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Some active asteroids have been proposed to be formed as a result of impact events1. Because active asteroids are generally discovered by chance only after their tails have fully formed, the process of how impact ejecta evolve into a tail has, to our knowledge, not been directly observed. The Double Asteroid Redirection Test (DART) mission of NASA2, in addition to having successfully changed the orbital period of Dimorphos3, demonstrated the activation process of an asteroid resulting from an impact under precisely known conditions. Here we report the observations of the DART impact ejecta with the Hubble Space Telescope from impact time T+ 15 min to T+ 18.5 days at spatial resolutions of around 2.1 km per pixel. Our observations reveal the complex evolution of the ejecta, which are first dominated by the gravitational interaction between the Didymos binary system and the ejected dust and subsequently by solar radiation pressure. The lowest-speed ejecta dispersed through a sustained tail that had a consistent morphology with previously observed asteroid tails thought to be produced by an impact4,5. The evolution of the ejecta after the controlled impact experiment of DART thus provides a framework for understanding the fundamental mechanisms that act on asteroids disrupted by a natural impact1,6.

We describe the Pan-STARRS Moving Object Processing System (MOPS), a modern software package that produces automatic asteroid discoveries and identifications from catalogs of transient detections from next-generation astronomical survey telescopes. MOPS achieves >99.5% efficiency in producing orbits from a synthetic but realistic population of asteroids whose measurements were simulated for a Pan-STARRS4-class telescope. Additionally, using a nonphysical grid population, we demonstrate that MOPS can detect populations of currently unknown objects such as interstellar asteroids. MOPS has been adapted successfully to the prototype Pan-STARRS1 telescope despite differences in expected false detection rates, fill-factor loss, and relatively sparse observing cadence compared to a hypothetical Pan-STARRS4 telescope and survey. MOPS remains highly efficient at detecting objects but drops to 80% efficiency at producing orbits. This loss is primarily due to configurable MOPS processing limits that are not yet tuned for the Pan-STARRS1 mission. The core MOPS software package is the product of more than 15 person-years of software development and incorporates countless additional years of effort in third-party software to perform lower-level functions such as spatial searching or orbit determination. We describe the high-level design of MOPS and essential subcomponents, the suitability of MOPS for other survey programs, and suggest a road map for future MOPS development.

We present here the Pan-STARRS Moving Object Processing System (MOPS) Synthetic Solar System Model (S3M), the first-ever attempt at building a comprehensive flux-limited model of the major small-body populations in the solar system. The goal of the S3M is to provide a valuable tool in the design and testing of the MOPS software, and will be used in the monitoring of the upcoming Pan-STARRS 1 all-sky survey, which started science operations during late spring of 2010. The model is composed of synthetic populations of near-Earth objects (NEOs with a subpopulation of Earth impactors), the main-belt asteroids (MBAs), Jovian Trojans, Centaurs, trans-Neptunian objects (classical, resonant, and scattered trans-Neptunian objects [TNOs]), Jupiter-family comets (JFCs), long-period comets (LPCs), and interstellar comets. The model reasonably reproduces the true populations to a minimum of V= 24.5, corresponding to approximately the expected limiting magnitude for Pan-STARRS's ability to detect moving objects. The NEO synthetic population has been extended to H< 25 (corresponding to objects of about 50 m in diameter), allowing for close flybys of the Earth to be modeled.