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Instrumentation And Methods For Astrophysics

1000 Days to First Light: Construction of the Perth-Lowell Telescope Facility 1968-71

Negotiations began 1n 1968 for a telescope facility at Perth Observatory for NASA's International Planetary Patrol Network. 1,000 days later the telescope saw first light. The facility bears no resemblance to other observatories. Inside a dome, the telescope sits on a 42 ft tall concrete pier with a wrap-around staircase and concrete legs. Surrounding forest is similar in height to the dome, the design of which is counter intuitive. This study investigated why, at the risk of compromising performance, there was a departure from standard design, and to to identify drivers for the decision making. Observatory visitors learn of a government architect, Tadeusz Andrzejaczek who made whimsical, successive increases to the height of the structure. Though designed in collaboration with Acting Government Astronomer, Bertrand Harris, it is improbable that a public servant architect would have such influence over a scientific installation. Vibration amelioration was met by designing massive strength and rigidity into the structure. Thermal expansion and wind stresses were reduced using features such as shade fins and protective walls, and ground thermal disturbance was addressed by simply making it tall. Seeing measurements were not a significant design consideration. The facility exists with its current floor height because of successive approvals for modification. The initial design was by Harris and requests for redesigns came from him but in close negotiation the Andrzejaczek who desired a structure of futuristic shape and proportions. Harris's designs were influenced by his personal English background and the Old Perth Observatory where he worked as an astronomer. Andrzejaczek's design was influenced by an observatory in his birth city, his alignment with contemporary designers and his artistic flair.

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Instrumentation And Methods For Astrophysics

2-aminooxazole in astrophysical environments: IR spectra and destruction cross sections for energetic processing

2-aminooxazole (2AO), a N-heterocyclic molecule, has been proposed as an intermediate in prebiotic syntheses. It has been demonstrated that it can be synthesized from small molecules such as cyanamide and glycoaldehyde, which are present in interstellar space. The aim of this work is to provide infrared spectra, in the solid phase for conditions typical of astrophysical environments and to estimate its stability toward UV photons and cosmic rays. Infrared (4000-600 cm ?? ) absorption spectra at 20 K, 180 K, and 300 K, IR band strengths, and room temperature UV (120-250 nm) absorption spectra are given for the first time for this species. Destruction cross-sections of 9.5 10 ??8 cm 2 and 2 10 ??6 cm 2 were found in the irradiation at 20 K of pure 2AO and 2AO:H 2 O ices with UV (6.3-10.9 eV) photons or 5 keV electrons, respectively. These data were used for the estimate of half-life times for the molecule in different environments. It is estimated that 2AO could survive UV radiation and cosmic rays in the ice mantles of dense clouds beyond cloud collapse. In contrast, it would be very unstable at the surface of cold Solar System bodies like Kuiper belt objects, but the molecule could still survive within dust grain agglomerates or cometesimals.

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Instrumentation And Methods For Astrophysics

A Brief Introduction to the Adomian Decomposition Method, with Applications in Astronomy and Astrophysics

The Adomian Decomposition Method (ADM) is a very effective approach for solving broad classes of nonlinear partial and ordinary differential equations, with important applications in different fields of applied mathematics, engineering, physics and biology. It is the goal of the present paper to provide a clear and pedagogical introduction to the Adomian Decomposition Method and to some of its applications. In particular, we focus our attention to a number of standard first-order ordinary differential equations (the linear, Bernoulli, Riccati, and Abel) with arbitrary coefficients, and present in detail the Adomian method for obtaining their solutions. In each case we compare the Adomian solution with the exact solution of some particular differential equations, and we show their complete equivalence. The second order and the fifth order ordinary differential equations are also considered. An important extension of the standard ADM, the Laplace-Adomian Decomposition Method is also introduced through the investigation of the solutions of a specific second order nonlinear differential equation. We also present the applications of the method to the Fisher-Kolmogorov second order partial nonlinear differential equation, which plays an important role in the description of many physical processes, as well as three important applications in astronomy and astrophysics, related to the determination of the solutions of the Kepler equation, of the Lane-Emden equation, and of the general relativistic equation describing the motion of massive particles in the spherically symmetric and static Schwarzschild geometry.

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Instrumentation And Methods For Astrophysics

A Comparison of Trapped Particle Models in Low Earth Orbit

Space radiation is well-known to pose serious issues to solid-state high-energy sensors. Therefore, radiation models play a key role in the preventive assessment of the radiation damage, duty cycles, performance and lifetimes of detectors. In the context of HERMES-SP mission we present our investigation of AE8/AP8 and AE9/AP9 specifications of near-Earth trapped radiation environment. We consider different circular Low-Earth orbits. Trapped particles fluxes are obtained, from which maps of the radiation regions are computed, estimating duty cycles at different flux thresholds. Outcomes are also compared with published results on in-situ measurements.

