> -----Original Message----- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@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 _______________________________________________ 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.
