This is a list of reviewers who served the Journal of Astronomical Telescopes, Instruments, and Systems in 2020.

We develop a simple coordinate transformation that can be employed to compensate for the nonlinearity introduced by a microwave kinetic inductance detector’s (MKID) homodyne readout scheme. This coordinate system is compared to the canonically used polar coordinates and is shown to improve the performance of the filtering method often used to estimate a photon’s energy. For a detector where the coordinate nonlinearity is primarily responsible for limiting its resolving power, this technique leads to increased dynamic range, which we show by applying the transformation to data from a hafnium MKID designed to be sensitive to photons with wavelengths in the 800- to 1300-nm range. The new coordinates allow the detector to resolve photons with wavelengths down to 400 nm, raising the resolving power at that wavelength from 6.8 to 17.

The guest editors summarize the Special Section on the Origins Space Telescope.

The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the Universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared (IR) wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of the Herschel Space Observatory, the largest telescope flown in space to date. We describe the baseline concept for Origins recommended to the 2020 US Decadal Survey in Astronomy and Astrophysics. The baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (Mid-Infrared Spectrometer and Camera Transit spectrometer) will measure the spectra of transiting exoplanets in the 2.8 to 20  μm wavelength range and offer unprecedented spectrophotometric precision, enabling definitive exoplanet biosignature detections. The far-IR imager polarimeter will be able to survey thousands of square degrees with broadband imaging at 50 and 250  μm. The Origins Survey Spectrometer will cover wavelengths from 25 to 588  μm, making wide-area and deep spectroscopic surveys with spectral resolving power R  ∼  300, and pointed observations at R  ∼  40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch, while the cryothermal system design leverages James Webb Space Telescope technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural background-limited sensitivity.

Quantum capacitance detectors (QCDs) are photon shot noise-limited terahertz detectors based on a single Cooper-pair box superconducting qubit. The QCD has demonstrated photon shot noise-limited performance for 1.5 THz radiation under loading conditions between ^{10  −  20} and 10^−  18  W and single-photon detection and counting at that frequency. We report here fabrication and preliminary characterization of a 441 pixel array of QCDs with readout frequencies between 700 and 850 MHz.

The Origins Space Telescope mission concept includes an exoplanet transit spectrometer that requires detector arrays with ultrahigh pixel-to-pixel stability. Superconducting nanowire single-photon detectors, or SNSPDs, have the potential to meet these stringent stability requirements due to their digital-like output. Traditionally used for applications at near-IR telecom wavelengths, SNSPDs have demonstrated near-unity detection efficiencies, ultralow dark-count rates, and high dynamic ranges. Until recently, however, SNSPD operation at the mid-infrared (mid-IR) wavelengths of interest for Origins had not been demonstrated, and SNSPD formats were limited to small arrays and active areas. Recent advances in SNSPD fabrication techniques have pushed SNSPD sensitivity to wavelengths beyond 7  μm and have enabled millimeter-scale active areas and kilopixel arrays. We report here on this progress and the outlook toward developing arrays of ultrastable superconducting nanowire single-photon detectors for mid-IR astronomy applications.

The Origins Space Telescope is one of four flagship missions under study for the 2020 Astrophysics Decadal Survey. With a 5.9-m cold (4.5 K) telescope deployed from space, Origins promises unprecedented sensitivity in the near-, mid-, and far-infrared from 2.8 to 588  μm. This mandates the use of ultrasensitive and stable detectors in all of the Origins instruments. At the present, no known detectors can meet Origins’ stability requirements in the near- to mid-infrared or its sensitivity requirements in the far-infrared. We discuss the applicability of transition-edge sensors, as both calorimeters and bolometers, to meet these requirements, and lay out a path toward improving the present state-of-the-art.

We report on our investigation into adapting the design of the James Webb Space Telescope (JWST) to the needs and requirements of the Origins Space Telescope. The modifications needed to the equipment and insulation of the JWST design to achieve the 4.5-K design temperature for Origins are introduced and detailed. The Webb thermal model is modified to the Origins design and used to predict the heat loads at 18 and 4.5 K. We also describe the needed development of the JWST Mid-Infrared Instrument’s cryocooler needed to reach the temperature necessary for Origins. The capabilities of the various modified cryocoolers are discussed. We show that three modified coolers are needed to achieve the performance required for Origins. Finally, we show that the baseline instruments and needed coolers can be accommodated for volume, mass, and power in the Webb architecture.

