COMetary dust TAIL Simulator (COMTAILS): A computer code to generate comet dust tail brightness images

Context. We present the COMetary dust TAIL Simulator (COMTAILS), a numerical Monte Carlo code to generate images of dust tail brightness from comets and active asteroids in the Solar System. Aims. We describe a numerical code, available to interested users, capable of generating simulated images of dust tail brightness for comparison with observations, to retrieve key dust parameters including size distribution, ejection velocities, and dust loss rates. An optional stellar field can be included in the background allowing for the assessment of stellar extinction by the tail, which can be compared with observational data. Methods. A Monte Carlo procedure was used to obtain the simulated images. The orbital parameters of the targets and their helio-centric positions and velocities were obtained from the JPL Horizons on-line ephemeris system. Results. Earlier versions of this code have been used to characterize the dust environment of various targets. In this study we present recent examples that demonstrate its ability to fit observed images of the long-period comets C/2024 N3 (NEOWISE) and C/2023 A3 (Tsuchinshan-ATLAS). The code is readily applicable to future targets that may be identified for the upcoming European Space Agency Comet Interceptor mission.