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The Origins Space Telescope (OST) is a NASA study for a large satellite mission to be submitted to the 2020 Decadal Review. The proposed satellite has a fleet of instruments including the HEterodyne Receivers for OST (HERO). HERO is designed around the quest to follow the trail of water from the ISM to disks around protostars and planets. HERO will perform high-spectral resolution measurements with 2x9 pixel focal plane arrays at any frequency between 468GHz to 2,700GHz (617 to 111 μm). HERO builds on the successful Herschel/HIFI heritage, as well as recent technological innovations, allowing it to surpass any prior heterodyne instrument in terms of sensitivity and spectral coverage.

The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, ARIEL, has been selected to be the next M4 space mission in the ESA Cosmic Vision programme. From launch in 2028, and during the following 4 years of operation, ARIEL will perform precise spectroscopy of the atmospheres of about 1000 known transiting exoplanets using its metre-class telescope, a three-band photometer and three spectrometers that will cover the 0.5 μm to 7.8 μm region of the electromagnetic spectrum. The payload is designed to perform primary and secondary transit spectroscopy, and to measure spectrally resolved phase curves with a stability of < 100 ppm (goal 10 ppm). Observing from an L2 orbit, ARIEL will provide the first statistically significant spectroscopic survey of hot and warm planets. These are an ideal laboratory in which to study the chemistry, the formation and the evolution processes of exoplanets, to constrain the thermodynamics, composition and structure of their atmospheres, and to investigate the properties of the clouds.

The next generation of space-borne instruments for far infrared astronomical spectroscopy will utilize large diameter, cryogenically cooled telescopes in order to achieve unprecedented sensitivities. Low background, ground-based cryogenic facilities are required for the cryogenic testing of materials, components and subsystems. The University of Lethbridge Test Facility Cryostat (TFC) is a large volume, closed cycle, 4 K cryogenic facility, developed for this purpose. This paper discusses the design and performance of the facility and associated metrology instrumentation, both internal and external to the TFC. Additionally, an apparatus for measuring the thermal and mechanical properties of carbon-fiber-reinforced polymers is presented.

Astronomy is driven by the quest for higher sensitivity and improved angular resolution in order to detect fainter or smaller objects. The far-infrared to submillimeter domain is a unique probe of the cold and obscured Universe, harboring for instance the precious signatures of key elements such as water. Space observations are mandatory given the blocking effect of our atmosphere. However the methods we have relied on so far to develop increasingly larger telescopes are now reaching a hard limit, with the JWST illustrating this in more than one way (e.g. it will be launched by one of the most powerful rocket, it requires the largest existing facility on Earth to be qualified). With the Thinned Aperture Light Collector (TALC) project, a concept of a deployable 20 m annular telescope, we propose to break out of this deadlock by developing novel technologies for space telescopes, which are disruptive in three aspects: • An innovative deployable mirror whose topology, based on stacking rather than folding, leads to an optimum ratio of collecting area over volume, and creates a telescope with an eight times larger collecting area and three times higher angular resolution compared to JWST from the same pre-deployed volume; • An ultra-light weight segmented primary mirror, based on electrodeposited Nickel, Composite and Honeycomb stacks, built with a replica process to control costs and mitigate the industrial risks; • An active optics control layer based on piezo-electric layers incorporated into the mirror rear shell allowing control of the shape by internal stress rather than by reaction on a structure. We present in this paper the roadmap we have built to bring these three disruptive technologies to technology readiness level 3. We will achieve this goal through design and realization of representative elements: segments of mirrors for optical quality verification, active optics implemented on representative mirror stacks to characterize the shape correction capabilities, and mechanical models for validation of the deployment concept. Accompanying these developments, a strong system activity will ensure that the ultimate goal of having an integrated system can be met, especially in terms of (a) scalability toward a larger structure, and (b) verification philosophy.

The Probe of Inflation and Cosmic Origins (PICO) is a NASA-funded study of a Probe-class mission concept. The top-level science objectives are to probe the physics of the Big Bang by measuring or constraining the energy scale of inflation, probe fundamental physics by measuring the number of light particles in the Universe and the sum of neutrino masses, to measure the reionization history of the Universe, and to understand the mechanisms driving the cosmic star formation history, and the physics of the galactic magnetic field. PICO would have multiple frequency bands between 21 and 799 GHz, and would survey the entire sky, producing maps of the polarization of the cosmic microwave background radiation, of galactic dust, of synchrotron radiation, and of various populations of point sources. Several instrument configurations, optical systems, cooling architectures, and detector and readout technologies have been and continue to be considered in the development of the mission concept. We will present a snapshot of the baseline mission concept currently under development., 11 pages, 5 Figure, submitted to SPIE, Proceedings of the Conference on Astronomical Telescopes and Instrumentation, 2018

