Re: [time-nuts] a link to a explanation of Rb vs Cs?
jimlux@earthlink.net said:
If there's nothing folks are aware of, I'll probably see if I can find some
nice schematic pictures of a Cs Beam, a gas cell, and an Hg ion trap, and
then a AVAR plot or something.
I think the GPS satellites have 3 Cs and 2 Rbs. There might be an
interesting story about why they decided to split their eggs into two baskets.
--
These are my opinions. I hate spam.
Hi
If you take a look at the standard weekly publications, the GPS system runs on Rb’s.
There is always one sat that has a Cs turned on. That’s been true as long as they
have been running the system. The simple answer for that choice is that the Rb’s
are easier to predict (better short term to medium term performance).
The Cs standards were originally on board to allow operation in the event that the ground control
system was unable to upload to the constellation. There also was concern in the 80’s
about the reliability of the Rb’s. The configuration has stayed the same, despite the
Rb’s being the main standard used.
Number of standards on board in the block IIF sats was 2 Rb’s and 2 Cs’s. That is a
petty typical “redundant” approach.
Bob
On Apr 12, 2017, at 2:41 AM, Hal Murray hmurray@megapathdsl.net wrote:
jimlux@earthlink.net said:
If there's nothing folks are aware of, I'll probably see if I can find some
nice schematic pictures of a Cs Beam, a gas cell, and an Hg ion trap, and
then a AVAR plot or something.
I think the GPS satellites have 3 Cs and 2 Rbs. There might be an
interesting story about why they decided to split their eggs into two baskets.
--
These are my opinions. I hate spam.
time-nuts mailing list -- time-nuts@febo.com
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A little of the thinking, and a bit of the history of the rb v cs is in "CESIUM AND RUBIDIUM FREQUENCY STANDARDS STATUS AND PERFORMANCE ON THE GPS PROGRAM"
http://www.stanson.ch/files/GPS/Vol%2027_14.pdf
Ole
Den 12. apr. 2017 kl. 08.41 skrev Hal Murray hmurray@megapathdsl.net:
jimlux@earthlink.net said:
If there's nothing folks are aware of, I'll probably see if I can find some
nice schematic pictures of a Cs Beam, a gas cell, and an Hg ion trap, and
then a AVAR plot or something.
I think the GPS satellites have 3 Cs and 2 Rbs. There might be an
interesting story about why they decided to split their eggs into two baskets.
--
These are my opinions. I hate spam.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
For the record, the original source to that PDF is:
http://tycho.usno.navy.mil/ptti/1995papers/Vol%2027_14.pdf
I've always enjoyed the NAVSTAR operational chart (attached) of Figure 7 on page 179 (PDF page 13). It's rather unique among technical, professional papers. You don't see that much these days...
/tvb
----- Original Message -----
From: "Ole Petter Rønningen" opronningen@gmail.com
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Sent: Wednesday, April 12, 2017 5:30 AM
Subject: Re: [time-nuts] a link to a explanation of Rb vs Cs?
A little of the thinking, and a bit of the history of the rb v cs is in "CESIUM AND RUBIDIUM FREQUENCY STANDARDS STATUS AND PERFORMANCE ON THE GPS PROGRAM"
http://www.stanson.ch/files/GPS/Vol%2027_14.pdf
Ole
Den 12. apr. 2017 kl. 08.41 skrev Hal Murray hmurray@megapathdsl.net:
jimlux@earthlink.net said:
If there's nothing folks are aware of, I'll probably see if I can find some
nice schematic pictures of a Cs Beam, a gas cell, and an Hg ion trap, and
then a AVAR plot or something.
I think the GPS satellites have 3 Cs and 2 Rbs. There might be an
interesting story about why they decided to split their eggs into two baskets.
--
These are my opinions. I hate spam.
Hi,
On 04/12/2017 01:17 PM, Bob kb8tq wrote:
Hi
If you take a look at the standard weekly publications, the GPS system runs on Rb’s.
There is always one sat that has a Cs turned on. That’s been true as long as they
have been running the system. The simple answer for that choice is that the Rb’s
are easier to predict (better short term to medium term performance).
The Cs standards were originally on board to allow operation in the event that the ground control
system was unable to upload to the constellation. There also was concern in the 80’s
about the reliability of the Rb’s. The configuration has stayed the same, despite the
Rb’s being the main standard used.
Number of standards on board in the block IIF sats was 2 Rb’s and 2 Cs’s. That is a
petty typical “redundant” approach.
For the block IIR they new cesium failed to get space-qualification, so
those birds only fly rubidium.
Cheers,
Magnus