Re: Schreiver AFB warns about leapsec

[Rob Seaman]

On Dec 20, 2005, at 1:30 AM, Poul-Henning Kamp wrote: There is an interesting PowerPoint (sigh...) at Schriever AFB's GPS support center: https://www.schriever.af.mil/GpsSupportCenter/archive/advisory/Leap_Second_Event.ppt Agreed.  Very interesting. They clearly know what the problem with leap seconds is :-) Agreed, although they simplify leap seconds as being: - Needed to compensate for changes in earth’s rotation Suggest folks read the entire presentation, which delivers common sense advice without editorial comment.  (That's our job.)   The authors start by assigning the responsibility appropriately: - User’s realization of UTC could incorrectly step by one second They describe limits to the affected systems: - Leap second should not affect stand alone navigation or positioning (affects timing output of receiver) - Adjustment transparent to users with GPS receivers in compliance with IS-GPS-200 - Some receivers may require manual adjustment by users - Systems (military, civil, commercial) using GPS timing with a tolerance less than 1 second, might be [emphasis in original] impacted if leap second adjustment is not made properly (either automatically or manually) A hint that the issue may be more complicated than it appears: - Often, use of GPS timing in embedded systems is difficult to discern – consult your system engineers / experts An interesting observation: - Leap second occurs at an awkward time - New Years Eve Maybe obscurity in scheduling and implementation is not a desirable characteristic after all.  Perhaps the problem would "solve itself" through market forces if leap seconds were simply required to occur on normal business days at 9:00 am EST, just in time for the opening of the NYSE. ...and they deal with the consequences pragmatically, rather than trying to legislate physical reality out of existence: - Contact your UE manufacturer to determine if your UE is IS-GPS-200D compliant with respect to leap seconds - Ensure documentation, procedures and personnel are in place to deal with potential problems - Monitor your system through the leap second event - Report if you have problems - We need to document so we can correct the problem for next event In addition to pondering how well such preparations would succeed for events three orders of magnitude larger occurring only every several centuries, this reader is left wondering what the corresponding presentation would look like if it were describing remediation to the same systems to support DUT1 > 0.9s. Rob Seaman National Optical Astronomy Observatory