Subaru/Gemini Time Exchange Program

1. Definition

According to the agreement between the Directors of Subaru Telescope and Gemini Observatory, Subaru users can apply for Gemini time through this Subaru-Gemini 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 Gemini 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 -> Gemini application.

3. Available Programs

3-1. Standard Semester Program

Programs requesting up to 5.0 nights in a single semester carried out in the queue mode or in a visiting mode. For the queue mode programs, 10 hours of Gemini queue observations (including overheads) are regarded as 1 night. With the decline in COVID restrictions, Priority Visitor (PV) mode and Classical proposals are both invited. If circumstances preclude having people on site, however, awarded PV time will revert to queue. PIs requesting Classical observing must, in their technical justification, state how the observations could be done in queue (with remote eavesdropping for data quality assessment and decision making).

ToO Program: There are two types of ToO observations. Rapid ToOs require observations within 24 hours, while Standard ToOs will have a slower response time of more than 24 hours. The PI must specify whether the observations require Rapid or Standard response. Rapid ToO programs will be charged for time spent on any observation that the Rapid ToO interrupts; both Rapid and Standard ToO programs will be charged for all on-sky calibrations. All instruments are available for ToO observations, but please be reminded that many of the instruments are available only during specific blocks as described below (see Sec.5).

3-2. Large and Long Programs (LLP)

Researchers in the Subaru community who are eligible for intensive programs can apply for the Gemini Large and Long Program (LLP), through the Subaru-Gemini time exchange program.
The application for Gemini LLPs is open only in the call for proposals for B semesters (March deadline).
In S25B, following the Subaru Intensive Program policy, LLP requesting Gemini ToO observation is not acceptable.

3-3. Fast Turnaround Programs (FT)

Fast Turnaround programs are available for Subaru Community (up to 4 hours per call). Their submission deadlines are monthly announced and independent from the deadline of the semester-based Call for Proposals. The review of Fast Turnaround programs is made following the rule set by Gemini and is done independently from Subaru TAC. The amount of FT time used by Subaru users will be reimbursed to Gemini from Subaru openuse time in later semesters.

3-4. Poor Weather Proposals (PW)

Subaru community can propose Gemini Band-4 (bad weather) observations at no time exchange cost. The Band-4 proposals may be submitted directly to Gemini, at any time using the Gemini Phase I Tool (PIT).

4. Telescope Downtime

Gemini North: No shutdown is planned for 26A. GPI commissioning is expected to take 15 days, no earlier than June 2026. Additionally, GNAO-LGSF tasks will require two extra weeks, with dates yet to be determined.
Gemini South: An engineering shutdown is currently anticipated to run from July 20 until July 30, 2026, for regular A&G maintenance.

5. Available Instruments and Target Accessibility

Gemini-North

Available for Semester 2026A:

GMOS: available. The GMOS-N B600 grating will not be offered because of its degraded sensitivity. The R-600 grating is only offered for observations in classical mode.
IGRINS-2: available in shared risk mode. New facility instrument. Users interested in using IGRINS-2 must check the IGRINS-2 web pages and the Gemini Call for Proposals.
`Alopeke (visiting instrument): anticipated to be available during specific blocks (pending agreements with the instrument team). The instrument is available in both speckle, and wide-field (users should contact support if using this mode) for 26A.
MAROON-X (visiting instrument): available during specific blocks. It is now possible to check for MAROON-X target duplication: please see the instructions in the Phase I checklist.
GNIRS: We anticipate that in 26A the instrument will be available in all modes: imaging, longslit, XD, LR-/HR-IFU, all with the possibility of being AO fed. As of 26A, we anticipate that the ShortRed camera is available in shared risk mode, which provides enhanced capabilities in the L and M bands.
Altair (Adaptive Optics; AO) NGS: Altair NGS modes (for GNIRS observations) will be offered.
Altair (Adaptive Optics; AO) LGS: We anticipate that Altair LGS+P1 mode will be available in 26A. However, PI’s requesting this mode, should provide backup observations to be done in NGS mode or IQ20.

Unavailable for Semester 2026A:

NIFS: Decommissioned, and therefore not available for semester 25B onwards. Programs involving NIR IFU observations should consider the GNIRS LR IFU instead.
NIRI: not available for semester 25B onwards. Near IR imaging (of smaller fields of ~16" field of view) will still be possible using the GNIRS acquisition "keyhole".
TEXES (visiting instrument): not available.
GRACES (visiting instrument): Decommissioned, and therefore not available for semester 25A onwards.

