Role of Topocentric Parallax in Near-Earth Object Initial Orbit Determination

Abstract Near-Earth Object (NEO) initial orbit determination typically uses astrometric measurements during a close approach over time window much shorter than the orbital period of NEO. The is only weakly determined with dominant uncertainties in distance NEO from Earth. Topocentric allow us to estimate distances using observed nonlinear motions NEOs relative observers, which come motion Earth plus topocentric parallax (parallax) diversity observatory locations center. We calculate ratio contributions and be approximately ( T Δ/(day au)) 2 , where arc length measured days Δ approach. for ranging comes center, due mainly differential solar gravitational acceleration, when ≳ 1 day au ≲ au. This confirmed by simulation data supported observational real NEOs. In regime au, are inversely proportional amplitude parallax. Introducing diversities hour angles latitudes (especially alternating between extreme values) into scheduled follow-up observations can improve amplitude, thus accuracy. Most newly discovered this regime, we recommend optimizing properly scheduling very synthetic tracking astrometry accuracy determination.