With a new probabilistic technique for sampling interstellar object (ISO) orbits with high efficiency, we assess the observability of ISOs under a realistic cadence for the upcoming Vera Rubin Observatory's Legacy Survey of Space and Time (LSST). Using the Ōtautahi-Oxford population model, we show that there will be complex on-sky structure in the pattern of direction and velocity revealed by the detected ISO population, with the expected enhanced northern flux complicating efforts to derive population parameters from the LSST's predominately southern footprint. For luminosity functions with slopes of 2. 5 qₛ 4. 0, the most discoverable ISOs have Hᵣ 14. 6-20. 7; for previously estimated spatial densities, between 6 and 51 total ISOs are expected. The slope of the luminosity function of ISOs will be relatively quickly constrained. Discoveries are evenly split around their perihelion passage and are biased to lower velocities. After their discovery by LSST, it will be rare for ISOs to be visible for less than a month; most will have mᵣ 23 for months, and the window for spectroscopic characterization could be as long as two years. These probabilistic assessments are robust against model or spatial density refinements that change the absolute numbers of ISO discoveries.
Dorsey et al. (Sun,) studied this question.