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ut1.

Table of TAI - UT1 values

Overview

Slight changes in the orientation of the Earth's crust (and therefore the sites and the reference frame they define) relative to the spin axis of the Earth cause systematic changes between tracking stations and the GPS satellites. These Earth Orientation Parameters (EOP's) are significant to and detectable in GPS processing.

Several sources for measured and predicted EOP's exist. The most common source for NOAA orbit production is the NEOS Bulletin A from the U.S. Naval Observatory. This information is reformated and the pole. and UT1. files created. The ut1. file simply lists the TAI - UT1 rotations during some time span. TAI is the Terrestrial Atomic Time, a time scale with no leap seconds and whose standard unit is the SI second. UT1 is Universal Time (UT1 = UT), also a time scale with no leap seconds but whose standard unit is the solar day, i.e. the daily rotation of the Earth. The file is ASCII.

Example 

(9508.04) Created at 09/12/96 11:40:02.00 from ser7.96256
(5X,I5,6I11,2X,I2)               4 2450303 2450352  6  1          1.E-06
     50303   29859880   29860644   29861394   29861986   29862726   29863480   6
     50309   29864244   29865170   29866166   29867238   29868396   29869584   6
     50315   29870744   29871886   29873030   29874130   29875280   29876430   6
     50321   29877628   29878864   29880406   29882116   29883834   29885702   6
     50327   29887390   29888808   29890192   29891466   29892652   29893626   6
     50333   29894514   29895420   29896444   29897602   29898846   29900144   6
     50339   29901576   29903150   29904760   29906400   29908008   29909552   6
     50345   29911068   29912582   29914134   29915772   29917548   29919486   6
     50351   29921592   29923816                                               2
where:

Line 1 is a descriptive header.

Line 2 gives the format for reading the file, a data type flag, the Julian date of the first and last entry, the number of entries per line, the interval between entries (days), and the scaling factor all entries. The data type flag has two valid values:
2 = regularized UT1 (UT1R)
4 = UT1

Thereafter, each line has the modified Julian day number for the first values on each line, the TAI - UT1. The last number on each line is the number of TAI - UT1 values on that line. A blank in this last field implies the maximum, i.e. the number of entries per line given on line 2.
NOTE: entry * scaling factor = seconds 

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ut1.html
January 14, 2000
Steve Hilla