Asteroid-PPM Appluses
Asteroid positions were computed for every 0.25 d in a given year and then compared against the position in a hybrid of the SAO and PPM (Positions and Proper Motions) Catalog.

If an initial approach within 0.25° was found, the position of the asteroid was recalculated using numerical integration at 1-minute intervals centered on the original JD of the "hit" to find the JD of the shortest angular (great circle) distance.

Calculations by Brian D. Warner.