Qulsar is prepared for a leap second – are you?

Introduction

From Wikipedia:

"A leap second is a one-second adjustment that is occasionally applied to Coordinated Universal Time (UTC) in order to keep its time of day close to the mean solar time (UT1)."

To ensure that the difference is kept below 0.9s, International Earth Rotation and Reference Systems Service (IERS) decided earlier this year that a positive leap second will be added at the end of June 2012. Here’s the latest Bulletin C from IERS:

     INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS)

SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE

SERVICE DE LA ROTATION TERRESTRE 
OBSERVATOIRE DE PARIS 
61, Av. de l'Observatoire 75014 PARIS (France)
Tel.      : 33 (0) 1 40 51 22 26
FAX       : 33 (0) 1 40 51 22 91
e-mail    : services.iers@obspm.fr
http://hpiers.obspm.fr/eop-pc

                                              Paris, 5 January 2012
                                                           
                                              Bulletin C 43
                                
                                              To authorities responsible
					      for the measurement and 
					      distribution of time


                                   UTC TIME STEP
                            on the 1st of July 2012
                      

 A positive leap second will be introduced at the end of June 2012.
 The sequence of dates of the UTC second markers will be:		
		
                          2012 June 30,     23h 59m 59s
                          2012 June 30,     23h 59m 60s
                          2012 July  1,      0h  0m  0s
              
 The difference between UTC and the International Atomic Time TAI is:

  from 2009 January 1, 0h UTC, to 2012 July 1  0h UTC  : UTC-TAI = - 34s
  from 2012 July 1,    0h UTC, until further notice    : UTC-TAI = - 35s
  
 Leap seconds can be introduced in UTC at the end of the months of December
 or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every
 six months, either to announce a time step in UTC or to confirm that there
 will be no time step at the next possible date.
 


                                              Daniel GAMBIS
                                              Head		
                                              Earth Orientation Center of IERS
					      Observatoire de Paris, France

 

Leap second impact on PTP devices

PTP time is not affected by leap seconds and it’s only if you care about UTC time that you have to do anything about it.  An example is the case when you have an NMEA TOD input connected to your PTP master device or when you use NMEA TOD output.

Qulsar system without firmware update

A Qulsar slave connected to a master which correctly handles UTC leap second adjusts its UTC offset and thereby its UTC time within plus/minus two announce intervals, i.e. as soon as the new UTC offset value is announced by the master. The leap61 flag is updated as well but its state does not affect any of the slave’s operation.

A Qulsar master connected to a PPS/CM TOD source which correctly handles UTC leap second will keep its PTP time continuous and will properly adjust its UTC offset as soon as the new UTC offset value is received from a TOD message.

A Qulsar master connected to a PPS/NMEA TOD source which correctly handles UTC leap second will exhibit a 1s time jump in its PTP time at leap second transition and will continue using and announcing the current UTC offset (34s) until it is changed manually to 35s with 'ptp2 time offset' command:

A:/root> ptp2 time offset 35
A:/root> UTC Offset: 35 sec

Regardless of TOD input format the upcoming leap second indicator, the leap61 flag transmitted in Announce message, will not be set or cleared automatically by a Qulsar master, but manual configuration is possible via 'ptp2 time leap 61' command:

A:/root> ptp2 time leap 61 1
A:/root> Leap61 flag: 1

From the 1st of July 2012 the default value for current UTC offset on any Qulsar system shall be set to 35s on every boot. It is neccessary when the system has no other means of receiving the correct value (like PTP or CM TOD) and should rely on its own configuration. This can be done by manually entering the 'ptp2 time offset' command if the PTP engine is started manually from the shell, by adding this command into the device’s /system/startup.ini file if the PTP engine is started from there or by using a corresponding C API function if the PTP engine is started from the user application.

A:/root> ptp2 start
PTP Time: 2012-07-01 12:00:00
*** PTPv2 up and running ***

A:/root> ptp2 time offset 35
A:/root> UTC Offset: 35 sec

 

Firmware update 2.4.20 for Qulsar devices

With the new FW a Qulsar master will properly indicate the upcoming UTC leap second with the leap61 flag. The flag will be automatically set 12 hours prior the leap second event and cleared after it, at the start of a new UTC day.

A:/root> ptp2 start
PTP Time: 2012-06-30 16:00:00
UTC Offset: 34 s
Leap second pending: UTC+1
*** PTPv2 up and running ***

With the new FW a Qulsar master will correctly handle NMEA TOD input during the leap second transition with any possible sequence of UTC time markers in TOD messages:

2012-06-30 23:59:59 2012-06-30 23:59:59 2012-06-30 23:59:59
2012-06-30 23:59:60 2012-06-30 23:59:59 2012-07-01 00:00:00
2012-07-01 00:00:00 2012-07-01 00:00:00 2012-07-01 00:00:00

With the new FW, all Qulsar devices will automatically adjust the current UTC offset and produce a correct sequence of UTC second markers in ASCII/NMEA/CM TOD output messages during a leap second transition:

2012-06-30 23:59:58
2012-06-30 23:59:59
2012-06-30 23:59:60
2012-07-01 00:00:00
2012-07-01 00:00:01

With the new FW there is no need to manually set the current UTC offset to 35s after the 1st of July 2012, it will be selected automatically according to the current time:

A:/root> ptp2 start
PTP Time: 2012-07-01 12:00:00
UTC Offset: 35 s
*** PTPv2 up and running ***

 

Download

The new FW version 2.4.20 which includes the handling of leap seconds for both master and slave can be downloaded from this link: Profile Download.

Questions

If you have any questions on how your Qulsar device will behave due to the leap second event and if you need to download this new FW or not, do not hesitate to send a mail to: support@qulsar.com.

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