Abstract. The statistical generation of an accurate, stable and reliable time scale from a clock ensemble calls for an efficient algorithm. Here we present a comparative study which points out conceptual differences and similarities between two different types of time scale algorithm used worldwide:

1. ALGOS (BIPM), which produces, bimonthly, the international reference TAI (temps atomique international) at the Bureau International des Poids et Mesures (Sèvres, France), and

2. AT1 (NIST), from which is obtained, in real-time, the AT1 time scale at the National Institute of Standards and Technology (Boulder, Colorado, USA).

These two algorithms rely basically upon weighted averages of clock readings, but the weight determination and the frequency prediction are of different types because they are adapted to different needs and to the peculiarities of the available time measurements.

Print publication: Issue 2 (1991)
Received 8 June 1990