List of time synchronization hardware and software
From: shoppa@trailing-edge.com (Tim Shoppa)
Subject: Re: [time-nuts] List of time synchronization hardware and software
Date: Mon, 16 Jan 2006 20:20:55 -0500
Message-ID: 20060117012055.37824BA483E@mini-me.trailing-edge.com
James Maynard james.h.maynard@usa.net wrote:
Brooke Clarke wrote:
Astronomical methods, such as sundials might deserve a place on the list.
Indeed. Sundials, or menhirs, such as those at Stonehenge!
Even better, pulsars. They have a period that is usually the same order
of magnitude as a second, and some of them are regular enough that they
are similar in stability as an atomic clock (how many of us have
cesium beam tubes that will last for billions of years, hmmm?)
How many of us have a pulsar-monitoring suitable parabol standing on the back
yard?
I think a new Caesium-beam cascade is MUCH cheaper.
But besides that, pulsars are cool. Since the planet is orbiting, a few pulsar
needs to be continously measured and compensation needs to be performed for the
rotation. Isn't those used for monitoring the UTC deviations in VLBI?
Cheers,
Magnus
In message 20060117.184050.74742848.cfmd@bredband.net, Magnus Danielson writes:
From: shoppa@trailing-edge.com (Tim Shoppa)
Subject: Re: [time-nuts] List of time synchronization hardware and software
Date: Mon, 16 Jan 2006 20:20:55 -0500
Message-ID: 20060117012055.37824BA483E@mini-me.trailing-edge.com
James Maynard james.h.maynard@usa.net wrote:
Brooke Clarke wrote:
Astronomical methods, such as sundials might deserve a place on the list.
Indeed. Sundials, or menhirs, such as those at Stonehenge!
Even better, pulsars. They have a period that is usually the same order
of magnitude as a second, and some of them are regular enough that they
are similar in stability as an atomic clock (how many of us have
cesium beam tubes that will last for billions of years, hmmm?)
Pulsars were considered for timekeeping several times in the past, and in
every instance the winning argument was "You want to base our timekeeping
on some cosmic phenomena we don't even know what is ?".
I guess we think we know what they are now, but the argument is
still pretty powerful as we don't know how stable we can expect
pulsar rates to be in the long term.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
In message 002b01c61b37$17377720$0500a8c0@darius.domain.actdsltmp, "Bill Hawkins" writes:
Not to mention the equipment that synchronizes the power grid
to UTC, seamlessly integrating leap seconds.
So far the existence of such equipment in contemporary power
grids is not really proven, is it ?
I know they try to hold the frequency and that they use UTC in
various forms for that, but not phase is not linked to UTC in
the sense that a synchronous clock would "loose" the leapsecond
at some point in the future.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
From: "Poul-Henning Kamp" phk@phk.freebsd.dk
Subject: Re: [time-nuts] List of time synchronization hardware and software
Date: Tue, 17 Jan 2006 18:52:59 +0100
Message-ID: 60347.1137520379@critter.freebsd.dk
Poul-Henning,
Even better, pulsars. They have a period that is usually the same order
of magnitude as a second, and some of them are regular enough that they
are similar in stability as an atomic clock (how many of us have
cesium beam tubes that will last for billions of years, hmmm?)
Pulsars were considered for timekeeping several times in the past, and in
every instance the winning argument was "You want to base our timekeeping
on some cosmic phenomena we don't even know what is ?".
I guess we think we know what they are now, but the argument is
still pretty powerful as we don't know how stable we can expect
pulsar rates to be in the long term.
Agreed.
We should expect a long term continous frequency drift, since it is
transmitting quite alot of energy and thus should be loosing mass (E=mc^2
anyone?) and thus the rotational speed of the phenomena should change over
time. That assuming fairly Newtonian physics with only a dash of Einstein on
top of the composition. The loss of mass should surely change the gravitational
pull and thus shift the pulsars sense of time and then naturally the expansion
of the Universe changes the relative speed between us and the pulsar. That was
only the simple stuff that me as a non-astronomer and non-physics guy cooked
up in a few minutes. No fancy stuff like dark matter and dark energy in the
process.
However, it may be stable enought for tau in the range of 1 Ms to 1Gs or so,
and that is still usefull.
Let's get these frequency comb-thingies working instead. Sounds promessing.
Cheers,
Magnus
In message 20060117.191541.78712161.cfmd@bredband.net, Magnus Danielson writes:
However, it may be stable enought for tau in the range of 1 Ms to 1Gs or so,
and that is still usefull.
Ohh, absolutely.
But how would we know ?
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
From: "Poul-Henning Kamp" phk@phk.freebsd.dk
Subject: Re: [time-nuts] List of time synchronization hardware and software
Date: Tue, 17 Jan 2006 19:21:39 +0100
Message-ID: 60557.1137522099@critter.freebsd.dk
In message 20060117.191541.78712161.cfmd@bredband.net, Magnus Danielson writes:
However, it may be stable enought for tau in the range of 1 Ms to 1Gs or so,
and that is still usefull.
Ohh, absolutely.
But how would we know ?
Oh, didn't you know? Agreement using the old bar-protocol over a few pints!
That's how most real decissions is made anyway. Physics? Naw... this is
politics!
Cheers,
Magnus
we could check it against the sundial !!
tom
w0kgw
----- Original Message -----
From: "Poul-Henning Kamp" phk@phk.freebsd.dk
To: "Magnus Danielson" cfmd@bredband.net
Cc: time-nuts@febo.com
Sent: Tuesday, January 17, 2006 12:21 PM
Subject: Re: [time-nuts] List of time synchronization hardware and software
In message 20060117.191541.78712161.cfmd@bredband.net, Magnus Danielson
writes:
However, it may be stable enought for tau in the range of 1 Ms to 1Gs or
so,
and that is still usefull.
Ohh, absolutely.
But how would we know ?
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by
incompetence.
time-nuts mailing list
time-nuts@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
"Poul-Henning Kamp" phk@phk.freebsd.dk wrote:
Pulsars were considered for timekeeping several times in the past, and in
every instance the winning argument was "You want to base our timekeeping
on some cosmic phenomena we don't even know what is ?".
Well, look at how dependent NTP and navigation and telecommunications
is on GPS sats today. There the uncertainty isn't the technology but
the military/government/funding/infrastructure behind them. Glonass
helps, as will Galileo. I'm a little surprised there aren't more
Glonass receivers out there (they seemed confined to a segment of
the surveying population although maybe my view isn't quite as global
as it should be.)
The threat isn't quite as big as the funding to the IERS = International
Earth Rotation Service. Cut off their budget and the earth may stop
turning, it's almost as bad as the Philosopher's Union!
Seafarers happily used astronomical fixes (along with a good
chronometer) for many years long before we understood stellar dynamics.
Full understanding of a phenomena is hardly necessary to use it as
part of a tool. That said, I think we understand pulsars a little
better than we did at first discovery (where the LGM hypothesis seemed
to stand out...)
Tim.
Defense News
January 16, 2006
DoD Plan Calls For Taking GPS Away From USAF
By Michael Fabey
To counter what they view as the U.S. Air Force's weak commitment to space
programs, some Pentagon officials are proposing shifting oversight of the
Global Positioning System (GPS) satellite navigation program from the
service to the Department of Defense (DoD) office that handles networks and
information integration.
The proposal is now in draft form, but if approved by top officials it would
place control of the successful GPS program - including a $12 billion plan
to upgrade the navigation network to, among other things, reduce its
susceptibility to jamming - within the Office of the Assistant Secretary of
Defense for Networks and Information Integration.
