The following capabilities and announcements are notable for the 2025B semester. Please see the relevant instrument pages and subsections of the call for proposals for details.

General:

• All proposals to use Gemini in 2025B must use the 2025B Phase 1 template. When preparing PDF attachments, prospective PIs must follow the proposals template font size requirements in all cases, and avoid using smaller fonts in all sections of Gemini proposals (including in figures and tables).
• Classical mode observing is offered in semester 2025B for facility instruments only.
• Priority Visitor mode is offered at both Gemini North and Gemini South; however if circumstances preclude having people on site, then awarded Priority Visitor time will revert to queue. PIs requesting Classical observing must state in their technical justification how the observations could be done in queue mode (with remote eavesdropping for data quality assessment and decision making). The "Bring One, Get One" Student Observer Support Program remains unavailable for semester 25B.
• Rapid Target of Opportunity (rToO) Proposals: These can be accommodated for most instruments and their modes (and this includes non-LGS modes), subject to instrument availability on the dates upon which observations are triggered.
• GMOS On-Sky Arcs: GMOS baseline arcs are now taken on sky mixed with the science observations. For details on the updated GMOS arc baseline policy, please see this page.
• Gemini North Engineering Time:
  • ​Shutdown time for (i) testing CEM-2 (Control Electronics Module associated with M2) with the existing top end and (ii) regular A&G maintenance. This will be combined into one single shutdown, which is expected to last approximately 5 weeks. We anticipate that the activity could start at the beginning of October, but cannot be precise at the time of this Call. The 25B shutdown will limit the availability of targets that are observable at RA 20 - 23 hours, and alternative targets should be prepared .
  • We also anticipate commencing work in mid-May until October on the GNIRS camera turret and other issues, including reinstating the short-red camera mode, hence GNIRS will not be available for the first two months of the semester 25B . The exact dates for this intervention are still to be determined.
• Gemini South is expected to be closed for the first 15 nights of semester 25B (August 01 - 15, 2025). These dates are provisional, and may be subject to change.
• Gemini North - IGRINS-2: The new IGRINS-2 instrument will be available for shared-risk observations during semester 25B. For further information, please see here.
• Gemini North - NIFS, NIRI & GRACES: No longer offered.
  Gemini South - GHOST PIs to receive reduced data products: The US NGO, in collaboration with Gemini, will offer reduced spectra for GHOST programs from all partner countries. The reduced files will be available through the Gemini Observatory Archive, together with the raw data.
• Graduate Student Visitor Program is temporarily suspended in 25B. Details of the Graduate Student Visitor program are available here.

Targets are generally limited to 17 < RA hours < 13.5 and -37 < Dec degrees < +90.  Additional constraints are described in the target accessibility and instrument restrictions page of this Call for Proposals. Note that the RA ranges with limited accessibility near the start and end of the semester are typically in very high demand, and so prospective PIs may wish to consider avoiding targets with these RAs, where possible.

Facility instruments offered in 2025B are:

• Altair AO system:  Altair is currently unavailable due to an ongoing technical issue. A one-day intervention is scheduled for March 17, 2025. Following the investigation, an update regarding Altair's availability and any potential impact on the telescope will be provided on the Altair Announcements page. Once the issue is resolved, Altair NGS modes will be available (for GNIRS observations, subject to GNIRS availability). Altair LGS will not be available in 25B unless it can be fixed.
• GMOS North (0.36-1.03 micron imager and spectrometer): Available throughout the semester. The GMOS-N B600 grating will not be offered because of its degraded sensitivity. The R600 grating will only be available for classical observing.
• IGRINS-2: New high-resolution (R~45,000) near-infrared spectrograph covering the wavelength range of 1.49-1.80μm (H-band) and 1.96-2.46μm (K-band) in a single exposure. Offered in shared-risk mode for semester 25B  during specific blocks, subject to RA demand.
• GNIRS (1-5 micron spectrometer): Currently anticipated to be available for the period of November - January in 25B (see the preceding “New and Notable” section for further details). When GNIRS becomes available during Semester 25B, it will support all operational modes (imaging, longslit, XD, LR-/HR-IFU, all with the possibility of being AO fed). Additionally, the ShortRed camera is slated for replacement during this intervention. If the replacement is successful, this mode will be offered in Semester 25B on a shared-risk basis.

Visiting instruments offered in 2025B (subject to demand) are:

• 'Alopeke: A dual-channel fast-readout visual-wavelength camera giving simultaneous diffraction-limited images in two filters over a 2.8 arcsec field of view; as well as a wide-field mode which provides simultaneous two-color imaging in standard SDSS filters over a 60" field of view. The scheduling and length of the 'Alopeke visiting block(s) will be subject to demand. ‘Alopeke may also be available outside those blocks on a best-efforts basis. Targets of Opportunity (Rapid or Standard) are accepted for 'Alopeke, but will only be executed during the instrument blocks.
• MAROON-X: a high-resolution (R~80,000), optical (500 - 900nm) radial velocity (RV) spectrometer,  is open to the community for high precision RV studies as well as general purpose high-resolution spectroscopy.  Please use the Maroon-X Exposure Time Calculator to evaluate the instrument performance.  It is now also possible to check for MAROON-X target duplication: please see the instructions in the Phase I checklist.

