[ntp:questions] GPS satellites started to announce Leap second for December 2008

Martin Burnicki martin.burnicki at meinberg.de
Tue Jul 29 08:35:14 UTC 2008

Hi all, just FYI: 

The GPS satellites just started to announce the upcoming leap second for end
of December 2008 in their broadcasted data sets.

Some technical details:

The current full GPS week number (i.e. the total number of weeks since GPS
was put into operation) is 0x5D2. The current week number broadcasted by
the satellites is truncated to 10 bits, i.e. is currently 0x1D2. 

The UTC parameters now sent by the satellites include the offset between GPS
time and UTC before the leap second:

delta_tls = 14

Offset between GPS time and UTC after the leap second:

delta tlsf = 15

The 8 LSBs of the week number and the number of the day at which the leap
second will be inserted:

WNlsf = 0xE8
DN = 4

Expanding the truncated week number WNlsf to a full week number yields
0x5E8, and together with the day number the resulting calendar date
specifies the UTC date changeover between 2008-12-31 and 2009-01-01.


Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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