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Proposal preparation

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Please check the relevant call for proposals whether IGRINS is offered. A brief overview of proposing for IGRINS at Gemini, along with a detailed checklist is given below. Please also refer to the IGRINS instrument pages which are externally maintained here, or contact the IGRINS instrument scientists if you have any queries. 

Proposal preparation

  • IGRINS exposures times can be made using the app, or the sensitivity tables. Please recall that IGRINS assumes different standard observing constraints to regular queue instruments. Since IGRINS is a near-infrared instrument, no SB constraint is recommended, unless demonstrably affecting science. 
  • IGRINS Band 1/2 conditions can use any constraints equal to or better than CC80/IQ85. Please ensure that any targets fainted than 13 in K requests IQ20.
  • IGRINS Band 3 assumes CC80/IQAny for targets brighter than 11 mag in K.
  • IGRINS Band 4 (Poor weather proposals) assumes no constraints with targets brighter than 9 mag in K. 

Timing windows and data taking

  • IGRINS is mostly operated at Gemini regular queue, owing to a significant number of trained observers. So, it is offered most nights when on the telescope. But please check whether IGRINS will be on the telescope using the relevant semester schedule if you have limited timing windows for your observations.

Data processing and reduction

  • Since IGRINS is a visiting instrument, the data are ingested into the archive sporadically. It is recommended to use reduced data provided to the PIs via emails (sent usually within a few weeks after the observations) from the IGRINS team. These data include the recipes used, final reduced spectra, and telluric calibrations. 

Checklist for IGRINS proposals

  • Instrument configuration
    • IGRINS has a standardized configuration for all observations, allowing for a wavelength coverage of 1.45-2.45 micron (R~45,000), with a slit width of 0.34". Generally, users observe an ABBA sequence with an on-slit separation of 2.4" between the two positions. 
  • Baseline calibrations
    • Daily ON/OFF flats are taken with dome closed, and are part of the instrument calibration. 
    • Baseline calibrations estimated by the PIT only include a 20% overhead of science time accounting only for time needed for telluric observations. 
  • Telescope guiding
    • IGRINS uses the PWFS2 wavefront sensor for guiding.
  • Observing constraints
    • IGRINS is usually operated in the queue mode, with the main driver being achieved SNR for the spectra. Therefore, we ask users to use the ITC applet to estimate the exposure time required for their target, but also mention the desired SNR in a table instead of the ITC summary. Observations may be taken in conditions better than requested, the exposure time adjusted to achieve the desired SNR. Details on the various constraint bins are here
    • Water vapor is not measured on Cerro Pachón, and should be set to Any. 
    • Sky background does not affect near-infrared observations in the H and K bands, and should be set to Any. 
    • If absolute spectrophotometric calibration is required, photometric conditions should be selected (CC50). Time for the necessary flux standard observations should also be included. Due to the slit width, absolute flux calibration with IGRINS is difficult in non-photometric, or poor seeing conditions.
  • Exposure times
    • The minimum IGRINS exposure time is the readout time of 1.63s.
    • The maximum exposure time is limited to SNR~250 for a single ABBA sequence for bright targets, to prevent persistence; and for faint targets the maximum recommended exposure time is 1200s. 
    • The desired exposure time for the target magnitude can be calculated using the ITC web app here (external link).
  • Scheduling constraints
    • Please mention any timing constraints on your observations. Also check that IGRINS will be available during the desired timing window using the instrument schedules here (please see the relevant semester schedule). 
    • Users needing to observe uninterrupted sequences (for example: an exo-planet transit) must ensure that their timing window is equal to or longer than the total duration of the observation. In addition, if the total time observed for one observation in a single visit is greater than 2hr, and conditions change after 2hr meaning the observation cannot be completed, all time observed is charged to the PI. In such situations, a note can be added in the Phase II mentioning the tolerance on changing conditions before the observer needs to abort. 
  • Overheads
    • Target acquisition and readout are not included in the PIT overhead estimate. This needs to be added to the science component. 
    • Target acquisition should be budgeted at 8 minutes per target. 
    • Readout is two minutes per a single ABBA sequence.  
    • Bright targets having total exposure time less than 300s, must use the minimum time request (0.2hr).