NASA IRTF Fall 2021 Newsletter

Last updated 01 September 2021

Proposal Deadline for Semester 2022A (February 1, 2022 to July 31, 2022) is Friday, October 1, 2021, 5PM Hawaii Standard time.

Please review the information and use our ONLINE application form

Available instruments are listed here. Remote observing is offered from any location with broadband Internet access for any project that utilizes IRTF facility instruments. Click here for more information.

COVID-19 Precautions and Impact on Observing

The IRTF remains operational but with strict COVID protocols in place. All observing will be done remotely for the remainder of semester 2021B and possibly 2022A. The only possible exceptions are the TEXES visitor instrument runs that require the presence of out-of-state support staff. Unfortunately, Hawaii is in the midst of a COVID-19 Delta variant surge with hospitals currently at capacity.

Due to social distancing needs, staff presence at the summit (the day crew and telescope operators) is more limited, resulting in reduced efficiency and inevitable delays in some upgrade work. Where possible, all other IRTF staff are encouraged to work from home. For nationwide COVID updates visit the CDC website. Hawaii COVID updates are available here and here. For IRTF updates please contact John Rayner (

Staff Update

We are close to recruiting an EEI for IfA Hilo and we will very soon advertise for an EEII to replace Eric Warmbier. On the day crew we are currently advertising for a Senior Mechanical Technician. Unfortunately, we did not renew the contract of the recently recruited day crew Electronic Technician. This position will be readvertised. There is also a day crew member on long term medical leave. Consequently, we are currently short staffed on the day crew. We also expect two senior IRTF staff members to retire within the next couple of years.

Engineering Time and Director Discretionary Time (DDT)

The IRTF schedule includes about 18 nights per semester for engineering. This time is used to address technical problems with the facility, calibrate instrumentation, and for IRTF staff science. Usually not all of this time is needed for engineering purposes, and some can be offered to observers in the form of Director’s Discretionary Time (DDT). DDT is reserved for follow-up of newly-discovered objects and of unexpected transient phenomena, or when developments since the last proposal cycle make time-critical observations necessary. A request for DDT should be submitted by email to both John Rayner ( and Bobby Bus (, and must include a strong programmatic or scientific justification, a technical description of the proposed observations (including target information, instrument settings, required S/N, and justification for the amount of time requested), and a discussion for why this work was not proposed in the last proposal cycle and why it can’t wait for the next proposal cycle. Evaluation of DDT requests will be based on the same criteria used for regular observing proposals, and on the urgency or time-critical nature of the observation. As with ToO interrupt proposals, DDT requests should include at least one team member capable of carrying out the observation without support from IRTF staff.

In addition, observers may request DDT observing time outside of the scheduled engineering time requiring fast response. Observers should not negotiate with scheduled observers. All program changes must be approved by the Director.

Maunakea Observatories Update

Following the protests over the construction of TMT, access to all Maunakea Observatories has returned to normal (COVID protocols permitting). The status quo is likely to be maintained until and if TMT decides to take further action. If that happens, access might become limited again but we will keep observers appraised of the situation. For updates contact John Rayner John Rayner (

Applying for Observing Time

The IRTF has been instructed by NASA Headquarters to implement Dual-Anonymous Peer Review (DAPR) procedures in the review and ranking of observing proposals beginning with the 2022A semester. To meet this requirement, some minor changes have been made to the Online Application Form (available September 7), and instructions for preparing the proposal attachment file (which contains the Science and Technical Justifications, figures, references, and target list) have been updated to meet the NASA DAPR guidelines. PLEASE follow the new directions for preparing your proposal for observing time CAREFULLY. Any proposal that does not make a good-faith effort to follow the guidelines for anonymity WILL BE REJECTED.

As part of the DAPR process we will no longer publicize the names of TAC members. Even so, under no circumstances should investigators contact TAC members regarding proposal feedback. In case of questions or concerns please contact the Director (

Telescope and Facility Update

The IRTF is a 42-year-old facility. While the observing instrumentation is continually upgraded, unsurprisingly, telescope systems are requiring increasing amounts of maintenance. Current projects include replacing dome shutter weather-proofing, optimizing telescope balance to reduce drive currents and gearbox loads, upgrading and maintaining the dome and primary mirror air chillers, improving mirror cover reliability, and maintaining the dome and shutter electrical and mechanical systems. This work is complicated by having to have the facility operational every night. As a consequence we are starting to plan for annual week-long summer shutdowns. If the pandemic relents we hope to start sometime in summer 2022.

