[time-nuts] 15 Seconds error...??
jimlux at earthlink.net
Wed Jan 18 19:37:36 EST 2012
On 1/18/12 3:15 PM, Tom Van Baak wrote:
>> On 1/18/2012 4:36 PM, Magnus Danielson wrote:
> I don't know if there is a "style guide" to timescales. There's no
> one to enforce it anyway. I'm just calling it like I see it used in
> the literature. The acronyms TAI, and especially UTC, can have
> many different connotations, so you have to gauge their use
> against your audience to minimize misunderstanding.
TAI is enshrined in many space standards.. I think there, it really
means a clock scale running at the TAI rate with the epoch defined in
terms of TAI (which is a paper time, and for which there's lots of cross
references to other time scales at that instant) (Jan 1, 1958)
For CCSDS Unsegmented time code (which is seconds and fractions of seconds)
e.g. CCSDS 301.0-B-3 says "The CCSDS recommended epoch is that of 1958
Jan 1 (TAI), but other Agency-defined epochs may be accommodated as a
Level 2 code".
So they're saying "zero" in the CCSDS unsegmented time code
(second.fractionsofseconds) is defined as an instant in the TAI scale
(which works, even with a paper scale, and in fact, can really only work
after the fact with a paper scale).
And no leap seconds.
The various segmented codes (DOY,H,M,S for instance) are UTC based and
must accommodate leapseconds
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