Characterising Radio Telescope Software With the Workload Characterisation Framework

We present a modular framework, the Workload Characterisation Framework (WCF), that is developed to obtain, store and compare key characteristics of radio astronomy processing software in a reproducible way. As a demonstration, we discuss the experiences using the framework to characterise a LOFAR calibration and imaging pipeline.Instrumentatio

Astronomical Data Analysis Software and Systems XXVI

This volume contains papers presented at the twenty-sixth annual conference on Astronomical Data Analysis Software and Systems (ADASS XXVI). The ADASS conference is the premier conference for the exchange of information about astronomical software and is held each year, hosted by a different astronomical institution. The conference provides a forum for astronomers, software engineers and data specialists from all around the world to discuss software, algorithms, technologies and recommendations applied to all aspects of astronomy, from telescope operations to data reduction, from data management to computing. The key themes for ADASS XXVI included: long-term data management in astronomical data archives, management of scientific and data analysis projects, connections between large databases and data reduction and analysis, HPC and distributed computing, the usage of Python in astronomy, and others. The conference also touched upon data modelling in astronomy and other topics, including demo booths, "bird of a feather" sessions, focus demos, and tutorials. This proceedings volume presents over a hundred and eighty reports from the oral, posters and other contributions to the conference

Studies of Asteroids with Exiguous Astrometry from Synoptic Surveys

Astrometry, i.e., the study of positions of stellar-appearing heavenly bodies, is the basis for all astronomical research. Each generation of new astronomical surveys delivers new insights into the structure of the Universe, including our Solar System. Small bodies of the Solar System, asteroids and comets, are the populations which reveal the initial conditions, overall structure, and previous processes shaping the Solar System. With the incremental development of the impressive survey programmes, certain types of objects will always be on the threshold of discoveries. Therefore, only a small number of data for these objects will ever be available. In this thesis, two such Solar System populations are investigated: Earth's temporary natural satellites, and asteroids discovered by the Gaia mission. The statistical properties and steady-state population of two sub-populations of Earth's natural satellites, temporarily-captured orbiters and flybys, are assessed. The challenges for detection and prospects for future investigation of Earth's natural satellites are discussed. Also, the detectability of Earth's temporarily-captured orbiters with the upcoming Large Synoptic Survey Telescope is investigated, raising the importance of dedicated treatment for small fast-moving objects in the processing. One of the many fields of astronomy where ESAs Gaia mission makes an important contribution is the discovery of newly discovered asteroids. Candidates for newly discovered asteroids are processed daily and distributed to follow-up observers. A new statistical orbital inversion method, random-walk ranging, is developed. Additionally, the method to improve follow-up predictions by lowering the effect of systematic errors is introduced. This thesis gives an overview of the phenomenon of the temporary capture of asteroids by planets. The statistical ranging-based orbital inversion methods are discussed. The advancements in the fields of stellar and asteroid astronomy over the ages, and respective breakthroughs in the relevant fields of astronomy are assessed.Astrometria, eli tähtimäisten taivaankappaleiden paikanmittaukseen keskittyvä tieteenala toimii perustana koko tähtitieteen tutkimukselle. Alati kehittyvät tähtitieteelliset seurantaohjelmat tuovat ilmi uusia näkökulmia maailmankaikkeuden rakenteeseen, sisältäen myös oman aurinkokuntamme. Aurinkokunnan pienkappaleiden, asteroidien ja komeettojen, populaatiot ovat avainasemassa paljastamassa aurinkokunnan alkuperäisiä olosuhteita yleisrakennetta ja aurinkokuntaa muokanneita menneitä prosesseja. Vaikuttavasta seurantaohjelmien harppauksisesta kehityksestä huolimatta tietyt kohteet tulevat aina olemaan hankalasti havaittavissa. Näin ollen näistä kohteista kerättävä data tulee aina olemaan määrältään hyvin vähäistä. Tässä väitöskirjassa tarkastellaan kahta aurinkokunnan pienkappalepopulaatiota, joista on ainoastaan harvoja havaintoja: Maapallon väliaikaisesti kaappautuvia kuita, sekä Gaia-mission löytämiä uusia asteroideja. Maapallon väliaikaisesti kaappautuvat kuut jakaantuvat kahteen alapopulaatioon: kiertäjiin ja ohilentäjiin. Molempien alapopulaation tilastolliset ominaisuudet ja pysyväispopulaatiot on määritelty. Maapallon väliaikaisesti kaappautuvien kuiden havaitsemisen ongelmat ja niitä koskevan tutkimuksen tulevaisuudennäkymiä on avattu. Myös väliaikaisesti kaappautuvien kuiden havaitsevuutta tulevan sukupolven LSST-teleskoopin avulla on tutkittu, korostaen pienten nopeasti liikkuvien kohteiden erityiskohtelun merkitystä datan käsittelyssä. Euroopan avaruusjärjestön Gaia-missiolla on tärkeä panos moneen tähtitieteen osa-alueeseen. Yksi näistä osa-alueista on entuudestaan tuntemattomien asteroidien havaitseminen. Uudet asteroidiehdokkaat käsitellään automaattisesti, ja niiden paikkaennusteet jaetaan jatkohavaitsijoille päivittäin. Gaia-mission asteroidihavaintoja varten on yhtäältä kehitetty uusi radanlaskentamenetelmä, ja toisaalta rakennettu metodi, jonka tarkoituksena on pienentää satunnaisvirheiden vaikutusta radanlaskentaan, mikä johtaa pienempiin ja helpommin hallittaviin ennusteisiin jatkohavaitsijoille. Tämän väitöskirjan johdanto-osiossa käsitellään yleisesti asteroidien väliaikaista kaappautumista planeettajärjestelmiin ja tilastollisia radanlaskentamenetelmiä. Lisäksi väitöskirjassa pohditaan tähti- ja asteroidiastrometrian historiallista kehitystä ja sen vaikutusta muihin tähtitieteen osa-alueisiin läpi vuosisatojen

