Time Bias Function (TBF) Overview

During the 10th International Workshop on Laser Ranging Instrumentation held in Shanghai, the CSTG resolved to adopt a standard file format for the global exchange of time bias functions (TBFs). A small working group drew up an outline proposal specifying the content of such files and this was adopted at the business meeting of the CSTG at the end of the workshop.

Good IRVs supplemented by frequently distributed, up-to-date TBFs give stations the best available predictions for every pass of every satellite. Having the correct time bias simplifies satellite acquisition, improves tracking during the pass and helps eliminate noise by using narrow range gates. Access to the Internet allows easy global distribution of TBFs at least daily for most satellites and more often for relatively difficult targets like GFZ-1.

Recognizing these facts the CSTG was keen to see accurate and comprehensive time bias data widely distributed in a compact form that could be easily assimilated into stations' operational systems, preferably automatically from email data files arriving with a standard subject header. The overall aims were: to provide TBFs with respect to all IRVs currently available from orbit groups; to incorporate TBFs produced by those groups into a single file in an agreed format; in that file to present one TBF for one satellite as a single line of data; all data quantities should be universally understood and unambiguous.

The NERC Space Geodesy Facility (NSGF, formerly RGO) group at Herstmonceux agreed to act as the clearing house for the collation and distribution of the new format TBF files. The files will be exploded to the community from the European Data Centre in Munich using a dedicated mailing list (slrtbf@dgfi.badw-muenchen.de). To unsubscribe to this service send a blank message with the subject header "unsubscribe" to slrtbf@dgfi.badw-muenchen.de. To join the list use the subject header "subscribe".

Responsible Government Official: Carey Noll
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