/// <summary>
/// For a given UTC date, calculate delta(AT) = TAI-UTC.
/// :------------------------------------------:
/// : :
/// : IMPORTANT :
/// : :
/// : A new version of this function must be :
/// : produced whenever a new leap second is :
/// : announced. There are four items to :
/// : change on each such occasion: :
/// : :
/// : 1) A new line must be added to the set :
/// : of statements that initialize the :
/// : array "changes". :
/// : :
/// : 2) The constant IYV must be set to the :
/// : current year. :
/// : :
/// : 3) The "Latest leap second" comment :
/// : below must be set to the new leap :
/// : second date. :
/// : :
/// : 4) The "This revision" comment, later, :
/// : must be set to the current date. :
/// : :
/// : Change (2) must also be carried out :
/// : whenever the function is re-issued, :
/// : even if no leap seconds have been :
/// : added. :
/// : :
/// : Latest leap second: 2016 December 31 :
/// : :
/// :__________________________________________:
/// </summary>
///
/// <remarks>
/// World Wide Astronomy - WWA
/// Set of C# algorithms and procedures that implement standard models used in fundamental astronomy.
///
/// This program is derived from the International Astronomical Union's
/// SOFA (Standards of Fundamental Astronomy) software collection.
/// http://www.iausofa.org
///
/// The WWA code does not itself constitute software provided by and/or endorsed by SOFA.
/// This version is intended to retain identical functionality to the SOFA library, but
/// made distinct through different function names (prefixes) and C# language specific
/// modifications in code.
///
/// Contributor
/// Attila Abrudán
///
/// Please read the ReadMe.1st text file for more information.
/// </remarks>
/// Given:
/// <param name="iy">year (Notes 1 and 2)</param>
/// <param name="im">month (Note 2)</param>
/// <param name="id">day (Notes 2 and 3)</param>
/// <param name="fd">fraction of day (Note 4)</param>
/// Returned:
/// <param name="deltat">TAI minus UTC, seconds</param>
/// <returns>
/// status (Note 5):
/// 1 = dubious year (Note 1)
/// 0 = OK
/// -1 = bad year
/// -2 = bad month
/// -3 = bad day (Note 3)
/// -4 = bad fraction (Note 4)
/// -5 = internal error (Note 5)
/// </returns>
public static int wwaDat(int iy, int im, int id, double fd, ref double deltat)
{
/* Release year for this version of wwaDat */
//enum { IYV = 2014};
//const int IYV = 2015;
const int IYV = 2016;
/* Reference dates (MJD) and drift rates (s/day), pre leap seconds */
double[,] drift = new double[, ] {
{ 37300.0, 0.0012960 },
{ 37300.0, 0.0012960 },
{ 37300.0, 0.0012960 },
{ 37665.0, 0.0011232 },
{ 37665.0, 0.0011232 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 39126.0, 0.0025920 },
{ 39126.0, 0.0025920 }
};
/* Number of Delta(AT) expressions before leap seconds were introduced */
//enum { NERA1 = (int) (sizeof drift / sizeof (double) / 2) };
int NERA1 = drift.GetLength(0); // by AA
/* Dates and Delta(AT)s */
Changes[] changes = new Changes[] {
new Changes {
iyear = 1960, month = 1, delat = 1.4178180
},
new Changes {
iyear = 1961, month = 1, delat = 1.4228180
},
new Changes {
iyear = 1961, month = 8, delat = 1.3728180
},
new Changes {
iyear = 1962, month = 1, delat = 1.8458580
},
new Changes {
iyear = 1963, month = 11, delat = 1.9458580
},
new Changes {
iyear = 1964, month = 1, delat = 3.2401300