The Heterodyne Receiver for Origins (HERO) is the first detailed study of a heterodyne focal plane array receiver for space applications. HERO gives the Origins Space Telescope the capability to observe at very high spectral resolution (R  =  10⁷) over an unprecedentedly large far-infrared (FIR) wavelengths range (111 to 617  μm) with high sensitivity, with simultaneous dual polarization and dual-frequency band operation. The design is based on prior successful heterodyne receivers, such as Heterodyne Instrument for the Far-Infrared /Herschel, but surpasses it by one to two orders of magnitude by exploiting the latest technological developments. Innovative components are used to keep the required satellite resources low and thus allowing for the first time a convincing design of a large format heterodyne array receiver for space. HERO on Origins is a unique tool to explore the FIR universe and extends the enormous potential of submillimeter astronomical spectroscopy into new areas of astronomical research.

The Origins Space Telescope’s (Origins) significant improvement over the scientific capabilities of prior infrared missions is based on its cold telescope (4.5 K) combined with low-noise far-IR detectors and ultrastable mid-IR detectors. A small number of new technologies will enable Origins to approach the fundamental sensitivity limit imposed by the natural sky background and deliver groundbreaking science. This paper describes a robust plan to mature the Origins mission, enabling cryocooler technology from current state-of-the-art (SOA) to Technology Readiness Level (TRL) 5 by 2025 and to TRL 6 by mission Preliminary Design Review. Entry TRLs corresponding to today’s SOA are 4 or 5, depending on the technology in question.

The Origins Space Telescope’s orders-of-magnitude improvement over the scientific capabilities of prior infrared (IR) missions is based on its cold telescope (4.5 K) combined with low-noise far-IR detectors and ultra-stable mid-IR detectors. A number of trades were made in favor of a design with staged cooling, avoiding warm objects in the cold zones and minimizing the number of deployments and their complexity. The result is an architecture that is easily to analyze thermally and straightforward to test in existing facilities.

Our paper discusses the optical design of the Origins Space Telescope. Origins is one of four large missions under study in preparation for the 2020 Decadal Survey in Astronomy and Astrophysics. Sensitive to the mid- and far-infrared spectrum (between 2.8 and 588  μm), Origins sets out to answer a number of important scientific questions by addressing NASA’s three key science goals in astrophysics. The Origins telescope operates at f  /  14. The design includes a 5.9-m-diameter primary mirror. The large on-axis primary consists of 18 “keystone” segments of two different prescriptions arranged in two annuli (six inner and twelve outer segments) that together form a circular aperture in the goal of achieving a symmetric point spread function. To accommodate the 46  ×  15  arc min full field of view (FOV) of the telescope at the design wavelength of λ  =  30  μm, a three-mirror anastigmat configuration is used. The design is diffraction-limited across its instruments’ FOV. A brief discussion of each of the three baselined instruments within the Instrument Accommodation Module is presented: (1) Origins Survey Spectrometer, (2) Mid-infrared Spectrometer, Camera transit spectrometer channel, and (3) Far-Infrared Polarimeter/Imager. In addition, the upscope options for the observatory are laid out as well including a fourth instrument: the Heterodyne Receiver for Origins.

The Origins Space Telescope (Origins) study team prepared and submitted a Mission Concept Study Report for the 2020 Decadal Survey in Astrophysics. During the study, a Materials Working Group was formed to evaluate materials for Origins. The Materials Working Group identified material candidates and evaluated the candidates using driving requirements and key material considerations. The evaluation resulted in several options to aid the study team in making a materials selection for the mission concept. Our paper details the approach to the materials evaluation and the results.

The Origins Space Telescope (Origins) concept is designed to investigate the creation and dispersal of elements essential to life, the formation of planetary systems, and the transport of water to habitable worlds and the atmospheres of exoplanets around nearby K- and M-dwarfs to identify potentially habitable—and even inhabited—worlds. These science priorities are aligned with NASA’s three major astrophysics science goals: How does the Universe work? How did we get here? and Are we alone? We briefly describe the science case that arose from the astronomical community and the science traceability matrix for Origins. The science traceability matrix prescribes the design of Origins and demonstrates that it will address the key science questions motivated by the science case.

