Astrometry during the past 2000 years

TL;DR

This paper reviews 2000 years of astrometry development, highlighting the recent advancements with space missions like Hipparcos and Gaia that drastically reduce measurement errors, and discusses the historical milestones and future prospects.

Contribution

It provides a comprehensive historical overview of astrometry over 2000 years and details the technological progress leading to modern space-based astrometry missions.

Findings

Gaia will reduce astrometric errors by a factor of 10,000

Hipparcos revolutionized space astrometry in the late 20th century

Historical milestones shaped modern astrometric techniques

Abstract

The satellite missions Hipparcos and Gaia by the European Space Agency will together bring a decrease of astrometric errors by a factor 10000, four orders of magnitude, more than was achieved during the preceding 500 years. This modern development of astrometry was at first obtained by photoelectric astrometry. An experiment with this technique in 1925 led to the Hipparcos satellite mission in the years 1989-93 as described in the following reports Nos. 1 and 10. The report No. 11 is about the subsequent period of space astrometry with CCDs in a scanning satellite. This period began in 1992 with my proposal of a mission called Roemer, which led to the Gaia mission due for launch in 2013. My contributions to the history of astrometry and optics are based on 50 years of work in the field of astrometry but the reports cover spans of time within the past 2000 years, e.g., 400 years of astrometry, 650 years of optics, and the "miraculous" approval of the Hipparcos satellite mission during a few months of 1980.