Characterization of precision premium in astrometry

TL;DR

This paper investigates the concept of precision premium in astrometry, demonstrating its effectiveness for separations under 100 arcseconds using Gaia DR2 data and modeling the precision variation with a sigmoidal function.

Contribution

It provides the first detailed analysis of the separation range where precision premium applies and models the precision variation with a sigmoidal function using recent data.

Findings

Precision premium is effective for separations less than 100 arcseconds.

Relative positional precision can be modeled by a sigmoidal function.

The study confirms the concept using Gaia DR2 and Uranian satellites data.

Abstract

Precision premium, a concept in astrometry that was firstly presented by Pascu in 1994, initially means that the relative positional measurement of the Galilean satellites of Jupiter would be more accurate when their separations are small. Correspondingly, many observations have been obtained of these Galilean satellites since then. However, the exact range of the separation in which precision premium takes effect is not clear yet, not to say the variation of the precision with the separation. In this paper, the observations of open cluster M35 are used to study precision premium and the newest star catalogue Gaia DR2 is used in the data reduction. Our results show that precision premium does work in about less than 100 arcsecs for two concerned objects, and the relative positional precision can be well fitted by a sigmoidal function. Observations of Uranian satellites are also reduced as an example of precision premium.