First use of a HyViSI H4RG for Astronomical Observations

We present the first astronomical results from a 4K2 Hybrid Visible Silicon PIN array detector (HyViSI) read out with the Teledyne Scientific and Imaging SIDECAR ASIC. These results include observations of astronomical standards and photometric measurements using the 2.1m KPNO telescope. We also report results from a test program in the Rochester Imaging Detector Laboratory (RIDL), including: read noise, dark current, linearity, gain, well depth, quantum efficiency, and substrate voltage effects. Lastly, we highlight results from operation of the detector in window read out mode and discuss its potential role for focusing, image correction, and use as a telescope guide camera

Genetic mechanisms of critical illness in COVID-19.

Host-mediated lung inflammation is present1, and drives mortality2, in the critical illness caused by coronavirus disease 2019 (COVID-19). Host genetic variants associated with critical illness may identify mechanistic targets for therapeutic development3. Here we report the results of the GenOMICC (Genetics Of Mortality In Critical Care) genome-wide association study in 2,244 critically ill patients with COVID-19 from 208 UK intensive care units. We have identified and replicated the following new genome-wide significant associations: on chromosome 12q24.13 (rs10735079, P = 1.65 × 10-8) in a gene cluster that encodes antiviral restriction enzyme activators (OAS1, OAS2 and OAS3); on chromosome 19p13.2 (rs74956615, P = 2.3 × 10-8) near the gene that encodes tyrosine kinase 2 (TYK2); on chromosome 19p13.3 (rs2109069, P = 3.98 ×  10-12) within the gene that encodes dipeptidyl peptidase 9 (DPP9); and on chromosome 21q22.1 (rs2236757, P = 4.99 × 10-8) in the interferon receptor gene IFNAR2. We identified potential targets for repurposing of licensed medications: using Mendelian randomization, we found evidence that low expression of IFNAR2, or high expression of TYK2, are associated with life-threatening disease; and transcriptome-wide association in lung tissue revealed that high expression of the monocyte-macrophage chemotactic receptor CCR2 is associated with severe COVID-19. Our results identify robust genetic signals relating to key host antiviral defence mechanisms and mediators of inflammatory organ damage in COVID-19. Both mechanisms may be amenable to targeted treatment with existing drugs. However, large-scale randomized clinical trials will be essential before any change to clinical practice

Hybrid CMOS SiPIN detectors as astronomical imagers

Charge Coupled Devices (CCDs) have dominated optical and x-ray astronomy since their inception in 1969. Only recently, through improvements in design and fabrication methods, have imagers that use Complimentary Metal Oxide Semiconductor (CMOS) technology gained ground on CCDs in scientific imaging. We are now in the midst of an era where astronomers might begin to design optical telescope cameras that employ CMOS imagers. The first three chapters of this dissertation are primarily composed of introductory material. In them, we discuss the potential advantages that CMOS imagers offer over CCDs in astronomical applications. We compare the two technologies in terms of the standard metrics used to evaluate and compare scientific imagers: dark current, read noise, linearity, etc. We also discuss novel features of CMOS devices and the benefits they offer to astronomy. In particular, we focus on a specific kind of hybrid CMOS sensor that uses Silicon PIN photodiodes to detect optical light in order to overcome deficiencies of commercial CMOS sensors. The remaining four chapters focus on a specific type of hybrid CMOS Silicon PIN sensor: the Teledyne Hybrid Visible Silicon PIN Imager (HyViSI). In chapters four and five, results from testing HyViSI detectors in the laboratory and at the Kitt Peak 2.1m telescope are presented. We present our laboratory measurements of the standard detector metrics for a number of HyViSI devices, ranging from 1k×1k to 4k×4k format. We also include a description of the SIDECAR readout circuit that was used to control the detectors. We then show how they performed at the telescope in terms of photometry, astrometry, variability measurement, and telescope focusing and guiding. Lastly, in the final two chapters we present results on detector artifacts such as pixel crosstalk, electronic crosstalk, and image persistence. One form of pixel crosstalk that has not been discussed elsewhere in the literature, which we refer to as Interpixel Charge Transfer (IPCT), is introduced. This effect has an extremely significant impact on x-ray astronomy. For persistence, a new theory and accompanying simulations are presented to explain latent images in the HyViSI. In consideration of these artifacts and the overall measured performance, we argue that HyViSI sensors are ready for application in certain regimes of astronomy, such as telescope guiding, measurements of fast planetary transits, and x-ray imaging, but not for others, such as deep field imaging and large focal plane astronomical surveys