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Instrumentation And Methods For Astrophysics

A Comprehensive Line-Spread Function Error Budget for the Off-Plane Grating Rocket Experiment

The Off-plane Grating Rocket Experiment (OGRE) is a soft X-ray grating spectrometer to be flown on a suborbital rocket. The payload is designed to obtain the highest-resolution soft X-ray spectrum of Capella to date with a resolution goal of R(λ/?λ)>2000 at select wavelengths in its 10--55 Angstrom bandpass of interest. The optical design of the spectrometer realizes a theoretical maximum resolution of R??000 , but this performance does not consider the finite performance of the individual spectrometer components, misalignments between components, and in-flight pointing errors. These errors all degrade the performance of the spectrometer from its theoretical maximum. A comprehensive line-spread function (LSF) error budget has been constructed for the OGRE spectrometer to identify contributions to the LSF, to determine how each of these affects the LSF, and to inform performance requirements and alignment tolerances for the spectrometer. In this document, the comprehensive LSF error budget for the OGRE spectrometer is presented, the resulting errors are validated via raytrace simulations, and the implications of these results are discussed.

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Instrumentation And Methods For Astrophysics

A D-term Modeling Code (DMC) for simultaneous calibration and full-Stokes imaging of very long baseline interferometric data

In this paper we present DMC, a model and associated tool for polarimetric imaging of very long baseline interferometry datasets that simultaneously reconstructs the full-Stokes emission structure along with the station-based gain and leakage calibration terms. DMC formulates the imaging problem in terms of posterior exploration, which is achieved using Hamiltonian Monte Carlo sampling. The resulting posterior distribution provides a natural quantification of uncertainty in both the image structure and in the data calibration. We run DMC on both synthetic and real datasets, the results of which demonstrate its ability to accurately recover both the image structure and calibration quantities as well as to assess their corresponding uncertainties. The framework underpinning DMC is flexible, and its specific implementation is under continued development.

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Instrumentation And Methods For Astrophysics

A Data-Taking System for Planetary Radar Applications

Most planetary radar applications require recording of complex voltages at sampling rates of up to 20 MHz. I describe the design and implementation of a sampling system that has been installed at the Arecibo Observatory, Goldstone Solar System Radar, and Green Bank Telescope. After many years of operation, these data-taking systems have enabled the acquisition of hundreds of data sets, many of which still await publication.

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Instrumentation And Methods For Astrophysics

A Fast Template Periodogram for Detecting Non-sinusoidal Fixed-shape Signals in Irregularly Sampled Time Series

Astrophysical time series often contain periodic signals. The large and growing volume of time series data from photometric surveys demands computationally efficient methods for detecting and characterizing such signals. The most efficient algorithms available for this purpose are those that exploit the O(NlogN) scaling of the Fast Fourier Transform (FFT). However, these methods are not optimal for non-sinusoidal signal shapes. Template fits (or periodic matched filters) optimize sensitivity for a priori known signal shapes but at a significant computational cost. Current implementations of template periodograms scale as O( N f N obs ) , where N f is the number of trial frequencies and N obs is the number of lightcurve observations, and due to non-convexity, they do not guarantee the best fit at each trial frequency, which can lead to spurious results. In this work, we present a non-linear extension of the Lomb-Scargle periodogram to obtain a template-fitting algorithm that is both accurate (globally optimal solutions are obtained except in pathological cases) and computationally efficient (scaling as O( N f log N f ) for a given template). The non-linear optimization of the template fit at each frequency is recast as a polynomial zero-finding problem, where the coefficients of the polynomial can be computed efficiently with the non-equispaced fast Fourier transform. We show that our method, which uses truncated Fourier series to approximate templates, is an order of magnitude faster than existing algorithms for small problems ( N??0 observations) and 2 orders of magnitude faster for long base-line time series with N obs ??10 4 observations. An open-source implementation of the fast template periodogram is available at this https URL.

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Instrumentation And Methods For Astrophysics

A High-Cadence UV-Optical Telescope Suite On The Lunar South Pole

We propose a suite of telescopes be deployed as part of the Artemis III human-crewed expedition to the lunar south pole, able to collect wide-field simultaneous far-ultraviolet (UV), near-UV, and optical band images with a fast cadence (10 seconds) of a single part of the sky for several hours continuously. Wide-field, high-cadence monitoring in the optical regime has provided new scientific breakthroughs in the fields of exoplanets, stellar astrophysics, and astronomical transients. Similar observations cannot be made in the UV from within Earth's atmosphere, but are possible from the Moon's surface. The proposed observations will enable studies of atmospheric escape from close-in giant exoplanets, exoplanet magnetospheres, the physics of stellar flare formation, the impact of stellar flares on exoplanet habitability, the internal stellar structure of hot, compact stars, and the early-time evolution of supernovae and novae to better understand their progenitors and formation mechanisms.

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Instrumentation And Methods For Astrophysics

A Measurement of Source Noise at Low Frequency: Implications for Modern Interferometers

We report on the detection of source noise in the time domain at 162MHz with the Murchison Widefield Array. During the observation the flux of our target source Virgo A (M87) contributes only ??1\% to the total power detected by any single antenna, thus this source noise detection is made in an intermediate regime, where the source flux detected by the entire array is comparable with the noise from a single antenna. The magnitude of source noise detected is precisely in line with predictions. We consider the implications of source noise in this moderately strong regime on observations with current and future instruments.

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