Airborne laser sensors and integrated systems

The underlying principles and technologies enabling the design and operation of airborne laser sensors are introduced and a detailed review of state-of-the-art avionic systems for civil and military applications is presented. Airborne lasers including Light Detection and Ranging (LIDAR), Laser Range Finders (LRF), and Laser Weapon Systems (LWS) are extensively used today and new promising technologies are being explored. Most laser systems are active devices that operate in a manner very similar to microwave radars but at much higher frequencies (e.g., LIDAR and LRF). Other devices (e.g., laser target designators and beam-riders) are used to precisely direct Laser Guided Weapons (LGW) against ground targets. The integration of both functions is often encountered in modern military avionics navigation-attack systems. The beneficial effects of airborne lasers including the use of smaller components and remarkable angular resolution have resulted in a host of manned and unmanned aircraft applications. On the other hand, laser sensors performance are much more sensitive to the vagaries of the atmosphere and are thus generally restricted to shorter ranges than microwave systems. Hence it is of paramount importance to analyse the performance of laser sensors and systems in various weather and environmental conditions. Additionally, it is important to define airborne laser safety criteria, since several systems currently in service operate in the near infrared with considerable risk for the naked human eye. Therefore, appropriate methods for predicting and evaluating the performance of infrared laser sensors/systems are presented, taking into account laser safety issues. For aircraft experimental activities with laser systems, it is essential to define test requirements taking into account the specific conditions for operational employment of the systems in the intended scenarios and to verify the performance in realistic environments at the test ranges. To support the development of such requirements, useful guidelines are provided for test and evaluation of airborne laser systems including laboratory, ground and flight test activities

Searching for gravitational waves from pulsars

The work presented here looks at several aspects of searching for continuous gravitational waves from pulsars, often referred to simply as continuous waves or CWs. This begins with an examination of noise in the current generation of laser interferometer gravitational wave detectors in the region below ~100 Hz. This frequency region is of particular interest with regards to CW detection as two prime sources for a first CW detection, the Crab and Vela pulsars, are expected to emit CWs in this frequency range. The Crab pulsar's frequency lies very close to a strong noise line due to the 60 Hz mains electricity in the LIGO detectors. The types of noise generally present in this region are discussed. Also presented are investigations into the noise features present in the LIGO S6 data and the Virgo VSR2 data using a program called Fscan. A particular noise feature present during VSR2 was discovered with the use of Fscan, which I report on and show how it degrades the sensitivity of searches for CWs from the Vela pulsar using this data. I next present search results for CWs from the Vela pulsar using VSR2 and VSR4 data. Whilst these searches did not find any evidence for gravitational waves being present in the data, they were able to place upper limits on the strength of gravitational wave emission from Vela lower than the upper limit set by the pulsars spin-down, making it only the second pulsar for which this milestone has been achieved. The lowest upper limit derived from these searches confines the spin-down energy lost from Vela due to gravitational waves as just 9% of Vela's total spin-down energy. The data from VSR2 and VSR4 are also examined, analysis of hardware injections in these datasets verify the calibration of the data and the search method. Similar results are also presented for a search for CWs from the Crab pulsar, where data from VSR2, VSR3, VSR4, S5 and S6 are combined to produce an upper limit on the gravitational wave (GW) amplitude lower than has been previously possible, representing 0.5% of the energy lost by the pulsar as seen through its spin-down. The same search method is also applied to analyse data for another 110 known pulsars, with five of these being gamma-ray pulsars that have been timed by the Fermi satellite. GWs from the pulsars timed by Fermi are expected at frequencies below 40 Hz, the LIGO detectors are not calibrated below these frequencies but the Virgo detector is. Hence the data used to search for GWs from these pulsars is the Virgo VSR4 data. The other 105 pulsars were analysed using out of date ephemerides obtained for the LIGO S5 run and the data analysed was from the LIGO S6 run, hence the results obtained for these pulsars are presented as an indication of what results can be expected with updated ephemerides only. For these 110 pulsars the spin-down limits were not able to be beaten, although there are a few pulsars for which this may be able to be achieved with an analysis combining all the possible datasets, in particular J1913+1011. The final part of this thesis reports extensions to the search method used for the analyses previously described. The first way in which this search method is extended is the use of a nested sampling algorithm to perform the parameter estimation stage of the analysis which was previously preformed using a MCMC. The nested sampling code also allows for model selection through the computation of the Bayesian evidence, I present results from characterisation tests of this nested sampling search code that demonstrate the equivalence of its results to those from the MCMC and grid based codes. The other extension to the search method looks at a new CW emission mechanism from a neutron star with a pinned superfluid core that is misaligned from the star's principle axes. This emission model predicts CWs at both the stars spin frequency f and twice its spin frequency 2f, providing an extra data channel with which to perform a search when compared to the triaxial rotator model which only emits at 2f. I present the development of a search for the emission from this new model, tests of the algorithm developed using simulated data, and results from a search using actual data from the VSR4 run for CWs from the Crab pulsar. The testing of the search algorithm shows that the posterior for the model is sufficiently complex to inhibit useful parameter estimation, but that the computation of the Bayesian evidence allows one to distinguish between this model and the triaxial rotator given a low SNR signal in the f data channel

