Emil Polisensky

EXPLORING THE TRANSIENT RADIO SKY WITH VLITE: EARLY RESULTS

We report on a search for radio transients at 340 MHz with the Jansky Very Large Array (VLA) Low band Ionospheric and Transient Experiment (VLITE). Between 2015 July 29 and 2015 September 27, operating in commensal mode, VLITE imaged approximately 2800 pointings covering 12,000 deg

Low frequency antenna options for the lunar surface

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The VLA Low Band Ionospheric and Transient Experiment (VLITE): A Commensal Sky Survey

on the sky, sampling timescales ranging from tens of seconds to several hours on a daily basis. In addition, between 2015 February 25 and 2015 May 9, VLITE observed 55 epochs of roughly 2-4 hours each toward the COSMOS field. Using existing radio source catalogs we have searched all the daily VLITE images for transients, while for the COSMOS field we compared individual images and the summed image to search for new sources in repeated observations of the same field. The wide range of timescales makes VLITE sensitive to both coherent and incoherent transient source classes. No new transients are found, allowing us to set stringent upper limits on transients at milliJansky levels and at low frequencies where comparatively few such surveys have been carried out to date. An all-sky isotropic rate of bursting radio transients with similar rates, duration, and intensity as the unusual transient GCRT J1745

Missile tracking and range safety: Tracking Interferometer Pathfinder System (TIPS)

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FIRST LIGHT FOR THE FIRST STATION OF THE LONG WAVELENGTH ARRAY

3009, discovered in wide-field monitoring toward the Galactic center, is ruled out with high confidence. The resulting non-detections allows us to argue that this is a coherent source, whose properties most resemble the growing class of nulling pulsars. We end with a discussion of the future prospects for the detection of transients by VLITE and other experiments.

Surveying the Dynamic Radio Sky with the Long Wavelength Demonstrator Array

There are a number of scientific motivations for low frequency radio observations from space. These include the possibility of detecting, and eventually imaging, the spectral line of neutral Hydrogen from the cosmic Dark Ages, before the first stars formed. This is the period between the creation of the cosmic microwave background and the formation of the first stars, massive black holes, and galaxies, a period of large-scale structure formation in the universe. The Hydrogen line from the Dark Ages is redshifted down to frequencies of tens of MHz. In addition, imaging and tracking of emission from solar and interplanetary radio bursts, and detecting electron cyclotron emission from extrasolar gas giant planets, all require observations at and below Earths ionospheric cutoff. Observations far from Earth can completely eliminate ionospheric absorption and distortion, and greatly reduce terrestrial interference (both natural and human-generated). But efficient antennas at low frequency are physically large. Consequently there has been a lot of work exploring concepts for low mass, wide bandwidth low frequency antennas that can be deployed in space. This paper summarizes recent work on deployable low frequency antennas, including thin film antennas that could be unrolled on the lunar surface and inflatable antennas for both free space and lunar locations.

The Radio Observatory on the Lunar Surface for Solar studies

The US Naval Research Laboratory (NRL) and the National Radio Astronomy Observatory (NRAO) have collaborated to develop, install, and commission a new commensal system on the Karl G. Jansky Very Large Array (VLA). The VLA Low Band Ionospheric and Transient Experiment (VLITE) makes use of dedicated samplers and fibers to tap the signal from 10 VLA low band receivers and correlate those through a real-time DiFX correlator. VLITE allows for the simultaneous use of the VLA to observe primary science using the higher frequencies receivers (1-50 GHz) through the NRAO WIDAR correlator and lower frequencies through the DiFX correlator. VLITE operates during nearly all observing programs and provides 64 MHz of bandwidth centered at 352 MHz. The operation of VLITE requires no additional resources from the VLA system running the primary science and produces an ad-hoc sky survey. The commensal system greatly expands the capabilities of the VLA through value-added PI science, stand-alone astrophysics, the opening of a new window on transient searches, and serendipity. In the first year of operation we have recorded more than 6300 hours spread across the sky. We present an overview of the VLITE program, discuss the sky coverage and depth obtained during the first year of operation, and briefly outline the astrophysics and transients programs.

Commensal low frequency observing on the NRAO VLA: VLITE status and future plans

The tracking of missiles at close range proximity has been an ongoing challenge for many launch environments. The ability to provide accurate missile trajectory information is imperative for range safety and early termination of flight. In an effort to provide a potential solution to tracking issues that have plagued many traditional techniques, the Tracking Interferometer Pathfinder System (TIPS) was developed at the Naval Research Laboratory, Washington, D.C. The paper herein describes the design, field test, and results of an interferometer deployed for missile tracking.