All‐sky imaging of meteor trails at 55.25 MHz with the first station of the Long Wavelength Array

Abstract

A new capability for high-sensitivity, all-sky monitoring of VHF meteor trail reflections with the first station of the Long Wavelength Array, or "LWA1, " is described. LWA1 is a ∼ 100 m diameter HF/VHF array of 256 crossed-dipole antennas with a unique transient buffer mode that allows it to monitor for meteor trails via all-sky imaging with the same sensitivity as a single-dish antenna ≳40 m in diameter. To demonstrate this capability, we have used a 2 h observing run conducted in August 2012 aimed at detecting and characterizing meteor trail reflections of analog TV transmissions at 55.25 MHz. The analysis techniques described here allowed for a detection rate of ∼9500 trails per hour, including the detection of two meteor streams with radiants in the Aries/Perseus and Aquila/Hercules regions that were not previously reported in the literature. In addition, we have found a population of relatively long-duration (∼1 to a few minutes), typically faint trails. These trails have implied horizontal speeds of 15-130 m s −1 , with a typical speed of ∼30 m s −1 . We have also used high-resolution time series of the brightest trails to characterize decay times over a relatively large geographical area (10• in longitude and latitude) and on short (∼5 min) time scales. Potential enhancements that could be enabled by the addition of more LWA stations are discussed.

Detection of Radio Emission From Fireballs

“…A typical reflection from an overdense trail reaches maximum brightness in just a few seconds and maintains a relatively constant average brightness while undergoing sporadic dimming and rebrightening. It then quickly decays away once it expands to the point that the density reaches the underdense criteria (Ceplecha et al 1998;Wislez 1995;Helmboldt et al 2014). The observed transients are also inconsistent with light curves from non-specular echoes, which vary greatly from one to the next, following no particular pattern.…”

“…First, typical transmitters are strongly polarized, resulting in reflections that are strongly polarized (Helmboldt et al 2014;Close et al 2011;Wislez 1995). However, no significant amount of linear or circular polarization has been detected from the observed transients.…”

The development of non-coherent passive radar techniques for space situational awareness with the Murchison Widefield Array

“…Radio interferometers such as Long Wavelength Array (LWA) Helmboldt et al, 2014) and LOw Frequency ARray (LOFAR) (van Haarlem et al, 2013;Gaussiran II et al, 2004) have detected reflections of non-cooperative transmitters from objects like meteors and aircrafts using correlated data in the past. In this work, we explore the use of the Murchison Widefield Array (MWA) for passive space surveillance in the FM band, building upon previous work.…”

Understanding instrumental Stokes leakage in Murchison Widefield Array polarimetry

“…The MWA operates in the 80-300 MHz band and consists of 128 aperture array "tiles" (Figure 1) spread over an area of approximately 3 km. It is closely related in frequency band to SKA LFAA pathfinders such as Low-Frequency Array [van Haarlem et al, 2013;Wijnholds et al, 2011] in Europe and Long Wavelength Array (LWA) in New Mexico, USA [Ellingson et al, 2009;Helmboldt et al, 2014]. Source tracking in low-frequency aperture arrays (LFAAs) is done solely by electronic scanning since LFAAs do not have moving parts.…”