Preliminary results of CCD observations of Himalia at Yunnan Observatories in 2015

TL;DR

This study demonstrates the potential of high-precision CCD astrometry for irregular satellites through preliminary observations of Himalia, achieving residuals around 0.04 arcsec.

Contribution

First experimental CCD astrometry of Himalia using Yunnan Observatories' telescopes, analyzing geometric and atmospheric effects for improved positional accuracy.

Findings

Residuals of about 0.004-0.002 arcsec in observed minus computed positions.

Standard deviation of residuals approximately 0.04 arcsec.

Successful measurement of Himalia's position relative to UCAC4 stars.

Abstract

In order to study the potential in high precision CCD astrometry of irregular satellites, we have made experimental observations for Himalia, the sixth and irregular satellite of Jupiter. A total of 185 CCD observations were obtained by using the 2.4 m telescope and 1 m telescope at Yunnan Observatories over ten nights. Preliminary analysis for the observations were made, including the geometric distortion, the atmospheric refraction, and also the phase effect. All positions of Himalia are measured relative to the reference stars from the catalogue UCAC4 in each CCD field of view. The theoretical positions of Himalia were retrieved from the IMCCE, while the positions of Jupiter were obtained based on the planetary theory INPOP13C. The results show that the mean (O-C) (observed minus computed) residuals are -0.004 and -0.002 arcsec in right ascension and declination, respectively. The standard deviation of (O-C) residuals are estimated at about 0.04 arcsec in each direction.