Use of IGS products in TAI applications

The Bureau International des Poids et Mesures (BIPM) is in charge of producing International Atomic Time TAI. In this aim, it uses clock data from more than 60 laboratories spread worldwide. For two decades, GPS has been an essential tool to link these clocks, and products from the International GNSS Service (IGS) have been used to improve the quality of these time links since its creation in the early 1990s. This paper reviews the various interactions between the IGS and time activities at the BIPM, and shows that TAI has greatly benefited from IGS products so that their availability is now an essential need for the quality of TAI links. On the other hand, IGS has also benefited from introducing time laboratories equipped with highly stable clocks in its network of stations. In the future, similar products will be needed for an ensemble of satellite systems, starting with GLONASS and GALILEO. It will be a major challenge to the IGS to obtain a consistent set of products, particularly for what concerns satellite clocks and inter-system bias values.