[time-nuts] Cheap Rubidium

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Wed Dec 23 22:04:11 UTC 2009


> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of John Ackermann N8UR
> Sent: Wednesday, December 23, 2009 1:30 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Cheap Rubidium
> 
> Lux, Jim (337C) said the following on 12/23/2009 03:17 PM:
> 
> > Typical (Cassini, MGS, etc., data from Sami Asmar) UltraStableOscillator (USO) specs as used in
> spaceflight do about 1E-13 at tau =10 to 1000 seconds, 3E-13 at 1 second.  Today, you can probably do
> maybe an order of magnitude better.  These are state of the art oscillators in a vacuum envelope with
> double ovens, etc.
> 
> As far as I know, the best OCXO you can get commercially today is an
> Oscilloquartz 8607 option 008 BVA
> (www.oscilloquartz.ch/file/pdf/8607.pdf), which is spec'd at 1.2x10e-13
> at 1 second and 8x10e-14 from 3 to 30 seconds.  TVB's page at
> http://www.leapsecond.com/pages/8607-drift shows it's in the 13s out to
> 10K seconds.  The spec sheet says the aging may be <3x10e-12/day after
> 30 days operation (there's one option for best aging, and another for
> best short term stability; it's not clear whether you can get both in
> the same package).

What they do for space applications where they care (gravity science experiments are a good example) is make a whole batch of crystals and their packages and then burn them in and look for the noise and aging properties and pick the ones they want. Each crystal will have a different turnover temperature, so that factors into the selection as well.

There's a paper from Greg Weaver at APL about USO performance.   It shows a daily drift rate of about 1E-11 for the GRACE USOs, and Figure 3 shows measured performance from 1 to 1000 seconds for 3 USOs. The Cassini USO has performance like John mentions (6E-14 at 10 seconds).  The New Horizons USOs have drifts of 1E-11/day and ADEV<1E-13 from 10-100 seconds.  Lots of other interesting stuff from Greg and his colleagues in the paper as well:
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA503333&Location=U2&doc=GetTRDoc.pdf



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