Algorithms to Determine Asteroid’s Physical Properties using Sparse and Dense Photometry, Robotic Telescopes and Open Data

The rapid pace of discovering asteroids due to advancements in detection techniques outpaces current abilities to analyze them comprehensively. Understanding an asteroid’s physical properties is crucial for effective deflection strategies and improves our understanding of the solar system’s formation and evolution. Dense photometry provides continuous time-series measurements valuable for determining an asteroid’s rotation period, yet is limited to a singular phase angle. Conversely, sparse photometry offers non-continuous measurements across multiple phase angles, essential for determining an asteroid’s absolute magnitude, albedo (reflectivity), and size. This paper presents open-source algorithms that integrate dense photometry from citizen scientists with sparse photometry from space and ground-based all-sky surveys to determine asteroids’ albedo, size, rotation, strength, and composition. Applying the algorithms to the Didymos binary asteroid, combined with data from GAIA, the Zwicky Transient Facility, and ATLAS photometric sky surveys, revealed Didymos to be 840 meters wide, with a 0.14 albedo, an 18.14 absolute magnitude, a 2.26-hour rotation period, rubble-pile strength, and an S-type composition. Didymos was the target of the 2022 NASA Double Asteroid Redirection Test (DART) mission. The algorithm successfully measured a 35-minute decrease in the mutual orbital period following the DART mission, equating to a 40-meter reduction in the mutual orbital radius, proving a successful deflection. Analysis of the broader asteroid population highlighted significant compositional diversity, with a predominance of carbonaceous (C-type) asteroids in the outer regions of the asteroid belt and siliceous (S-type) and metallic (M-type) asteroids more common in the inner regions. These findings provide insights into the diversity and distribution of asteroid compositions, reflecting the conditions and processes of the early solar system. This work empowers citizen scientists to become planetary defenders, contributing significantly to planetary defense and enhancing our understanding of solar system composition and evolution.