The Probe of Inflation and Cosmic Origins (PICO) is a probe-class mission concept currently under study by NASA. PICO will probe the physics of the Big Bang and the energy scale of inflation, constrain the sum of neutrino masses, measure the growth of structures in the universe, and constrain its reionization history by making full sky maps of the cosmic microwave background with sensitivity 80 times higher than the Planck space mission. With bands at 21-799 GHz and arcmin resolution at the highest frequencies, PICO will make polarization maps of Galactic synchrotron and dust emission to observe the role of magnetic fields in Milky Way's evolution and star formation. We discuss PICO's optical system, focal plane, and give current best case noise estimates. The optical design is a two-reflector optimized open-Dragone design with a cold aperture stop. It gives a diffraction limited field of view (DLFOV) with throughput of 910 square cm sr at 21 GHz. The large 82 square degree DLFOV hosts 12,996 transition edge sensor bolometers distributed in 21 frequency bands and maintained at 0.1 K. We use focal plane technologies that are currently implemented on operating CMB instruments including three-color multi-chroic pixels and multiplexed readouts. To our knowledge, this is the first use of an open-Dragone design for mm-wave astrophysical observations, and the only monolithic CMB instrument to have such a broad frequency coverage. With current best case estimate polarization depth of 0.65 microK(CMB}-arcmin over the entire sky, PICO is the most sensitive CMB instrument designed to date., 12 pages, 8 Figures, Submitted to SPIE, Proceedings of the 2018 Conference on Astronomical Telescopes and Instrumentation

International audience; Euclid, an ESA mission designed to characterise dark energy and dark matter, passed its Mission Critical Design Review in November 2018. It was demonstrated that the project is ready to start integration and test of the main systems, and that it has the ability to fulfil its top-level mission requirements. In addition, based on the performances at M-CDR, the scientific community has verified that the science requirements can be achieved for the Weak Lensing and Galaxy Clustering dark energy probes, namely a dark energy Figure of Merit of 400 and a 2% accuracy in the growth factor exponent gamma. We present the status of the main elements of the Euclid mission in the light of the demanding high optical performance which is the essential design driver is the to meet the scientific requirements. We include the space segment comprising of a service module and payload module hosting the telescope and its two scientific instruments, and the ground segment, which encompasses the operational and science ground segment. The elements for the scientific success of the mission for a timely release of the data are shortly presented: the processing and calibration of the data, and the design of the sky survey. Euclid is presently on schedule for a launch in September 2022.

Coronagraph instruments on future space telescopes will enable the direct detection and characterization of Earth-like exoplanets around Sun-like stars for the first time. The quest for the optimal optical coronagraph designs has made rapid progress in recent years thanks to the Segmented Coronagraph Design and Analysis (SCDA) initiative led by the Exoplanet Exploration Program at NASA's Jet Propulsion Laboratory. As a result, several types of high-performance designs have emerged that make use of dual deformable mirrors to (1) correct for optical aberrations and (2) suppress diffracted starlight from obstructions and discontinuities in the telescope pupil. However, the algorithms used to compute the optimal deformable mirror surface tend to be computationally intensive, prohibiting large scale design surveys. Here, we utilize the Fast Linearized Coronagraph Optimizer (FALCO), a tool that allows for rapid optimization of deformable mirror shapes, to explore trade-offs in coronagraph designs for obstructed and segmented space telescopes. We compare designs for representative shaped pupil Lyot and vortex coronagraphs, two of the most promising concepts for the LUVOIR space mission concept. We analyze the optical performance of each design, including their throughput and ability to passively suppress light from partially resolved stars in the presence of low-order aberrations. Our main result is that deformable mirror based apodization can sufficiently suppress diffraction from support struts and inter-segment gaps whose widths are on the order of $\sim$0.1% of the primary mirror diameter to detect Earth-sized planets within a few tens of milliarcseconds from the star., To appear in the Proceedings of the SPIE, vol. 10698

One of the major goals of the exoplanet community in the coming decades is to detect Earth-like exoplanets (exoEarths) and look for biomarkers in their atmospheres. High-dispersion coronagraphy (HDC) may allow detection and characterization to be done simultaneously, as well as relax the starlight suppression requirements of the telescope and coronagraph. However, similar to other direct imaging techniques, HDC faces challenging thermal and/or exozodiacal background levels. In this paper, we present simulations of coronagraphic observations using a variety of space telescope apertures ranging in diameter from 1 to 15 m, specifically incorporating thermal and exozodiacal background. We investigate the effects of instrument temperature and aperture on the maximum usable wavelength, as well as the effects of exozodiacal disk inclination and thickness on observational SNR. We then identify the spectral resolutions which maximize observational SNR subject to detector noise and the required starlight suppression levels for the detection of various potential biomarker molecules (H_2O, O_2, CO_2, and CH_4).

The HabEx (Habitable Exoplanet) space telescope mission concept carries two complementary optical systems as part of its baseline design, a coronagraph and a starshade, that are designed to detect and characterize planetary systems around nearby stars. The starshade is an external occulter which would be 72 m in diameter and fly some 124,000 km ahead of the telescope. A starshade instrument on board the telescope enables formation flying to maintain the starshade within 1 m of the line of sight to the star. The starshade instrument has various modes, including imaging from the near UV through to the near infrared and integral field spectroscopy in the visible band. The coronagraph would provide imaging and integral field spectroscopy in the visible band and would reach out to 1800 nm for low resolution spectroscopy in the near infrared. To provide the necessary stability for the coronagraph, the telescope would be equipped with a laser metrology system allowing measurement and control of the relative positions of the principal mirrors. In addition, a fine guidance sensor is needed for precision attitude control. The requirements for telescope stability for coronagraphy are discussed. The design and requirements on the starshade will also be discussed.

