Leap second set to occur 2012 June 30, 23h 59m 60s UTC

[gary]

As announced by the International Earth Rotation and Reference System Service (IERS)
in Paris on 5 January 2012 -

Originally Posted by IERS

 A positive leap second will be introduced at the end of June 2012.
 The sequence of dates of the UTC second markers will be:		
		
                          2012 June 30,     23h 59m 59s
                          2012 June 30,     23h 59m 60s
                          2012 July  1,      0h  0m  0s

IERS Bulletin here -
http://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat

For those on the east cost of Australia, we are currently +10 hours ahead of UTC
so the leap second will occur on 2012 July 1, at 09h 59m 60s AEST.

When it takes place, you should probably be able to see the leap second occur here -
http://time.gov/timezone.cgi?UTC/s/0/java

* UT1 or Universal Time is based on Earth rotation and was the successor to GMT.
* TAI or International Atomic Time is the time kept by the weighted average of over 200 atomic clocks around the world.
* UTC or Universal Co-ordinated Time is the time standard we all use day to day, is based on TAI but it was agreed in 1972 to keep it within 0.9 seconds of the old UT1 despite the fact the Earth's rotation was slowing in an irregular fashion.
* To keep UTC within the 0.9 second requirement, a leap second is added either at the end of June or the end of December if deemed to be required by the responsible body, which is the International Earth Rotation Service.

A decision on the proposal to abandon leap seconds was delayed by the International Telecommunications Union (ITU) in January 2012 until the World Radio Conference in 2015.

Astronomical observatories (and telescope computer programmers) are mindful of leap seconds because the apparent position of objects in the sky at any one instant is a function of Earth rotation.

There are additional time standards in use as well such as TT or Terrestrial Time
which is defined by the IAU and is commonly used for ephemeris of the Moon
and Sun.

GPST or Global Positioning System Time is that used by the atomic clocks aboard
the GPS satellites and is not corrected for Earth rotation and unlike UTC, does
not contain leap seconds. It was initially synchronized to UTC in 1980 and has
steadily diverged since then and is currently more than 15 seconds ahead of UTC.

[mikerr (Michael)]

So we have to re-set all the clocks in the house again!! Wish they would leave things alone!










Michael

[astroron (Ron)]

Thanks Gary, Does the ARGO NAVIS have built into it the correction?

Cheers

[gary]

Originally Posted by astroron

Thanks Gary, Does the ARGO NAVIS have built into it the correction?

Cheers

Hi Ron,

In the forthcoming firmware release the Moon has been included as an object
and funny enough we had to take into account leap seconds in order to compute
its position accurately.

So the leap second doesn't impact on many people's lives in any significant way
but as far as astronomical computation is concerned, it turns out to be something
I have had to personally specifically take allowance for in the writing of our software.

Anyway, come the morning of July 1 everyone can sleep in for another full second and not feel too guilty.

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au

[astroron (Ron)]

(Quote)
In the forthcoming firmware release the Moon has been included as an object
and funny enough we had to take into account leap seconds in order to compute
its position accurately.

Gary,Does that also include the Moon drifting away at 2.5 centimeters per year?
Cheer

[gary]

Originally Posted by astroron

Gary,Does that also include the Moon drifting away at 2.5 centimeters per year?
Cheer

Hi Ron,

LOL! Thankfully not!

But according to this NASA web page from 1994, it is receding at about 3.8cm a year.
http://eclipse.gsfc.nasa.gov/SEhelp/ApolloLaser.html

An improbably small amount, but knowing that may make the difference to
winning the trivia competition on a cloudy night at a star party.

By the way, speaking of star parties, where they do the laser range finding
to the reflectors on the Moon is from the McDonald Observatory, which we
visited in Texas, only a few miles away from where the Texas Star Party is held.
They'd probably say, "That's some more trivia for y'all".

[astroron (Ron)]

Originally Posted by gary

Hi Ron,

LOL! Thankfully not!

But according to this NASA web page from 1994, it is receding at about 3.8cm a year.
http://eclipse.gsfc.nasa.gov/SEhelp/ApolloLaser.html

An improbably small amount, but knowing that may make the difference to
winning the trivia competition on a cloudy night at a star party.

By the way, speaking of star parties, where they do the laser range finding
to the reflectors on the Moon is from the McDonald Observatory, which we
visited in Texas, only a few miles away from where the Texas Star Party is held.
They'd probably say, "That's some more trivia for y'all".

I will remember that for future reference
Cheers