Tracklet-less Heliocentric Orbit Recovery

THOR (Tracklet-less Heliocentric Orbit Recovery) is an algorithm for asteroid discovery that does not require tracklets. Traditional approaches require consecutive observations (tracklets) of the same sky region to detect moving objects, limiting asteroid searches to datasets with specific observational cadences.

Developed by Joachim Moeyens at the University of Washington and B612 Asteroid Institute, THOR can discover asteroids in datasets regardless of observational cadence by linking observations across arbitrary time spans.

Performance Characteristics

• 97% efficiency at finding asteroids in Zwicky Transient Facility (ZTF) data
• 1.5-2× improved performance over existing discovery algorithms
• Applicable across astronomical surveys regardless of cadence
• Computationally feasible for large-scale dataset processing

Algorithm

THOR uses a statistical approach to identify sets of observations that could belong to the same moving object across arbitrary time spans. The algorithm tests orbital hypotheses against observational evidence to link observations separated by days, weeks, or months.

Applications

The tracklet-less approach enables:

• Asteroid searches in general-purpose astronomical datasets
• Increased discovery rates in existing surveys
• Improved orbit determination through longer observational arcs
• Processing of archival survey data for Solar System mapping

The algorithm is being integrated into ADAM’s discovery pipeline.