The mid-infrared spectrometer and camera transit spectrometer (MISC-T) is one of the three baseline instruments for Origins Space Telescope (Origins) and provides the capability to assess the habitability of nearby exoplanets and search for signs of life. MISC-T employs a densified pupil optical design, and HgCdTe and Si:As detector arrays. This optical design allows the instrument to be relatively insensitive to minor line-of-sight pointing drifts and telescope aberrations, and the detectors do not require a sub-Kelvin refrigerator. MISC-T has three science spectral channels that share the same field-of-view by means of beam splitters, and all channels are operated simultaneously to cover the full spectral range from 2.8 to 20  μm at once with exquisite stability and precision (<5  ppm between 2.8 to 11  μm, <20  ppm between 11 and 20  μm). A Lyot-coronagraph-based tip–tilt sensor located in the instrument fore-optics uses the light reflected by a field stop, which corresponds to 0.3% of the light from the target, to send fine pointing information to the field steering mirror in the Origins telescope. An additional MISC Wide Field Imager (WFI) is studied as an upscope option for the Origins. MISC-WFI offers a wide field imaging (3^′  ×  3^′ ) and low-resolution spectroscopic capability with filters and grating-prisms (grisms) covering 5 to 28  μm. The imaging capability of the MISC-WFI will be used for general science objectives. The low-resolution spectroscopic capability in MISC-WFI with a resolving power R (  =  λ  /  Δλ) of a few hundreds will be used to measure the mid-infrared dust features and ionic lines at z up to ∼1 in the Origins mission’s Rise of Metals and Black Hole Feedback programs. The MISC-WFI also serves as a focal plane pointing and guiding instrument for the observatory, including when the MISC-T channel is performing its exoplanet spectroscopy observations.

The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? We describe how Origins was designed to answer these alluring questions. We discuss the key decisions taken by the Origins mission concept study team, the rationale for those choices, and how they led through an exploratory design process to the Origins baseline mission concept. To understand the concept solution space, we studied two distinct mission concepts and descoped the second concept, aiming to maximize science per dollar and hit a self-imposed cost target. We report on the study approach and describe the concept evolution. The resulting baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. The chosen architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch. The cryo-thermal system design leverages James Webb Space Telescope technology and experience.

The Origins Space Telescope (Origins) will have a 5.9-m diameter primary mirror cooled to 4.5 K and will be equipped with three instruments, two of which will cover the far-IR (λ  =  25 to 588  μm). These far-IR instruments will require large arrays (∼10⁴ detectors) of ultrasensitive detectors, with noise equivalent powers (NEPs) as low as 3  ×  10^−  20  W Hz^−  1/2. Kinetic inductance detectors (KIDs) have already demonstrated the array format, modularity, and readout multiplexing density requirements for Origins; the only aspect that requires improvement is the per-pixel sensitivity. We show how KIDs can meet the sensitivity target, focusing on two existing architectures that together demonstrate the key necessary attributes. Arrays of antenna-coupled coplanar waveguide resonators have achieved NEPs of 3  ×  10^−  19  W Hz^−  1/2 in laboratory demonstrations at 350  μm; they demonstrate excellent material properties as well as array-level integration and performance. Lumped element detectors such as those under development for balloon-borne spectroscopy at 10 to 350  μm demonstrate flexibility in coupling to shorter-wavelengths, reducing active volume, and providing a means for suppressing capacitor noise. A straightforward combination of the elements of these already-demonstrated devices points to a low-volume design that is expected to meet the Origins sensitivity targets.

The far-infrared imager and polarimeter (FIP) for the Origins Space Telescope (Origins) is a basic far-infrared imager and polarimeter. The camera will deliver continuum images and polarization measurements at 50 and 250  μm. Currently available detector technologies provide sufficient sensitivity for background limited observations from space, at least on a single pixel basis. FIP incorporates large next-generation superconducting detector arrays and our technology development plan will push the pixel numbers for the arrays to the required size of 8000. Two superconducting detector technologies are currently candidates for the instrument: transition edge sensors or microwave kinetic inductance devices. Using these detectors and taking advantage of the cryogenic telescope that is provided by Origins, FIP will achieve mapping speeds of up to eight orders of magnitude faster than what has been achieved by existing observatories. The science drivers for FIP include observations of solar system objects, dust properties, and magnetic field studies of the nearby interstellar medium, and large scale galaxy surveys to better constrain the star formation history of the universe to address one of the main themes of Origins: “How does the Universe work?” In addition to the science, the FIP instrument plays a critical functional role in aligning the mirrors during on orbit observatory commissioning.

The Origins Survey Spectrometer (OSS) is a multi-purpose far-IR spectrograph for Origins. Operating at the photon background limit, OSS covers the 25- to 588-μm wavelength range instantaneously at a resolving power (R) of 300 using six logarithmically spaced grating modules. Each module couples at least 30 and up to 100 spatial beams simultaneously, enabling true [three-dimensional (3D)] spectral mapping. In addition, OSS provides two high-resolution modes. The first inserts a long-path Fourier-transform spectrometer (FTS) into a portion of the incoming light in advance of the grating backends, enabling R up to 43  ,  000  ×    [  λ  /  112  μm  ]  , while preserving the grating-based sensitivity for line detection. The second incorporates a scanning etalon in series with the FTS to provide R up to 300,000 for the 100-to 200-μm range.

