IGRINS  @ McDonald Observatory

IGRINS acknowledgement in publications:

“This work used The Immersion Grating Infrared Spectrometer (IGRINS) was developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the US National Science Foundation under grants AST-1229522, AST-1702267 and AST-1908892, McDonald Observatory of the University of Texas at Austin, the Korean GMT Project of KASI, the Mt. Cuba Astronomical Foundation and Gemini Observatory."

Instrument Overview

IGRINS (Immersion GRating INfrared Spectrometer) is a compact high-resolution near-infrared spectrograph that primarily disperses light with a silicon immersion grating. Individual volume phase holographic (VPH) gratings serve as cross-dispersing elements for separate spectrograph arms covering the H and K bands. IGRINS observations cover the entire wavelength range between 1.45 and 2.45μm, and do so in a single exposure with a resolving power of R~45,000. As there are no moving cryogenic parts, all observations have the same spectral format (Yuk et al. 2010, Park et al. 2014, Mace et al. 2016, Mace et al. 2018). 

Since commissioning in July 2014, IGRINS has been scheduled for more that 1000 nights on the 2.7m Harlan J. Smith Telescope at McDonald Observatory, the 4.3m Discovery Channel Telescope at Lowell Observatory, and the 8.1m Gemini South telescope.

Proposing for IGRINS time at McDonald Observatory

The general process for submitting McDonald 2.7m proposals is provided on the Observatory webpage.

The standard operating mode for IGRINS at McDonald is Classical Observing. IGRINS is not currently available in remote or queue observing modes.

All IGRINS observations will have a proprietary period of 18 months.

IGRINS proposals must include a member of the instrument team or an experienced observer. It is the role of this team member to provide technical guidance on the instrument and ensure that PIs get observer training. Broader collaboration is not required or expected but can be discussed between the PI and their proposal members. The current (January 2025) list of experienced observers is:

UT: Greg Mace Kyle Kaplan UeeJeong Jeong Erica Sawczynec

KASI: Heeyoung Oh Jae-Joon Lee Yesol Kim

Lowell: Lisa Prato Joe Llama

Rice: Chris Johns-Krull Shih-Yun Tang

Greg Mace and Kyle Kaplan are the default contacts for IGRINS proposals at this time, but you may contact any of the people on the above list when writing your proposals. 

To be considered experienced, you will need to complete ~2 nights of observing with someone named above.  New IGRINS users will, generally,  be scheduled adjacent to experienced observers to receive training on overlapping observing nights. 

Standard Observing Practices

• Aim for multiples of 4 exposures per target (e.g. ABBA) to get the best cosmic ray correction, reduce sources of readout noise, and get 0th and 1st order corrections to the sky emission lines (2 exposures only gets 0th order correction).

• Limit exposures to 10 minutes (600 seconds) to reduce sky+background variation, provide redundancy to changing conditions, and reduce cosmic rays per exposure. 

• Complex observations are encouraged but require an experienced observer to oversee (could be telescope operator, PI, IGRINS Team member, depending on the complexity of observations and observer experience).

• Keep the A and B nod positions for stellar (point) sources the same throughout a night. This will help reduce problems in differences in wavelength between targets and standards, which can be caused by the target and standard not being at a matching position on the slit. 

Additional Resources

More information about IGRINS and/or observing with IGRINS can be found on the IGRINS wiki pages.

Data reduction will need to be performed by the program PI or a collaborator. The IGRINS team member or experienced observer is not a default collaborator. They will assist in proposal writing and observing training,  but to get help beyond this, each PI will need to discuss the full extent of their collaboration with the team member or experienced observer. 

The IGRINS PLP v3 is available with instructions on Github.

The Raw and Reduced IGRINS Spectral Archive (RRISA) contains all public IGRINS data products spanning the last 10 years of use at McDonald Observatory, the Lowell Discovery Telescope, and Gemini South. Check to see if your target has already been observed!

Additional questions? Send the IGRINS team an email at igrins.contact [at] gmail.com.