The primary science goal of the Habitable Exoplanet Imaging Mission (HabEx), one of four candidate flagship missions under investigation, is to image and spectrally characterize Earth-like exoplanets. It is well known that pupil obscurations degrade coronagraphic performance and complicate coronagraph design, so HabEx is planned to have an off-axis, unobscured primary mirror. We utilize the circular symmetry of the aperture to investigate 1D-radial coronagraph optimization methods that are prohibitively time-consuming or intractable in 2D, such as diffractive pupil remapping and concurrent, multi-plane optimization. We also directly constrain sensitivities to dynamic, low-order Zernike aberrations, which are separable in polar coordinates and can thus be propagated as 1D-radial integrals. The mask technologies in our designs claim heritage from the extensive modeling and testbed experiments performed by the Wide-Field Infrared Survey Telescope (WFIRST) Coronagraph Instrument (CGI) project. In this paper, we detail our optimization methods and outline future work to complete our design survey.

The Fast Linearized Coronagraph Optimizer (FALCO) is an open-source toolbox of routines for coronagraphic focal plane wavefront correction. The goal of FALCO is to provide a free, modular framework for the simulation or testbed operation of several common types of coronagraphs. FALCO includes routines for pair-wise probing estimation of the complex electric field and Electric Field Conjugation (EFC) control, and we ask the community to contribute other wavefront correction algorithms. FALCO utilizes and builds upon PROPER, an established optical propagation library. The key innovation in FALCO is the rapid computation of the linearized response matrix for each deformable mirror (DM), which facilitates re-linearization after each control step for faster DM-integrated coronagraph design and wavefront correction experiments. FALCO is freely available as source code in MATLAB at github.com/ajeldorado/falco-matlab and will be available later this year in Python 3 at github.com/ajeldorado/falco-python.

Deformable mirrors (DMs) are increasingly becoming part of nominal coronagraph designs, such as the hybrid Lyot coronagraph, in addition to their role counteracting optical aberrations. Previous studies have investigated the effects of the inter-DM Fresnel number on achievable contrast, throughput, and tip/tilt sensitivity for apodized coronagraphs augmented with DMs to suppress diffraction from struts and segment gaps. In this paper, we build upon that previous work by directly suppressing tip/tilt sensitivity with the controller, both for coronagraphs with and without apodizers. We also explore the effects of other important design parameters such as actuator density and tip/tilt controller weighting on performance. These comprehensive coronagraph design studies are enabled by the Fast Linearized Coronagraph Optimizer (FALCO) software toolbox, which provides rapid re-calculation of the DM response matrix for a variety of coronagraphs.

The OSS on the Origins Space Telescope is designed to decode the cosmic history of nucleosynthesis, star formation, and supermassive black hole growth with wide-area spatial-spectral 3-D surveys across the full 25 to 590 micron band. Six wideband grating modules combine to cover the full band at R=300, each couples a long slit with 60-190 beams on the sky. OSS will have a total of 120,000 background-limited detector pixels in the six 2-D arrays which provide spatial and spectral coverage. The suite of grating modules can be used for pointed observations of targets of interest, and are particularly powerful for 3-D spectral spectral surveys. To chart the transition from interstellar material, particularly water, to planetary systems, two high-spectral-resolution modes are included. The first incorporates a Fourier-transform spectrometer (FTS) in front of the gratings providing resolving power of 25,000 (δv = 12 km/s) at 179 µm to resolve water emission in protoplanetary disk spectra. The second boosts the FTS capability with an additional etalon (Fabry-Perot interferometer) to provide 2 km/s resolution in this line to enable detailed structural studies of disks in the various water and HD lines. Optical, thermal, and mechanical designs are presented, and the system approach to the detector readout enabling the large formats is described.

The Habitable-Exoplanet Observatory (HabEx) is a candidate flagship mission being studied by NASA and the astrophysics community in preparation of the 2020 Decadal Survey. The first HabEx mission concept that has been studied is a large (~4m) diffraction-limited optical space telescope, providing unprecedented resolution and contrast in the optical, with extensions into the near ulttraviolet and near infrared domains. We report here on our team’s efforts in defining a scientifically compelling HabEx mission that is technologically executable, affordable within NASA’s expected budgetary envelope, and timely for the next decade. We also briefly discuss our plans to explore less ambitious, descoped missions relative to the primary mission architecture discussed here.

The Origins Space Telescope (OST) is the mission concept for the Far-Infrared Surveyor, one of the four science and technology definition studies of NASA Headquarters for the 2020 Astronomy and Astrophysics Decadal survey. "Concept-1" is a cold (4 K) 9 m space telescope with five instruments, while "concept 2" consists of a cold 5.9 m telescope and four instruments, providing imaging and spectroscopic capabilities between 5μm and 600μm. The sensitivity provided by the observatory will be a three to four orders of magnitude improvement over currently achieved observational capabilities, allowing to address a wide range of new and so far inaccessible scientific questions, ranging from bio-signatures in the atmospheres of exo-planets to the production of the first metals in the universe right after the end of re-ionization. Here we present the Far Infrared Imager and Polarimeter (FIP) for OST. The camera will cover four bands, 50μm, 100μm, 250μm, and 500μm. In the "concept 1" version of the instrument, FIP will allow for differential polarimetry with the ability to observe two colors simultaneously, while all four bands can be observed simultaneously in total power mode. The confusion limit in the total power mode will be reached in only 8 ms at 500μm, while at 50μm the source density in the sky is so low that at OST's angular resolution of (see manuscript for symbol) 2" in this band the source confusion limit will only be reached after about two hours of integration with the "concept-2" version of FIP ("concept-1" FIP will not be confusion limited at 50m, no matter how long it integrates). Science topics that can be addressed by the camera include, but are not limited to, galactic and extragalactic magnetic field studies, deep galaxy surveys, and outer Solar System objects.

