1 Introduction

When we became involved in the design of the photometric system for GAIA, which is under evaluation by ESA as the next Cornertone 5 mission, we realized how useful it would have been to have a nearly complete census of the existing ground-based and space-born photometric systems. The completion of the Asiago proposal for the GAIA photometric system (Munari ) was originally conceived to follow the realization of the Asiago Database on Photometric Systems (ADPS), but actually the reverse happened because the preparation of ADPS has been a tougher task than anticipated. This paper intends to summarise this extensive census in an interesting way for the general reader.

Some compilations of photometric systems have already been presented, among others by Lamla (), Bessell (), in the books by Golay () and Straizys () and on the world wide web by Mermilliod et al. (). The latter focuses mainly on the data collected in various photometric systems (with entries for more than $2\ 10^5$ stars). At the same time, the Mermilliod et al. www version available at the time of submission of the ADPS provides a census of photometric systems by listing and describing 82 of them. Even if our compilation was independent, we undoubtedly benefited by checking against Mermilliod et al.'s work.

In compiling the ADPS we have tried to be as complete as possible for the optical region (from 0.3 to 1.0 $\mu$m, where GAIA is currently planned to collect data), but effort has also been made to include ultraviolet as well as infrared photometric systems (even if at a lower degree of completeness). The ADPS www site will be regularly updated as new information becomes available.

In this paper we rely only on data from literature (instrumental set-ups, transmission curves, calibration and transformation functions, zero points, etc.), with preference for those provided by the authors of the photometric systems in the original papers. Unfortunately, accurate and complete information is available only for a small minority of the surveyed systems. We have been able to locate in literature (or derive ourselves from published graphs) the tabular band transmission profiles for 105 systems. Calibration and transformation functions with any kind of accuracy have been published only for a fraction of the 167 surveyed systems. Even when calibration and transformation functions are available, it is not always easy to inter-compare them because of the heterogeneous methods adopted by the different authors (see Sect. 2). As a contribution toward a clarification of the whole issue, in a forthcoming Paper II we will inter-compare, calibrate and parameterise the systems by means of synthetic photometry using uniform criteria and the same set of synthetic and observed input spectra and extinction laws.

GAIA is a candidate ESA Cornerstone 5 mission designed to obtain extremely precise astrometry (in the micro-arcsec regime), multi-band photometry and medium/high resolution spectroscopy for a large sample of stars. The goals as depicted in the mission Red Book call for astrometry and broad band photometry to be collected for all stars down to $V \sim 20$ mag over the entire sky ($\sim$$1\ 10^9$ stars), with brighter magnitude limits for spectroscopy and intermediate band photometry. Each target star should be measured over a hundred times during the five year mission life-time, in a fashion similar to the highly successful Hipparcos operational mode. The astrophysical guidelines of the GAIA mission are discussed by Gilmore et al. (, and references therein) and Perryman (). An overview of the GAIA payload and spacecraft is presented by Mérat et al. ().