iSHELL: a 1–5 micron R = 80,000 Immersion Grating Spectrograph for the NASA Infrared Telescope Facility

iSHELL is a 1.06–5.3 μm high spectral resolution spectrograph built for the 3.2 m NASA Infrared Telescope Facility (IRTF) on Maunakea, Hawaii. Dispersion is accomplished with a silicon immersion grating in order to keep the instrument small enough to be mounted at the Cassegrain focus of the telescope. The white pupil spectrograph produces resolving powers of up to about R ≡ λ/δλ = 80,000 (0.″375 slit). Cross-dispersing gratings mounted in a tiltable mechanism allow observers to select different wavelength ranges and, in combination with a slit wheel and Dekker mechanism, slit widths ranging from 0.″375 to 4.″0 and slit lengths ranging from 5″ to 25″. One Teledyne 2048 × 2048 HAWAII-2RG array is used in the spectrograph, and one Raytheon 512 × 512 Aladdin 2 array is used in a 1–5 μm slit viewer for object acquisition, guiding, and scientific imaging. iSHELL has been in productive regular use on IRTF since first light in 2016 September. In this paper we discuss details of the science case, design, construction and astronomical use of iSHELL.

Here Today, Gone Tomorrow

This chapter talks about Mike Mumma and his team, which chronologically is the first group to publicly stake a claim to having discovered methane in the atmosphere of Mars in 2003. It explores the May 2003 abstract that served as a placeholder for a presentation Mumma would give at an American Astronomical Society Division of Planetary Sciences meeting. It also cites Mumma's report on his team's attempt to detect methane on Mars using three different telescopes: NASA's 3-meter Infrared Telescope Facility (IRTF), the 8-meter Gemini South telescope in Chile, and the 10-meter Keck-2 telescope. The chapter provides the details of Mumma's measurements that show that the level of methane in the Martian atmosphere was about 10 parts per billion, averaged across the full atmosphere of Mars. It points out how all the early 2004 announcements about methane on Mars received immediate attention in the popular press.

Physical and dynamical characterization of the Euphrosyne asteroid family

Aims. The Euphrosyne asteroid family occupies a unique zone in orbital element space around 3.15 au and may be an important source of the low-albedo near-Earth objects. The parent body of this family may have been one of the planetesimals that delivered water and organic materials onto the growing terrestrial planets. We aim to characterize the compositional properties as well as the dynamical properties of the family. Methods. We performed a systematic study to characterize the physical properties of the Euphrosyne family members via low-resolution spectroscopy using the NASA Infrared Telescope Facility. In addition, we performed smoothed-particle hydrodynamics (SPH) simulations and N-body simulations to investigate the collisional origin, determine a realistic velocity field, study the orbital evolution, and constrain the age of the Euphrosyne family. Results. Our spectroscopy survey shows that the family members exhibit a tight taxonomic distribution, suggesting a homogeneous composition of the parent body. Our SPH simulations are consistent with the Euphrosyne family having formed via a reaccumulation process instead of a cratering event. Finally, our N-body simulations indicate that the age of the family is 280−80+180 Myr, which is younger than previous estimates.

The Infrared Telescope Facility (IRTF) spectral library

Context. Stellar population studies in the infrared (IR) wavelength range have two main advantages with respect to the optical regime: they probe different populations, because most of the light in the IR comes from redder and generally older stars, and they allow us to see through dust because IR light is less affected by extinction. Unfortunately, IR modeling work was halted by the lack of adequate stellar libraries, but this has changed in the recent years. Aims. Our project investigates the sensitivity of various spectral features in the 1−5 μm wavelength range to the physical properties of stars (Teff, [Fe/H], log g) and aims to objectively define spectral indices that can characterize the age and metallicity of unresolved stellar populations. Methods. We implemented a method that uses derivatives of the indices as functions of Teff, [Fe/H] or log g across the entire available wavelength range to reveal the most sensitive indices to these parameters and the ranges in which these indices work. Results. Here, we complement the previous work in the I and K bands, reporting a new system of 14, 12, 22, and 12 indices for Y, J, H, and L atmospheric windows, respectively, and describe their behavior. We list the equivalent widths of these indices for the Infrared Telescope Facility (IRTF) spectral library stars. Conclusions. Our analysis indicates that features sensitive to the effective temperature are present and measurable in all the investigated atmospheric windows at the spectral resolution and in the metallicity range of the IRTF library for a signal-to-noise ratio greater than 20−30. The surface gravity is more challenging and only indices in the H and J windows are best suited for this. The metallicity range of the stars with available spectra is too narrow to search for suitable diagnostics. For the spectra of unresolved galaxies, the defined indices are valuable tools in tracing the properties of the stars in the IR-dominant stellar populations.

