Greg in cleanroom with iSHELL First light with iSHELL

iSHELL: 1.1-5.3 micron high-resolution spectrograph and imager

Introduction

iSHELL is a high-resolution 1.1-5.3 micron spectrograph built at the Institute for Astronomy (IfA), for the NASA Infrared Telescope Facility (IRTF) on Maunakea. The instrument saw first light in Sept. 2016. iSHELL uses a silicon immersion grating to achieve high spectral resolution in a relativly compact instrument. iSHELL's detectors are a Raytheon Aladdin 3 512x512 InSb array in the guider and a Teledyne 2048x2048 Hawaii-2RG array for the spectrograph. Astronomical Research Cameras, Inc. controllers run both arrays. iSHELL's wavelength range is covered in 17 discrete settings of the cross disperser turret, while custom wavelength settings are available. A data reduction tool is available via SpeXtool5.

Instrument Properties

iSHELL News

Look here for updates and news. OBSERVERS ARE STRONGLY RECOMMENDED TO READ THE UPDATES BEFORE EACH RUN.

Acknowledgements

Observers publishing results obtained with iSHELL are requested to reference the following paper:

iSHELL: construction, assembly, and testing
J. T. Rayner, A. Tokunaga, D. Jaffe, M. Bonnet, G. Ching, M. Connelley, D. Kokubun, C. Lockhart, E. Warmbier (2016, SPIE, 9908E, 84R)

Observers who use Spextool are also kindly asked to reference the following papers:

Spextool: A Spectral Extraction Package for SpeX, a 0.8-5.5 micron Cross-Dispersed Spectrograph
Michael C. Cushing, William D. Vacca and John T. Rayner
(2004, PASP 116, 362).

A Method of Correcting Near-Infrared Spectra for Telluric Absorption
William D. Vacca, Michael C. Cushing and John T. Rayner
(2003, PASP 115, 389).

Note: The general version of the telluric correction routines, xtellcor_general, previously available as a stand alone package, has now been incorporated into the Spextool package. Users must download the full Spextool package in order to use xtellcor_general.

Another paper may be of interest to iSHELL users:

Nonlinearity Corrections and Statistical Uncertainties Asociated with Near-Infrared Arrays
William D. Vacca, Michael C. Cushing and John T. Rayner
(2004, PASP 116, 352).

Observer Documentation

These pages are updated irregularly.

ALWAYS CONSULT WITH A SUPPORT ASTRONOMER BEFORE USING OR PROPOSING TO USE iSHELL.

iSHELL MANUAL (23 March 2018).

  • Observing Logs for the Spectrograph and the Guider/Imager
  • Parallactic angle calculator
  • Form to locate A0V Stars and G2V Stars near a target.

  • Spectrograph Exposure Time Calculator

  • iSHELL Echelle Format Simulator

    iSHELL Data

    With the 2048x2048 H2RG array in the spectrograph the individual file size is 16.8MB. However, we now store three files per image: pedestal minus signal, pedestal, and signal, for a total image size of 50MB. The reason for the extra fiiles, which are stored as extensions to each image, is to accurately compute corrections for non-linearity. Consequently,

    Observers can compress data for transfer and uncompress on arrival by using the -C flag: 'sftp -C yourname@yourhost'. This should only be used for slow links since it requires extra CPU time.

    Data Reduction Tool

    Spextool5 is an IDL-based spectral reduction program to reduce iSHELL cross-dispersed and prism data. It is written and maintained by Mike Cushing and Bill Vacca.

    October 2017 Spextool version v5. Spextool v5 reduces data obtained with iSHELL only, and is currently limited to reducing the discrete cross disperser settings. Future versions of SpeXtool will reduce both SpeX and iSHELL data. All users should read Sections 1 and 2 of the manual (found in Spextool/manuals/) before attempting to run the software, if only because some new IDL libraries are required. Raw K-band and L-band data can be downloaded to test drive the downloaded Spextool5 package. Comments, suggestions for improvements, and bug reports should be directed to Mike Cushing at michael.cushing@gmail.com.

    Technical Documentation