Combining and comparing astrometric data from different epochs: A case study with Hipparcos and Nano-JASMINE

TL;DR

This paper presents a method to optimally combine astrometric data from different missions, demonstrated by merging Hipparcos and simulated Nano-JASMINE data, resulting in improved proper motion estimates before Gaia's final data release.

Contribution

The paper introduces a joint astrometric solution method for combining data from multiple missions, enhancing accuracy over traditional catalogue comparisons.

Findings

Significant improvement in proper motion accuracy using joint solutions.

Effective combination of Hipparcos and Nano-JASMINE data.

Method outperforms conventional catalogue combination techniques.

Abstract

The Hipparcos mission (1989-1993) resulted in the first space-based stellar catalogue including measurements of positions, parallaxes and annual proper motions accurate to about one milli-arcsecond. More space astrometry missions will follow in the near future. The ultra-small Japanese mission Nano-JASMINE (launch in late 2013) will determine positions and annual proper motions with some milli-arcsecond accuracy. In mid 2013 the next-generation ESA mission Gaia will deliver some tens of micro-arcsecond accurate astrometric parameters. Until the final Gaia catalogue is published in early 2020 the best way of improving proper motion values is the combination of positions from different missions separated by long time intervals. Rather than comparing positions from separately reduced catalogues, we propose an optimal method to combine the information from the different data sets by making a joint astrometric solution. This allows to obtain good results even when each data set alone is insufficient for an accurate reduction. We demonstrate our method by combining Hipparcos and simulated Nano-JASMINE data in a joint solution. We show a significant improvement over the conventional catalogue combination.