We develop the theoretical foundation for primary objective grating (POG) telescopy. In recent years, a wide range of telescope designs that collect the light over a large grating and focus it with a secondary receiving optic that is placed at grazing exodus have been proposed by Thomas D. Ditto and are sometimes referred to as Dittoscopes. Applications include discovery and characterization of exoplanets, discovery of near-Earth asteroids, and spectroscopic surveys of the sky. These telescopes would have small aerial mass, and therefore, provide a path forward to launch large telescopes into space. Because this series of telescope designs departs from traditional telescope designs, it has been difficult to evaluate which applications are most advantageous for this design. We define a figure of merit, the “spectral étendue,” that characterizes the photon collection capability of a POG. It is demonstrated that the diffraction limit for observations is determined by the length of the grating. We evaluate the effects of atmospheric seeing for ground-based applications and the disambiguation of position versus wavelength in the focal plane using a second dispersing element. Finally, some strategies for fully reaping the benefits of POG optical characteristics are discussed.

The filter wheel (FW) assembly (FWA), developed by the CBK Institute, is one of the critical subsystems of the wide field imager (WFI) instrument on board the Advanced Telescope for High Energy Astrophysics—mission of the ESA Cosmic Vision 2015-25 space science program (launch scheduled around 2035). The instrument has to collect soft x-rays with very high quantum efficiency, thus WFI requires extremely thin optical blocking filter (OBF). Due to its thickness (∼150 nm) and large area (∼170 mm × 170 mm) needed to achieve a 40 ^′ × 40 ^′ instrument field of view, the filter is extremely vulnerable to acoustic loads generated during Ariane 6 rocket launch. On the other side, FW mechanism has to provide high overall reliability, so it is more favourable to launch the instrument in atmospheric pressure (without vacuum enclosure for filter protection). Design efforts of the FW subsystem were focused on two issues: providing maximal possible sound pressure level suppression and smallest possible differential pressure across the OBF, which should prevent filters from damaging. We describe the design of a reconfigurable acoustic-demonstrator model (DM) of WFI FWA created for purposes of acoustic testing. Also, the acoustic test campaign is described: test methodology, test criteria, and results discussion and its implication on future FWA design. In general, tests conducted with the FWA DM showed that current design of WFI is feasible and the project can be continued without introducing a vacuum enclosure, which would significantly increase system complexity and mass.

LiteBIRD is a space mission intended for the late 2020s that aims to observe the large-angular-scale polarization pattern of the cosmic microwave background. The low-frequency telescope (LFT) aboard LiteBIRD has a crossed-Dragone design and observes at 34 to 161 GHz with a field of view (FoV) of 18 deg × 9 deg. The LFT antenna optics is predicted to induce polarization angle rotation by up to around 1.5 deg in its FoV, while polarization angles among the detectors should be corrected to a few arcminutes level to distinguish E- and B-mode polarizations. To characterize the polarization angle rotation by the antenna optics and to develop a ground calibration method, we performed polarization angle measurements with a small compact-antenna-test-range setup. We measured the polarization angles of a 1/4-scaled LFT antenna across the FoV at correspondingly scaled frequencies of 140 to 220 GHz (35 to 55 GHz for the full-scale LFT). We placed a collimated-wave source near the scaled-LFT aperture and rotated the scaled-LFT feed polarization. The measured polarization angles agree with those measured by rotating the collimated-wave polarization at the 15″ level for the on-axis case. The measurements are consistent with simulation and determined the polarization angles with an uncertainty of less than 1.9′.

Long mirrors coated with thin films are used for a wide range of applications, e.g., focusing or collimating high-energy optics. Focusing of incident x-ray radiation is one of the major applications for high-energy astronomical telescopes, and collimation of divergent x-ray sources is used for experimental setups to confine or expand x-ray radiation. Both applications utilize grazing angle reflection, which is typically enhanced using x-ray reflective thin films. One of the challenges with thin film coatings is the deposition induced nonuniformities. For x-ray reflecting mirrors, nonuniformity in the thin film deposition influences the thickness, roughness, and density of the thin film, which affects the predicted performance of the mirror. As part of the thin film coating development for the 456-mm-long parabolic mirror used in the Beam Expander Testing X-ray facility, our work presents the challenge of coating long x-ray reflective mirrors. We used x-ray reflectometry to investigate the nonuniformity in platinum and chromium thin films deposited using direct current magnetron sputtering.