1,000 to First Light: Construction of the Perth-Lowell Telescope Facility 1968-71

Negotiations began in 1968 for a telescope facility at Perth Observatory for NASA's International Planetary Patrol Network. 1000 days later the telescope saw first light. The facility bears no resemblance to other observatories. Inside a dome, the telescope sits on 42 ft tall concrete pier with wrap around staircase and concrete legs. Surrounding forest is similar in height to the dome, the design of which is counter intuitive. This study investigated why, at the risk of compromising performance, there was a departure from standard design, and to identify drivers for the decision making. Observatory visitors learn of a government architect, Tadeusz Andrzejaczek who made whimsical, successive increases to the height of the structure. Though designed in collaboration with Acting Government Astronomer, Bertrand Harris, it is improbable that a public servant architect would have such influence over a scientific installation. Vibration amelioration was met by designing massive strength and rigidity into the structure. Thermal expansion and wind stresses were reduced by features including shade fins and protective walls, and ground thermal disturbance was addressed by simply making it tall. Seeing measurements were not a significant design consideration. The facility exists with its current floor height because of successive approvals for modifications. The initial design was by Harris and requests for redesigns came from him but in close negotiation with Andrzejaczek who desired a structure of futuristic shape and proportions. Harris's designs were influenced by his personal English background and the Old Perth Observatory where he worked as an astronomer. Andrzejaczek’s design was influenced by an observatory in his birth city, his alignment with contemporary designers and his artistic flair.

HDO and SO2 thermal mapping on Venus

Since January 2012, we have been monitoring the behavior of sulfur dioxide and water on Venus, using the Texas Echelon Cross-Echelle Spectrograph imaging spectrometer at the NASA InfraRed Telescope Facility (IRTF, Mauna Kea Observatory). Here, we present new data recorded in February and April 2019 in the 1345 cm−1 (7.4 μm) spectral range, where SO2, CO2, and HDO (used as a proxy for H2O) transitions were observed. The cloud top of Venus was probed at an altitude of about 64 km. As in our previous studies, the volume mixing ratio (vmr) of SO2 was estimated using the SO2/CO2 line depth ratio of weak transitions; the H2O volume mixing ratio was derived from the HDO/CO2 line depth ratio, assuming a D/H ratio of 200 times the Vienna standard mean ocean water. As reported in our previous analyses, the SO2 mixing ratio shows strong variations with time and also over the disk, showing evidence for the formation of SO2 plumes with a lifetime of a few hours; in contrast, the H2O abundance is remarkably uniform over the disk and shows moderate variations as a function of time. We have used the 2019 data in addition to our previous dataset to study the long-term variations of SO2 and H2O. The data reveal a long-term anti-correlation with a correlation coefficient of −0.80; this coefficient becomes −0.90 if the analysis is restricted to the 2014–2019 time period. The statistical analysis of the SO2 plumes as a function of local time confirms our previous result with a minimum around 10:00 and two maxima near the terminators. The dependence of the SO2 vmr with respect to local time shows a higher abundance at the evening terminator with respect to the morning. The dependence of the SO2 vmr with respect to longitude exhibits a broad maximum at 120–200° east longitudes, near the region of Aphrodite Terra. However, this trend has not been observed by other measurements and has yet to be confirmed.

Characterization of material around the centaur (2060) Chiron from a visible and near-infrared stellar occultation in 2011

ABSTRACT The centaur (2060) Chiron exhibits outgassing behaviour and possibly hosts a ring system. On 2011 November 29, Chiron occulted a fairly bright star (R ∼ 15 mag) as observed from the 3-m NASA Infrared Telescope Facility (IRTF) on Mauna Kea and the 2-m Faulkes Telescope North (FTN) at Haleakala. Data were taken as visible wavelength images and simultaneous, low-resolution, near-infrared (NIR) spectra. Here, we present a detailed examination of the light-curve features in the optical data and an analysis of the NIR spectra. We place a lower limit on the spherical diameter of Chiron's nucleus of 160.2 ± 1.3 km. Sharp, narrow dips were observed between 280 and 360 km from the centre (depending on event geometry). For a central chord and assumed ring plane, the separated features are 298.5–302 and 308–310.5 km from the nucleus, with normal optical depth ∼0.5–0.9, and a gap of 9.1 ± 1.3 km. These features are similar in equivalent depth to Chariklo's inner ring. The absence of absorbing/scattering material near the nucleus suggests that these sharp dips are more likely to be planar rings than a shell of material. The region of relatively increased transmission is within the 1:2 spin-orbit resonance, consistent with the proposed clearing pattern for a non-axisymmetric nucleus. Characteristics of possible azimuthally incomplete features are presented, which could be transient, as well as a possible shell from ∼900–1500 km: future observations are needed for confirmation. There are no significant features in the NIR light curves, nor any correlation between optical features and NIR spectral slope.