On August 22, 2019, the Origins Space Telescope (OST) Study Team delivered the OST Mission Concept Study Report and the OST Technology Development Plan to NASA Headquarters. A key component of this study report includes the technology roadmap for detector readout and how new radio frequency-system-on-chip (RFSoC)-based technology would be used to advance the far-infrared polarimeter instrument concept for a spaceflight mission. We present our current results as they pertain to the implementation of algorithms, hardware, and architecture for instrument signal processing of this proposed observatory using RFSoC technology. We also present a small case study, comparing a more conventional readout system with one based on the RFSoC and show a trade of system complexity versus technology readiness level.

Athena, a future high-energy mission, is expected to consist of a large aperture x-ray mirror with a focal length of 12 m. The mirror surface is to be coated with iridium and a low Z overcoat. To define the effective area of the x-ray telescope, the atomic scattering factors of iridium with an energy resolution less than that (2.5 eV) of the x-ray integral field unit are needed. We measured the reflectance of the silicon pore optics mirror plate coated with iridium in the energy range of 9 to 15 keV and that near the iridium L-edges in steps of 10 and 1.5 eV, respectively, at the synchrotron beamline SPring-8. The L3, L2, and L1 edges were clearly detected around 11,215, 12,824, and 13,428 eV, respectively. The measured scattering factors were ∼3  %   smaller than the corresponding values reported by Henke et al., likely due to the presence of an overlayer on the iridium coating, and were consistent with those measured by Graessle et al. The angular dependence of the reflectivity measured indicates that the iridium surface was extremely smooth, with a surface roughness of 0.3 nm.

Conventional two-mirror optical telescope designs are well known. An attempt to improve the performance of a two-mirror telescopic system using freeform surface is reported. Four variants of the optical design that use symmetric and off-axis freeform surfaces for achieving superior performances in the spectral range from 400 to 900 nm are proposed. These designs are compared with the conventional Ritchey–Chretien and equivalent two-mirror off-axis telescope designs with rotationally symmetric surfaces. The optical design with freeform surfaces shows marked improvements compared with its counterpart comprising of conics and higher order aspherics. The incorporation of freeform surfaces is obtained by an overlay of fringe Zernike polynomial either on the base sphere or on the conic itself, which is used as a surface descriptor in the envisaged designs. This approach aids in correction of asymmetrical aberrations and also extends the performances to a wider field, which is quite advantageous in the case of off-axis (de-centered and tilted) optical systems.

The Off-plane Grating Rocket Experiment (OGRE) is a soft x-ray grating spectrometer to be flown on a suborbital rocket. The payload is designed to obtain the highest-resolution soft x-ray spectrum of Capella to date with a resolution goal of R  (  λ  /  Δλ  )    >  2000 at select wavelengths in its 10 to 55 Å bandpass of interest. The optical design of the spectrometer realizes a theoretical maximum resolution of R  ≈  5000, but this performance does not consider the finite performance of the individual spectrometer components, misalignments between components, and in-flight pointing errors. These errors all degrade the performance of the spectrometer from its theoretical maximum. A comprehensive line-spread function (LSF) error budget has been constructed for the OGRE spectrometer to identify contributions to the LSF, to determine how each of these affects the LSF, and to inform performance requirements and alignment tolerances for the spectrometer. In this document, the comprehensive LSF error budget for the OGRE spectrometer is presented, the resulting errors are validated via raytrace simulations, the implications of these results are discussed, and future work is identified.

The Wide-Area Linear Optical Polarimeter (WALOP)-South instrument will be mounted on the 1-m South African Astronomical Observatory telescope in South Africa as part of the Polar-Areas Stellar Imaging Polarization High Accuracy Experiment (PASIPHAE) program to carry out a linear imaging polarization survey of the Galactic polar regions in the optical band. Designed to achieve polarimetric sensitivity of 0.05% across a 35  ×  35  arc min field of view (FOV), it will be capable of measuring the Stokes parameters I, q, and u in a single exposure in the R broadband and narrowband filters between 0.5 to 0.7  μm. For each measurement, four images of the full field corresponding to linear polarization angles of 0 deg, 45 deg, 90 deg, and 135 deg in the instrument coordinate system will be created on four detectors from which the Stokes parameters can be found using differential photometry. In designing the optical system, major challenges included correcting for the dispersion introduced by large split angle Wollaston prisms used as analysers and other aberrations from the entire field to obtain imaging quality point spread function (PSF) at the detector. We present the optical design of the WALOP-South instrument which overcomes these challenges and delivers near seeing limited PSFs for the entire FOV.

