Calculating Meteoroid Orbits via Head Echo Observations at Jicamarca Radio Observatory, and Quantifying Uncertainty of Potentially Interstellar Meteoroids

For the purpose of meteor detection, the Jicamarca Radio Observatory (JRO) is one of the most sensitive high-power large-aperture (HPLA) facilities, and its 50 MHz antenna is capable of observing more than 100 head echoes per minute. Head echoes are observed when radio waves scatter from the meteor head plasma, which surrounds the meteoroid and travels with it as it enters Earth's atmosphere. Although many HPLA radar facilities are only capable of determining head echo position and velocity along the beam, JRO utilizes interferometric measurements via separate receiving quadrants of its array to measure head echo position in all three dimensions. Fitting a line to the head echo position yields the three-dimensional velocity vector of the meteoroid, along with the point at which it originates in the sky. The covariance matrices obtained via the linear fits in each dimension are used to quantify uncertainty due to measurement noise. Meteoroid motion is then simulated backwards in time in an Earth-centric, then heliocentric frame. The third-body perturbative effects of the Moon, Earth, and Jupiter, in addition to atmospheric drag and solar radiation pressure are taken into account. We use Monte Carlo simulation with our radar measurement uncertainties to determine the resulting heliocentric orbital element uncertainties. The orbits of hundreds of meteors observed at JRO on October 10th, 2019 are determined. This experiment was not timed to coincide with any meteor showers, so the observed population is assumed to be mostly, if not purely sporadic. Near 6am local time, most of the meteoroids are observed from the North and South Apex sources, and some are observed from the Helion and Anti-Helion sources. The majority originate from asteroidal orbits within the inner solar system, but numerous cometary meteoroids with orbits beyond Jupiter are also observed. A small fraction of meteoroids with orbital eccentricities greater than 1 are observed (i.e. meteoroids on interstellar trajectories), but in each case, their propagated orbital uncertainty is large enough to indicate that such events are likely due to radar measurement uncertainty. Future work seeks to analyze thousands more meteoroid trajectories in the search for definitive interstellar observations.