Re:Leap second

grc@spica.usno.navy.mil
Wed, 30 Dec 98 12:05:35 -0500

Bruno, et. al.

I don't know the answer to the first question, but I assume that all elements
generated *after* the leap second is inserted will reflect the change. 
Ephemerides generated with older elsets will be in error by 1 second as measured
by UTC.

As for question 2, the leap second is *not* incorporated into the GPS clocks. 
Rather, there is a correction factor incorporated into the NAV data stream
downlinked by each satellite which carries the cumulative corrections for GPS
time since the beginning of the GPS time epoch.  An explanation of GPS Time
Transfer may ve viewed at:

ftp://tycho.usno.navy.mil/pub/gps/gpstt.txt

Cheers,
Geoff

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____________________Reply Separator____________________
Subject:    Leap second 
Author: <SeeSat-L@blackadder.lmsal.com>
Date:       30-Dec-98 8:54 AM

Hello,

on 31 December at 23:59:59 UTC a leap second will be injected into UTC
to bring UTC back in line with UT to better than 0.9 second.

In this context two questions came to my mind, and perhaps somebody
on the list has the answer:

1. Is the epoch of TLEs measured in UT or UTC ? The epoch is given to
   8 decimal places, i.e. about one thousandth of a second.

2. Do GPS receivers which show the time indicate UT or UTC ?


Happy New Year!

Bruno Tilgner
Paris, France