This paper proposes an optical system of the telescope for space research. The system comprises a segmented spherical mirror with a diameter of 10 m and a secondary aspherical mirror. The focal length of the telescope is equal to the radius of a spherical primary mirror. The paraxial focal point of the spherical mirror is aligned with the focal point of the whole system. The closest analog of the proposed optical system is the optical system of the Millimetron space observatory (Spektr-M). The physical aperture ratio of the proposed system is ten times that of the Millimetron telescope with the same overall dimensions. The proposed system rigorously satisfies the Abbe sine condition. The focal length of the system is 7070 mm, and the numerical aperture is 0.7071. The Airy disk diameter of the proposed system is more than ten times smaller than the diffraction circle of the Millimetron telescope. The angular field of the system is determined by the selected image quality criteria and specific wavelength.

Molecular clouds are a crucial stage in the lifecycle of a star, and the far ultraviolet (FUV) spectral range is a prime observation band. Hyperion is an FUV space telescope that investigates the birth clouds of stars using a high-resolution spectrometer. To meet the scientific requirements, we developed and evaluated a spectrometer that covers the 140.5 to 164.5 nm wavelength range with a spectral resolution higher than 30,000. We employed on-axis and on-plane dispersive optic layouts to control the aberration from a large aspect ratio slit (10  arcmin  ×  2.5  arcsec, aspect ratio R  =  240). The cross-dispersion isolates three orders from the échelle grating (n  =    −  19, −18, and −17), and the subsequent two-mirror freeform imaging optics form a two-dimensional spectral distribution on a 50  mm  ×  50  mm detector array. The geometrical and spectral performances of this innovative design are evaluated.

Fiber positioning technology is widely used in spectroscopic telescopes, and the accurate identification of the fiber position on the focal plane directly affects the efficiency of the astronomical spectrum. At present, fiber positioning usually uses the “back-illuminate” technique to illuminate one end of the fiber. The other end of the fiber is used for detection. The fiber could be stressed or twisted during locator motion, resulting in a difference between the detected fiber position and the actual fiber core. However, the fiber-optic back-illuminated device in the spectrometer system increases the complexity of the system and the time loss of fiber positioning. This paper attempts to use a new method combining image processing with deep learning to identify the fiber ferrule by the front-illuminated method. We built an experimental platform in the lab and experimented with a CMOS camera and telecentric lens. We tested the repeated errors and displacement measurement errors of the two methods. A series of comparative experimental results show that the final detection accuracy of this method can meet the needs of optical fiber positioning in the laboratory, although it has not yet reached the accuracy of the back-illuminated approach. In the future, if the light source and fiber ferrule were specifically designed for the front-illuminated method, its accuracy could be further improved.

The development of the Skipper-charge-coupled devices (Skipper-CCDs) has been a major technological breakthrough for sensing very weak ionizing particles. The sensor allows to reach the ultimate sensitivity of silicon material as a charge signal sensor by unambiguous determination of the charge signal collected by each cell or pixel, even for single electron–hole pair ionization. Extensive use of the technology was limited by the lack of specific equipment to operate the sensor at the ultimate performance. A simple, single-board Skipper-CCD controller designed by the authors is presented and aimed for the operation of the detector in high sensitivity scientific applications. Our article describes the main components and functionality of the so-called low threshold acquisition controller together with experimental results when connected to a Skipper-CCD sensor. Measurements show unprecedented deep subelectron noise of 0.039  erms−/pix by nondestructively measuring the charge 5000 times in each pixel.

The Dual-channel Extreme Ultraviolet Continuum Experiment (DEUCE) is a rocket-borne, ultraviolet spectrograph specifically designed to obtain the first flux-calibrated spectra of nearby B stars ϵ and β Canis Majoris (CMa) across the Lyman limit at 912 Å. These observations will help quantify the contribution of such stars to modern ionization in the intergalactic medium. The payload operates in two channels over the 700 to 1150 Å extreme ultraviolet/far ultraviolet (EUV/FUV) bandpass, with resolving powers of 180 (1850) and net effective areas (including slit transmission) of 4  cm² (  .  15  cm²) in its large and small-slit channels, respectively. DEUCE features a large format 200  ×  200  mm² low-noise atomic layer deposition-activated microchannel plate detector of the type baselined for the Large Ultraviolet Optical Infrared (LUVOIR) Surveyor and has demonstrated its flight performance. DEUCE has obtained the first flux-calibrated spectrum of ϵ CMa from 730 to 895 Å. This paper outlines the science objectives, instrument design, calibration, launches, and observations of the mission.

