GPS World: USNO's Fountain: Time at 100 Trillionths of a Second

USNO's Fountain: Time at 100 Trillionths of a Second
http://uc.gpsworld.com/gpsuc/content/printContentPopup.jsp?id=576197

Jan 19, 2009
GPS World

The ultra-precise timing technology that enables GPS and high-speed Internet communication
soon may resolve the measure of time to 100 trillionths of a second, according to the U.S.
Naval Observatory, a central contributor to the international determination of time.

"To know when an event occurred, you need a clock. We are that clock," said Geoff Chester,
public affairs officer at the USNO. He explained the development of this new timing
technology during the January 15 "Armed with Science: Research and Applications for the
Modern Military" radio program on BlogTalkRadio.com.

"Atomic clocks define time scales in terms of a certain number of oscillations of a
certain type of atom that take place in the course of one second. The master clock at the
Naval Observatory is an ensemble of dozens of these devices, and we take a weighted
average of all of them to determine our base-reference time scale."

"We guarantee that no two seconds that come out of here over the course of a year will
differ by more than one billionth of a second," Mr. Chester said. "Our clock is so precise
that it will not gain or lose one second on the order of 3 million years."

By 2010, USNO hopes to release an operational version of its fountain clock, which uses
laser beams to induce oscillations of the rubidium atom. This rubidium fountain clock will
provide a measure of time accurate to 100 trillionths of a second, about 10 to 100 times
more precise than the current master clock.

"Rubidium atoms are smaller and easier to manipulate [than cesium atoms]," Mr. Chester
explained. "They allow us to keep a much better time scale than what we keep today."

The U.S. Naval Observatory, one of about 50 scientific laboratories concerned with
timekeeping, maintains one-third of the operational atomic clocks deployed around the world.

 

----------------------
Please note carefully what is written here
just above !!!

GPS is not based on GR theory!!!

it is a rial and error technique !!!
just write it before yourself
and internalize the conclusions
ie dont boggle our minds
that GPS is a profe for GR !!

ATB
Y.Porat
-----------------------------

 

The relativity corrections are written into the Interface Control
Document ICD-GPS-200D, Porat.
http://www.navcen.uscg.gov/gps/geninfo/IS-GPS-200D.pdf

Perhaps Porat would benefit from a bit of self education
http://edu-observatory.org/gps/gps_books.html#relativity

 

Hmmm... You are taking a couple poorly written application notes as
the Bible.

When conducting an acquisition, if you have three satellites, it is
necessary to synchronize the ground and the satellite clocks.
However, when four satellites are acquired, there is no need to impose
a synchronization of the ground and the satellite clocks as long as
the clocks on all the satellites are synchronized among themselves.
Synchronization of the clocks between the ground and the satellite is
much more difficult to achieve than satellite-to-satellite.

That so-called professor from Norway somewhere realized that. To
continue to spread the nonsense of GR, he immediately pounded his feet
to claim the synchronization must be achieved through the operating
frequencies of the satellites and ground equipments. Well, given 500
parts in a trillion, just how accurate do you want these frequency
errors to be? Remember we are talking about a broadband application
with very low actual data bit rate.

Defending a passage from an application note that you know nothing
about is very hilarious indeed, Sam! This is another example of why
the engineers in general are more intelligent than physicists.
<shrug>

 

The beautiful thing about GPS is that observational data is available
to all most anyone and be compared to predictions of GTR... GPS is a
wonderful relativity laboratory.

Relativistic Effects on Satellite Clocks
http://relativity.livingreviews.org/open?pubNo=lrr-2003-1&page=node5.html
http://relativity.livingreviews.org/Articles/lrr-2003-1/frctfrq.png

Take some time to learn what really happens.

 

The bottom line is that GPS has no applications of SR or GR anywhere
in the system. To claim so, is a lie where:

** FAITH IS THEORY
** MYSTICISM IS WISDOM
** IGNORANCE IS KNOWLEDGE
** PLAGIARISM IS CREATIVITY
** CONJECTURE IS REALITY
** BELIEVING IS LEARNING
** LYING IS TEACHING

Just because your idol Einstein the nitwit, the plagiarist, and the
liar was indeed a liar, you don’t have to blatantly lie about GPS.

