Leap Second added 1 January 2009

The Earth Orientation Center of IERS has announced the addition of another leap second on January 1, 2009.

                                   UTC TIME STEP
                            on the 1st of January 2009
                      
 A positive leap second will be introduced at the end of December 2008.
 The sequence of dates of the UTC second markers will be:		
		
                          2008 December 31,     23h 59m 59s
                          2008 December 31,     23h 59m 60s
                          2009 January   1,      0h  0m  0s
              
 The difference between UTC and the International Atomic Time TAI is:

  from 2006 January 1, 0h UTC, to 2009 January 1  0h UTC  : UTC-TAI = - 33s
  from 2009 January 1, 0h UTC, until further notice       : UTC-TAI = - 34s 
  

Pocket Stars has an internal table which is used to set the number of leap seconds in effect as well as a table containing the values for deltaT.  Because of this change, Pocket Stars results will be off by one second until the next release is issued with the internal table updated.

A little used and mostly untested feature of Pocket Stars is that you can override the default, internal values of DeltaT and also of Leap Seconds.  To override the default values of deltaT, create a text file named “DeltaT”.  To override Leap Seconds, create a file named “LeapSeconds”.  Place either or both of these files in the Pocket Stars install directory in the format shown below.  Whatever you put in these files will override the default tables in Pocket Stars.    The first column is the Julian date, and the second column is either deltaT or is the value for leap seconds.  No commas or comments allowed.

Custom DeltaT file example

2415020.5000000 -2.7000
2416846.5000000  3.9200
2418672.5000000 10.3840
2420498.5000000 17.1870
2422324.5000000 21.4070
2424151.5000000 23.6340
2425977.5000000 24.0210
2427803.5000000 23.9070
2429629.5000000 24.3470
2431456.5000000 26.8100
2433282.5000000 29.0700
2435108.5000000 30.9640
2436934.5000000 33.1500
2438761.5000000 35.7380
2440587.5000000 40.1820
2442413.5000000 45.4770
2444239.5000000 50.5400
2446066.5000000 54.3430
2447892.5000000 56.8550
2449718.5000000 60.7850
2451544.5000000 63.83
2453371.5000000 64.63
2453736.5000000 64.8547
2455197.5000000 65.0  

Here’s the equivalent data structure within Pocket Stars showing the corresponding calendar dates:

double DeltaT[][2] = {
     // Julian           Year          DeltaT
     2415020.5000000, /*1900.0000,*/   -2.7000,
     2416846.5000000, /*1905.0000,*/    3.9200,
     2418672.5000000, /*1910.0000,*/   10.3840,
     2420498.5000000, /*1915.0000,*/   17.1870,
     2422324.5000000, /*1920.0000,*/   21.4070,
     2424151.5000000, /*1925.0000,*/   23.6340,
     2425977.5000000, /*1930.0000,*/   24.0210,
     2427803.5000000, /*1935.0000,*/   23.9070,
     2429629.5000000, /*1940.0000,*/   24.3470,
     2431456.5000000, /*1945.0000,*/   26.8100,
     2433282.5000000, /*1950.0000,*/   29.0700,
     2435108.5000000, /*1955.0000,*/   30.9640,
     2436934.5000000, /*1960.0000,*/   33.1500,
     2438761.5000000, /*1965.0000,*/   35.7380,
     2440587.5000000, /*1970.0000,*/   40.1820,
     2442413.5000000, /*1975.0000,*/   45.4770,
     2444239.5000000, /*1980.0000,*/   50.5400,
     2446066.5000000, /*1985.0000,*/   54.3430,
     2447892.5000000, /*1990.0000,*/   56.8550,
     2449718.5000000, /*1995.0000,*/   60.7850,
     2451544.5000000, /*2000.0000,*/   63.83,     
     2453371.5000000, /*2005.0000,*/   64.63,     
     2453736.5000000, /*2006.0000,*/   64.85478,  
     2455197.5000000, /*2010.0000,*/   65.0,      
};

Custom LeapSeconds file example

with the added change for Jan 1, 2009:

2441317.5 10.0
2441499.5 11.0
2441683.5 12.0
2442048.5 13.0
2442413.5 14.0
2442778.5 15.0
2443144.5 16.0
2443509.5 17.0
2443874.5 18.0
2444239.5 19.0
2444786.5 20.0
2445151.5 21.0
2445516.5 22.0
2446247.5 23.0
2447161.5 24.0
2447892.5 25.0
2448257.5 26.0
2448804.5 27.0
2449169.5 28.0
2449534.5 29.0
2450083.5 30.0
2450630.5 31.0
2451179.5 32.0
2453736.5 33.0
2454832.5 34.0

Here’s the equivalent internal table in Pocket Stars showing the dates:

// Leap Second table
double LeapSeconds [][2] = {
    // Date                     TAI-UTC
    /*1972 JAN  1 */ 2441317.5,  10.0, 
    /*1972 JUL  1 */ 2441499.5,  11.0,
    /*1973 JAN  1 */ 2441683.5,  12.0,
    /*1974 JAN  1 */ 2442048.5,  13.0,
    /*1975 JAN  1 */ 2442413.5,  14.0,
    /*1976 JAN  1 */ 2442778.5,  15.0,
    /*1977 JAN  1 */ 2443144.5,  16.0,
    /*1978 JAN  1 */ 2443509.5,  17.0,
    /*1979 JAN  1 */ 2443874.5,  18.0,
    /*1980 JAN  1 */ 2444239.5,  19.0,
    /*1981 JUL  1 */ 2444786.5,  20.0,
    /*1982 JUL  1 */ 2445151.5,  21.0,
    /*1983 JUL  1 */ 2445516.5,  22.0,
    /*1985 JUL  1 */ 2446247.5,  23.0,
    /*1988 JAN  1 */ 2447161.5,  24.0,
    /*1990 JAN  1 */ 2447892.5,  25.0,
    /*1991 JAN  1 */ 2448257.5,  26.0,
    /*1992 JUL  1 */ 2448804.5,  27.0,
    /*1993 JUL  1 */ 2449169.5,  28.0,
    /*1994 JUL  1 */ 2449534.5,  29.0,
    /*1996 JAN  1 */ 2450083.5,  30.0,
    /*1997 JUL  1 */ 2450630.5,  31.0,
    /*1999 JAN  1 */ 2451179.5,  32.0,
    /*2006 JAN  1 */ 2453736.5,  33.0,         
    /*2009 JAN  1 */ 2454832.5,  34.0,  // to be added in the next release        
};