Mid-resolution Infrared Astronomical Spectrograph (MIRADAS) is a near-infrared multi-object echelle spectrograph for Gran Telescopio de Canarias. It selects targets from a 5-arc min field of view using up to 12 deployable probe arms with pick-off mirror optics. The focal plane where the probe arms move has a diameter around 250 mm. The specific geometry of the probe arms requires an optimized collision detection algorithm for the determination of the target assignment and the trajectories determination. We present the general polygonal chain intersection algorithm, which is used to detect the possible collisions and avoid them. It is a generalization of the Polygonal Chain Intersection algortihm, allowing to work with vertical segments, providing a solution for the intersection of any class of polygons. Its use has reduced the time required to detect the collisions between 3 and 4 times compared with a naive solution when used in MIRADAS.

This paper introduces an analytical method to calculate segment-level wavefront error (WFE) tolerances to enable the detection of faint extra-solar planets using segmented-aperture telescopes in space. This study provides a full treatment of the case of spatially uncorrelated segment phasing errors for segmented telescope coronagraphy, which has so far only been approached using ad-hoc Monte Carlo (MC) simulations. Instead of describing the wavefront tolerance globally for all segments, our method produces spatially dependent requirement maps. We relate the statistical mean contrast in the coronagraph dark hole to the standard deviation of the WFE of each individual segment on the primary mirror. This statistical framework for segment-level tolerancing extends the Pair-based Analytical model for Segmented Telescope Imaging from Space (PASTIS), which is based uniquely on a matrix multiplication for the optical propagation. We confirm our analytical results with MC simulations of end-to-end optical propagations through a coronagraph. Comparing our results for the Apodized Pupil Lyot Coronagraph designs for the Large Ultraviolet Optical Infrared telescope to previous studies, we show general agreement but we provide a relaxation of the requirements for a significant subset of segments in the pupil. These requirement maps are unique to any given telescope geometry and coronagraph design. The spatially uncorrelated segment tolerances we calculate are a key element of a complete error budget that will also need to include allocations for correlated segment contributions. We discuss how the PASTIS formalism can be extended to the spatially correlated case by deriving the statistical mean contrast and its variance for a non-diagonal aberration covariance matrix. The PASTIS tolerancing framework therefore brings a new capability that is necessary for the global tolerancing of future segmented space observatories.

The KM3NeT infrastructure consists of two deep-sea neutrino telescopes being deployed in the Mediterranean Sea. The telescopes will detect extraterrestrial and atmospheric neutrinos by means of the incident photons induced by the passage of relativistic charged particles through the seawater as a consequence of a neutrino interaction. The telescopes are configured in a three-dimensional grid of digital optical modules, each hosting 31 photomultipliers. The photomultiplier signals produced by the incident Cherenkov photons are converted into digital information consisting of the integrated pulse duration and the time at which it surpasses a chosen threshold. The digitization is done by means of time to digital converters (TDCs) embedded in the field programmable gate array of the central logic board. Subsequently, a state machine formats the acquired data for its transmission to shore. We present the architecture and performance of the front-end firmware consisting of the TDCs and the state machine.

Electron multiplying charge-coupled devices (EMCCDs) are a variant of standard CCD technology capable of single-optical photon counting at MHz pixel readout rates. For photon counting, thermal dark signal and clock-induced charge (CIC) are the dominant source of noise and must be minimized to reduce the likelihood of coincident events. Thermal dark signal is reduced to low levels through cooling or operation in inverted mode (pinning). However, mitigation of CIC requires precise tuning of both parallel and serial clock waveforms. Here, we present a detailed study of CIC within Teledyne-e2v EMCCDs with a goal of better understanding the physical mechanisms that dominate CIC production in both noninverted and inverted mode operations (IMO). Measurements are presented as a function of parallel and serial clock timings, clock amplitudes, and device temperature. The effects of radiation damage and annealing are also discussed. A widely accepted view is that CIC is signal generated through impact ionization of energetic holes as the clock phase is driven high. While this explanation holds for IMO, we propose that the majority of CIC generated in noninverted mode is in fact due to a secondary effect of light emission from hot carriers. The information from this study is then used to optimize CIC on Teledyne e2v CCD201s operating at 1-MHz pixel rate in NIMO. For the CCD201, we obtained total CIC levels as low as 6.9  ×  10^−  4  e⁻  /  pix  /  frame with ≥90  %   detective quantum efficiency. We conclude with proposals to further reduce CIC based upon modifications to clocking schemes and device architecture.

Charge-coupled device (CCD)-based technologies exposed to high-energy radiation are susceptible to the formation of stable defects within the charge transfer channel that defer signal to subsequent pixels and limit the lifetime of the detector. Performance degradation due to these defects depends upon the interplay between the clock timings used to operate the device and the properties of defects introduced by irradiation. Characterization of both the type and number of post-irradiation defects makes it possible to minimize charge loss though the appropriate selection of clock timings for a given operating temperature. This technique has the potential to increase nominal mission lifetimes by several years for CCD-based instruments and is of particular significance to electron multiplying charge-coupled devices (EMCCDs) for photon counting applications where the effect of charge traps on low signal levels is expected to be most severe. We present a study of charge traps within CCDs, specifically within EMCCDs irradiated at room temperature to proton fluences up to and including 1.45  ×  10¹⁰  p⁺  /  cm² (74 MeV). Defects are characterized through the “single-trap pumping” technique, with clocking schemes specifically designed for the 2-phase pixel architecture of the EMCCD. Five dominant trap species are thought to be introduced by the irradiation, the Si-E center, Si-A center, double and single acceptor charge states of the silicon divacancy (VV^{−    −}, VV⁻), and an as yet unidentified defect referred to here as the Si-U center (the “unknown” trap). Energy-level and cross-section values are presented that allow inference of the defect landscape for a range of proton fluences and operating temperatures. While the study focuses specifically on EMCCDs, in more general terms, the results for trap properties are interpreted as being applicable to all CCD types following irradiation and can serve as a foundation for future charge loss correction and optimization techniques.

As the crisis of climate change affects more people every year and leads to more severe weather patterns with unprecedented socio-economical consequence, all actors on the planet need to understand their responsibility and contribute to solving this generational problem. To tackle this issue, individuals and corporations first need to assess their carbon footprint, which then represents the groundwork for the future implementation of significant changes required to reduce that footprint. We present the carbon emissions attributed to the Canada–France–Hawaii Telescope (CFHT) for the year 2019. We partnered with CarbonBuddy and followed their method to break down the greenhouse gas (GHG) emissions of various activities at CFHT for the entire year of 2019: air travel in and out of state, ground vehicle usage, electricity consumption, and other fossil fuel utilization. The total GHG emissions of CFHT for the year 2019 amount to about 749 tons of CO₂ equivalent, which corresponds to more than 16 tons per employee. About 63% of the emissions are related to electricity usage at the summit facility, about 25% to out-of-state travel, about 6% to the use of our fleet of vehicles, and about 5% to electricity usage at headquarters. We show that significant improvements have occurred in the recent past at CFHT, with the installation of solar panels and a remarkable reduction in electricity consumption at headquarters. We list suggestions to further decrease the GHG emissions in the short to long term: offset current emissions by support local projects, invest in more efficient equipment, and establish environmentally friendly habits. The fundamental work presented will facilitate the official planning at CFHT for a drastic reduction in GHG emissions with the goal to meet the objectives laid out in the 2015 Paris Accord. It will also support the design of the Maunakea Spectroscopic Explorer (MSE), the future transformation of CFHT, and allow the project to seize this opportunity and incorporate the fight against climate change as one of its core missions. By choosing to implement those changes, CFHT and MSE can become part of the solution to climate change and lead the way, locally and in the world of astronomy.

Contamination is always troublesome in spacecraft development, but it has yet to be investigated because outgassing, transportation, deposition, and re-emission largely depend on spacecraft design. Designing spacecraft requires an accurate estimate of contaminant emission and deposition. Particularly for today’s sophisticated spacecraft, analytical tools would be indispensable—but current simulations need to be improved. Our study addresses the first phase in the occurrence of contamination: improving the outgassing model. We focused on diffusion-limited phenomena because the diffusion rate of outgassing molecules in materials is thought to be much slower than their desorption rate at the surface. A new outgassing test method and analytical procedure was originally devised for extracting the parameters of the diffusion model. In comparing the desorption and diffusion models, we developed a model for the emission of outgassing molecules based on the diffusion theory and updated some functions of Japan’s Spacecraft Induced Contamination Environment analysis software (J-SPICE). From this, we developed J-SPICE2 and installed the diffusion model to the software for calculating outgassing behavior.