The Galaxy Evolution Probe (GEP) is a concept for a mid and far-infrared space observatory designed to survey sky for star-forming galaxies from redshifts of z = 0 to beyond z = 4. Furthering our knowledge of galaxy formation requires uniform surveys of star-forming galaxies over a large range of redshifts and environments to accurately describe star formation, supermassive black hole growth, and interactions between these processes in galaxies. The GEP design includes a 2 m diameter SiC telescope actively cooled to 4 K and two instruments: (1) An imager to detect star-forming galaxies and measure their redshifts photometrically using emission features of polycyclic aromatic hydrocarbons. It will cover wavelengths from 10 to 400 μm, with 23 spectral resolution R = 8 filter-defined bands from 10 to 95 μm and five R = 3.5 bands from 95 to 400 μm. (2) A 24 – 193 μm, R = 200 dispersive spectrometer for redshift confirmation, identification of active galactic nuclei, and interstellar astrophysics using atomic fine-structure lines. The GEP will observe from a Sun-Earth L2 orbit, with a design lifetime of four years, devoted first to galaxy surveys with the imager and second to follow-up spectroscopy. The focal planes of the imager and the spectrometer will utilize KIDs, with the spectrometer comprised of four slit-coupled diffraction gratings feeding the KIDs. Cooling for the telescope, optics, and KID amplifiers will be provided by solar-powered cryocoolers, with a multi-stage adiabatic demagnetization refrigerator providing 100 mK cooling for the KIDs.

The largest source of noise in exoplanet and brown dwarf photometric time series made with Spitzer/IRAC is the coupling between intra-pixel gain variations and spacecraft pointing fluctuations. Observers typically correct for this systematic in science data by deriving an instrumental noise model simultaneously with the astrophysical light curve and removing the noise model. Such techniques for self-calibrating Spitzer photometric datasets have been extremely successful, and in many cases enabled near-photon-limited precision on exoplanet transit and eclipse depths. Self-calibration, however, can suffer from certain limitations: (1) temporal astrophysical signals can become aliased as part of the instrument model; (2) for some techniques adequate model estimation often requires a high degree of intra-pixel positional redundancy (multiple samples with nearby centroids) over long time spans; (3) many techniques do not account for sporadic high frequency telescope vibrations that smear out the point spread function. We have begun to build independent general-purpose intra-pixel systematics removal algorithms using three machine learning techniques: K-Nearest Neighbors (with kernel regression), Random Decision Forests, and Artificial Neural Networks. These methods remove many of the limitations of self-calibration: (1) they operate on a dedicated calibration database of approximately one million measurements per IRAC waveband (3.6 and 4.5 microns) of non-variable stars, and thus are independent of the time series science data to be corrected; (2) the database covers a large area of the "Sweet Spot, so the methods do not require positional redundancy in the science data; (3) machine learning techniques in general allow for flexibility in training with multiple, sometimes unorthodox, variables, including those that trace PSF smear. We focus in this report on the K-Nearest Neighbors with Kernel Regression technique. (Additional communications are in preparation describing Decision Forests and Neural Networks.)

The Origins Space Telescope (OST) mission concept study is the subject of one of the four science and technology definition studies supported by NASA Headquarters to prepare for the 2020 Astronomy and Astrophysics Decadal Survey. OST will survey the most distant galaxies to discern the rise of metals and dust and to unveil the co-evolution of galaxy and blackhole formation, study the Milky Way to follow the path of water from the interstellar medium to habitable worlds in planetary systems, and measure biosignatures from exoplanets. This paper describes the science drivers and how they drove key requirements for OST Mission Concept 2, which will operate between ~5 and ~600 microns with a JWST sized telescope. Mission Concept 2 for the OST study optimizes the engineering for the key science cases into a powerful and more economical observatory compared to Mission Concept 1.

The flux difference between a terrestrial exoplanet and a much brighter nearby star creates an enormous optical design challenge for space-based imaging systems. Coronagraphs are designed to block the star’s flux and obtain a high-dynamic-range image of the exoplanet. The contrast of an optical system is calculated using the point spread function (PSF). Contrast quantifies starlight suppression of an imaging system at a given separation of the two objects. Contrast requirements can be as small as 10^(−10) for earth-like planets. This work reports an analysis of the September 2017 Habitable Exoplanet Imaging Mission (HabEx) end-to-end optical system prescription for geometric and polarization aberrations across the 450 to 550 nm channel. The Lyot coronagraph was modeled with a vector vortex charge 6 mask but without adaptive optics (AO) to correct the phase of the Jones pupil. The detector plane irradiance was calculated for three states of the telescope/coronagraph system: (1) free of geometric and polarization aberrations; (2) isotropic mirror coatings throughout the end-toend system; and (3) isotropic mirrors with form birefringence on the primary mirror. For each of these three states the system response both with and without a coronagraph mask was calculated. Two merit functions were defined to quantify the system’s ability to attenuate starlight: (1) normalized polychromatic irradiance (NPI), and (2) starlight suppression factor (SSF). Both of these are dimensionless and their values are functions of position across the focal plane. The NPI is defined as the irradiance point-by-point across the detector plane with a coronagraph mask divided by the value of the on-axis irradiance without a coronagraph mask. The SSF is the irradiance point-by-point across the detector plane with a coronagraph mask divided by the pointby-point value of the irradiance across the detector plane without a coronagraph mask. Both the NPI and the SSF provide insights into coronagraph performance. Deviations from the aberration-free case are calculated and summarized in table 2. The conclusions are: (1) the HabEx optical system is well-balanced for both geometric and polarization aberrations; (2) the spatially dependent polarization reflectivity for the HabEx primary mirror should be specified to ensure the coating is isotropic; (3) AO to correct the two orthogonal polarization-dependent wavefront errors is essential.

