NASA IRTF Spring 2024 Newsletter

Last updated 1 March 2024

Proposal Deadline for Semester 2024B (August 1, 2024 to January 31, 2025) is Monday, April 1, 2024, 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.

NASA Independent Review of IRTF

NASA HQ conducted an Independent Review of IRTF in February 2023, visiting the telescope on February 1 and meeting with IRTF staff in Hilo on February 2. An extensive written review was submitted to the review panel prior to the visit. IRTF is the only NASA-owned ground-based astronomical telescope. The objective of the review was to examine the IRTF’s scientific productivity and to assess its role in meeting NASA goals, in particular solar system science and mission support, and to decide if operations should continue. IRTF’s value to more general astrophysics was also evaluated.

Overall the panel rated IRTF’s performance and value to the community as ‘excellent/very good’. The panel’s report and the documents submitted by IRTF are published online at:

One of the panel’s recommendations is that IRTF should conduct a strategic planning exercise and get input on future needs from the community. We are starting this process now. Visit the IRTF booth at upcoming DPS and AAS meetings. We will also gather input from an online survey and possibly from an in-person meeting.

Staff Update

We welcome our new IRTF Deputy Director Tom Jarrett. Tom starts March 1 and will be based in Hilo. He replaces Bobby Bus, who retired effective May 1, 2023. Tom comes from the University Of Cape Town, South Africa, where he jointly headed the Astronomy Department. Tom is a very experienced infrared astronomer, specializing in sky surveys with 2MASS, Spitzer and WISE. Prior to his time at UCT Tom held positions at JPL and IPAC.

Dwight Chan started as Electrical Engineer II in November 2023. Dwight will split his time between the day crew and Hilo (50%). Dwight is a Hilo native, with two decades of experience working at the Keck telescopes. We have also recruited Richard Soswe as ancillary support on the IRTF day crew, Richard started in December 2023.

Sadly we say goodbye to TO Dave Griep and Senior Software Engineer Tony Denault, both of whom retired in December. Dave was a TO at IRTF for an astonishing 42 years. Tony was not far behind him at 33 years with IRTF. We wish them all the very best for happy retirements.

Callie Matulonis started as an IRTF TO in January 2024. Callie comes to IRTF from a JCMT TO position but she has a long association with IRTF as both a temporary TO and as a student intern at IRTF in the mid-1990s. Callie is 50% TO and 25% other duties. The other duties include scheduling the TOs (replacing Dave) and night assistants, and hiring night assistants.

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 Adwin Boogert (, 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. Observers should avoid DDT requests if the request could have been proposed as a ToO proposal with specific interrupt criteria (e.g., comets, novae, NEO flybys etc.). 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.

Applying for Observing Time

The IRTF was 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 changes were made to the Online Application Form, and instructions for preparing the proposal attachment file were updated to meet the NASA DAPR guidelines. We realize that this first implementation of the DAPR rules was particularly strict, and that for some investigators, made it difficult to prepare compelling scientific justifications, especially in cases for long-term observing programs. To better align with the needs of the IRTF user community, we are relaxing some of the DAPR rules beginning with the 2023A semester. PLEASE follow the directions for preparing your proposal for observing time CAREFULLY. Any proposal that does not make a good-faith effort to maintain anonymity WILL BE REJECTED.

Should you have any questions about the DAPR rules please contact Adwin Boogert (

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 late 2024. For more details contact Mike Connelley (

John Rayner is currently working with IfA graduate student Cookie Dinh to assess IRTF image quality in preparation for the installation of FELIX and the prototype Adaptive Secondary Mirror (see the following).

Adaptive Secondary Mirror (ASM) project

The IRTF is working with UH astronomer, Mark Chun, to test a prototype 36-actuator ASM on IRTF during 2024. Mark has NSF funding to develop an ASM using the variable reluctance technology being developed by the Dutch company TNO. If successful we may eventually use the ASM for slow active control (not adaptive) of the telescope image quality using the FELIX wavefront sensor. The prototype ASM was delivered in February 2024 and is planned for testing on the telescope from April onwards. ASM testing forms part of the thesis project for IRTF student Ellen Lee. For more information contact John Rayner (

Facility Instrumentation Update

Available facility instruments include:

(1) 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 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 (

(2) 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 automatically generated. For more information, see the instrument page and instrument manual or contact Bobby Bus (

(3) 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 (

(4) 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 (MOC, similar to MORIS). First light with the upgraded instrument occurred in April 2020. During semester 2023B, the current engineering grade array was replaced with a science grade array. Current MIRSI capabilities are given here. Initial estimates are that sensitivity has not significantly improved (possibly since performance is already background limited) although array systematics and cosmetics are better. We are not offering spectroscopy in 2024B (see the Call for Proposals). In the longer term we are hoping to improve performance by replacing degraded filters and by adding a chopping capability to the hexapod secondary stage. For more information contact Mike Connelley (

(5) ‘Opihi is a wide-angle finder mounted to and aligned with IRTF. ‘Opihi consists of a 17" Planewave CDK telescope, a CCD having a 32’ FOV, and a filter wheel with g'r'i'z' and open filters. Its goals are to recover asteroids with large position uncertainties for SpeX and MORIS, to monitor extinction and cloud cover (similar to CFHT’s Skyprobe), and to flux calibrate SpeX prism or SXD spectra by simultaneously imaging in z'-band. ‘Opihi can locate asteroids down to V~20 in about one minute, propagate its motion across the sky, and send that ephemeris to the TCS. ‘Opihi is independent of other facility instruments and can thus be used in parallel with SpeX. For more details contact Mike Connelley (

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. SPECTRE successfully completed a Preliminary Design Review in July, 2023 and received a NASA Task Order of $1.7M to begin construction in October 2023. The Task Order funding must be spent before the end of the current NASA contract with UH to operate IRTF (about July 2024). IRTF also submitted a funding proposal for SPECTRE to NSF MRI in October, 2023 (mostly for long-lead optical components). For more information contact John Rayner (

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.

To keep our online bibliography up to date, we ask that you send us citations to your latest IRTF publications. You can verify that your refereed publications are listed in our bibliography at:

Please send any missing references to Bobby Bus ( Bobby is still helping us with IRTF metrics despite his retirement.

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

Spextool for the SpeX instrument is being converted from IDL to Python by Mike Cushing (University of Toledo) and Adam Burgasser (UC San Diego). This eliminates the need for computers with an IDL license, and enables scripted data reduction. It is expected that the Python programs for the Prism and SXD modes will be released at the start of semester 2024B (August 2024), while the LXD mode will follow a few months later. Users will reduce their data on the Python command line, with scripts, and with Jupyter notebooks. We are conducting a short survey to get an idea of how important it is for observers to also be able to reduce their data with GUIs (Graphical User Interfaces), comparable to the existing IDL programs. Please give your opinion about this and a few other items by filling out this short survey: before the end of March.

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 now at IRTF

The ClO monitor has been installed in the IRTF bunker (the small building at the perimeter of the IRTF site) and is operating as designed.

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: