I spoke too soon on Celestial Mechanics and Dynamical Astronomy (Celest. Mech. Dyn. Astron. for “short”) for Feb (vol.138 #1). They’re still going:
Liu, X. Armellin, R, Pirovano, L. et al. Analyzing collision probability for asteroids detected on too short arcs 11 s10569-026-10280-8
The world’s telescopes, by program or just by chance, detect asteroids. A small fraction of those Solar System bodies are Near-Earth Objects (NEOs), not Main Belt asteroids or what have you. And a small fraction of those NEOs will be Potentially Hazardous (PHOs). This occurs when, as we gain better and better tracking on the object, we determine its current position in the Solar System, its general orbit, and with time, a finer and finer solution for its orbit. Very rarely, that fine orbit solution results in an Earth-crossing trajectory. Then it is imperative to examine the object in even finer detail.
However, sometimes the above process does not unroll smoothly. Bodies go behind the Sun, making them unobservable from Earth (and even from space telescopes in Earth orbit). Some bodies are just small (like 2024 YR4), making them too dim when they are far from Earth (yet still not behind the Sun). How do we still determine what’s a threat, requiring action, and what isn’t?
Smart people are on it. When there isn’t the luxury of time to simply take observations over a sufficient span (a long “observing arc”), then we have to sharpen our pencils on the orbit solution. Liu et al. have a new procedure for computing the possible future trajectories of a given asteroid (its “admissible region”). If this pans out, we can better determine what asteroids compel us to use our limited telescope resources, and what asteroids turn out to be no real threat.