A major science goal of future, large-aperture, optical space telescopes is to directly image and spectroscopically analyze reflected light from potentially habitable exoplanets. To accomplish this, the optical system must suppress diffracted light from the star to reveal point sources approximately ten orders of magnitude fainter than the host star at small angular separation. Coronagraphs with microdot apodizers achieve the theoretical performance needed to image Earth-like planets with a range of possible telescope designs, including those with obscured and segmented pupils. A test microdot apodizer with various bulk patterns (step functions, gradients, and sinusoids) and 4 different dot sizes (3, 5, 7, and 10 $��$m) made of small chrome squares on anti-reflective glass was characterized with microscopy, optical laser interferometry, as well as transmission and reflectance measurements at wavelengths of 600 and 800 nm. Microscopy revealed the microdots were fabricated to high precision. Results from laser interferometry showed that the phase shifts observed in reflection vary with the local microdot fill factor. Transmission measurements showed that microdot fill factor and transmission were linearly related for dot sizes >5 $��$m. However, anomalously high transmittance was measured when the dot size is, Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

The James Webb Space Telescope (JWST) telescope’s Secondary Mirror Assembly (SMA) and eighteen Primary Mirror Segment Assemblies (PMSAs) are each actively controlled in rigid body position via six hexapod actuators. Each of the PMSAs additionally has a radius of curvature actuator. The mirrors are stowed to the mirror support structure to survive the launch environment and then must be deployed 12.5 mm to reach the nominally deployed position before the Wavefront Sensing & Control (WFSC) alignment and phasing process begins. JWST requires testing of the full optical system in a Cryogenic Vacuum (CV) environment before launch. The cryo vacuum test campaign was executed in Chamber A at the Johnson Space Center (JSC) in Houston Texas. The test campaign consisted of an ambient vacuum test, a cooldown test, a cryo stable test at 65 Kelvin, a warmup test, and finally a second ambient vacuum test. Part of that test campaign was the functional and performance testing of the hexapod actuators on the flight mirrors. This paper will describe the testing that was performed on all 132 hexapod and radius of curvature actuators. The test campaign first tests actuators individually then tested how the actuators perform in the hexapod system. Telemetry from flight sensors on the actuators and measurements from external metrology devices such as interferometers, photogrammetry systems and image analysis was used to demonstrate the performance of the JWST actuators. The mirror move commanding process was exercised extensively during the JSC CV test and many examples of accurately commanded moves occurred. The PMSA and SMA actuators performed extremely well during the JSC CV test, and we have demonstrated that the actuators are fully functional both at ambient and cryo temperatures and that the mirrors will go to their commanded positions with the accuracy needed to phase and align the telescope.

HabEx Architecture A is a 4m unobscured telescope mission concept optimized for direct imaging and spectroscopy of potentially habitable exoplanets, and also enables a wide range of general astrophysics science. The exoplanet detection and characterization drives the enabling core technologies. A hybrid starlight suppression approach of a starshade and coronagraph diversifies technology maturation risk. In this paper we assess these exoplanet-driven technologies, including elements of coronagraphs, starshades, mirrors, jitter mitigation, wavefront control, and detectors. By utilizing high technology readiness solutions where feasible, and identifying required technology development that can begin early, HabEx will be well positioned for assessment by the community in 2020 Astrophysics Decadal Survey.

We present a database of reduced data for all staring mode observations taken with the Infrared Array Camera (IRAC) during the Spitzer warm mission to monitor instrument performance, predict future instrument performance, and facilitate exoplanet and brown dwarf science. Our motivation is to be informed so that we can mitigate the impact of changing thermal conditions on science. Monitoring current trends allows us to predict future instrument performance and to adjust our recommended suite of best practices and calibrations accordingly. From this database we show that instrumental effects detrimental to high precision photometry either remain stable or improve. A uniform reduction of all IRAC light curves has never before been published, and will enable powerful science including accurate comparative studies of exoplanets and brown dwarfs. IRAC has been performing well throughout the warm mission and we expect performance to remain excellent.

The extragalactic background light (EBL) is the integrated emission from all objects outside of the Milky Way galaxy. Imprinted by the history of stellar emission, the EBL in the near infrared traces light back to the birth of the first stars in the Universe and can allow tight constraints on structure formation models. Recent studies using data from the Spitzer Space Telescope and the first Cosmic Infrared Background ExpeRiment (CIBER-1) find that there are excess fluctuations in the EBL on large scales which have been attributed to either high redshift galaxies and quasars, or to stars that were stripped from their host galaxies during merging events. To help disentangle these two models, multi-wavelength data can be used to trace their distinctive spectral features. Following the success of CIBER-1, CIBER-2 is designed to identify the sources of the EBL excess fluctuations using data in six wavebands covering the optical and near infrared. The experiment consists of a cryogenic payload and is scheduled to launch four times on a recoverable sounding rocket. CIBER-2 has a 28.5 cm telescope coupled with an optics system to obtain wide-field images in six broad spectral bands between 0.5 and 2.5 μm simultaneously. The experiment uses 2048 × 2048 HAWAII-2RG detector arrays and a cryogenic star tracker. A prototype of the cryogenic star tracker is under construction for a separate launch to verify its performance and star tracking algorithm. The mechanical, optical, and electrical components of the CIBER-2 experiment will have been integrated into the payload by mid-2018. Here we present the final design of CIBER-2 and our team’s instrument characterization efforts. The design and analysis of the optical focus tests will be discussed. We also report on the performance of CIBER-2 support systems, including the cooling mechanisms and deployable components. Finally, we outline the remaining tasks required to prepare the payload for launch.