 

Light speed is 3x10^8 m/s. A 500 part per trillion error corresponds
to a 15 centimeter positioning error. You need to remember that GPS
doesn't work how _you_ would have designed it, it works differently.
The timing information is how position is determined, as the receiver
has access to precious little else.

You'll note that the relativistic corrections are 100 times larger
than this - ~50,000 ns/day.

Engineers are neither smarter nor dumber, but they have different
educations. You'll note that engineers were the ones who actually
built the global positioning system which happens to use relativity as
a highly important correction, one of many. Did the atmospheric
science cabal force the GPS designers to include ionospheric
corrections in the timing signal too, or is it as important as the
relativistic correction?

 

Those Sagnac corrections are from the Hafele and Keating
Experiment, right ?



http://www.zeiss.com/C125716F004E0776/0/DB95426F0494AB1DC125717500445CEE/$File/Innovation_10_18.pdf

Sue...

 

So how do you know there is no relativity in the global positioning
system when literally every document involing signal timing cites
relativity at one point or another?

Show us proof that GPS has no relativity in it, if you can. You
somehow know it is true so it should be simple for you to point at the
thing that convinced you, unless it is irrational and emotional
arguments that have no basis in reality.

 

This is just plain false. Koobee does not know what the GPS actually is.

In particular, the actual GPS has a ground segment with many clocks that
are REQUIRED to remain synchronized with the clocks in the space segment
[#]. In addition, GPS time must remain within 1 microsecond of UTC
modulo leap seconds. Remember that the actual GPS is a military system,
and they require the space segment to continue to meet its requirements
for a month without any ground segment (in military jargon, the
satellites are MUCH more survivable than the ground segment is).

That clearly requires that the time variations predicted and modeled by
GR be incorporated into the system clocks. And, of course, they are.
That simple fact disproves Koobee's claims.

[#] Synchronization is of course in the ECI frame. Note also
that "clock" here means the reading of the clock AFTER the
corrections are applied. The raw reading of the clock is
adjusted for the basic GR effect, but the corrections handle
clock drift and other minor errors. The basic GR effect is about
38 microseconds per day for satellites, far larger than the
corrections. GR is also used to compute some of the corrections
(e.g. time offsets due to the sun and moon; time offsets due
to improper orbit, etc.).


Koobee, please stop making things up and discussing them as if they were
facts.


Tom Roberts

 

Roberts is a lying shit.

Clearly Roberts cannot do the math and KW can.
http://www.androcles01.pwp.blueyonder.co.uk/GPS/GPS.htm

However, KW is an aetherialist cretin.

 

http://www.androcles01.pwp.blueyonder.co.uk/AC/AC.htm

Nice to see Androcles continues to get basic E&M wrong after several
years.

 

From "Living Reviews in Relativity" by Neil Ashby" (emphasis added)
-----------------------------
Figure 2 shows the net fractional frequency offset of an atomic clock
in a circular orbit, which is essentially the left side of Eq. (35)
plotted as a function of orbit radius , with a change of sign. Five
sources of relativistic effects contribute in Figure 2. The effects
are emphasized for several different orbit radii of particular
interest. For a low earth orbiter such as the Space Shuttle, the
velocity is so great that slowing due to time dilation is the dominant
effect, while for a GPS satellite clock, the gravitational blueshift
is greater. The effects cancel at . The Global Navigation Satellite
System GALILEO, which is currently being designed under the auspices
of the European Space Agency, will have orbital radii of approximately
30,000 km.

There is an interesting story about this frequency offset. At the time
of launch of the NTS-2 satellite (23 June 1977), which contained the
first Cesium atomic clock to be placed in orbit, it was recognized
that orbiting clocks would require a relativistic correction, but
there was uncertainty as to its magnitude as well as its sign.
*Indeed, there were some who doubted that relativistic effects were
truths that would need to be incorporated [5]!* A frequency
synthesizer was built into the satellite clock system so that after
launch, if in fact the rate of the clock in its final orbit was that
predicted by general relativity, then the synthesizer could be turned
on, bringing the clock to the coordinate rate necessary for operation.
After the Cesium clock was turned on in NTS-2, it was operated for
about 20 days to measure its clock rate before turning on the
synthesizer [11]. The frequency measured during that interval was
+442.5 parts in compared to clocks on the ground, while general
relativity predicted +446.5 parts in . The difference was well within
the accuracy capabilities of the orbiting clock. This then gave about
a 1% verification of the combined second-order Doppler and
gravitational frequency shift effects for a clock at 4.2 earth radii.