Ongoing telescope facility upgrades include FELIX and ‘Opihi:

      FELIX: new off-axis guider and low-order wavefront sensor

FELIX will replace the current off-axis telescope guider (Smokey). It consists of a CCD, optics and pick-off mirror on an XY stage. The pick-off mirror patrols a U-shaped 50 square arcminute field surrounding the 80 arcsec diameter on-axis FOV available to Cassegrain-mounted instruments. In addition to imaging an 80 arcsec diameter FOV, the optics can switch to a 2x2 Shack-Hartman wavefront sensor. By measuring the wavefront and controlling the hexapod secondary the system will initially provide real-time focus and alignment correction. Since only slow correction is needed, closed loop correction can be done on stars to V=18 in about one minute. Aside from atmospheric seeing, defocus is currently the largest error in the telescope’s image quality budget. FELIX will be available for use with all Cassegrain-mounted facility and visitor instruments. Through the resulting better focus control, we expect sensitivity improvements of up to 0.5 mags for the slit spectrographs. The design is complete. Purchasing and assembly is in progress. We expect FELIX to be operational by 2023. For more details contact Mike Connelley (

      'Opihi: wide angle finder

'Opihi is a wide-angle finder for IRTF. The goals are to acquire asteroids with large position uncertainties for SpeX and MORIS, to monitor extinction and cloud cover (like CFHT’s Skyprobe), and to provide general context imaging. ‘Opihi consists of a 17-inch diameter Planewave corrected-Dall-Kirkham telescope with Andor 2k x 2k CCD array to provide a 0.5 degree FOV. ‘Opihi will mount (‘cling’) to the side of the mirror cell. We hope to install ‘Opihi' in late 2021 with commissioning in 2022. All components have been delivered and we are about to start assembly and testing. For more details contact Mike Connelley (

Facility Instrumentation Update

SpeX is a 0.7-5.3 micron medium-resolution (R=50-2500) spectrograph and imager. The 0.8 micron cut-on dichroic was replaced with a 0.7 micron dichroic during semester 2017A. This modification increases the spectral wavelength grasp for optically guided solar system targets. Sub-arrays and movie mode are working again in the IR guider. When observing point sources, we strongly recommend that at least three nodded pairs of integrations are acquired, even if the source is bright. This allows for more accurate measurement of the spectral slope in the presence of seeing and guiding variations. Longer integration times also help even out variations, even if they are not required to achieve the desired S/N. Electronic observing logs are now automatically generated. Real-time spectral extraction runs automatically in the background and can be visualized in the data viewer (DV). For more information, see the instrument page and instrument manual or contact Mike Connelley (

MORIS is a 512x512 pixel Andor CCD camera mounted at the side-facing, dichroic-fed window of the SpeX cryostat (60"x60" field-of-view). MORIS can be used as an optical imager and as an optical guider for SpeX. For visible targets guiding with MORIS can significantly improve spectral sensitivity (better than one magnitude compared to IR guiding due to reduced slit losses). Electronic observing logs are now automatically generated. For more information, see the instrument page and instrument manual or contact Bobby Bus (

iSHELL is a 1.06 – 5.3 micron cross-dispersed echelle spectrograph (up to about R=80,000) and imager. Slight fringing (5% contrast, spatial frequencies 20 pixels at J to 70 pixels at M) is observed in the flat fields. To reach S/N>100 on features at these pixel frequencies, more frequent flat fielding is required (for details contact your support astronomer). Commissioning observations involving radial velocities have yielded good results, with precisions better than 10 m/s achieved for targets brighter than K=10. The RV data reduction code is available on github or by request from Peter Plavchan ( The general purpose data reduction tool for iSHELL is available as part of the Spextool package. We have developed a version of Xtellcor (called Xtellcor_model) that uses atmospheric models instead of standard stars to remove telluric absorption lines in iSHELL spectra. For now we recommend that observers still take standard stars until they have compared both methods. For details see the IRTF data reduction pages. Electronic observing logs are automatically generated. Observers are reminded that darks are automatically taken following observing and can be downloaded. Real-time spectral extraction now runs automatically in the background and can be visualized in the data viewer (DV). For more information, see the instrument page and instrument manual or contact Adwin Boogert (

MIRSI/MOC is a 5-20 micron camera and grism spectrograph and optical imager. MIRSI was recently upgraded with a closed-cycle cooler to replace its liquid nitrogen and liquid helium cryostat and a dichroic-fed optical channel added. First light with the upgraded instrument occurred in April 2020. Following this further work was required to optimize performance with the current Si:As BIB 320x240 engineering grade array earlier in 2021. For 2022A we are offering MIRSI in shared risk and with more limited capability. For more information, see the instrument page and instrument manual or contact Mike Connelley (

In the longer term we are planning to replace the engineering grade array that currently limits performance with a science grade array on long-term loan from Gemini. However, we are currently unable to take delivery of this device due to the pandemic. In the future we also hope to offer chopping and spectroscopy with MIRSI.

Information on available facility instruments and performance can be found here. The instrument manuals were updated in August 2021. Exposure time calculators for SpeX and iSHELL are available on the respective instrument webpages. The ETC for iSHELL has been adjusted to allow for the lower throughput at J0.

