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diff --git a/math/slalib/doc/dat.hlp b/math/slalib/doc/dat.hlp new file mode 100644 index 00000000..20777dc5 --- /dev/null +++ b/math/slalib/doc/dat.hlp @@ -0,0 +1,55 @@ +.help dat Jun99 "Slalib Package" +.nf + + DOUBLE PRECISION FUNCTION slDAT (UTC) + + - - - - + D A T + - - - - + + Increment to be applied to Coordinated Universal Time UTC to give + International Atomic Time TAI (double precision) + + Given: + UTC d UTC date as a modified JD (JD-2400000.5) + + Result: TAI-UTC in seconds + + Notes: + + 1 The UTC is specified to be a date rather than a time to indicate + that care needs to be taken not to specify an instant which lies + within a leap second. Though in most cases UTC can include the + fractional part, correct behaviour on the day of a leap second + can only be guaranteed up to the end of the second 23:59:59. + + 2 For epochs from 1961 January 1 onwards, the expressions from the + file ftp://maia.usno.navy.mil/ser7/tai-utc.dat are used. + + 3 The 5ms timestep at 1961 January 1 is taken from 2.58.1 (p87) of + the 1992 Explanatory Supplement. + + 4 UTC began at 1960 January 1.0 (JD 2436934.5) and it is improper + to call the routine with an earlier epoch. However, if this + is attempted, the TAI-UTC expression for the year 1960 is used. + + + :-----------------------------------------: + : : + : IMPORTANT : + : : + : This routine must be updated on each : + : occasion that a leap second is : + : announced : + : : + : Latest leap second: 1999 January 1 : + : : + :-----------------------------------------: + + P.T.Wallace Starlink 31 May 1999 + + Copyright (C) 1999 Rutherford Appleton Laboratory + Copyright (C) 1995 Association of Universities for Research in Astronomy Inc. + +.fi +.endhelp |