Keck Call & Proposal Instructions

Call for Proposals: UC time on the Keck telescopes
Semester 2026A (Feb. 1, 2026 through Jul 31, 2026)
Deadline: Proposals are due on Wednesday, September 17, 2025 by 5:00pm PT

Note:   Please be aware of the telescope shutdowns and instrument non-availability (DEIMOS, Keck II-AO, NIRSPEC, etc..)  Read the updates on your favorite instrument below.

Note:  UC will now accept engineering proposals through the same call process and will be reviewed on a case-by-case basis but should include a discussion on why UC should provide this engineering time instead of Keck operations, and the response from Keck operations to the proposal for both feasibility and support.1.1 Due Date

Proposals for UC observing time on the Keck Telescopes for Semester 2026A are due by 5:00 pm PDT on Wednesday, September 17th, 2025.  Normally this is due on Thursday but due to the Keck Science Meeting we have moved the deadline back one day. There will be 58.5 nights available on K1 and 51.5 nights available on K2 spread evenly across the semester and lunar phase.  There are 7 one-hour Partnership ToO interrupts available. A PI may ask for a larger number of UC-time only ToO interrupts as well.

1.2 Proposal Process

This semester UCO is continuing to offer funding for participation in the The Pilina and Kōkua Initiative <https://www.ucobservatories.org/observatory/keck-observatory/the-pilina-and-kokua-initiative/>, a project to facilitate observers from our constituencies to travel to Hawaiʻi, observe at WMKO headquarters, meet and perhaps give informal talks to WMKO staff about science and their scientific program, and most importantly participate in Hawaiʻi community (not necessarily astronomy related) activities. The Pilina (relationship to people and place) and Kōkua (to help in ways that are called for) Initiative will provide travel support for observers for the period of their observations in addition to two extra days to provide time for connection and service to people and place. Participants will spend at least one full day devoted to community engagement programs while at WMKO.   If you wish apply for participation in The Pilina and Kōkua Initiative please indicate this in section 3.5 <https://www.ucobservatories.org/observatory/keck-observatory/keck-proposal-guidelines/> of your proposal.

The principal consideration in evaluating proposals will be the scientific merit of the proposed project. Projects that take maximum advantage of the unique capabilities of the Keck Telescopes will be given high weight. A brief description should be given of backup programs that will be carried out if conditions are not suitable for the primary program. Please see https://www.ucobservatories.org/observatory/keck-observatory/keck-proposal-instructions/ which describes the UC online proposal submission process, and https://www.ucobservatories.org/observatory/keck-observatory/keck-proposal-guidelines/ which describes the required sections and their page limits. The Time Allocation Committees take page limits very seriously, so please pay close attention as you draft your proposal.

Keck is continuing the login-password system to allow you to retrieve and modify your coversheets. Returning observers should use the same account information as last semester. New observers may request an account from the page http://www2.keck.hawaii.edu/inst/PILogin/login.php <https://www2.keck.hawaii.edu/inst/PILogin/login.php>

The coversheet form is available through the login page link above. Once you have created a coversheet and you are logged in, please go to the instructions for submitting Keck proposals at: https://spg.ucolick.org/cgi-bin/TAC/login.cgi to create the rest of your proposal as a PDF file to upload to the UC proposal server. Note that the coversheet has been modified again this semester, so please pay close attention when filling it out.

You may use the extra page allocated to the project update if this is a resubmission to respond to the previous TAC comments, even if the previous submission was unsuccessful.  It would be useful to mention the previous proposal title (if different), PI (if different) and proposal number.

1.3 Be Kind to your TAC Members

Please read the page limits carefully on the keck-guidelines web page (https://www.ucobservatories.org/observatory/keck-observatory/keck-proposal-guidelines/) and adhere to them. TAC members will be instructed to stop reading any text beyond the stated page limits. Note that the text format is 12 point font; single-spaced; one-inch margins.

Although there is not a formal limit on the number of Keck proposals that one PI can submit, experience has shown that TAC members view one PI submitting numerous proposals as a real burden on the reviewing process; it generally does not increase the odds of a PI getting Keck time. Please use moderation.

