THOR: An Algorithm for Cadence-independent Asteroid Discovery

We present "Tracklet-less Heliocentric Orbit Recovery" (THOR), an algorithm for linking of observations Solar System objects across multiple epochs that does not require intranight tracklets or a predefined cadence within search window. By sparsely covering regions interest in the phase space with "test orbits," transforming nearby over few nights into corotating frame test orbit at each epoch, and then performing generalized Hough transform on transformed detections followed by determination filtering, candidate clusters belonging to same can be recovered moderate computational cost little no constraint cadence. validate effectiveness this approach running simulations as well real data from Zwicky Transient Facility (ZTF). Applied short, two-week slice ZTF observations, we demonstrate THOR recover 97.4% all previously known discoverable targeted (a > 1.7 au) population five more purity between 97.7% 100%. This includes 10 likely new discoveries, recovery e ? 1 comet C/2018 U1 (the would have been discovery had 2018 when were taken). The package demo Jupyter notebooks are open source available https://github.com/moeyensj/thor.