Diffraction effects of large segmented mirror gaps and secondary mirror support struts produce diffraction peaks or flares that are a detriment to exoplanet detection. In this paper we present detailed parametric diffraction analyses of an innovative “Pinwheel Pupil” segmented mirror concept utilizing curved segment gaps and secondary support struts that can potentially eliminate these diffraction flares that can obscure a faint exoplanet image. The resulting numerical diffraction performance predictions are quantitatively compared to that of both ideal monolithic circular pupils and classical annular pupils with straight secondary mirror struts. We utilize performance – based merit functions consisting of both radial and azimuthal profiles of the resulting telescope point spread function.

SPHEREx, a mission in NASA’s Medium Explorer (MIDEX) program recently selected for Phase-A implementation, is an all-sky survey satellite that will produce a near-infrared spectrum for every 6 arcsecond pixel on the sky. SPHEREx has a simple, high-heritage design with large optical throughput to maximize spectral mapping speed. While the legacy data products will provide a rich archive of spectra for the entire astronomical community to mine, the instrument is optimized for three specific scientific goals: to probe inflation through the imprint primordial non-Gaussianity left on today’s large-scale cosmological structure; to survey the Galactic plane for water and other biogenic ices through absorption line studies; and to constrain the history of galaxy formation through power spectra of background fluctuations as measured in deep regions near the ecliptic poles. The aluminum telescope consists of a heavily baffled, wide-field off-axis reflective triplet design. The focal plane is imaged simultaneously by two mosaics of H2RG detector arrays separated by a dichroic beamsplitter. SPHEREx assembles spectra through the use of mass and volume efficient linear variable filters (LVFs) included in the focal plane assemblies, eliminating the need for any dispersive or moving elements. Instead, spectra are constructed through a series of small steps in the spacecraft attitude across the sky, modulating the location of an object within the FOV and varying the observation wavelength in each exposure. The spectra will cover the wavelength range between 0.75 and 5.0 µm at spectral resolutions ranging between R=35 and R=130. The entire telescope is cooled passively by a series of three V-groove radiators below 80K. An additional stage of radiative cooling is included to reduce the long wavelength focal plane temperature below 60K, controlling the dark current. As a whole, SPHEREx requires no new technologies and carries large technical and resource margins on every aspect of the design.

Terrestrial exoplanets shine in light reflected from a parent star. Optical spectra are required to provide evidence of a life-supporting environment. Exoplanets are very faint and their optical spectra are contaminated by the spectrum of the parent star. High angular resolution provided by large apertures is needed to distinguish between the spectrum of the exoplanet and its star. Today, large aperture telescopes use segmented primary mirrors that employ close-packed hexagonal segments. The telescope primary mirror is periodically discontinuous with straight lines. These discontinuities scatter unwanted radiation from the much brighter parent star across the field of view to obscure the light from the very faint terrestrial exoplanet. These discontinuities, which mimic a diffraction grating, result in a non-uniform distribution of background light across the image plane. This non-uniformity masks or hides exoplanets from view, to reduce the number of exoplanets that can be observed with a large aperture telescope or to reduce the quality of spectra and thus lead to misinterpretation of data. Here we introduce the concept of the pinwheel pupil whose unique diffraction pattern significantly reduces the non-uniform distribution of background radiation. Diffraction patterns from pinwheel pupils are compared to the monolithic filled aperture, the classical Cassegrain, the 60-degree symmetry of the hexagonal segments (JWST, E-ELT, etc.). Diffraction “spikes” are reduced by at least 105. We discuss the “pinwheel pupil” advantages to spectroscopy, image processing, and observatory operations. We show that, segment fabrication of curved-sided mirrors is not more difficult than fabrication of hexagonal mirror segments. . This is the report of quantitative study of Fraunhofer (far field) diffraction patterns produced by three different topologies or architectures of mirror segmentation, when illuminated by a plane wave of monochromatic white-light. A plot, in angular units of the intensity as a function of azimuth, Phi_f , within annular rings at different FOVs, centered on the system axis of the diffraction pattern will be presented. The advantages of the segmented pinwheel pupil is discussed.

The Origins Space Telescope (OST) 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 the universe evolve in response to its changing ingredients? How common are life-bearing planets? To accomplish its scientific objectives, OST will operate at mid- and far-infrared wavelengths and offer superlative sensitivity and new spectroscopic capabilities. The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics. To understand the concept solution space, our team studied two alternative mission concepts. We report on the study approach and describe both of these concepts, give the rationale for major design decisions, and briefly describe the mission-enabling technology.

