AO188 instead of the visible wavefront sensor)
- FIRST-PL: NIRWFS-Ao3k mode with SCExAO
- Proposals to use visiting instruments/devices must include the relevant PIs as Co-investigators
LGS-AO: A detailed set of guidelines for LGS-AO nights and information on the capabilities of the systems may be found on the LGS-AO page. Backup programs for LGS proposals are essential. Backup programs for LGS on Keck II may be either NGS programs or NIRES. On Keck I, either NGS-OSIRIS and non-AO HIRES may serve as a backup.
KOA (Keck Observatory Archive): Data from all instruments will be archived in the Keck Observatory Archive (KOA). The default proprietary period for data is 18 months except for data taken with NASA as the allocating institution which has a default proprietary period of 12 months. If observers desire a different proprietary period they may request this through the Keck coversheet. Please see the KOA homepage for information on the archive. Please also see the KOA proprietary period policy.
For detailed information about the instruments, please check the Instruments Home Page
(further observing
information)
This page last updated 04 August 2026 ccj.
Telescope-scheduling@keck.hawaii.edu