The low thermal expansion glass ceramic ZERODUR^® has a long and successful history in spaceborne optical applications. This material is especially used where precise shape invariance is required, i.e., for the mirror substrates dimensional stability when subject to temperature gradients and transients. In space, temperature may not be the exclusive driving force impacting the form stability; influence from ionizing radiations require considerations. The real impact of ionizing radiation on ZERODUR^® has become a matter of reconciling, on the one hand, in situ experience, e.g., that the secondary mirror of low Earth orbit (LEO) Hubble Space Telescope crossing the South Atlantic Anomaly or the overall optics of geosynchronous equatorial orbit (GEO) Chandra X-ray Observatory are not reporting any specific problems related to dimensional stability at the optical form level. On the other hand, finite element simulation based on early lab experiments of ZERODUR^® compaction are suggesting the opposite. This debate was brought to the forefront with the SILEX mission, where radiative ageing models were significantly overestimating the deformation experimentally observed on the lab replicas and were in even stronger disagreement with the observations collected over the mission. It has been speculated that an erroneous form factor in the physical model used to derive the phenomenological compaction law was responsible for these discrepancies. Following this hypothesis, we readdressed the effect of ionizing radiation induced by γ, electron, and proton fluences on ZERODUR^® compaction. For each of these, we present and discuss the irradiation source, the experimental setup, the sample design, and the measurement procedure as well as the observations. Consistent with the feedback gathered over many different space missions, we confirm that the compaction observed is significantly smaller than the estimations available in the prior literature.

The 511 keV γ-ray emission from the galactic center region may fully or partially originate from the annihilation of positrons from dark matter particles with electrons from the interstellar medium. Alternatively, the positrons could be created by astrophysical sources, involving exclusively standard model physics. We describe here a new concept for a 511 keV mission called 511-CAM (511 keV gamma-ray camera using microcalorimeters) that combines focusing γ-ray optics with a stack of transition edge sensor microcalorimeter arrays in the focal plane. The 511-CAM detector assembly has a projected 511 keV energy resolution of 390 eV full width half maximum or better, and improves by a factor of at least 11 on the performance of state-of-the-art Ge-based Compton telescopes. Combining this unprecedented energy resolution with sub-arcmin angular resolutions afforded by Laue lens or channeling optics could make substantial contributions toward identifying the origin of the 511 keV emission through discovering and characterizing point sources and measuring line-of-sight velocities of the emitting plasmas.

The Advanced X-ray Imaging Satellite (AXIS) is a probe-class mission concept with a large collecting area with a point-spread-function of order 1 to 2 arcsec. We describe a possible X-ray grating spectrometer (XGS) that could be added to AXIS with minimal design changes to the telescope itself and costs a small fraction of the total mission budget. The XGS would be based on critical-angle transmission (CAT) gratings, a technology already matured for Arcus and Lynx. Using detailed ray-tracing, we investigate several options for subaperturing that provide a trade-off between effective area and spectral resolving power. Depending on how much of the full aperture is covered with gratings (e.g., 17% to 100%), we find a high spectral resolving power up to λ / Δλ = 4000 can be achieved with effective area of 1500 cm² in the 1.2 to 2.8 nm range or λ / Δλ = 6000 with effective area 500 cm². An important benefit of CAT gratings is that they are mostly transparent at high energies, and thus hard x-rays can still be used for simultaneous imaging spectroscopy. We study different grating sizes and other enhancements, but even in the basic configuration an XGS can be added to AXIS to provide high-resolution spectral capabilities, opening a range of new science investigations. Our ray-tracing shows that this concept is mature and can be added to AXIS with minimal impact on other instruments. We discuss one exemplary science case that would be enabled by the XGS.