Targets are generally limited to 16 < RA hours < 12 and -90° < Dec degrees < +28°. There are additional constraints as described in the target accessibility and instrument restrictions page of this Call for Proposals. Note that the RA ranges with limited accessibility near the start and end of the semester are typically in very high demand, and so prospective PIs may wish to consider avoiding targets with these RAs, where possible.

Facility instruments offered in 2025B are:

• GMOS South (0.36-1.03 micron imager and spectrometer): Available throughout the semester. The R600 grating will only be available for classical observing. The B600 grating will not be offered in 25B. Instead, the B480 grating with similar spectral resolution but with better performance can be used.
• FLAMINGOS-2 (0.9-2.4 micron wide-field imager and spectrometer): Available in imaging, long-slit and MOS modes throughout the semester. For F2MOS observations, pre-imaging is often required, and prospective PIs should factor the additional time needed for this into their proposals.
• GSAOI (0.9-2.4 micron adaptive optics imager) with the GeMS Adaptive Optics system: Due to guide star limitations, investigators must check the availability of Guide Star constellations using the Observing Tool before submitting a proposal.  Observations in IQ85 are possible for programs that can use delivered images with full-width half-maximum of ~0.2 arcseconds as opposed to the ≤ 0.1 arcseconds delivered in IQ70 or IQ20 conditions. Observations under non-photometric conditions with 0.1 mag uniform extinction are also possible under very good IQ conditions.  The expectation is to have two or three laser runs of 7 nights each during the semester, the actual schedule will be based on the demand from the community.
• GHOST: A high-resolution optical spectrograph (383–1,000 nm) delivers R~56,000 (standard-res) and R~76,000 (high-res). In 2025B, 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. Available throughout the semester during scheduled blocks. Potential users should check for updates on the GHOST web pages for further details and status updates.

Visiting instruments offered in 2025B (subject to demand) are:

• Zorro: a dual-channel fast-readout visual-wavelength camera giving simultaneous diffraction-limited images in two filters over a 2.8 arcsec field of view; as well as a wide-field mode which provides simultaneous two-color imaging in standard SDSS filters over a 60" field of view. The scheduling and length of the Zorro visiting block(s) will be subject to community demand.  Targets of Opportunity (Rapid or Standard) are accepted for Zorro, but will only be executed during the instrument blocks.

Visiting instruments not available in 2025B :

• IQUEYE: The instrument uses an interferometric approach, combining light from multiple small sub-apertures to achieve high-resolution imaging (in the milliarcsecond range). Observing run is already done (25A). Depending on the performance of the instrument and the quality of the data produced, the IQUEYE PI will decide whether to request a return visit. If they do, the instrument will be offered to the community.

The exchange of time between the Gemini and Subaru communities will continue in 2025B; around 5 nights are expected to be available on Subaru for the Gemini community via the exchange program. Subaru exchange time is open to all Gemini partners, including Chile. A summary of the Subaru capabilities in 2025B is given below, PIs should also consult the Subaru Call for Proposals.

In addition, the Gemini community can propose shorter programs for Subaru's Service mode. PIs must indicate on the proposal whether regular or service time is requested. Service programs must be short programs of less than 4 hours duration including calibration and overheads, using one of IRCS, HDS, FOCAS or MOIRCS. Up to 1 night is expected to be available in this mode for the Gemini community. Prospective investigators must carefully review the Service Program web page. In particular, some additional, detailed technical information must be provided at the time of Phase-1 submission. Service proposals are reviewed by the National TACs together with the regular proposals.

Details:

• Duplicate Subaru proposals submitted via other routes: If eligible PIs submit a proposal for Gemini Subaru exchange time and also submit the same proposal to a different TAC in parallel (e.g. researchers via the open use time offered in the Subaru Call, Gemini community PIs via the Gemini time-exchange program or Keck community PIs via the Keck time-exchange program), the proposers are asked to explicitly note the double submission in the proposal.
• Proposal submission: Proposals for time on Subaru via the Gemini time-exchange program are submitted via the normal Gemini Phase I process.
• HSC/PFS proposal length limits: For semester 25B, Gemini users can request no more than 3.5 nights (35 hours science time including overhead) in the case of HSC?PFS queue, and no more than 5.0 nights in the case of HSC classical requests.
• Subaru Strategic Programs (SSP): In S25B, PFS-SSP will be assigned about ~10-20 nights over ~3-4 observing runs. IRD-SSP is expected to be completed in S25A.
• Deformable Mirror (DM) upgrade for AO188: As part of the AO3k project, the DM has been upgraded from a 188-element bimorph mirror to a 3228-actuator magnetic mirror. AO188 provides three modes:
  • NGS/AO188 mode: Uses the 188-element Wave Front Sensor (WFS) + 3k-element DM);
  • LGS/AO188 mode: Uses the 188-element WFS + 3k-element DM;
  • NIRWFS/AO3k mode: Uses the NIR WFS + 3k-element DM.

