Semester 2025A Instrument Restrictions and Target Accessibility

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

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

• Gemini North Engineering Time: At some point in the semester, we anticipate taking the top end off for testing of new control computer/electronics with the tip-tilt system. The work, when it happens, is expected to last three weeks. We will avoid the period of peak RA demand (March-April) but cannot be precise at the time of this Call. If you have targets at the start or end of the semester, you should identify alternates if possible.
• 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) - Currently anticipated to be available for imaging, long slit and cross-dispersed spectroscopy for the period of February - May in 25A (see the above “New and Notable” section of this Call for further details). GNIRS can be used with or without AO capability. As before, the short red camera is NOT available. YJHK imaging is available via the acquisition keyhole. The Low-Resolution (LR) and High-Resolution (HR) IFUs will be available for science during semester 25A.
• Altair (Adaptive Optics; AO) (North) - Altair NGS modes (for GNIRS imaging and IFU observations) will be available for semester 25A. Altair LGS may also be offered, subject to diagnosis and correction of current ongoing Altair technical issues. Users interested in observations involving the Altair AO system should check the Altair Announcements page for updates on availability.
• IGRINS-2 - Available for shared-risk observations in semester 25A during specific blocks, subject to RA demand.
  • Data reduction will be carried out with the Python pipeline provided by the KASI team (PLP), as the DRAGONS version has not yet been delivered. PLP is currently being tuned for IGRINS-2 based on data taken during System Verification; it is not yet fully functional - work is continuing.
  • Improvements in the detector read noise levels are ongoing, and as a result, the estimated S/N ratio may be subject to ~10 - 20% uncertainty. For faint targets (K > 14mag), the S/N estimates derived from ITC may be overestimated. We therefore recommend exercising caution when interpreting these estimates.
• `Alopeke (visiting instrument) - Available during specific blocks, subject to demand, in semester 25A. 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 2025A:

• 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 25A.

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

• Gemini South is expected to be closed for the last 11 nights of semester 25A. An engineering shutdown is currently anticipated to run from July 21, 2025 (semester 25A) - Aug 8, 2025 (semester 25B). The 25A shutdown will limit the availability of targets at RA 23 - 02 hours, and back up targets should be prepared.
• GMOS (South) - Available. The R600 grating will only be available for classical observing.
• GHOST - Available as part of the regular semester 25A Call for Proposals. The instrument will be available throughout the semester during scheduled blocks. Potential users should check for updates on the GHOST web pages for further details. 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 25A. 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 2025A:

• IGRINS (visiting instrument, South) - No longer available, for 25A onwards.

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.