Magnetic shielding has been used during past and current x-ray astronomy missions to shield detectors from electrons entering through telescope optics, and soft proton diverters have also been planned for future missions. However, simulations performed throughout the past decade have discovered that a significant proportion of x-ray-like background originates from secondary electrons produced in spacecraft shielding surrounding x-ray detectors, which hit detectors isotropically from all directions. Here, the results from Geant4 simulations of a simple dual solenoid magnetic field surrounding a 450 μm thick detector with several on-chip layers based on the structure of preliminary designs for the ATHENA Wide Field Imager are presented. We found that for a magnetic field strength at the middle between the two coils of equal to or greater than ∼12 mT, a dual solenoid magnetic field is extremely effective at preventing secondary electrons depositing between 2 and 7 keV and induced by galactic cosmic protons from reaching the detector. While the exact level of background reduction would depend on specific spacecraft and detector design, this magnetic shielding method could remove almost all background associated with backscattering and absorbed electrons, which are expected to account for approximately two thirds of the expected off-axis background in silicon-based x-ray detectors of several hundred microns in thickness and would likely be even more effective for thinner detectors where x-ray-like background is even more dominated by electrons. The magnetic field structure necessary for doing this could be produced using a set of solenoids or neodymium magnets providing that power requirements can be sufficiently optimized or neodymium fluorescence lines can be sufficiently attenuated, respectively. Testing would also have to be done to ensure that detectors it is used on are sufficiently magnetically hard; for context, the current limit for magnetic field strength around the ATHENA Wide Field Imager is 1 mT although CCD97s, another type of space-based x-ray detector, are magnetically hard at least above 6.4 mT.

Of the over 5000 exoplanets that have been detected, only about a dozen have ever been directly imaged. Earth-like exoplanets are on the order of 10 billion times fainter than their host star in visible and near-infrared, requiring a coronagraph instrument to block primary starlight and allow for the imaging of nearby orbiting planets. In the pursuit of direct imaging of exoplanets, scalar vortex coronagraphs (SVCs) are an attractive alternative to vector vortex coronagraphs (VVCs). VVCs have demonstrated 2 × ^{10 − 9} raw contrast in broadband light but have several limitations due to their polarization properties. SVCs imprint the same phase ramp as VVCs on the incoming light and do not require polarization splitting, but they are inherently chromatic. Discretized phase ramp patterns such as a wrapped staircase help reduce SVC chromaticity and simulations show it outperforms a chromatic classical vortex in broadband light. We designed, fabricated, and tested a wrapped staircase SVC, and here we present the broadband characterization on the high contrast spectroscopy testbed. We also performed wavefront correction on the in-air coronagraph testbed at NASA’s Jet Propulsion Laboratory and achieved an average raw contrasts of 3.2 × 10 ^{− 8} in monochromatic light and 2.2 × 10 ^{− 7} across a 10% bandwidth.

Starshades are a leading technology to enable the direct detection and spectroscopic characterization of Earth-like exoplanets. To maintain high contrast during observations, the starshade and telescope must keep within 1 m of relative alignment over large separations (>20,000 km). This formation flying is made possible with precise spacecraft position information obtained through accurate sensing of the occulted star’s diffraction peak (referred to as the spot of Arago) incident on the telescope aperture. We present a lightweight image processing method based on a convolutional neural network paired with a simulation-based inference technique to estimate the position of the spot of Arago and its uncertainty. On simulated images, the method achieves an accuracy of a few centimeters across the entire telescope aperture. By deploying our method at the Princeton Starshade Testbed, we demonstrate that the neural network can be trained on simulated images and used on real images and that it can successfully be integrated in the control system for closed-loop formation flying.

Integrated optics are used to achieve astronomical interferometry inside robust and compact materials, improving the instrument’s stability and sensitivity. To perform differential phase measurements at the Hα line (656.3 nm) with the 600- to 800-nm spectro-interferometer fibered imager for a single telescope (FIRST), a photonic integrated circuit (PIC) is being developed in collaboration with TEEM Photonics. This PIC performs the interferometric combination of the beams coming from subapertures selected in the telescope pupil, thus implementing the pupil remapping technique to restore the diffraction limit of the telescope. In this work, we report on the latest developments carried out within the FIRST project to produce a high-performance visible PIC. The PICs are manufactured by TEEM Photonics, using their technology based on K ₊ : Na ₊ ion exchange in glass. The first part of the study consists in the experimental characterization of the fundamental properties of the waveguides, to build an accurate model, which is the basis for the design of more complex functions. In the second part, theoretical designs and their optimization for three types of combiner architectures are presented: symmetric directional coupler, asymmetric directional couplers, and ABCD cells, including achromatic phase shifters.