The Optimal Optical Coronagraph (OOC) Workshop at the Lorentz Center in September 2017 in Leiden, the Netherlands gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. In this first installment of a series of three papers summarizing the outcomes of the OOC workshop, we present an overview of design methods and optical performance metrics developed for coronagraph instruments. The design and optimization of coronagraphs for future telescopes has progressed rapidly over the past several years in the context of space mission studies for Exo-C, WFIRST, HabEx, and LUVOIR as well as ground-based telescopes. Design tools have been developed at several institutions to optimize a variety of coronagraph mask types. We aim to give a broad overview of the approaches used, examples of their utility, and provide the optimization tools to the community. Though it is clear that the basic function of coronagraphs is to suppress starlight while maintaining light from off-axis sources, our community lacks a general set of standard performance metrics that apply to both detecting and characterizing exoplanets. The attendees of the OOC workshop agreed that it would benefit our community to clearly define quantities for comparing the performance of coronagraph designs and systems. Therefore, we also present a set of metrics that may be applied to theoretical designs, testbeds, and deployed instruments. We show how these quantities may be used to easily relate the basic properties of the optical instrument to the detection significance of the given point source in the presence of realistic noise., To appear in Proceedings of the SPIE, vol. 10698

Segmented telescopes are a possibility to enable large-aperture space telescopes for the direct imaging and spectroscopy of habitable worlds. However, the complexity of their aperture geometry, due to the central obstruction, support structures and segment gaps, makes high-contrast imaging challenging. The High-contrast Imager for Complex Aperture Telescopes (HiCAT) testbed was designed to study and develop solutions for such telescope pupils using wavefront control and coronagraphic starlight suppression. The testbed design has the flexibility to enable studies with increasing complexity for telescope aperture geometries: off-axis telescopes, on-axis telescopes with central obstruction and support structures - e.g. the Wide Field Infrared Survey Telescope (WFIRST) - to on-axis segmented telescopes, including various concepts for a Large UV, Optical, IR telescope (LUVOIR). In the past year, HiCAT has made significant hardware and software updates to accelerate the development of the project. In addition to completely overhauling the software that runs the testbed, we have completed several hardware upgrades, including the second and third deformable mirror, and the first custom Apodized Pupil Lyot Coronagraph (APLC) optimized for the HiCAT aperture, which is similar to one of the possible geometries considered for LUVOIR. The testbed also includes several external metrology features for rapid replacement of parts, and in particular the ability to test multiple apodizers readily, an active tip-tilt control system to compensate for local vibration and air turbulence in the enclosure. On the software and operations side, the software infrastructure enables 24/7 automated experiments that include routine calibration tasks and high-contrast experiments. We present an overview and status update of the project, on the hardware and software side, and describe results obtained with APLC WFC., Comment: 16 pages, 12 figures

The Coronagraph Instrument (CGI) for NASA's Wide Field Infrared Survey Telescope (WFIRST) will constitute a dramatic step forward for high-contrast imaging, integral field spectroscopy, and polarimetry of exoplanets and circumstellar disks, aiming to improve upon the sensitivity of current ground-based direct imaging facilities by 2-3 orders of magnitude. Furthermore, CGI will serve as a pathfinder for future exo-Earth imaging and characterization missions by demonstrating wavefront control, coronagraphy, and spectral retrieval in a new contrast regime, and by validating instrument and telescope models at unprecedented levels of precision. To achieve this jump in performance, it is critical to draw on the experience of ground-based high-contrast facilities. We discuss several areas of relevant commonalities, including: wavefront control, post-processing of integral field unit data, and calibration and observing strategies., Comment: Published in Proceedings of the SPIE; Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave. 13 pages, 6 figures

The presence of large amounts of dust in the habitable zones of nearby stars is a significant obstacle for future exo-Earth imaging missions. We executed the HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey to determine the typical amount of such exozodiacal dust around a sample of nearby main sequence stars. The majority of the data have been analyzed and we present here an update of our ongoing work. Nulling interferometry in N band was used to suppress the bright stellar light and to detect faint, extended circumstellar dust emission. We present an overview of the latest results from our ongoing work. We find seven new N band excesses in addition to the high confidence confirmation of three that were previously known. We find the first detections around Sun-like stars and around stars without previously known circumstellar dust. Our overall detection rate is 23%. The inferred occurrence rate is comparable for early type and Sun-like stars, but decreases from 71+11 -20% for stars with previously detected mid- to far-infrared excess to 11+9 -4% for stars without such excess, confirming earlier results at high confidence. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal luminosity function of the dust, we find upper limits on the median dust level around all stars without previously known mid to far infrared excess of 11.5 zodis at 95% confidence level. The corresponding upper limit for Sun-like stars is 16 zodis. An LBTI vetted target list of Sun-like stars for exo-Earth imaging would have a corresponding limit of 7.5 zodis. We provide important new insights into the occurrence rate and typical levels of habitable zone dust around main sequence stars. Exploiting the full range of capabilities of the LBTI provides a critical opportunity for the detailed characterization of a sample of exozodiacal dust disks to understand the origin, distribution, and properties of the dust.

This paper describes the beginning of the Far-Infrared Surveyor mission study for NASA's Astrophysics Decadal 2020. We describe the scope of the study, and the open process approach of the Science and Technology Definition Team. We are currently developing the science cases and provide some preliminary highlights here. We note key areas for technological innovation and improvements necessary to make a Far-Infrared Surveyor mission a reality., 8 pages, SPIE proceedings of the Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave conference

Conceptual architectures are now being developed to identify future directions for post JWST large space telescope systems to operate in the UV Optical and near IR regions of the spectrum. Here we show that the cost of optical surfaces within large aperture telescope/instrument systems can exceed $100M/reflection when expressed in terms of the aperture increase needed to over come internal absorption loss. We recommend a program in innovative optical design to minimize the number of surfaces by considering multiple functions for mirrors. An example is given using the Rowland circle imaging spectrometer systems for UV space science. With few exceptions, current space telescope architectures are based on systems optimized for ground-based astronomy. Both HST and JWST are classical “Cassegrain” telescopes derived from the ground-based tradition to co-locate the massive primary mirror and the instruments at the same end of the metrology structure. This requirement derives from the dual need to minimize observatory dome size and cost in the presence of the Earth’s 1-g gravitational field. Space telescopes, however function in the zero gravity of space and the 1- g constraint is relieved to the advantage of astronomers. Here we suggest that a prime focus large aperture telescope system in space may have potentially have higher transmittance, better pointing, improved thermal and structural control, less internal polarization and broader wavelength coverage than Cassegrain telescopes. An example is given showing how UV astronomy telescopes use single optical elements for multiple functions and therefore have a minimum number of reflections.