Proposed New IRTF Facility Instrument

SPECTRE (Spectrograph Express) is a 0.4-4.2 micron, R=150, integral field spectrograph (IFS). For optimum efficiency, the wavelength range is covered simultaneously in three channels - 0.4-0.9 micron, 0.9-2.4 micron, and 2.4-4.2 micron, and the IFS has a 7x7 arcsec FOV to remove slit losses and to acquire absolute photometry on point sources. Object acquisition and guiding is done with an external cryostat-mounted 3 arcmin FOV CCD. There are no cold mechanisms, facilitating easy and once-per-night calibration. High priority science cases include: the characterization of NEOs and small bodies, and optical-IR transient follow-up and variability. IRTF submitted a funding proposal for SPECTRE to the preliminary round of the NSF MSIP program in December 2019 and although it was selected for the full proposal round (16 out of 41) it was not selected for funding. We plan on submitting a new and improved proposal in early 2022 following a formal preliminary design review in late 2021. In the meantime, we are polling IRTF users about an improved science case. If you would like to contribute please contact John Rayner (

Astro 2020: Decadal Survey on Astronomy and Astrophysics

IRTF submitted white papers to both the astrophysics and planetary decadal review panels. The papers were required to concentrate on three thematic areas. For the astrophysics panel we chose Planetary Systems, Star and Planet Formation, and Stars and Stellar Evolution. For the planetary panel we chose Primitive Bodies, Planetary Defense, and Ground-based Telescopes. The white papers were partly based on input from the community workshop held in 2018. Workshop presentations are viewable here.

Help Keep Our Publications List Current

Please continue to acknowledge the IRTF in your publications following the instructions shown here. It is important that you include in your papers the name of the instrument used and the citation for the instrument, as this helps to ensure future funding of IRTF instruments.

IRTF Bibliography

To keep our bibliography up to date, and to ensure future funding of the IRTF, we ask that you send us citations to your latest IRTF publications. You can check your publications using our website bibliography page for refereed papers:

Please send any missing references to Bobby Bus (, and please continue to include in your paper the acknowledgement to the IRTF and the name of the instrument used as described at:

We are in the process of compiling a list of PhD Dissertations that have utilized observations obtained with the IRTF. If you (or your student) has written a dissertation based on IRTF data that is not yet included in this list, please send the appropriate information (including a web link to the dissertation, if possible) to Bobby Bus (

IRTF Spectral Libraries

Users are encouraged to make use of the spectral library of FGKM stars, which is available here. An extended spectral library including late-type non-solar stars observed by Alexa Villaume and collaborators is available here. Contact John Rayner ( for more details.

A library of more than 1000 prism spectra of low-mass stars and brown dwarfs is maintained by Adam Burgasser, and is available here.

The MIT-IRTF Near-Earth Object spectral survey is underway, and many spectra are publicly available. For more information go to

IRTF Data Reduction Update

As of June 2021, IRTF observers have the option to reduce their SpeX and iSHELL data remotely, on a dedicated IRTF computer. This computer, which is accessed via VNC, has IDL and the latest versions of Spextool for SpeX and iSHELL installed. Observers can request a temporary guest account by emailing their support astronomers. For more information, see here.

Fully automated "quicklook" reduction of SpeX and iSHELL spectra is operational during every observing session. This enables observers to assess the quality of their data in (near-) real-time and make better informed decisions. During an observing session, the software determines from the FITS headers if sufficient data is available to run a scripted version of Spextool. It then automatically extracts spectra and displays the signal and signal-to-noise values as a function of wavelength in DV (before division over a standard star). For more information, visit the Quicklook web page.

A beta version of Xtellcor_model is available, which uses atmospheric models instead of standard stars to remove telluric absorption lines in iSHELL spectra. The software, sample data, and a manual can be downloaded from the IRTF data reduction pages. Optimization of the atmospheric column densities to the observed spectra is typically required, and thus the method works best if at least a few telluric lines are separated from stellar features. Xtellcor_model also includes a method to correct the iSHELL echelle order curvature using flat fields. This typically leaves more instrumental artifacts than when using standard stars, and observers should keep planning to take standard star spectra until they have verified that Xtellcor_model satisfies the calibration needs for their science programs.

Please visit the IRTF data reduction pages for downloading the Spextool software for both SpeX and iSHELL, as well as sample data and other useful resources, and do not hesitate to contact Adwin Boogert ( for requests and questions about the reduction of IRTF data.

Chlorine Monoxide (ClO) monitor to be housed at IRTF

We are currently in process of modifying the small building on the IRTF site to house the ClO monitor that is being moved from soon to be decommissioned CSO. The small building, known as the 'IRTF bunker' houses a large exhaust fan for the telescope dome that is no longer needed. MKSS Utilities are doing the building modifications.

The ClO monitor is an infrared FTS operating at about 230 Ghz. It measures the abundance of ClO in the stratosphere. ClO is formed when chlorine from man made CFCs reacts with and destroys ozone. Ozone absorbs harmful UV radiation from the sun. Diurnal measurement of ClO is vital to monitor the effectiveness of international treaties put in place to restrict the use of CFCs. To make these measurements the ClO monitor needs to operate at high altitude. Data from the monitor is public and can be found here: