From ksenior at rom.usno.navy.mil Fri Feb 15 11:35:44 2002 From: ksenior at rom.usno.navy.mil (Ken Senior) Date: Fri, 15 Feb 2002 19:35:44 +0000 Subject: [IGSMAIL-3742]: IGS Timescales Message-ID: <3C6D6310.1050905@rom.usno.navy.mil> ****************************************************************************** IGS Electronic Mail 15 Feb 14:52:59 PST 2002 Message Number 3742 ****************************************************************************** Author: Ken Senior Dear Colleagues, With reference to the new IGS clock products described in IGS Mails #3470 and #3615, we have made several more changes to the system which generates the Rapid (IGRT) and Final (IGST) IGS timescales. The complete set of plots and .clk product files have been regenerated for each timescale from the beginning of receiver clock availability (late 2000). We expect this to be the last major enhancement to the system. Any future changes should not require replacement of timescale data already posted. The changes implemented are: * The upper limit of weights each clock can carry in the ensemble is now set nominally to the maximum of {0.1, 2.5/# masers, 2.5/# clocks}. This change was necessary particularly for the Rapid timescale IGRT which has suffered from a number of data dropouts (sometimes resulting in only 1 or 2 masers available for certain days). * By request, Allan deviation plots are now included for all clocks (including crystals). * Chi-Square statistics using the appropriate equivalent degrees of freedom for overlapping Allan deviation computations are now performed for the calculation of confidence limits in the Allan deviation plots. Results are available at http://clockdev.usno.navy.mil/igst and ftp://clockdev.usno.navy.mil/igst Regards, Ken Senior Time Service Department--Clock Development U.S. Naval Observatory Ken Senior