Static Zernike phase-contrast plates have been used extensively in microscopy for half a century and, more recently, in optical telescopes for wavefront sensing. A dynamic Zernike wavefront sensor (WFS) with four phase shifts, for reducing error due to spurious light and eliminating other asynchronous noise, has been proposed for use in adaptive optics. Here, we propose adapting this method for co-phasing the primary mirror of a segmented space telescope. In order to extend the dynamic range of the WFS, which has a maximum range of +/ − λ/2, a phase- contrast plate with multiple steps, both positive and negative, has been developed such that errors as large as +/ − 10λ can be sensed. The manufacturing tolerances have been incorporated into simulations, which demonstrate that performance impacts are minimal. We show that the addition of this small optical plate along with a high precision linear translation stage at the prime focus of a telescope and pupil viewing capability can provide extremely accurate segment phasing with a simple white-light fringe fitting algorithm and a closed-loop controller. The original focal-plane geometry of a centro-symmetric phase shifting element is replaced with a much less constrained shape, such as a slot. Also, a dedicated pupil imager is not strictly required; an existing pupil sampler such as a Shack-Hartmann (SH) WFS can be used just as effectively, allowing simultaneous detection of wavefront errors using both intensity and spot positions on the SH-WFS. This could lead to an efficient synergy between Zernike and SH-WFS, enabling segment phasing in conjunction with high-dynamic range sensing.

The Far Infrared Spectroscopic Explorer (FIRSPEX) is a novel European-led astronomy mission concept developed to enable large area ultra high spectroscopic resolution surveys in the THz regime. FIRSPEX opens up a relatively unexplored spectral and spatial parameter space that will produce an enormously significant scientific legacy by focusing on the properties of the multi-phase ISM, the assembly of molecular clouds in our Galaxy and the onset of star formation; topics which are fundamental to our understanding of galaxy evolution. The mission uses a heterodyne instrument and a ~1.2 m primary antenna to scan large areas of the sky in a number of discreet spectroscopic channels from L2. The FIRSPEX bands centered at [CI] 809 GHz, [NII]1460 GHz, [CII]1900 GHz and [OI]4700 GHz have been carefully selected to target key atomic and ionic fine structure transitions difficult or impossible to access from the ground but fundamental to the study of the multi-phase ISM in the Universe. The need for state-of-the-art sensitivity dictates the use of superconducting mixers configured either as tunnel junctions or hot electron bolometers. This technology requires cooling to low temperatures, approaching 4K, in order to operate. The receivers will operate in double sideband configuration providing a total of 7 pixels on the sky. FIRSPEX will operate from L2 in both survey and pointed mode enabling velocity resolved spectroscopy of large areas of sky as well as targeted observations.

We present here a four mirror anastigmatic optical collimator design intended for the calibration of an earth observation satellite instrument. Specifically, the collimator is to be applied to the ground based calibration of the Sentinel-4/UVN instrument. This imaging spectrometer instrument itself is expected to be deployed in 2019 in a geostationary orbit and will make spatially resolved spectroscopic measurements of atmospheric contaminants. The collimator is to be deployed during the ground based calibration only and does not form part of the instrument itself. The purpose of the collimator is to provide collimated light within the two instrument passbands in the UV-VIS (305 – 500 nm) and the NIR (750 – 775 nm). Moreover, that collimated light will be derived from a variety of slit like objects located at the input focal (object) plane of the collimator which is uniformly illuminated by a number of light sources. The collimator must relay these objects with exceptionally high fidelity. To this end, the wavefront error of the collimator should be less than 30 nm rms across the collimator field of view. This field is determined by the largest object which is a large rectangular slit, 4.4° x 0.25°. Other important considerations affecting the optical design are the requirements for input telecentricity and the size (85 mm) and location (2500 mm ‘back focal distance’) of the exit pupil. The design of the instrument against these basic requirements is discussed in detail. In addition an analysis of the straylight and tolerancing is presented in detail.

Euclid-VIS is the large format visible imager for the ESA Euclid space mission in their Cosmic Vision program, scheduled for launch in 2020. Together with the near infrared imaging within the NISP instrument, it forms the basis of the weak lensing measurements of Euclid. VIS will image in a single r+i+z band from 550-900 nm over a field of view of ~0.5 deg2. By combining 4 exposures with a total of 2260 sec, VIS will reach to deeper than mAB=24.5 (10sigma) for sources with extent ~0.3 arcsec. The image sampling is 0.1 arcsec. VIS will provide deep imaging with a tightly controlled and stable point spread function (PSF) over a wide survey area of 15000 deg2 to measure the cosmic shear from nearly 1.5 billion galaxies to high levels of accuracy, from which the cosmological parameters will be measured. In addition, VIS will also provide a legacy dataset with an unprecedented combination of spatial resolution, depth and area covering most of the extra-Galactic sky. Here we will present the results of the study carried out by the Euclid Consortium during the period up to the Critical Design Review., 16 pages, 15 figures, 1 table