Superconducting transition-edge sensors (TESs) carried by x-ray telescopes are powerful tools for the study of neutron stars and black holes. Several methods, such as optimal filtering or principal component analysis, have already been developed to analyze x-ray data from these sensors. However, these techniques may be hard to implement in space. Our goal is to develop a lower-computational-cost technique that optimizes energy and time resolution when x-ray photons are detected by a TES. Current pulses, in TESs, exhibit a non-linear response to photon energy. Therefore, at low energies, we focus on the current-pulse height, whereas at high energies, we consider the current-pulse width, to retrieve energy and arrival time of x-ray photons. For energies between 0.1 and 30 keV and with a sampling rate of 195 kHz, we obtain an energy resolution (full-width at half-maximum) between 1.32 and 2.98 eV. We also get an arrival-time resolution (full-duration at half-maximum) between 163 and 3.85 ns. To improve the accuracy of these results, it will be essential to get a thorough description of non-stationary noise in a TES and develop a robust on-board identification method of pile-up events.

Astrobot swarms are used to capture astronomical signals to generate the map of the observable universe for the purpose of dark energy studies. The convergence of each swarm in the course of its coordination has to surpass a particular threshold to yield a satisfactory map. The current coordination methods do not always reach desired convergence rates. Moreover, these methods are so complicated that one cannot formally verify their results without resource-demanding simulations. Thus we use support vector machines to train a model that can predict the convergence of a swarm based on the data of previous coordination of that swarm. Given a fixed parity, i.e., the rotation direction of the outer arm of an astrobot, corresponding to a swarm, our algorithm reaches a better predictive performance compared to the state of the art. Additionally, we revise our algorithm to solve a more generalized convergence prediction problem according to which the parities of astrobots may differ. We present the prediction results of a generalized scenario, associated with a 487-astrobot swarm, which are interestingly efficient and collision free given the excessive complexity of this scenario compared to the constrained one.

Daniel K. Inouye Solar Telescope (DKIST) is designed to deliver accurate spectropolarimetric solar data across a wide wavelength range, covering a large field of view simultaneously using multiple facility instruments for solar disk, limb, and coronal observations. We show successful design and implementation of National Solar Observatory Coudé Laboratory Spectropolarimeter, a custom metrology tool for efficient continuous broadband polarization calibration of the telescope mirrors through a coudé laboratory focus. We compare multiple fitting techniques for the 10 to >140 variable DKIST system polarization models. We compare results with the first DKIST solar calibration observations and find small thermally forced retardance changes of ±0.2  deg and ±0.5  deg for two separate SiO₂ retarders. Modulation matrices derived are stable to <  ±  0.01 per element during the first on-Sun calibration tests. We achieve good fit agreement to our metrology-based model over a 390- to 1600-nm bandpass. The solutions are robust and efficient using only 10 input Stokes vectors from elliptical calibration retarders. We developed a custom polarizer assembly used with metrology tools to orient the DKIST polarization coordinates to better than 0.1-deg clocking angle.

Adaptive optics (AO) has become an indispensable tool for ground-based telescopes to mitigate atmospheric seeing and obtain high angular resolution observations. Predictive control aims to overcome latency in AO systems: the inevitable time delay between wavefront measurement and correction. A current method of predictive control uses the empirical orthogonal functions (EOFs) framework borrowed from weather prediction, but the advent of modern machine learning and the rise of neural networks (NNs) offer scope for further improvement. Here, we evaluate the potential application of NNs to predictive control and highlight the advantages that they offer. We first show their superior regularization over the standard truncation regularization used by the linear EOF method with on-sky data before demonstrating the NNs’ capacity to model nonlinearities on simulated data. This is highly relevant to the operation of pyramid wavefront sensors (PyWFSs), as the handling of nonlinearities would enable a PyWFS to be used with low modulation and deliver extremely sensitive wavefront measurements.

We describe an approach to coronagraphic focal-plane wavefront control that utilizes gradient-based nonlinear optimization along with analytical gradients obtained with algorithmic differentiation to find deformable mirror solutions. In addition to eliminating the cost of calculating a high-dimensional finite-difference Jacobian matrix, we show that this approach leads to improved asymptotic computational efficiency. With very high-actuator deformable mirrors such as the 128  ×  128 actuators baselined for the Large UV/Optical/IR Surveyor mission concept, the proposed algorithm reduces memory consumption by approximately 95  %   compared to a Jacobian-based algorithm.

This erratum corrects errors in Table 2.