 

You make these distorted statements because you do not understand the
simple mathematics. <shrug>

Here is the mathematics that you need to understand first to
understand GPS.

http://groups.google.com/group/sci.physics.relativity/msg/9971008d6e75fbae?hl=en

When conducting an acquisition, if you have three satellites, it is
necessary to synchronize the ground and the satellite clocks.
However, when four satellites are acquired, there is no need to
impose
a synchronization of the ground and the satellite clocks as long as
the clocks on all the satellites are synchronized among themselves.
Synchronization of the clocks between the ground and the satellite is
much more difficult to achieve than satellite-to-satellite.
That so-called professor from Norway somewhere realized that. To
continue to spread the nonsense of GR, he immediately pounded his
feet
to claim the synchronization must be achieved through the operating
frequencies of the satellites and ground equipments. Well, given 500
parts in a trillion, just how accurate do you want these frequency
errors to be? Remember we are talking about a broadband application
with very low actual data bit rate.

And what are these clocks again?

Why is that again?

It sounds like you know nothing about defense system. Only

Again, this claim is not necessary in the explanation I gave you.

I am afraid you are the one who is making things up. <shrug>

 

Then show us the evidence - the 'actual' specifications - that support
your claims.

[snip rest]

 

I guess the manufacturer of GPS receivers disagree with you.

http://www8.garmin.com/aboutGPS/waas.html

You still don’t understand the idea behind the data acquisition of

Hmmm... Physicists like Professor Roberts did Lucent in. Not only
that, he still has trouble like yourself to understand how Garmin’s
concept of receiver design. It says the engineers are making things
work that physicists are still perplexed. In doing so, physicists
just choose to hold on to their mysticism. <shrug>

 

I guess the manufacturer of GPS receivers disagree with you.

http://www.gpsinformation.org/dale/theory.htm

You still don’t understand the idea behind the data acquisition of

Hmmm... Physicists like Professor Roberts did Lucent in. Not only
that, he still has trouble like yourself to understand how Garmin’s
concept of receiver design. It says the engineers are making things
work that physicists are still perplexed. In doing so, physicists
just choose to hold on to their mysticism. <shrug>

 

"The satellite itself has an atomic clock to keep the time very
precisely, but your unit is probably not big enough nor expensive
enough to have an atomic clock built in, so your clock is likely to be
in error! For this reason our assumptions about the distance
calculation are likely to have considerable error and the fourth
satellite fix will reveal this to us. However, if we assume the error
is caused by an error in our clock then we can adjust our clock a
little and recompute all 4 fixes, continuing to do this iteratively
until the error disappears! We will then have a good position fix and
as a side effect we will also have the correct time to about 200
nanoseconds or so. One of the applications of gps technology is to
provide the correct time even when we don't care about our position."

Precision of < 200ns requires relativistic corrections. Demonstrated
amply by NTS-2, Hafele-Keating, anyone who does accurate timekeeping
at NIST, etc, etc.

He doesn't describe the atmospheric corrections used against the
timing signal either like the signal specification says, so is the
spec lying about that too or is this guy's information not complete?

You still don't understand that the system works differently than from
how you wish it did.

Why do the signaling specifications say otherwise? Why does experiment
show otherwise?

Why can't you prove otherwise by citing actual specifications instead
of a hobbyist writeup that is clearly not complete?

The receivers are irrelevant as they perform no signal corrections, as
has been amply explained to you personally and in the literature on
the subject. Furthermore, the page you cited isn't a valid substitute
for signal specifications.

Apparently you feel that since a hobbyist writeup of how a GPS
receiver works does not describe the relativistic corrections, then
they do not exist. Even though the signal specifications published by
the United States military who had the system designed say otherwise.

So why is the military's publication not proof enough of the content
of the sattelite signal? Do you wish to assume yet another massive
conspiracy?

 

You never did understand how the time and space is calculated in a GPS
receiver, and there is no point to continue. <shrug>

 

Why even respond with anything other than "NURRRRR HURF DURF" if you
are just going to do that?