[time-nuts] Orbiting crystals

Magnus Danielson magnus at rubidium.dyndns.org
Sun Jun 28 19:30:35 EDT 2009


iovane at inwind.it wrote:
> Magnus Danielson wrote:
> 
>> Do read the article I referred to on aging. I think that any 
>> gravitational issues during the eclipse event is far less than the 
>> effect of sudden cooling, loss of sunlight. Does the ionspheric TEC 
>> change drastically? You need a good L1/L2 GPS receiver for that.
>> What is the means of comparision? 100 kHz radio transmissions? GPS? What 
>> medium was used? Can any eclipse effects be seen in that medium?
>> Multiple phase comparision methods is needed to rinse out the effects of 
>> them from that of the clocks themselves. Expect everything to change and 
>> figure out ways to measure that to clear out what was affected and not.
>>
>> For freak-events like this, everyone has their favorite root cause.
>>
> 
> We are aware that there are hidden traps, and we try to 
> diversify and cross-correlare experiments of different nature.
> The progress is very slow because eclipses are rare events at 
> any given location, but they occur twice a year on the planet,
> and I just thought to take advantage of satellites to possibly
> speed-up the work. I don't believe the idea is completely new.
> What is new, I think, is looking for sudden jumps, which may 
> have been filtered out by other workers. The thermal shock at 
> crossing the shadow is a severe issue, but some instruments 
> detected effects before and after the optical eclipse and on 
> the anti-eclipse path (the other side of the planet).

I think I have found just the article for you!

On the 1993 FCS there was a presentation of an article titled "ANALYSIS 
OF THE FREQUENCY STABILITY OF ON-ORBIT GPS NAVSTAR CLOCKS". This article 
goes into some details as showing the thermal shock and the effect of 
eclipse seasons on especially the rubidium clocks onboard. If you have 
UFFC access, search-terms such as "space" and "orbit" should get you 
going, but the "orbit" seems to give you better experience rather than 
expectance properties.

> There is
> a non-official position of NASA on this, read MSG#26 at 
> 
> http://xoomer.virgilio.it/iovane/mails.htm
> 
> (....We have a number of anomalies recorded on different....).
> 
> Not sure my idea is good, but what to do waiting for the next 
> eclipse here? Should it be within my reach, I would be pleased
> to try looking at sats. 

There are people looking after their sats, which could give you insight, 
maybe already published.

> Or, maybe, time-nuts who happen to be in the eclipse path in 
> the future with their cesium clocks, could help. Or, further, 
> time-nuts may have suggestions such as I'm getting from you. 
> In the future, in case, I will ask you what you mean by "good"
> L1/l2 receiver.

You want a geodesic style receiver which can be hooked to an external 
frequency source, act as a base-station and produce RINEX data on a 
continous operational mode for the vissible sats (12 is an acceptable 
limit). An example of such a receiver is the Ashtech Z-12. A suitable 
phase-stable antenna is also assumed.

Beware that options of a particular receiver may prohibit you from the 
use you intend.

Oh, if you are good at math, you could predict when a particular sat is 
hit by moon shadow and when it goes out again.

You do want to check what clock each sat is running. Not all of them run 
Cesium, infact most of them operate one of their Rubidium clocks, which 
IS more sensitive to eclipses.

GPS OPERATIONAL ADVISORY        179
SUBJ: GPS STATUS      28 JUN 2009

1. SATELLITES, PLANES, AND CLOCKS (CS=CESIUM RB=RUBIDIUM):
A. BLOCK I : NONE
B. BLOCK II: PRNS  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14
    PLANE   : SLOT B2, D1, C2, D4, B6, C5, A6, A3, A1, E3, D2, B4, F3, F1
    CLOCK   :      RB, RB, CS, RB, RB, RB, RB, CS, CS, CS, RB, RB, RB, RB
    BLOCK II: PRNS 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28
    PLANE   : SLOT F2, B1, C4, E4, C3, E1, D3, E2, F4, D5, A5, F5, A4, B3
    CLOCK   :      RB, RB, RB, RB, RB, RB, RB, RB, RB, CS, RB, RB, CS, RB
    BLOCK II: PRNS 29, 30, 31, 32
    PLANE   : SLOT C1, B5, A2, E5
    CLOCK   :      RB, CS, RB, RB

CS: 7 sats
RB: 25 sats

The GPS birds do see eclipses twice a year. Their timing signals is 
readily available and should allow you to monitor them.

Notice that much of the timing error is canceled though broadcasted 
corrections, do study the GPS ICD 200.

> (I apologize for for some OT content)

I think it is sufficiently on-topic and enligthens yeat another aspect 
of our hobby in a perfectly good maner.

Cheers,
Magnus




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