This page provides best estimates, at the time of the Call for Proposals, of instrument restrictions and target (RA, DEC) accessibility for 2025B.

All instruments are restricted for sky visibility as described in the Table below. In addition:

• Gemini North Engineering Time: Shutdown time for (i) testing CEM-2 with the existing top end and (ii) regular A&G maintenance. This will be combined into one single shutdown, scheduled to begin on October 13, 2025, and conclude on November 14th, 2025. The 25B shutdown will limit the availability of targets that are observable at RA 20 - 23 hours, and alternative targets should be prepared..
• Commissioning of GPI-2. A total of 10 days has been allocated for this activity. It is anticipated that the commissioning run will be conducted during bright time, tentatively scheduled between November 30 and December 08. Please note that this may impact programs requiring infrared observations or those targeting objects within the RA range of 23 to 01 hours.
• Observations using the Gemini North laser guide star (LGS) system are restricted to greater than 40 degrees elevation. How this translates into RA and DEC restrictions is indicated in the table below.
• GMOS (North) - Available.  The GMOS-N B600 grating will not be offered because of its degraded sensitivity. The R600 grating will only be available for classical observing.
• GNIRS (North) - An intervention is scheduled to commence in mid-May and continue through October. As a result, GNIRS will be unavailable for the first two months of Semester 25B. The precise dates for this intervention have yet to be finalized.
  • When GNIRS becomes available during Semester 25B, it will support all operational modes, including imaging, longslit, cross-dispersed (XD), low-resolution and high-resolution integral field unit (LR-/HR-IFU), all of which can be adaptive optics (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.
• Altair (Adaptive Optics; AO) (North) - There is an ongoing technical issue with Altair , a resolution for which is being worked on. The NGS mode, LGS+P1 (super-seeing) and LGS modes will be available in the 2025B semester, if they can be fixed. Prospective PIs should check the instrument web page for news updates.
• IGRINS-2 - Available for shared-risk observations in semester 25B during specific blocks, subject to RA demand. Users interested in using IGRINS-2 must check the IGRINS-2 web pages.
• `Alopeke (visiting instrument) - Available during specific blocks, subject to demand, in semester 25B. In addition, ‘Alopeke may also be available outside those blocks on a best-efforts basis. Scheduling will be driven by the demand.
• MAROON-X (visiting instrument) - Available during specific blocks, subject to RA demand. Note that it is now possible to check for MAROON-X prior target duplication: please see the instructions in the Phase I checklist for further details.

^**Due to limited sky availability during the semester, GMOS MOS programs requiring pre-imaging should not have targets in this region, and other programs with targets in this region should not require a large amount of time, or have strict timing or observing constraints.

The following Gemini North instrumentation will not be available for Semester 2025B:

• NIRI - No longer available. Near IR imaging (of smaller fields of ~16” field of view) will still be possible using the GNIRS acquisition “keyhole”.
• TEXES - Not available for semester 25B.

All instruments are restricted for sky visibility as described in the Table below. In addition:

• Gemini South is expected to be closed for the first 15 nights of semester 25B.An engineering shutdown is currently anticipated to run from July 21, 2025 (semester 25A) - Aug 15, 2025 (semester 25B) for regular A&G maintenance. The 25B shutdown will limit the availability of targets that are only observable early in the semester (at RA 16 - 18 hours), and alternative targets should be prepared at later RAs.
• GMOS (South) - Available. The R600 grating will only be available for classical observing. The B600 grating will not be offered in 25B.
• GHOST - Available as part of the regular semester 25B Call for Proposals. 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. 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.
• FLAMINGOS-2 (0.9-2.4 micron wide-field imager and spectrometer)- Available in imaging, long-slit and MOS modes throughout the semester. The multi-object spectroscopy (MOS) mode allows the simultaneous observation of up to 150 targets per mask over an area of 6’x2’.
• Observations using GSAOI + GeMS are restricted to greater than 45 degrees elevation. How this translates into RA and DEC restrictions is indicated in the Table below. The expectation is to have two or three laser runs of 7 nights, therefore up to about 150 hours will be scheduled at ITAC (Queue only, Bands 1 & 2 with IQ70 & IQ85). However, GeMS availability and scheduling will ultimately be driven by demand.
• Zorro - Available during specific blocks, subject to demand, in semester 25B. Scheduling will be driven by the demand.

^**Due to limited sky availability during the semester, GMOS and FLAMINGOS-2 MOS programs requiring pre-imaging should not have targets in this region, and other programs with targets in this region should not require a large amount of time, or have strict timing or observing constraints.

The following Gemini South instrumentation will not be available for Semester 2025B:

• IGRINS (visiting instrument, South) - No longer available, for 25A onwards.
• IQUEYE (visiting instrument, South) - Not offered in 25B.

At each Gemini telescope, instruments are mounted at the Cassegrain focus on the instrument support structure (ISS). A science fold mirror mounted inside the ISS can be rotated to send the light from the telescope to any of four side-looking ports, or can be retracted so that the light goes to the up-looking port. At each site, the calibration unit and the Adaptive Optics system use two of the side ports, leaving two side-looking and one up-looking port for other instrumentation. As more than three instruments are offered each semester, instrument swaps are required and not all instruments will be available for the entire semester. Instrument swaps are driven by demand and scheduled to minimize impact on the queue. Certain targets or entire programs may not be feasible once the final schedule is determined, at ITAC or thereafter. If an instrument is requested for less than 6% of the Bands 1+2 time, the Observatory reserves the right to limit the RA range available to programs, or to not schedule the instrument.

Non-sidereal targets can have a broader range in RA than indicated in the Tables above due to, for example, the need to observe comets relatively close to the Sun. The ephemeris for any submitted target however must include a position that is accessible between evening and morning twilight at some point in the semester. For rapidly moving targets PIs should specify in the proposal when the target is accessible, and the coordinates of the target at that time, so that the observation can be checked for feasibility.

Gemini Observatory attempts to schedule all time-critical observations whenever possible within the constraints imposed by instrument availability, instrument configuration, weather, and science ranking band. Additionally, nights not scheduled for multi-instrument queue including classical and other observing modes, shutdowns, commissioning, etc., impose additional constraints on time-critical programs. Short observations (~1 hour) can often be accommodated during priority visitor periods. Programs with time-critical observations are asked to include detailed scheduling constraints with their proposal, such that they can be considered along with other constraints when developing the telescope schedule each semester.