We propose an x-ray imaging system, multi-image x-ray interferometer module (MIXIM), with which a very high angular resolution can be achieved even with a small system size. MIXIM is composed of equally spaced multiple slits and an x-ray detector, and its angular resolution is inversely proportional to the distance between them. Here, we report our evaluation experiments of MIXIM with a newly adopted CMOS sensor with a high spatial resolution of 2.5 μm. Our previous experiments with a prototype MIXIM were limited to one-dimensional imaging, and more importantly, the achieved angular resolution was only ∼1 ^″ , severely constrained due to the spatial resolution of the adopted sensor with a pixel size of 4.25 μm. By contrast, one-dimensional images obtained in this experiment had a higher angular resolution of 0.5″ when a configured system size was only ∼1 m, which demonstrates that MIXIM can simultaneously realize a high angular resolution and compact size. We also successfully obtained a two-dimensional profile of an x-ray beam for the first time for MIXIM by introducing a periodic pinhole mask. The highest angular resolution achieved in our experiments is smaller than 0.1″ with a mask-sensor distance of 866.5 cm, which shows the high scalability of MIXIM.

The Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE-C) mission is designed to directly image debris disks and exozodiacal dust around nearby stars from a high-altitude balloon using a 60 cm diameter off-axis telescope and a vector vortex coronagraph. During its second flight from Fort Sumner, New Mexico, on September 28, 2022, PICTURE-C successfully used its high and low-order wavefront control systems to perform focal plane wavefront correction for the first time on an observatory in a near-space environment. The coronagraph achieved a modest broadband (20%) contrast of 5 × ^{10 − 6}, with performance limited by dynamic pointing transients. The low-order wavefront control system achieved optical pointing stabilization of 1 milliarcseconds (mas) root mean squared (RMS) over 30 second timescales.

The Michigan Young Star Imager at CHARA (MYSTIC) is a K-band interferometric beam combining instrument funded by the U.S. National Science Foundation, designed primarily for imaging sub-au scale disk structures around nearby young stars and to probe the planet formation process. Installed at the CHARA Array in July 2021, with baselines up to 331 m, MYSTIC provides a maximum angular resolution of λ / 2B ∼ 0.7 mas. The instrument injects phase-corrected light from the array into inexpensive, single-mode, polarization maintaining silica fibers, which are then passed via a vacuum feedthrough into a cryogenic dewar operating at 220 K for imaging. MYSTIC uses a high frame rate, ultra-low read noise SAPHIRA detector and implements two beam combiners: a six-telescope image plane beam combiner, based on the MIRC-X design, for targets as faint as 7.7 Kmag, as well as a four-telescope integrated optic beam-combiner mode using a spare chip leftover from the GRAVITY instrument. MYSTIC is co-phased with the MIRC-X (J + H band) instrument for simultaneous fringe-tracking and imaging and shares its software suite with the latter to allow a single observer to operate both instruments. We present the instrument design, review its operational performance, present early commissioning science observations, and propose upgrades to the instrument that could improve its K-band sensitivity to 10th magnitude in the near future.