1.4 Time Domain Astronomy (TDA)

Observers will continue to have the ability to propose both Target of Opportunity (ToO) and Cadence programs using the Keck Cover Sheet. Keck policies related to Target of Opportunity (ToO) and Cadence proposals can be found at https://www2.keck.hawaii.edu/inst/common/Keck_TDA_ToO_policy_SSC_Approved.pdf and https://www2.keck.hawaii.edu/inst/common/Keck_TDA_Cadence_policy_SSC_Approved.pdf.
If your project involves both Classical and TDA observing, you MUST put in two separate cover sheets so that the Keck TDA software can clearly distinguish between the two. Instead of submitting the same text twice, please submit the actual proposal text under the Classical cover sheet; the text submitted under the TDA (ToO or Cadence) cover sheet should merely include the proposal title, PI, and proposal number, together with a sentence stating that the main text can be found under the proposal number of the Classical cover sheet. The Cover Sheet form will not let you submit one proposal requesting both Classical and TDA observing time.

For Semester 2026A, two types of ToO requests can be made.  TAC- approved ToO projects which are able to interrupt observers at any of the four institutions, to increase the utility of the ToO process. These are called Partnership ToO proposals. There is a limit to the number of Partnership ToO interrupts.   The second kind of TAC approved ToO program (Institutional) can only interrupt UC programs.   Note that there is not a limit to the number of “Institutional” ToO interrupts of fellow UC observers. But because UC nights are only a fraction of the total available Keck nights, the probability of a successful ToO interrupt using UC time alone is smaller than for Partnership ToOs. Also note that UC Institutional ToO time can be interrupted by a Partnership ToO, so think through your strategy carefully.   Both Partnership and Institutional ToO interrupts are counted in full 1 hour increments even if less than 1 hour of time is used.  All ToO proposal requests should be made in units of 1 hour interrupts.

In 2026A, partial-night observations can be interrupted. The Keck guidelines state that “Individual TACs may designate a few nights (partial or whole) as exempt from ToO interrupts. This designation must be scientifically motivated, namely that such interruptions would seriously compromise the scientific return of the entire observing time. Proposers should make any such requests to their individual TACs as part of their observing proposal. Use of these exemptions is expected to be rare.” So if you think your project deserves, for scientific reasons, to have one of these rare exemptions from interruptions, please state so in your proposal and give a very strong justification for your request.

1.5 Cadence Observations

Keck’s policies for Cadence observing (https://www2.keck.hawaii.edu/inst/common/Keck_TDA_Cadence_policy_SSC_Approved.pdf) are reasonably complicated. These include a new category called “Partnership Snapshot” observatories. If you are contemplating applying for Cadence time, please read the guidelines carefully.

Keck continues to reconcile cross-institutional cadence and ToO allocations. Scheduled cadence time is returned to the institution at a one to one rate, and ToO time is returned at a rate of two hours for every one hour interruption because the ToO PI will not choose to call for a trigger if the weather is unacceptable.

1.6  Twilight Cadence Observations

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.

1.7 Large Multi-Year Projects

UC LMAP observing projects with well-defined scientific objectives that require a large number of nights to bring to completion (normally 10 or more nights per semester). The UC LMAP program allows projects extending for more than one semester to be carried out with multi-year approval from the beginning. LMAPs should generally be directed toward obtaining a high quality, coherent, homogeneous data set that will allow scientific questions of major importance to be addressed in a thorough, systematic manner. Please consult https://www.ucobservatories.org/observatory/keck-observatory/keck-telescope-time-for-lmap-proposals/ <https://www.ucobservatories.org/observatory/keck-observatory/keck-telescope-time-for-lmap-proposals/> for current policies regarding LMAPs.   Please note the additional requirement of inclusion of a Collaboration Management Plan listed at the top of section 1.2.

A full Collaboration Plan should be submitted to the UCO Director’s office once a proposal has been granted LMAP status, the team must submit a Collaboration Management Plan to the Director’s Office within 2 months. It is not the intent of this policy to require specific terms in CMPs, but  to ensure that collaboration policies are known to members and clearly defined.  The plan should include:

Publication Policy indicating how authorship and co-authorship is determined/merited.   This should include when this policy will no longer apply, ie. what will the publication policy be once the LMAP data collection is over or proprietary periods have expired.
How collaboration leadership is structured, e.g. a single PI, committee, rotating spokesperson, etc.
How membership in the collaboration is determined
Code of Conduct for the collaboration members and how issues with code of conduct violations will be arbitrated.
An acknowledgement that the policy has been shared with all members of the collaboration (including early career researchers.)

