Innovations in Modern Survey Simulation: Predicting Interstellar Objects in LSST

Survey simulation is a numerical tool used to contextualize the discoveries of modern surveys. In Solar System science, telescopic campaigns yield biased subsets of the overall intrinsic small body populations. Understanding the observational biases of a given group of objects is imperative to interpreting the survey discoveries (or lack thereof).

Interstellar objects (ISOs) are planetesimals, either asteroidal or cometary, which are unbound from their origin planetary system. ISOs are expected to be bountiful in the Milky Way; simulations have shown that the Solar System ejected most of its planetesimals during its early evolution and it is sensible to extrapolate that other planetary systems may do the same. Even so, to date there have only been two confirmed serendipitous ISO passages through the Solar System, 1I\`Oumuamua and 2I\Borisov. Discovery of the next interstellar object, 3I, is uncertain; the physical size and number density of ISOs are largely unconstrained. However, recent analysis of the solar neighbourhood using data from the Gaia mission (Hopkins et al. 2025) has provided a model for the characteristics of the local ISO population with which to survey simulate discoveries in upcoming surveys.

In this dissertation talk, I will discuss the challenges of simulating ISOs in a realistic survey, introduce the new innovations in survey simulating used in this work (in comparison to historical approaches), and provide probabilistic predictions for the characteristics of the ISO discoveries in the upcoming Legacy Survey of Space and Time (LSST).