While the NIR WFS provides high-performance AO correction, NGS and LGS mode performance is unchanged because they use 188-element WFS. Please consult the AO3k web page for more information.

• Instrument switches during the night: Switching between IRD, REACH, CHARIS, VAMPIRES and Fast PDI during a single or half-night observation is possible. Please check the Subaru Call for Proposals for the time required for switching instruments.
• Subaru telescope / instrument downtime:
  • There is a possibility of three (3) weeks of downtime after October for repairs to the dome's main shutter.
  • NsIR Downtime: All instruments except for IRD on the NsIR focus - including IRCS, SCExAO(CHARIS, VAMPIRES, FastPDI), and REACH - will be unavailable for about 2-3 months from August. After the installation, all IRCS, SCExAO, and REACH observations will be done with the NBS under shared-risk mode. Please see the IRCS and SCExAO webpage(s) for the possible impacts of the NBS.
• Subaru instrument and telescope restrictions:
  • The laser guide star (LGS) system for AO188 will be operated with TBAD (Transponder Based Aircraft Detector) with a shared-risk policy. Please consult the AO188 web page for the latest information.
  • The windscreen of the Subaru telescope is out of operation in 2025B, and thus tracking of target may not be possible in high winds. It is recommended that PIs have targets across a range of RAs so that different azimuth angles are available.

Facility instruments offered in 2025B:

• AO188 (Subaru 188-elements Adaptive Optics system) is available.
• FOCAS (optical camera and spectrograph) is available.
• HDS (optical high dispersion spectrometer) is available.
• Hyper Suprime-Cam (HSC - very wide field optical to far-red imager): There will be at most two (2) or three (3) HSC observing runs in the S25B semester, depending on the number of PFS commissioning runs as well as the timing of the facility maintenance works. Note that some filters require permission from the PI of the filters. All applicants must explicitly describe the filters they intend to use, in their proposal. The desired set as well as the minimum acceptable set should be clearly specified. Please check the HSC website for full details.
• IRCS (infrared camera and spectrometer, with AO188 capability) is available. Please note that LGS-AO mode will be operated with TBAD in a shared-risk policy. All proposals requesting LGS mode observation should prepare a backup plan with NGS Mode. Prospective PIs should check the filter availability for the instrument before submitting a proposal. The polarimetry mode is a shared-risk mode, accessible via collaboration with the waveplate PI.
• MOIRCS (Multi-Object Infrared Camera and Spectrograph) is available. MOS Mode will be conditionally available for Service Mode.
• PFS (Prime Focus Spectrograph; 2400-fiber spectrograph spanning 0.38μm - 1.26μm with a FoV of 1.25 deg^2) is available for open use in semester 25B, in shared risk mode. For the latest information and application procedures, please refer to the PFS webpage. Most importantly, all PFS proposals (including exchange time programs) must provide the "target upload ID" in the proposal. Also, please note that targets must be fixed at the time of proposal submission - targets cannot be changed at later stages. The default observing mode of PFS is queue mode. Fibers will be shared by different programs.

Visiting instruments offered in 2025B, are listed below. Proposals to use visiting instruments must include the instrument PIs as Co-investigators. 

• CHARIS (with SCExAO + AO188, including spectropolarimetric mode): Coronagraphic High Angular Resolution Imaging Spectrograph - provides high contrast images of exoplanets, disks, brown dwarfs with SCExAO.
• Fast PDI (in shared-risk mode; with SCExAO + AO188): polarization differential imaging (PDI) with a high speed (>kHz) near-IR (950 - 1860 nm) low-noise camera (C-RED One), optimized for high contrast imaging of circumstellar disks with with SCExAO + AO188. 
• IRD - Infrared Doppler (in shared-risk mode; NGS-AO or LGS-AO): infrared high-dispersion, high resolution (up to 70,000) fiber-fed spectrometer. The IRD SSP (Subaru Stragetic Program) was started in 2019A – any IRD proposal must clarify how its scientific aim is different from the SSP. The observing mode REACH (SCExAO + IRD), is available (see below).
• REACH (combination of SCExAO and IRD for single-mode fiber spectroscopy): REACH can be used simultaneously with CHARIS with any dispersion modes, but the wavelength coverage of CHARIS will be from 1850 nm to the longest wavelengths (please see the CHARIS website for details).
  VAMPIRES: The Visible Aperture Masking Polarimetric Imager for Resolved Exoplanetary Structures (VAMPIRES) is a visible light instrument on the SCExAO system.  Cameras have been upgraded for improved sensitivity, speed and dynamic range. A new multi-band imaging mode is available.
• NsIR Wave Plate Unit: a visiting device for IRCS/SCExAO polarimetry mode.
• NIR-WFS: Near Infrared Wavefront Sensor. Located inside the AO188 instead of the visible curvature wavefront sensor of AO188 for SCExAO and IRCS.

​CHARIS, Fast PDI and VAMPIRES can be used together at the same time as the modules of SCExAO (Subaru Coronagraphic extreme Adaptive Optics). Please check the relevant instrument web pages for the latest information.