Revealing two radio active galactic nuclei extremely near PSR J0437−-4715

Newton's gravitational constant $G$ may vary with time at an extremely low level. The time variability of $G$ will affect the orbital motion of a millisecond pulsar in a binary system and cause a tiny difference between the orbital period-dependent measurement of the kinematic distance and the direct measurement of the annual parallax distance. PSR J0437$-$4715 is the nearest millisecond pulsar and the brightest at radio. To explore the feasibility of achieving a parallax distance accuracy of one light-year, comparable to the recent timing result, with the technique of differential astrometry, we searched for compact radio sources quite close to PSR J0437$-$4715. Using existing data from the Very Large Array and the Australia Telescope Compact Array, we detected two sources with flat spectra, relatively stable flux densities of 0.9 and 1.0 mJy at 8.4 GHz and separations of 13 and 45 arcsec. With a network consisting of the Long Baseline Array and the Kunming 40-m radio telescope, we found that both sources have a point-like structure and a brightness temperature of $\geq$10$^7$ K. According to these radio inputs and the absence of counterparts in the other bands, we argue that they are most likely the compact radio cores of extragalactic active galactic nuclei rather than Galactic radio stars. The finding of these two radio active galactic nuclei will enable us to achieve a sub-pc distance accuracy with the in-beam phase-referencing very-long-baseline interferometric observations and provide one of the most stringent constraints on the time variability of $G$ in the near future.Comment: 9 pages, 3 tables, 3 figures. Accepted for publication in MNRA

A new method to calibrate ionospheric pulse dispersion for UHE cosmic ray and neutrino detection using the Lunar Cherenkov technique

UHE particle detection using the lunar Cherenkov technique aims to detect nanosecond pulses of Cherenkov emission which are produced during UHE cosmic ray and neutrino interactions in the Moon's regolith. These pulses will reach Earth-based telescopes dispersed, and therefore reduced in amplitude, due to their propagation through the Earth's ionosphere. To maximise the received signal to noise ratio and subsequent chances of pulse detection, ionospheric dispersion must therefore be corrected, and since the high time resolution would require excessive data storage this correction must be made in real time. This requires an accurate knowledge of the dispersion characteristic which is parameterised by the instantaneous Total Electron Content (TEC) of the ionosphere. A new method to calibrate the dispersive effect of the ionosphere on lunar Cherenkov pulses has been developed for the LUNASKA lunar Cherenkov experiments. This method exploits radial symmetries in the distribution of the Moon's polarised emission to make Faraday rotation measurements in the visibility domain of synthesis array data (i. e. instantaneously). Faraday rotation measurements are then combined with geomagnetic field models to estimate the ionospheric TEC. This method of ionospheric calibration is particularly attractive for the lunar Cherenkov technique as it may be used in real time to estimate the ionospheric TEC along a line-of-sight to the Moon and using the same radio telescope.Comment: 4 pages, 2 figures, Proceedings of ARENA 2010, Nantes, France; doi:10.1016/j.nima.2010.10.12

EMBRACE@Nancay: An Ultra Wide Field of View Prototype for the SKA

A revolution in radio receiving technology is underway with the development of densely packed phased arrays for radio astronomy. This technology can provide an exceptionally large field of view, while at the same time sampling the sky with high angular resolution. Such an instrument, with a field of view of over 100 square degrees, is ideal for performing fast, all-sky, surveys, such as the "intensity mapping" experiment to measure the signature of Baryonic Acoustic Oscillations in the HI mass distribution at cosmological redshifts. The SKA, built with this technology, will be able to do a billion galaxy survey. I will present a very brief introduction to radio interferometry, as well as an overview of the Square Kilometre Array project. This will be followed by a description of the EMBRACE prototype and a discussion of results and future plans.Comment: to appear in proceedings of the INFIERI Summer School INtelligent Signal Processing for FrontIEr Research and Industry, Paris 201

Compendium of Applications Technology Satellite user experiments

The achievements of the user experiments performed with ATS satellites from 1967 to 1973 are summarized. Included are fixed and mobile point to point communications experiments involving voice, teletype and facsimile transmissions. Particular emphasis is given to the Alaska and Hawaii satellite communications experiments. The use of the ATS satellites for ranging and position fixing of ships and aircraft is also covered. The structure and operating characteristics of the various ATS satellite are briefly described

Optical satellite-tracking program Semiannual progress report, 1 Jan. - 30 Jun. 1969

Research in Satellite Tracking Progra

Youthworx media: youth media and social enterprise as intervention and innovation

This research explores the impact of Youthworx, a community-based cross-sector response to the problem of youth marginalisation and social exclusion. Preface Youthworx is a successful model of a practical, community-based, cross-sector response to the problem of youth marginalisation and social exclusion. It combines professional expertise, networks and material resources across social service delivery agencies (Salvation Army and Youth Development Australia (YDA)), youth-run community media (SYN Media), an educational provider (North Melbourne Institute of Technology TAFE (NMIT)) and research organisations (the ARC Centre of Excellence for Creative Industries and Innovation (CCI), at the Swinburne Institute for Social Research (SISR)). Media training and production is used to build capacity to re-engage with learning, education and employment. After some years in development between 2008, when Youthworx effectively began operations, and 2013, the program has provided open access multimedia workshops, accredited training and, more recently, paid traineeships for more than 400 youth disconnected from formal learning, with experience of homelessness, juvenile justice or alcohol and drug abuse. Participants broadcast and distribute their works through SYN Media, local festivals and screenings, as well as online. They also make commissioned creative products for external clients and not-for-profit organisations. Research undertaken by Swinburne University’s SISR between 2005 and 2013 explored impact of Youthworx on these young people and the broader lessons for debates on social innovation, community media and creative economies, informal learning, opportunity and enterprise. The integrated R&D is a unique element of Youthworx, allowing documentation, analysis and capacity-building. It combined longitudinal on-site research, a comparative study of best practices across parallel international youth media initiatives, and mobilisation of established academic and industry networks. Although our findings to date have appeared in a range of publications, this document offers the first comprehensive report on the project. It discusses the development of Youthworx and the results of the 2008-13 period. The presented findings draw on a qualitative fieldwork at Youthworx and semistructured follow-up interviews with a group of Youthworx graduates who participated in the program between 2009-2011. In combination, this material is used to document and explore the specific institutional structure and cultural context in which Youthworx’s media training and production took place, the ways in which young people experienced, engaged with and valued the project, as well as the project’s social outcomes. The longitudinal account of Youthworx presented here integrates and summarises multiple voices, including industry partners, service organisations, practitioners, researchers and, importantly, young people themselves. It reflects arguments developed across the team, including material previously published