[time-nuts] Proper MJD for a leap second?

Bob bobhome at pacbell.net
Sat Dec 31 23:55:13 EST 2005


Is there a convention for MJD with a leap second?

My homebrew display decodes the M12+ output and displays computed MJD as
well as receiver reported UTC. 

The M12+ reported 58, 59, 60 as expected... and MJD displayed 53735.00000
for the 60 second. This was a programming error on my part with MJD
displayed as the start of the day just ended. The fractional part of the MJD
date rolled over and was lost.

Not really sure what would be right, but 53735.99999 displayed twice would
have been a more reasonable choice.

Anyone know the right answer?

Regards,
Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bill Beam
Sent: Saturday, December 31, 2005 8:45 PM
To: Discussion of precise time and frequency measurement;
kirbybq at bellsouth.net
Subject: Re: [time-nuts] no 23:59:60 in TAC32

I have since compared UT+ raw data with TAC32 display
as follows:

UT+ raw data             TAC32 display

12/31/05 23:59:59     same
12/31/05 23:59:60     1/1/06 00:00:00
12/31/05 23:59:60     1/1/06 00:00:01
1/1/2006 00:00:00     1/1/06 00:00:01
1/1/2006 00:00:01     same

I assume the UT+ raw data is correct UTC.
During the  23:59:60 UTC second TAC32 gave two displays.

The TAC32 apears to have 'stumbled' for a couple of seconds.
The UT+ performed correctly.

I obtained my data using a Nikon D70 digital still camera
operated in 'burst' mode taking about three frames per second
of the computer screen.  Both the TAC32 display and UT+
raw data are shown together on the screen.

If any one is interested I can send the data. I have 19 images.
Each image is about 3MB.


On Sat, 31 Dec 2005 22:05:14 -0600, Brian Kirby wrote:

>I was using a M12+ with TAC32+ - what I observed is it displayed 
>00:00:01 twice ! - it never indicated 23:59:60.
>
>Bill Beam wrote:
>
>>TAC32 failed to display 23:59:60.
>>
>>Within a few seconds (possibly/probably one second)
>>the TAC32 time display was correct.
>>
>>The raw data stream from Motorola UT+ correctly
>>showed 23:59:60 as the last second of 2005.
>>
>>TAC32 queries the UT+ for UTC-GPS offset at 20sec
>>after each minute and at 00:00:22 'UTC=GPS+14 seconds'
>>was correctly displayed.
>>
>>I have lots of uninteresting photos of TAC32 display...
>>and one interesting photo of the raw data stream from
>>the UT+.  If anyone cares to post it I can send a photo.
>>


Bill Beam
NL7F
wbeam at gci.net or NL7F at amsat.org





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