Gemini-South

Available for Semester 2026A:

GMOS: available. The GMOS-S B600 grating will not be offered, and the B480 grating is strongly recommended for use, as it has better throughput. The R600 grating will be offered only for observations in classical mode.
GHOST: available. A high-resolution optical spectrograph (383-1,000 nm) delivers R~56,000 (standard-res) and R~76,000 (high-res). In 2026A, GHOST is offered in both modes, as well as for non-sidereal targets and faint objects requiring blind offsets. The precision radial velocity mode (with simultaneous calibration) is not offered.
FLAMINGOS-2: imaging, long-slit, and MOS modes are available.
Zorro (visiting instrument): available during specific blocks dependent on demand (and pending agreements with the instrument team). Zorro is available in both speckle, and wide-field (users should contact support if using this mode) for 26A.

Unavailable for Semester 2026A:

GSAOI+GeMS: Not offered for semester 26A
IGRINS (visiting instrument): No longer available, for semester 25A onwards.
IQUEYE (visiting instrument): Not offered for semester 26A.

6. Available Amount of Time

Subaru users can request maximum 5.0 nights of Gemini time for each program (following the maximum request allowed for other normal openuse programs). For each semester, Subaru typically exchange ~5.0 nights in total with Gemini, but the total amount of exchange nights will be determined semester by semester in discussions between the Subaru and Gemini Observatories.

7. Proposal Preparation for Programs using Gemini Telescopes

Table 1. Guide for Applicants Applying for Gemini Time
Phase-I Subaru Submission	Step 1. Applicants should submit their proposals via the webform by the deadline in Subaru Call for Proposals (see Open Use Schedule).
Phase-I Gemini Submission	Step 2. They also need to file their proposals to Gemini by the electronic submission using PIT (Phase I Tool) by the deadline described in Gemini Call for Proposals.
Phase-II Submission	Step 3. For the accepted proposals, Phase-II submission to Gemini Observatory is necessary.

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

Applicants intending to apply Gemini 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 Gemini are treated as a part of the 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 Keck) 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.
"1-13" (Scheduling Requirements):
If your request includes "queue" observations, please provide detailed information here.
"1-15" (Observing Method and Technical Details):
Describe by referring to Gemini webpage.
Please describe observing methods such as mode, grism, slit width, etc., using the backup instruments, too.
If you want to use FOCAS as the backup 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 to this page about the pre-image observations.

7-2. Step 2. Phase-I Submission to Gemini

All the proposals requesting Gemini time should also be submitted to Gemini's Phase I Application, by the deadline for Gemini's Call for Proposals. Gemini will be updating the Phase-I Tool every semester, so please be sure to download the latest version from the website. With the new Tool, the science and technical cases, with Figures, Tables and References, are attached as a single PDF file. Latex and Word templates are available for download from the Gemini page, which explain the required contents and page limits.

We understand that such double submissions are inconvenient, but it is needed to match the current proposal processing systems of Subaru and Gemini. Your description in the technical justification section in the Gemini Phase-I form will be used for technical evaluation by Gemini. Regarding the scientific justification (SJ) section, you can just give the same SJ (of 2 pages; i.e., you do not have to reduce it) as submitted to Subaru TAC, despite that the prescribed SJ length in Gemini Phase-I form is only 1 page. SJ is used by Gemini staff for the purpose of understanding the science goal in order to provide adequate support. The target names cannot be concealed in Gemini Phase-I submission.

Please read the instruction in Gemini Call for Proposals carefully, when available. Subaru users should use Gemini PIT and submit their proposal by the deadline. Please select "Subaru" for the "partner" in PIT submission tab page.

Gemini is producing gender statistics to measure and monitor gender equality across the submitted and successful proposals. We kindly ask you to fill the gender field in the investigator details section of the PIT.

A rapid ToO and a follow-up observation must be requested in two separate Phase-I submissions, one for the rapid ToO and another one for the follow-up as a Standard ToO.

7-3. Step 3. Phase-II Submission to Gemini

The PIs of the accepted programs have to complete the Phase-II proposal submission to Gemini by themselves, following the instruction in the web page, Phase-II Overview.

8. Phase-I Contact

Please contact .

updated on August 5, 2025