The Space-based Telescopes for Actionable Refinement of Ephemeris (STARE) mission

Recent events, such as the February 2009 Iridium 33-Cosmos 2251 collision, have brought attention to the changing nature of the Low Earth Orbit (LEO) environment. The population of objects recorded by the US Space Catalog has doubled since 1992, resulting in an increased risk of on-orbit collisions. USSTRATCOM’s Space Surveillance Network (SSN) tracks resident space objects (RSO) and publicly releases a subset of these data to support conjunction (collision probability) analyses. However, these early warning systems did not prevent the Iridium – Cosmos collision. Conversely, there have been a number of high profile ISS false alarms where the crew has unnecessarily interrupted operations to take shelter. These examples highlight the need for better Space Situational Awareness (SSA) in LEO. The Space-based Telescopes for Actionable Refinement of Ephemeris (STARE) mission will improve SSA using a low-cost small satellite constellation. An operational STARE constellation of 18 nanosatellites will be able to assess greater than 99% of all conjunctions involving objects larger than 10 cm and has the capability to reduce the current collision false alarm rate by two orders of magnitude up to 24 hours ahead of closest approach, in effect reducing the number of actionable alerts to one per satellite lifetime. This is a significant improvement over today’s capability, which provides so many false alarms (estimated at one per month per satellite for a LEO sun-synchronous orbit) that alerts are regularly ignored due to the inability of the space assets to move frequently

Telescope Guiding with a HyViSI H2RG Used in Guide Mode

We report on long exposure results obtained with a Teledyne HyViSI H2RG detector operating in guide mode. The sensor simultaneously obtained nearly seeing-limited data while also guiding the Kitt Peak 2.1 m telescope. Results from unguided and guided operation are presented and used to place lower limits on flux/fluence values for accurate centroid measurements. We also report on significant noise reduction obtained in recent laboratory measurements that should further improve guiding capability with higher magnitude stars

Government-owned CubeSat Next Generation Bus Reference Architecture

The number of CubeSats and small satellites placed in orbit has been growing exponentially since 1999 as demonstrated by more than 40 CubeSats being launched in the last quarter of 2013 from the USA alone. While CubeSats were initially used for academic purpose and generally tailored towards technology demonstration, it has become more evident that small satellites can play a role in some operational contexts such as earth observation, space weather, or situational awareness, to name just a few. In the past, each institution involved in Small Satellites has often designed their own proprietary system with regards to communication, software, avionics, and command and control, with incremental improvements based on previous successes. While this may make sense in an academic environment, where it provides students with a wide range of learning opportunities, it distracts teams exploring scientific or operational missions from focusing primarily on the payload technology. Building upon previous work funded by the National Reconnaissance Office (NRO) and known as the Colony I and Colony II bus programs, the Lawrence Livermore National Laboratory (LLNL), in partnership with the Naval Postgraduate School (NPS) is developing a CubeSat bus reference architecture and a set of minimum specifications useful for government applications. The architecture has application to software, electrical, and mechanical interfaces and aims at providing a flexible platform that can be endorsed by industry, supporting interchangeability of components while retaining customization for payload integration. We intend to present the framework of the architecture and its first embodiment in a flat satellite prototype

The Cosmic X-Ray Background NanoSat (CXBN): Measuring the Cosmic X-Ray Background using the CubeSat Form Factor

The CXBN mission goal is to significantly increase the Cosmic X-Ray Background measurement precision in the 30-50 keV range. The mission addresses a fundamental science question central to our understanding of the structure, origin, and evolution of the universe by potentially lending insight into the high energy background radiation. The CXBN spacecraft will map the Extragalactic Diffuse X-Ray Background (DXRB) with a new Cadmium Zinc Telluride (CZT) detector. The DXRB measurement will pose a powerful tool for understanding the early universe and a window to the far-away universe. The science objectives were condensed into a novel spacecraft concept characterized by a sun-pointing, spinning spacecraft in LEO with moderate inclination. Launch trajectories allow four nominal passes per day over the primary Earth station at Morehead State University (Morehead, KY). The science mission requirements fortunately allow adoption of the economical CubeSat form factor. The major subsystems comprising the satellite are new —having been developed by the team. Innovative systems include power distribution, command and data handling, and attitude determination and control systems. The launch is scheduled for August 2012 from Vandenberg AFB through the NASA ELaNa program. CXBN was developed at low cost and on a highly constrained 12 month timeline