Download or view UT1.frink in plain text format
/** This file is generated by makeUT1.frink ! Do not update this manually.
This contains short-term calculations for UT1 and UT2. These are time
corrections for DeltaT:
DeltaT = 32.184 s + (TAI-UTC) - (UT1-UTC)
TT = TAI + 32.184 s
Where TAI-UTC can be obtained from the function TAIMinusUTC[date]. In Frink
notation, DeltaT can be predicted *in the short-term* by:
deltaTPred[date] := 32.184 s + TAIMinusUTC[date] - UT1MinusUTC[date]
The primary source of UT1-UTC corrections is IERS Bulletin A, found at:
https://www.iers.org/IERS/EN/DataProducts/EarthOrientationData/eop.html
as well as:
https://maia.usno.navy.mil/products/deltaT
*/
// This is just to get the definition of BesselianDate. Should probably be
// made into a native Frink function.
use sun.frink
/** Return (UT2-UT1). This equation is found at the top of IERS Bulletin A. */
UT2MinusUT1[date] :=
{
T = BesselianDate[date]
return (0.022 sin[2 pi T] - 0.012 cos[2 pi T] - 0.006 sin[4 pi T] + 0.007 cos[4 pi T]) s
}
/** This uses the extrapolating equation from IERS Bulletin A which states
"The following formulas will not reproduce the predictions given below,
but may be used to extend the predictions beyond the end of this table."
LOL.
For more accuracy in the short term, this value should be interpolated from
the values published in IERS Bulletin A.
*/
UT1MinusUTC[date] :=
{
return (0.0637 + 0.00005 ((MJD[date]/day) - 61049) ) s - UT2MinusUT1[date]
}
/** Short-range predictions for deltaT */
deltaTPred[date] := 32.184 s + TAIMinusUTC[date] - UT1MinusUTC[date]
Download or view UT1.frink in plain text format
This is a program written in the programming language Frink.
For more information, view the Frink
Documentation or see More Sample Frink Programs.
Alan Eliasen, eliasen@mindspring.com