},
new Changes {
iyear = 1964, month = 4, delat = 3.3401300
},
new Changes {
iyear = 1964, month = 9, delat = 3.4401300
},
new Changes {
iyear = 1965, month = 1, delat = 3.5401300
},
new Changes {
iyear = 1965, month = 3, delat = 3.6401300
},
new Changes {
iyear = 1965, month = 7, delat = 3.7401300
},
new Changes {
iyear = 1965, month = 9, delat = 3.8401300
},
new Changes {
iyear = 1966, month = 1, delat = 4.3131700
},
new Changes {
iyear = 1968, month = 2, delat = 4.2131700
},
new Changes {
iyear = 1972, month = 1, delat = 10.0
},
new Changes {
iyear = 1972, month = 7, delat = 11.0
},
new Changes {
iyear = 1973, month = 1, delat = 12.0
},
new Changes {
iyear = 1974, month = 1, delat = 13.0
},
new Changes {
iyear = 1975, month = 1, delat = 14.0
},
new Changes {
iyear = 1976, month = 1, delat = 15.0
},
new Changes {
iyear = 1977, month = 1, delat = 16.0
},
new Changes {
iyear = 1978, month = 1, delat = 17.0
},
new Changes {
iyear = 1979, month = 1, delat = 18.0
},
new Changes {
iyear = 1980, month = 1, delat = 19.0
},
new Changes {
iyear = 1981, month = 7, delat = 20.0
},
new Changes {
iyear = 1982, month = 7, delat = 21.0
},
new Changes {
iyear = 1983, month = 7, delat = 22.0
},
new Changes {
iyear = 1985, month = 7, delat = 23.0
},
new Changes {
iyear = 1988, month = 1, delat = 24.0
},
new Changes {
iyear = 1990, month = 1, delat = 25.0
},
new Changes {
iyear = 1991, month = 1, delat = 26.0
},
new Changes {
iyear = 1992, month = 7, delat = 27.0
},
new Changes {
iyear = 1993, month = 7, delat = 28.0
},
new Changes {
iyear = 1994, month = 7, delat = 29.0
},
new Changes {
iyear = 1996, month = 1, delat = 30.0
},
new Changes {
iyear = 1997, month = 7, delat = 31.0
},
new Changes {
iyear = 1999, month = 1, delat = 32.0
},
new Changes {
iyear = 2006, month = 1, delat = 33.0
},
new Changes {
iyear = 2009, month = 1, delat = 34.0
},
new Changes {
iyear = 2012, month = 7, delat = 35.0
},
new Changes {
iyear = 2015, month = 7, delat = 36.0
},
new Changes {
iyear = 2017, month = 1, delat = 37.0
}
};
/* Number of Delta(AT) changes */
//const int NDAT = sizeof changes / sizeof changes[0];
//enum { NDAT = (int) (sizeof changes / sizeof changes[0]) }; // 2015 Február 27
int NDAT = changes.GetLength(0); // by AA
/* Miscellaneous local variables */
int j, i, m;
double da, djm0 = 0, djm = 0;
/* Initialize the result to zero. */
deltat = da = 0.0;
/* If invalid fraction of a day, set error status and give up. */
if (fd < 0.0 || fd > 1.0)
{
return(-4);
}
/* Convert the date into an MJD. */
j = wwaCal2jd(iy, im, id, ref djm0, ref djm);
/* If invalid year, month, or day, give up. */
if (j < 0)
{
return(j);
}
/* If pre-UTC year, set warning status and give up. */
if (iy < changes[0].iyear)
{
return(1);
}
/* If suspiciously late year, set warning status but proceed. */
if (iy > IYV + 5)
{
j = 1;
}
/* Combine year and month to form a date-ordered integer... */
m = 12 * iy + im;
/* ...and use it to find the preceding table entry. */
for (i = NDAT - 1; i >= 0; i--)
{
if (m >= (12 * changes[i].iyear + changes[i].month))
{
break;
}
}
/* Prevent underflow warnings. */
if (i < 0)
{
return(-5);
}
/* Get the Delta(AT). */
da = changes[i].delat;
/* If pre-1972, adjust for drift. */
if (i < NERA1)
{
da += (djm + fd - drift[i, 0]) * drift[i, 1];
}
/* Return the Delta(AT) value. */
deltat = da;
/* Return the status. */
return(j);
}