Accession Number : ADP009108

Title :   A Real-Time Prediction of UTC,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GREENBELT MD GODDARD SPACE FLIG HT CENTER

Personal Author(s) : Thomas, Claudine ; Allan, David W.

Report Date : 02 DEC 1993

Pagination or Media Count : 13

Abstract : The reference time scale for all scientific and technologic applications on the Earth, the Universal Coordinated Time UTC, must be as stable, reliable and accurate as possible. With this in view the BIPM and before it the BIH, have always calculated and then disseminated UTC with a delay of about 80 days. There are three fundamental reasons for doing this. (1) It takes some weeks for data, gathered from some 200 clocks spread world-wide, to be collected and for errors to be eliminated. (2) Changes in clock rates can only be measured with high precision well after the fact. (3) The measurement noise originating in time links, in particular using Loran-C, is smoothed out only when averaging over an extended period. Until mid-1992, the ultimate stability of UTC was reached at averaging times of about 100 days and corresponded to an Allan deviation oy(T) of about 1,5xl0-14 when compared to the best primary clock in the world, the PTB CS2.

Descriptors :   *PRECISION, *TIME STANDARDS, *TIME STUDIES, *NAVIGATION REFERENCE, DELAY, ERRORS, LORAN, MEASUREMENT, NOISE, STABILITY, TIME, FRANCE, PRECISION.

Subject Categories : Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE