Reconstruction and Accuracy Analysis of 2016HO3 Ephemeris Based on Ground Observations

Objectives The ephemeris of small bodies is an important and basic supporting data in small body exploration missions, which has strong practical significance in engineering and science. We aim at the near-Earth asteroid, 2016HO3, one of the exploration targets of the Tianwen 2 mission.

Methods First, we introduce and analyze the available ground-based observation data, and establish the process of using ground-based observation data to solve the ephemeris of small celestial body, 2016HO3. According to solving epoch, weighting and observation selection, 16 orbit determination schemes were compared.

Results The results show that the observed residuals after fitting in the right ascension and declination directions are almost within 1.0″, which confirms the rationality of the data processing flow and the calculation strategy. Compared with the ephemeris published by Jet Propulsion Laboratory（JPL）, during one year the differences between the two are less than 0.025″ and 0.25″ in the right ascension and declination directions respectively. It has been also noticed that different weighting models and the processing of observations significantly affect the orbit determination of 2016HO3.

Conclusions When using observations excluding two observations at 2004 combined with the vfcc17 weight model, the root mean square of position difference with respect to the ephemeris provided by JPL Horizons during 50 a is about 87.393 km. This study can provide some reference and basic data support for the measurement data processing of the upcoming Tianwen 2 mission.