[LEAPSECS] leap second and DUT1 database

[Tom Van Baak]

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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