An Open-Access Web Tool for Light Curve Simulation and Analysis of Small Solar System Objects

TL;DR

The paper tackles the challenge of interpreting light curves of small Solar System bodies where traditional inversion is limited by non-convex shapes and sparse multi-geometry data. It introduces a web-based tool that starts from predefined 3D shape models and computes sky-plane projections and rotational light curves using both empirical and Hapke photometric models, plus a dedicated occultation-silhouette module for direct comparison with observed chords. The approach supports non-convex shapes, surface heterogeneity, tumbling, and phase-angle effects, and is accessible via a Python/Django implementation with Horizons geometry integration and optional data uploads. Validation on well-characterized targets (Haumea, Bennu, Eros) demonstrates good agreement with observations and highlights the tool's utility for photometric interpretation, ongoing campaigns, and future mission planning.

Abstract

We present a web-based application designed to simulate rotational light curves of small airless Solar System bodies under user-defined geometrical and physical conditions. The tool integrates both physical and empirical photometric models and enables users to input custom shape models, surface properties, and viewing geometries. A dedicated module also computes projected silhouettes at the epoch of stellar occultations, allowing direct comparison with observed chords. The application, developed in Python and Django, has been validated using well-characterized targets such as (136108) Haumea, (101955) Bennu, and (433) Eros, showing excellent agreement between synthetic and observed light curves and silhouettes. Beyond standard light curve simulations, the tool supports scenarios including surface heterogeneity, non-principal axis rotation (tumbling), and phase-angle effects. This flexible and accessible platform provides a powerful resource for interpreting photometric data, supporting ongoing observation campaigns, and aiding future mission planning.

Figures (7)

• Figure 1: Workflow of the web application from user input to result rendering.
• Figure 2: Haumea on January 21, 2017, as seen from Earth. On this date, Ortiz2017 reported observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multi-chord stellar occultation). These observations allowed them to constrain the shape of Haumea’s projected ellipse on the sky. The pink lines represent the projected occultation chords derived from the reported timings, while the yellow endpoints indicate the associated uncertainties in the ingress and egress times. The facet colors on the projected body indicate the relative level of irradiance received by each facet, with red corresponding to lower incidence angles and therefore higher irradiation. The overall agreement between the projected shape and the occultation chords supports the validity of our simulation.
• Figure 3: Projected view of Bennu, generated with a $\sim$20,000-facet downsampled shape model, as seen from Earth on 15 September 2005 (phase angle of $61.9^\circ$).
• Figure 4: Black dots represent the observational data from the light curve published by Hergenrother2013. Colored lines show the synthetic rotational light curves of Bennu as seen from Earth on 14–17 September 2005, sampled at one point per degree of rotation. An offset has been applied to synthetic light curves for clarity.
• Figure 5: Projected view of Eros, generated with a $\sim$20,000-facet downsampled shape model, as seen from Earth on 17 July 2016 (phase angle of $24.07^\circ$).