NASA IRTF Spring 2023 Newsletter

Last updated 4 March 2023

Proposal Deadline for Semester 2023B (August 1, 2023 to January 31, 2024) is Monday, April 3, 2023, 5PM Hawaii Standard time.

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, 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 is 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 will also be evaluated. The review panel has presented their findings to NASA management for further evaluation. We expect to hear the results of the review within a few months.

COVID-19 Precautions and On-site Observing

IRTF operations have returned to pre-pandemic levels but we remain vigilant against the possibility of another surge. We encourage remote observing to reduce our carbon footprint. However, we also encourage first-time student observers to visit. Should you have any questions please contact John Rayner (jrayner@hawaii.edu).

Shutter problems and scheduled summer shutdown

Following a routine maintenance visit in September, 2022, the shutter vendor (Alimak) found that the shutter safety brakes were out of warranty and recommended that we cease operations until they could be replaced. Following delays in Alimak meeting IRS tax compliance due to unresponsiveness of the Hawaii tax office, and ordering and shipping parts to the telescope, the safety brakes were replaced and successful operations resumed on January 19. The total downtime was just over 11 weeks.

IRTF operations will be shut down during the first half of September (tbc) for telescope maintenance. Observers should avoid requesting observations during this period. The shutdown is needed for preventative maintenance of the shutter and for additional telescope maintenance.

Staff Update

Deputy Director Bobby Bus is retiring effective May 1, 2023. Bobby has been with IRTF for 23 years. We (and you) will miss him. However, we are hoping that Bobby will return in a part-time capacity after about six months (UH rules). We are currently advertising for a new Deputy Director, see the imminent job advertisement here. Interested candidates are encouraged to contact John Rayner (jrayner@hawaii.edu).

We are also recruiting for an Electrical Engineer II and a Software Engineer for Hilo, and an Electronic Technician for the day crew. These positions are proving difficult to recruit due to a lack of suitable applicants. Please contact John Rayner (jrayner@hawaii.edu) if you would like more details on these open positions.

Please contact John Rayner (jrayner@hawaii.edu) if you would like more details on these open positions.

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 (jrayner@hawaii.edu) and Adwin Boogert (aboogert@hawaii.edu), 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.

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. After fine tuning during the first few semesters of DAPR, the guidelines were relaxed to better align with the needs of the IRTF user community for 2023A and remain unchanged this 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 (aboogert@hawaii.edu).

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 2024. For more details contact Mike Connelley (mconnell@hawaii.edu).

Facility Instrumentation Update

Available facility instruments include (but note the important qualification for MIRSI/MOC):

(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 (mconnell@hawaii.edu).

(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 Mike Connelley (mconnell@hawaii.edu).

(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 (pplavcha@gmu.edu). 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 (aboogert@hawaii.edu).

(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, with work starting in August 2023, the engineering grade array will be replaced with a science grade array (on long-term loan from Gemini/NOIRLab). Consequently, MIRSI/MOC will not be formally available. However, engineering time will probably be available during the second half of the semester. Interested observers should contact John Rayner (jrayner@hawaii.edu) about the possibility of engineering time with MIRSI/MOC. The pre-2023 upgrade capabilities are given here. In the future we also hope to offer chopping and spectroscopy with MIRSI.

(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. ‘Opihi is offered on a shared risk basis for asteroid acquisition and SpeX flux calibration. For more details contact Mike Connelley (mconnell@hawaii.edu).

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. High priority science cases include: the characterization of NEOs and small bodies, and optical-IR transient follow-up and variability. We are currently working towards a preliminary design review, scheduled for May, 2023. IRTF is planning to submit a funding proposal for SPECTRE to NSF MRI in October, 2023. For more information contact John Rayner (jrayner@hawaii.edu).

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 the IRTF and its instrumentation.

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:

https://ui.adsabs.harvard.edu/search/q=bibgroup%3A%22irtf%22&sort=date%20desc%2C%20bibcode%20desc&p_=0

Please send any missing references to Bobby Bus (sjbirtf@gmail.com).

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 (sjbirtf@gmail.com):

http://irtfweb.ifa.hawaii.edu/research/biblio/dissertations.html

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 (jrayner@hawaii.edu) 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 http://smass.mit.edu/minus.html.

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 (aboogert@hawaii.edu) 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:

https://ndacc.larc.nasa.gov/instruments/microwave-radiometer