Rights and wrongs of the Hipparcos data: A critical assessment of the Hipparcos catalogue

TL;DR

This paper critically evaluates the Hipparcos catalogue's data quality, identifying defects and assessing reliability, with insights applicable to future astrometric missions like Gaia.

Contribution

It provides a new analysis of raw Hipparcos data, identifies specific data defects, and discusses implications for astrometric accuracy and future missions.

Findings

Identified scan-phase discontinuities and external hit effects.

Confirmed stability of the basic angle during the mission.

Discussed the impact of observing conditions on data reliability.

Abstract

A critical assessment of the quality of the Hipparcos data, partly supported by a completely new analysis of the raw data, is presented with the aim of clarifying reliability issues that have surfaced since the publication of the Hipparcos catalogue in 1997. A number of defects in the data are identified, such as scan-phase discontinuities and effects of external hits. These defects can be repaired when re-reducing the raw data. Instabilities in the great-circle reduction process are recognised and identified in a number of data sets. These resulted mainly from the difficult observing conditions imposed by the anomalous orbit of the satellite. The stability of the basic angle over the mission is confirmed, but the connectivity between the two fields of view has been less than optimal for some parts of the sky. Both are fundamental conditions for producing absolute parallaxes. Although there is clear room for improvement of the Hipparcos data, the catalogue as published remains generally reliable within the quoted accuracies. Some of the findings presented here are also relevant for the forthcoming Gaia mission.