This plan can mirror or reference other research organization’s plans/codes, e.g. SDSS, AAS, KSM; or can be entirely new.  The Collaboration Management Plan can take as many pages as required, but may be as short as 1-2 pages.   The UCO Director will appoint a group to review the Collaboration Management Plan (CMP) for completeness.  If clarification or changes are recommended by the review committee the LMAP team will have adequate time to respond before the next semester.  The final accepted CMP will be published on the UCO LMAP web pages.

1.8 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.

2.0 Notes on Instruments and Availability

See the following web page for detailed notes on the availability of instruments for 2026A: https://www2.keck.hawaii.edu/observing/instavail.html.  Please note that the coversheet has been updated with questions about providing KOA data access to observers and Co-Is.  Please contact Cover_Sheet (cover_sheet@keck.hawaii.edu <mailto:cover_sheet@keck.hawaii.edu>) if you receive any reports of problems with the coversheet form.

SPECIAL NOTES AND CONSIDERATIONS FOR 2026A:

KPF and 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.

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.

SCALES: SCALES is scheduled to arrive at the Observatory in early 2026 and undergo commissioning after HAKA commissioning.  It will not be offered for science in 26a, however if institutions want to assign Director’s time in July for use with SCALES if commissioning is complete, they may choose to do so.  For more information on SCALES, see https://arxiv.org/pdf/2208.10721

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  <https://www2.keck.hawaii.edu/inst/deimos/detector_issues.html%C2%A0>for the latest on the current DEIMOS detector’s performance status.

NIRSPEC: NIRSPEC will be unavailable for 5 weeks beginning May 6th for routine service.

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.

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 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 <mailto: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.

SUBARU exchange:  The SUBARU-KECK exchange will continue as in previous semesters with the number of exchanged nights determined by the demand from each community.  Keck will offer LRIS, HIRES, OSIRIS, KPF, and MOSFIRE on Keck I, and DEIMOS, ESI, KCWI, NIRSPEC, NIRES, and NIRC2 on Keck II.   Subaru will offer facility instruments Hyper Suprime-Cam (HSC), HDS, IRCS, MOIRCS, FOCAS, and PFS as well as visiting instruments IRD,  CHARIS, SCExAO, VAMPIRES, REACH, Fast PDI, NIR-WFS, and NsIR.  Note that PIs must contact the instrument PI for visiting instruments in advance.  Subaru may support half night allocations, but whole night allocations are preferred.   Queue observing is the default observing mode for HSC, applicants who desire classical mode must justify their request. Please check the HSC queue mode website https://www.naoj.org/Observing/queue/index.html for more details.

Notes regarding Subaru facility and instrument availability in 26a:

Keck users can apply for the HSC Queue Filler and PFS Community Filler Program without time exchange cost. All Filler proposals must be submitted directly to the Subaru proposal submission system PROMS, https://proms.naoj.hawaii.edu/proms2/login.php not via Keck’s TAC. The deadline is the same as that for Subaru Normal and Intensive programs. The PFS Community Filler program is open for proposals only during “A” semesters.  For further details, please refer to the PFS page  https://subarutelescope.org/Instruments/PFS/observations.html#observations
Telescope Downtime:  Downtime for the S26A period is expected to be up to 11 nights.
Nasmyth Beam Switcher (NBS):  Once installed, the NBS will be used for all IRCS, SCExAO, and REACH observations in shared-risk mode.
SSP in S26A:  PFS SSP will use about 30 nights and IRD SSP has 0.5 night compensation in S26A.
Change in deadline for Filler proposals for HSC Queue Mode: The Filler proposals must be submitted by the deadline for Normal/Intensive proposals, not for Service proposals.
LGS-mode of AO188: The laser guide star (LGS) system for AO188 will be operated with TBAD (Transponder Based Aircraft Detector).
New Filters for MOIRCS: Three new Medium-band filters (J2, H2, and K2) and two narrow-band filters (BrG_ON amd BrG_OFF) are available for use with some conditions.
Available facility instruments: Adaptive Optics (AO188-mode/AO3k-mode), FOCAS, HDS, HSC, IRCS, MOIRCS, PFS
Available PI-type instruments/devices: CHARIS, Fast PDI, IRD, REACH, SCExAO, VAMPIRES, NsIR-WPU, NIR-WFS
As usual, proposals using the visiting instruments/devices must include the relevant PIs as Co-investigators.