European Southern Observatory (ESO)’s Very Large Telescope Interferometer (VLTI), Paranal, Chile, is one of the most proficient observatories in the world for high angular resolution astronomy. It has hosted several interferometric instruments operating in various bandwidths in the infrared. As a result, the VLTI has yielded countless discoveries and technological breakthroughs. We propose to ESO a new concept for a visitor instrument for the VLTI: Asgard. It is an instrumental suite comprised of four natively collaborating instruments: High-Efficiency Multiaxial Do-it ALL Recombiner (HEIMDALLR), an all-in-one instrument performing both fringe tracking and stellar interferometry with the same optics; Baldr, a Strehl optimizer; Beam-combination Instrument for studying the Formation and fundamental paRameters of Stars and planeTary systems (BIFROST), a combiner whose main science case is studying the formation processes and properties of stellar and planetary systems; and Nulling Observations of dusT and planeTs (NOTT), a nulling interferometer dedicated to imaging young nearby planetary systems in the L band. The overlap between the science cases across different spectral bands yields the idea of making the instruments complementary to deliver sensitivity and accuracy from the J to L bands. Asgard is to be set on the former AMBER optical table. Its control architecture is a hybrid between custom and ESO-compliant developments to benefit from the flexibility offered to a visitor instrument and foresee a deeper long-term integration into VLTI for an opening to the community.

The Single-Electron Sensitive Read Out (SiSeRO) is an on-chip charge detector output stage for charge-coupled device image sensors. Developed at MIT Lincoln Laboratory, this technology uses a p-MOSFET transistor with a depleted internal gate beneath the transistor channel. The transistor source–drain current is modulated by the transfer of charge into the internal gate. At Stanford, we have developed a readout module based on the drain current of the on-chip transistor to characterize the device. In our earlier work, we characterized a number of first prototype SiSeROs with the MOSFET transistor channels at the surface layer. An equivalent noise charge of around 15 electrons root mean square was obtained. In this work, we examine the first buried-channel SiSeRO. We have achieved substantially improved noise performance of around 4.5eRMS− and a full-width half-maximum energy resolution of 132 eV at 5.9 keV, for a readout speed of 625 kpixel / s. We also discuss how digital filtering techniques can be used to further improve the SiSeRO noise performance. Additional measurements and device simulations will be essential to further mature the SiSeRO technology. This new device class presents an exciting technology for the next-generation astronomical x-ray telescopes requiring fast, low-noise, radiation-hard megapixel imagers with moderate spectroscopic resolution.

The Silesian University of Technology Observatories (SUTO) group’s solar patrol station, SUTO Solar, is designed to collect patrol images of the Sun. The observatory is operated remotely and equipped with a 60-mm Lunt telescope for imaging in the Hα 656.28 nm hydrogen line and an 80-mm Sky Watcher refractor for imaging in the continuum centered at 540 nm. Both telescopes use complementary metal-oxide-semiconductor (CMOS) cameras. A set of environmental sensors measuring temperature, humidity, and pressure provide information about the optical instruments. Real-time full-disk images and archival data are shared via a dedicated web page. In future work, low-resolution images generated by SUTO Solar will be used as training datasets for dedicated machine learning algorithms designed to enhance images acquired by small instruments.

Acquisition and guiding services have been provided at major telescopes in order to improve the quality and efficiency of scientific observations. Field stabilization (FS) is an essential component of the telescope control system. With the arrival of new-generation instruments, the stabilization requirements have increased. Higher correction frequency is required to minimize the residuals. A major re-engineering of the CCD acquisition software now enables an increase of the operational frequency from 25 to 87 Hz. We analyze and discuss the performances of FS at various frequencies on the Very Large Telescope with its 8-m telescopes including the Adaptive 8-m telescope equipped with a deformable secondary mirror. We will report on the analysis of the residuals in function of several operational key parameters, e.g., the loop frequency, the magnitude of the selected telescope guide star, etc. We will also discuss the possible automatization of the FS during night operations.

Electron-multiplying charge-coupled devices are efficient imaging devices for low-surface-brightness ultraviolet astronomy from space. The large amplification allows photon counting (PC), the detection of events versus nonevents. This paper provides the statistics of the observation process, the photon-counting process, the amplification process, and the compression. The expression for the signal-to-noise of PC is written in terms of the polygamma function. The optimal exposure time is a function of the clock-induced charge. The exact distribution of amplification process is a simple-to-compute powered matrix. The optimal cutoff for comparing to the read noise is close to a strong function of the read noise and a weak function of the electron-multiplying gain and photon rate. A formula gives the expected compression rate.

