The Advanced X-ray Imaging Satellite (AXIS), a concept recently submitted to NASA’s Astrophysics Probe Explorer competition, will offer low-background, arcsecond-resolution imaging in the 0.3–10 keV band across a 450-arcmin2 field of view, with an effective area at 1 keV of at least 4200 cm2. AXIS will bring X-ray astronomy back to the forefront of modern mainstream astrophysics, reaching equivalent depths in X-rays to many of the major facilities of the 2030’s (e.g., JWST, Roman, Rubin, ngVLA, LISA) to address the most important questions identified by the Astro2020 Decadal Survey. Here, we present an update on the status of AXIS.
The Wide-Field Infrared Transient Explorer (WINTER) is a new fully robotic infrared time-domain survey instrument at the Palomar Observatory, commissioned in June 2023. WINTER is performing a seeing-limited time domain survey of the infrared (IR) sky to detect, discover, and characterize astrophysical time-domain phenomena. As a dedicated observatory for real-time detection and rapid follow-up of infrared transient and variable targets, WINTER represents a new capability for multi-messenger astrophysics. We will describe the robotic software architecture of the WINTER Supervisor Program (WSP) which handles autonomous scheduling of both surveys and target-of-opportunity interrupts, as well as control and remote monitoring of the observatory, telescope, and cameras.
The Wide-Field Infrared Transient Explorer (WINTER) is a new near-infrared time-domain survey instrument installed on a dedicated 1-meter robotic telescope at Palomar Observatory in June of 2023. WINTER’s science goals include robotic follow-up of kilonovae from binary neutron star (BNS) and neutron-star black-hole (NSBH) mergers, surveys to study galactic and extragalactic transients and variables, along with building up a deep, coadded image of the near-infrared sky. The project also serves as a technology demonstration for new large-format Indium Gallium Arsenide (InGaAs) detectors for cost-effective near-infrared photometry without cryogenic cooling. WINTER’s custom camera combines six InGaAs detectors as a first run of a newly-designed 1920 x 1080 pixel read out integrated circuit (ROIC). It uses a novel tiled fly’s-eye optical design to cover a > 1 degree-squared field of view in Y-, J-, and shortened-H-band filters (0.9-1.7μm). The survey currently operates with a median limiting magnitude of JAB ≈ 18.5, running nightly robotic surveys and target of opportunity programs. In parallel to these science programs, there is ongoing work to improve WINTER’s performance, which shows a factor of ∼ 10 decreased instrument efficiency from the design. Laboratory and on-sky testing suggest the sensor’s InGaAs diode array is performing properly, but sensitivity is being lost during amplification in the ROIC’s pixel amplifier. We present the laboratory and on-sky performance newly-commissioned WINTER observatory along with ongoing and future efforts to improve performance.
The Advanced X-ray Imaging Satellite (AXIS) is a Probe-class concept that will build on the legacy of the Chandra x-ray Observatory by providing low-background, arcsecond-resolution in the 0.3-10 keV band across a 450 arcminute2 field of view, with an order of magnitude improvement in sensitivity. AXIS utilizes breakthroughs in the construction of lightweight segmented x-ray optics using single-crystal silicon, and developments in the fabrication of large-format, small-pixel, high readout rate CCD detectors with good spectral resolution, allowing a robust and cost-effective design. Further, AXIS will be responsive to target-of-opportunity alerts and, with onboard transient detection, will be a powerful facility for studying the time-varying x-ray universe, following on from the legacy of the Neil Gehrels (Swift) x-ray observatory that revolutionized studies of the transient x-ray Universe. In this paper, we present an overview of AXIS, highlighting the prime science objectives driving the AXIS concept and how the observatory design will achieve these objectives.
The Wide-Field Infrared Transient Explorer (WINTER) is a new time-domain instrument which will perform a seeing-limited survey of the near-infrared sky. Deployed on a dedicated 1-meter robotic telescope at Palomar Observatory, WINTER is designed to study transients of particular interest in the near-infrared including kilo-novae from gravitational-wave sources, supernovae, tidal disruption events, and transiting exoplanets around low mass stars with surveys to a depth of J=21 magnitudes. WINTER’s custom camera combines six commercial large-format Indium Gallium Arsenide (InGaAs) sensors, observing in Y, J, and a short-H (Hs) band filters (0.9-1.7 microns), and employs a novel tiled optical design to cover a >1 degree squared field of view with 90% fill factor. Each wide-format (1920 x 1080 pixels) InGaAs sensor operates at T = -50°C with a thermoelectric cooler, achieving background-limited photometry without cryogenic cooling. The tiled InGaAs sensors result in a wide field-of-view instrument with significant cost savings when compared to HgCdTe sensors. We present WINTER’s novel readout scheme, which includes custom electronics, firmware, and software for low-noise, real-time readout of the InGaAs sensors, including up to a 30x speed up of data reduction using GPUs. This work also outlines the cooling design for warm (T = -50°C) operation of the sensors with a two-stage thermometric cooler, copper heat pipes, and liquid cooling. We conclude with updates on the alignment, integration, and test of the WINTER instrument with a projected first light in Fall 2022.
The Wide-Field Infrared Transient Explorer (WINTER) is a new infrared time-domain survey instrument which will be deployed on a dedicated 1 meter robotic telescope at Palomar Observatory. WINTER will perform a seeing-limited time domain survey of the infrared (IR) sky, with a particular emphasis on identifying r-process material in binary neutron star (BNS) merger remnants detected by LIGO. As a dedicated observatory for real-time detection and rapid follow-up of infrared transient events, WINTER represents a new capability for multi-messenger astrophysics. We present the status of the WINTER instrument, including laboratory characterization and initial results from commissioning at its robotic observatory.
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