Compute ΔTT,
the increment to be applied to Coordinated Universal Time UTC to give Terrestrial Time
TT.
CALL:
D = sla_DTT (DJU)
GIVEN:
DJU
D
UTC date as a modified JD
(JD−2400000.5)
RETURNED:
sla_DTT
D
TT−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 be guaranteed only up to the end of the second 23h59m59s.
(2)
Pre 1972 January 1 a fixed value of 10 + ET−TAI
is returned.
(3)
TT is one interpretation of the defunct time scale Ephemeris Time, ET.
(4)
See also the routine sla_DT, which roughly estimates ET−UT
for historical epochs.