The thermal behavior of the reflector system under solar radiation has great effects on the pointing accuracy of large radio telescopes. To estimate the dynamic pointing error of large radio telescopes caused by the thermal behavior of the reflector system under solar radiation, the nonuniform temperature field and the thermal deformation of the Wuqing 70 m radio telescope (WRT70) on three specific sunny days are first simulated by finite-element (FE) software. Then the pose variations of the reflector system are calculated equivalently based on the FE thermal-structural coupling analysis of the reflector system. Finally, the dynamic pointing errors of the WRT70 on three specific sunny days, caused by the thermal behavior of the reflector system, are estimated according to the beam deviation factor. The research results show that the rotations of the main reflector and the offsets of the subreflector on sunny days have great influences on the pointing error of large radio telescopes. In addition, the pointing error caused by the rotations of the main reflector and the pointing error caused by the offsets of the subreflector cancel each other out, but the pointing error caused by the rotations of the main reflector plays a dominant role. Furthermore, the effect of the thermal behavior of the reflector system on the pointing accuracy of large radio telescopes is less than the influence of the thermal behavior of the alidade. These findings could provide valuable references for the compensation of dynamic pointing errors of large radio telescopes.

Wide field-of-view millimeter-wave telescopes with a bolometric detector array have been developed for cosmic microwave background radiation observations. For the purpose of laboratory verification of these telescopes, several studies have demonstrated near-field antenna measurements using a phase-sensitive detector that replaces a few representative pixels of the focal-plane detector array. We present a holographic phase-retrieval method that enables near-field measurements with the bolometric detector array as it is. We place a reference emitter at a fixed position and scan a signal emitter at the telescope aperture. These two emitters are phase-locked and generate interference patterns (holograms) on the focal plane, from which the amplitude and phase of the aperture field can be retrieved. We experimentally demonstrated this method with a crossed-Dragone telescope with a field-of-view that is 18 deg × 9 deg. In the demonstration, we placed a phase-sensitive detector at three detector positions on the focal plane. The antenna patterns calculated from the hologram, neglecting the directly measured phase information, were consistent with those calculated from both intensity and phase measurements at the −60-dB level at 180 GHz. Applying this method, the antenna patterns for all of the bolometric detectors on the focal plane can theoretically be measured simultaneously.

Kernel phase interferometry (KPI) is a data processing technique that allows for the detection of asymmetries (such as companions or disks) in high-Strehl images, close to and within the classical diffraction limit. We show that KPI can successfully be applied to hyperspectral image cubes generated from integral field spectrographs (IFSs). We demonstrate this technique of spectrally dispersed kernel phase by recovering a known binary with the SCExAO/CHARIS IFS in high-resolution K-band mode. We also explore a spectral differential imaging (SDI) calibration strategy that takes advantage of the information available in images from multiple wavelength bins. Such calibrations have the potential to mitigate high-order, residual systematic kernel phase errors, which currently limit the achievable contrast of KPI. The SDI calibration presented is applicable to searches for line emission or sharp absorption features and is a promising avenue toward achieving photon-noise-limited kernel phase observations. The high angular resolution and spectral coverage provided by dispersed kernel phase offers opportunities for science observations that would have been challenging to achieve otherwise.

The differential polarization visibilities R_Q and R_U of an object are the ratios of its visibilities corresponding to orthogonal polarizations, the interferometric analogs to Stokes Q and U intensity images. The measurement of differential polarization visibilitites can be used for constraining inner parts of circumstellar envelopes of young or evolved stars at the diffraction limited resolution of the feeding telescope. We demonstrate the estimation of both amplitude and phase of R_Q and R_U from data obtained using SCExAO VAMPIRES through the full pupil of the 8-m Subaru telescope using the differential speckle polarimetry technique. The correction for biases arising due to instrumental polarization effects is discussed. The accuracy of R_Q and R_U measurement with VAMPIRES is limited by imperfect knowledge of instrumental polarization and amounts to 5 × ^{10 − 3}.

