Hello Brian, Welcome to the list. Just wanted to point out that the wavelength at 1.5GHz is about 20cm (not 2mm). This takes your 7ps estimate to 700ps (which is more realistic). There are LOTS of noise sources that have to be accounted for to get precision measurements, including - ionospheric effects, tropospheric effects, satellite orbit uncertainties, satellite clock uncertainties, measuring instrument uncertainty (as Bob pointed out), and even more. The ability to deal with these is different between one-way measurements and common-view measurements. And even one-way measurements can have some corrections applied (dual frequency receivers can correct for ionospheric effects, for instance). Welcome to time-nuts and feel free to ask questions, there is a lot of knowledge at your fingertips. Regards, Skip Withrow

Just to set realistic expectations on what you can do with "not exotic" hardware but on a moving platform, without ionosphere effects. We get timing to around a hundred nanoseconds in real time at GEO with a patch antenna on SunRISE (well, using simulators, we've not flown yet - ULA keeps pushing the launch to the right) and no "external corrections" - that's using standard Real Time GipsyX (RTGx) for the processing at a fairly low SNR (because we're on the opposite side of the Earth - 10 dB hit in SNR from 3x distance).  A fairly non-exotic OCXO, not fancy signal processing, L1 and L2, though.  That's somewhat worse than you get from off the shelf GPS modules for a variety of reasons. With post processing, we can get "hundreds of ps" kind of timing performance - We do precision orbit determination, which solves for our orbit, then determines the clock offset (and rate).  This relies also on having precise orbits for the GPS space vehicles. This document describes the receiver and the acquisition and handling of the GPS observables. https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=doi:10.48577/jpl.8M0MKX On 1/18/26 7:57 AM, Skip Withrow via time-nuts wrote: > Hello Brian, > Welcome to the list. > Just wanted to point out that the wavelength at 1.5GHz is about 20cm (not > 2mm). This takes your 7ps estimate to 700ps (which is more realistic). > > There are LOTS of noise sources that have to be accounted for to get > precision measurements, including - ionospheric effects, > tropospheric effects, satellite orbit uncertainties, satellite clock > uncertainties, measuring instrument uncertainty (as Bob pointed out), and > even more. > > The ability to deal with these is different between one-way measurements > and common-view measurements. And even one-way measurements can have some > corrections applied (dual frequency receivers can correct for > ionospheric effects, for instance). > > Welcome to time-nuts and feel free to ask questions, there is a lot of > knowledge at your fingertips. > > Regards, > Skip Withrow > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com >