Hi Warner,
Keeping cold spares is a good example. I can see that having to acquire GPS
lock and waiting up to 12.5 minutes for current leap second information would
be a problem. There must be a way to cache that state so rapid failover is
possible, in both the hot and cold spare case.
I know radio stations like WWV and WWVB that broadcast leap second and UT1
corrections face a very similar problem.
With all the PhD's and technology at their disposal, NIST has developed a
cost-effective, highly reliable solution. Note that their communication
infrastructure and UT1 database is compatible with all versions of Linux and
Windows, does not require access to the internet, and the storage system is
protected from power failures and floods. It provides rapid access in case of
emergency and maintains both current and historical values of leap seconds and
DUT1. Redundant copies of the database can be placed in an iPhone, as seen
below. I was very impressed and plan to implement their solution in my own lab.
For details, see: http://leapsecond.com/pages/wwvb/
On close inspection this NIST system, as currently designed, will fail if DUT1
were allowed to exceed its current range of 0.7 seconds; perhaps another reason
to keep leap seconds.
/tvb
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