A comparison of radiometric calibration techniques for lunar impact flashes

Abstract

Video observations of lunar impact flashes have been made by a number of researchers since the late 1990's and the problem of determination of the impact energies has been approached in different ways Bellot Rubio et al. (2000a, b), Yanagisawa et al. (2008), Bouley et al. (2012), Suggs et al. (2014), Rembold and Ryan (2015), Ortiz et al. (2015), Madiedo et al. (2015). The wide spectral response of the unfiltered video cameras in use for all published measurements necessitates color correction for the standard filter magnitudes available for the comparison stars but this is not typically considered. In our approach, the published color of the comparison star and an estimate of the color of the impact flash is used to correct it to the chosen filter bandpass. Magnitudes corrected to standard filters are then used to determine the luminous energy in the filter bandpass according to the stellar atmosphere calibrations of Bessell et al. (1998). In this paper we compare the various photometric calibration techniques and calculation of luminous energy (radiometry) of impact flashes. This issue has significant implications for determination of luminous efficiency, predictions of impact crater sizes for observed flashes, and the determination of the flux of meteoroids in the 10s of grams to kilograms mass range.