Calibration of fish-eye lens and error estimation on fireball trajectories: application to the FRIPON network

Abstract

Context. Fireball networks are developing over the whole planet, with the aim of recovering meteorites and at the same time determining their orbits. The ultimate goal of such networks is to identify the parent bodies of meteorite families to achieve this, orbit accuracy is critical. Yet, the determination of an orbit relies on a long and complex reduction process including: (1) astrometry, with heavy distortion for fish-eye lenses, (2) estimation of the external bias on the observation, (3) fit of the trajectory, (4) deceleration model, and (5) actual orbit computation. Aims. Our goal is to compute accurate trajectories with an estimate of internal and external errors as realistic as possible, taking advantage of the dense observation network FRIPON (Fireball Recovery and InterPlanetary Observation Network), which comprises more than 100 cameras in France and Europe. In particular, we pay special attention to the distortion of images due to fish-eye lenses. In the present paper, we describe the analytical protocol that allows us to compute trajectories and their uncertainties. Methods. We developed a general distortion model to be used on the FRIPON fish-eye cameras. Such a model needs to be accurate even at low elevation, as most fireball observations are performed low on the horizon. The radial distortion is modelled by a nine-degree odd polynomial, hence by five parameters. In addition, we used three parameters to describe the geometry of the camera and two for non-symmetrical distortion. Lastly, we used a new statistical method taking systematic errors into account, which allows us to compute realistic confidence intervals. We tested our method on a fireball that fell on 2017-08-94 UT 00:06. Results. The accuracy of our astrometrical model for each camera is 2 arcmin (1σ), but the internal error on the fireball of 2017-08-94 UT 00:06 measurement is 0.7 arcmin (better than 1/10 pixel). We developed a method to estimate the external error considering that each station is independent and found it equal to 0.8 arcmin. Real residuals are coherent with our estimation of internal and external error for each camera, which confirms the internal consistency of our method. We discuss the advantages and disadvantages of this protocol.

Cavezzo, the first Italian meteorite recovered by the PRISMA fireball network. Orbit, trajectory, and strewn-field

“…At this time of writing, PRISMA has deployed 52 stations, among which 37 are fully operating and 15 are in installation phase. The PRISMA project is part of the international collaboration initiated by the FRIPON project (Fireball Recovery and InterPlanetary Observation Network, Colas et al 2014, Jeanne et al 2019and Colas et al 2020.…”

Luminous efficiency of meteors derived from ablation model after assessment of its range of validity

“…To compute the pre-atmospheric mass of the recorded meteoroids and asteroids the FRIPON pipeline utilizes an optimization of a fit through the velocity data, which is a slightly modified method of the one introduced by Gritsevich (2008). For details about the data processing we refer to Jeanne et al (2019).…”

“…Our method to compute the mass of an entering meteoroid is a variation on the procedure introduced by Gritsevich (2008). The origin of the method is based on the work by Stulov et al (1995), and the adapted variations to the methodology are detailed in Jeanne et al (2019) and Drolshagen et al (2021, accepted). The mass is computed based on the measured velocity and height of the recorded meteor.…”

“…We also direct the reader to this paper for more details on the method to derive the peak brightness as well as its assumed error. For a discussion on the errors of the parameters that were generated by the FRIPON pipeline, we refer to Jeanne et al (2019) and Colas et al (2020).…”

“…We computed the similarity between the orbits of the recorded meteoroids with the ones of established stream meteoroids from the database of the IAU Meteor Data Center (accessed 08.08.2020). The orbital elements of the investigated FRIPON meteoroids are computed within the FRIPON pipeline (see Jeanne et al (2019) and Colas et al (2020) for details) and extracted from the database for this work. With this method 719 could be classified as stream meteoroids and 1201 as sporadics.…”