Rubin Observatory LSST Transients and Variable Stars Roadmap

The Vera C. Rubin Legacy Survey of Space and Time holds the potential to revolutionize time domain astrophysics, reaching completely unexplored areas of the Universe and mapping variability time scales from minutes to a decade. To prepare to maximize the potential of the Rubin LSST data for the exploration of the transient and variable Universe, one of the four pillars of Rubin LSST science, the Transient and Variable Stars Science Collaboration, one of the eight Rubin LSST Science Collaborations, has identified research areas of interest and requirements, and paths to enable them. While our roadmap is ever-evolving, this document represents a snapshot of our plans and preparatory work in the final years and months leading up to the survey\u27s first light

Commissioning and First Science Results of the Desert Fireball Network: a Global-Scale Automated Survey for Large Meteoroid Impacts

This thesis explores the first results from the Desert Fireball Network, a distributed global observatory designed to characterise fireballs caused by meteoroid impacts. To deal with the >50 terabytes of data influx per week, innovative data reduction techniques have been developed. The science topics investigated in this work include airbursts caused by large meteoroids impacting the Earth's atmosphere, the recovery of a meteorite and its orbital history, and the structure of a meteor shower

Hunting for the electro-magnetic counterpart to gravitational waves

The detection of GW170817, the first known binary neutron star merger, ushered in the era of multi-messenger astronomy. The Gravitational-Wave Optical Transient Observer (GOTO) is a new multi-camera instrument designed to cover large gravitational-wave localisation regions quickly, with the aim of identifying gravitational-wave counterparts quickly. This thesis covers the deployment of GOTO and the technical development of an automatic focus script, a real-time image subtraction pipeline, and a machine learner all with the aims of finding and announcing transients in real-time. The methods developed here can be used in other highcadence optical surveys. The thesis is motivated in the introduction, summarising the history of gravitational-wave astronomy and the importance of finding counterparts. GOTO is introduced properly in the methodology section. Here, I explain how GOTO is built and optimised for rapid transient discovery. From there, I show the development of an automatic focus script that exploits source geometry to quickly achieve focus. The following two chapters detail the the development of a new image-subtraction pipeline, which proves to be faster and better quality than the techniques currently used in the literature. Finally, I conclude this work using GOTO's first Gravitational-Wave follow-up campaign in compliment with the techniques developed in this thesis to find transients coincident with Gravitational- Wave detections. Showing GOTO is indeed capable and primed to find transients associated with gravitational-waves quickly

Data Mining by Grid Computing in the Search for Extrasolar Planets

A system is presented here to provide improved precision in ensemble differential photometry. This is achieved by using the power of grid computing to analyse astronomical catalogues. This produces new catalogues of optimised pointings for each star, which maximise the number and quality of reference stars available. Astronomical phenomena such as exoplanet transits and small-scale structure within quasars may be observed by means of millimagnitude photometric variability on the timescale of minutes to hours. Because of atmospheric distortion, ground-based observations of these phenomena require the use of differential photometry whereby the target is compared with one or more reference stars. CCD cameras enable the use of many reference stars in an ensemble. The more closely the reference stars in this ensemble resemble the target, the greater the precision of the photometry that can be achieved. The Locus Algorithm has been developed to identify the optimum pointing for a target and provide that pointing with a score relating to the degree of similarity between target and the reference stars. It does so by identifying potential points of aim for a particular telescope such that a given target and a varying set of references were included in a field of view centred on those pointings. A score is calculated for each such pointing. For each target, the pointing with the highest score is designated the optimum pointing. The application of this system to the Sloan Digital Sky Survey (SDSS) catalogue demanded the use of a High Performance Computing (HPC) solution through Grid Ireland. Pointings have thus been generated for 61,662,376 stars and 23,697 quasars