[LEAPSECS] UTC Redefinition Advanced

Rob Seaman seaman at noao.edu
Fri Oct 22 23:14:19 EDT 2010

On Oct 22, 2010, at 5:14 PM, Jonathan E. Hardis wrote:

> On Oct 22, 2010, at 1:16 PM, Rob Seaman wrote:


>> It will, for instance, cost astronomers many millions of dollars simply to restore current functionality to thousands of interoperating systems.


> Oh ... come, come.


> How do these "thousands of interoperable systems" currently get the time?


> You're free to insert an inexpensive interface box between your data source and the systems that use the data that adds or subtracts however many integer number of seconds you wish. For example, it would be trivial to set a private collection of NTP servers that provide a well-documented time offset from other NTP servers that maintain UTC.


> In other words, if you want a time scale that preserves leap seconds, you're perfectly free to maintain one yourself for astronomical purposes -- whether or not the rest of the world follows suit.

Ah! I see. We're free to inherit the crappy project management paradigm gifted to us by the ITU-R! So the fact that NTP on dozens of hosts in the observatory dome will report a different time than the laptops brought by the observers is nothing to be concerned with. That radio time signals (the "R" in ITU-R) will report a time different from our "inexpensive interface boxes" is not fretworthy. Clocks appear in numerous places in the workflow. It is no simple feat to coordinate all these clocks with vintages ranging over the last quarter century. GPS? Phones? Web apps?

Data start at a mountaintop telescope, but flow downhill to archives and pipelines and virtual observatory portals. Redefining UTC will put a permanent kink in scientific and historical timescales, as when performing the frequent chore of combining data from different epochs - or from different telescopes. Astronomers assemble light curves from observations taken worldwide (and in space - wanna estimate the cost of a space certified interface box). These systems have to interoperate, something that is automatically provided by UTC's current definition as an approximation to mean solar time.

What about space missions in progress? What about preserving a coherent data set from decade-long synoptic surveys? Telescopes aren't just the cartoon illustration of Palomar, what about radio interferometers, gravity wave detectors, neutrino telescopes buried beneath Antarctic ice? The increasingly common networks of robotic telescopes pursuing common investigations? Telescopes and instruments and data archives and web services are all built and maintained by different teams.

This is a massive system engineering project to even begin to pretend to address all the implications. Astronomers chose to actually fix their Y2K issues, not install pivots pushing the trouble further into the future. Oh! That's what the ITU-R is poised to do. The leap seconds don't just evaporate away folks.

These are areas that could and should be addressed in any coherent and even marginally complete proposal to - what? - reinvent timekeeping for the entire world. This is yet another variation on privatizing the profits and socializing the costs.


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