While the GPS program is widely regarded as a model of efficient acquisition
and operation, the service's track record for other space efforts is fraught
with delays, cost overruns and technological overreach. Maj. Regina
Winchester, an Air Force spokeswoman, said service leaders are unaware of
any effort to wrest control of GPS.
"It's been a very successful program," Winchester said.
But other Air Force officials say they have seen the draft memo proposing
the shift, but question whether the Networks and Information Integration
office has the authority to pull off the move. These officials said that the
memo suggests giving oversight of both operations and acquisition to the
office - two fields that are nearly always handled by separate entities -
adding that the memo itself was far from becoming policy.
One expert on space programs, however, said that while the memo may prove
unimportant, its message is clear: The Air Force isn't serious about space
acquisitions.
A series of Air Force space programs have come under intense scrutiny for
cost and schedule problems, including the Space Based Infrared System High,
the Space Based Radar, the Future Imagery Architecture and the National
Polar-orbiting Operational Environmental Satellite System. even the
Transformation Satellite program, aimed at revolutionizing military
communications, is likely to experience deep budget cuts in the wake of the
upcoming Quadrennial Defense Review.
Air Force officials contend their commitment to space is ironclad - the
service is the government's lead agency for military space programs, which
includes some of the most classified programs as well as the GPS
constellation, a centerpiece of global navigation. They add that cost
overruns and schedule delays are less a question of commitment, and more a
complex blend of increasingly sophisticated technologies and challenges
associated with complex modern space architectures.
"OSD [Office of the Secretary of Defense] simply does not trust the Air
Force when it comes to space acquisition, and this memo is just another
proof of that," said the Lexington Institute's Loren Thompson, expressing a
view echoed by some Air Force officials, who said the memo illustrates DoD
concerns about the service's commitment to space. "OSD is worried that the
Air Force will find a way to spend the money on planes," he said.
It also shows how infighting has broken out since the March departure of Air
Force undersecretary Peter Teets, who kept a firm grasp on several top space
programs. Analysts and officials said Teets' departure left a power vacuum
that has allowed various services and agencies to wrestle for programs,
platforms and money.
Space programs, with their odd combination of interests - Air Force, CIA,
National Security Agency and National Reconnaissance Office among them -
have proved particularly problematic.
Thompson and Air Force space officials note that the Defense Department,
which assumed oversight of the service's biggest programs when several top
posts went vacant last year, has returned most of the job to service leaders
since Michael Wynne took the service's top job in November.
But space acquisition milestone authority - the right to approve major
funding steps during program development - remains with DoD.
Thompson also pointed to DoD's decision on the E-10 Multi-Sensor Command and
Control Aircraft. The Air Force was counting on the E-10 to help find moving
targets on the ground and in the air and provide key battle management
command and control. It would be a central element in the Air Force's
Command and Control Constellation, which envisions a fully connected array
of land-, platform- and space-based sensors that use common standards and
communication protocols.
But the Defense Department wanted more capability in space and less aboard
the E-10, Thompson said.
At 6:40 PM +0100 1/17/06, Magnus Danielson wrote:
But besides that, pulsars are cool. Since the planet is orbiting, a few pulsar
needs to be continously measured and compensation needs to be
performed for the
rotation. Isn't those used for monitoring the UTC deviations in VLBI?
Cheers,
Magnus
Magnus,
I work on the Heinrich Hertz submillimeter telescope on Mt. Graham.
We are going to be doing a VLBI run in early April.
I just asked our resident VLBI guy what we'll be using for
synchronizing our telescope to the others for our upcoming run at
~230 GHz. He said that GPS is used, since it's better than a
microsecond and is readily available with no fuss. Each site will
have a hydrogen maser for the data clock. These masers are currently
being calibrated against each other.
Pulsars are nearly invisible at that frequency. We have plans to look
for an existing bright pulsar at 80 GHz and expect to need to
integrate photons for a week to see it.
--
--David Forbes, Tucson, AZ
http://www.cathodecorner.com/