Cosmic rays are particles from the upper atmosphere, which often leave bright spots and trails in images from telescope charge-coupled devices (CCDs). We investigate so-called “fat” cosmic rays seen in images from Vera C. Rubin Observatory and the Subaru Telescope. These tracks are much wider and brighter than typical cosmic ray tracks and therefore are more capable of obscuring data in science images. By understanding the origins of these tracks, we can better ensure that they do not interfere with on-sky data. We compare the properties of these tracks to simulated and theoretical models to identify both the particles causing these tracks as well as the reason for their excess spread. We propose that the origin of these tracks is cosmic ray protons, which deposit much greater charge in the CCDs than typical cosmic rays due to their lower velocities. The generated charges then repel each other while drifting through the detector, resulting in a track that is much wider than typical tracks.

The sensitivity limits of space telescopes are imposed by uncalibrated errors in the point spread function, photon-noise, background light, and detector sensitivity. These are typically calibrated with specialized wavefront sensor hardware and with flat fields obtained on the ground or with calibration sources, but these leave vulnerabilities to residual time-varying or non-common path aberrations and variations in the detector conditions. It is, therefore, desirable to infer these from science data alone, facing the prohibitively high dimensional problems of phase retrieval and pixel-level calibration. We introduce a new Python package for physical optics simulation, ∂ Lux, which uses the machine learning framework Jax to achieve graphics processing unit acceleration and automatic differentiation (autodiff), and apply this to simulating astronomical imaging. In this first of a series of papers, we show that gradient descent enabled by autodiff can be used to simultaneously perform phase retrieval and calibration of detector sensitivity, scaling efficiently to inferring millions of parameters. This new framework enables high dimensional optimization and inference in data analysis and hardware design in astronomy and beyond, which we explore in subsequent papers in this series.

Space-based stellar coronagraph instruments aim to directly image exoplanets that are a fraction of an arcsecond separated from and 10 billion times fainter than their host star. To achieve this, one or more deformable mirrors (DMs) are used in concert with coronagraph masks to control the wavefront and minimize diffracted starlight in a region of the image known as the “dark zone” or “dark hole (DH).” The DMs must have a high number of actuators (50 to 96 across) to allow for DHs that are large enough to image a range of desired exoplanet separations. In addition, the surfaces of the DMs must be controlled at the picometer level to enable the required contrast. Any defect in the mechanical structure of the DMs or electronic system could significantly impact the scientific potential of the mission. Thus NASA’s Exoplanet Exploration Program procured two 50 × 50 microelectromechanical DMs manufactured by Boston Micromachines Corporation to test their robustness to the vibrational environment that the DMs will be exposed to during launch. The DMs were subjected to a battery of functional and high-contrast imaging tests before and after exposure to flight-like random vibrations. The DMs did not show any significant functional nor performance degradation at ^{10 − 8} contrast levels.

The interferometric calibration and measurement of deformable mirrors for adaptive optics are often performed on complex optical system with spider arms. The spider shadows may divide the mirror surface into separate islands on the detector, so the interferometer fails in reconnecting them to a common phase value. The calibration measurements then suffer from such artificial differential pistons across islands, which is converted into a wrong actuator command and in general into a poor calibration. We review the effects of spider arms shadowing as experienced during the optical calibration of large format adaptive mirrors, such as the Large Binocular Telescope and Very Large Telescope ones; we describe the procedures that we tested to cope with these issues and their effectiveness; and we present a laboratory assessment of the effect of such a shadowing with a dedicated test setup. Our work is part of a preparatory activity for the optical test of the European Extremely Large Telescope adaptive mirror M4.

This publication presents an active lateral support system for the thin 1-m meniscus mirror of a Ritchey-Chrétien telescope system. The goal is to keep the mirror at its position under varying external influences, such as gravity and temperature, therefore maintaining the alignment and optical image quality. To achieve this, the lateral support consists of eight actuators, based on stepper motors with gearboxes, with local force measurement and three laser triangulation sensors to measure the mirror’s lateral position. A cascaded control structure with local force feedback in the inner loop and position feedback in the outer loop is proposed. In the outer loop, three single-input single-output PI-controllers are implemented to maintain mirror position in the three lateral degrees of freedom. The developed system is able to position the mirror with root mean square errors of 0.27 and 0.18 μm in translational directions and 5.1 μrad in the rotational direction over the operational altitude range with a slewing speed of 0.2 deg / s.