Hi Hesham, You do not acquire the time from a LEO satellite but directly from the GPS satellites which carry an atomic clock on board. I'd not be aware of any LEO providing a GNSS signal but Xona plan such system (although not carrying proper atomic clocks but probably chip-sized atomic clocks that require frequent syncing with proper atomic clocks): https://twitter.com/Megaconstellati/status/1708091536439673323 There are efforts to build trapped-ion quantum clocks that are expected to become significantly smaller and cheaper than traditional atomic clocks while as accurate which would make it viable to put an atomic clock-equivalent on small LEO satellites. Once that happens you would have an independent alternative to the big GNSS birds in MEO but with stronger signals. I'm told that we are 5-10 years away from such trapped-ion quantum clocks. But for NTP clients, the described method (running a local NTP server in the satellite terminal synced to GPS) should be good enough. Christian Am 2. März 2024 18:02:47 OEZ schrieb Hesham ElBakoury : >Hi Christian, >How you synchronize the time of the satellites in the network? Are you >saying each satellite has a master clock? > >Hesham > >On Sat, Mar 2, 2024, 7:38 AM Christian von der Ropp wrote: > >> Why not acquire the time directly from by the satellite terminal and run >> local NTP servers instead of syncing via the Internet? LEO satellite >> terminals always have onboard GNSS antennas for geolocation which is >> necessary to find the satellites, so integrating a local GNSS-disciplined >> Stratum-1 NTP server seems trivial to me. >> >> >> Am 2. März 2024 17:25:59 OEZ schrieb Hesham ElBakoury via Starlink < >> starlink@lists.bufferbloat.net>: >> >>> Hi Sebastian, >>> Can we still use PTP and NTP for time synchronization in Satellite >>> networks or we need new protocols? If we need new protocols, do such >>> protocols exist? >>> >>> Thanks >>> Hesham >>> >>> On Sat, Mar 2, 2024, 7:18 AM Sebastian Moeller wrote: >>> >>>> Hi Hesham >>>> >>>> > On 2. Mar 2024, at 16:03, Hesham ElBakoury via Starlink < >>>> starlink@lists.bufferbloat.net> wrote: >>>> > >>>> > Time synchronization, for satellite networks, faces several challenges: >>>> > 1. Signal Propagation Delays: Unlike terrestrial networks where >>>> signals travel through cables at the speed of light, >>>> >>>> [SM] The speed of light in your typical glas fibers (and accidentally >>>> the information propagation speed in metallic conductors) comes in roughly >>>> at 2/3 of the speed of light in vacuum, while the speed of light in air at >>>> see level is a mere 90 KM/s slower than in vacuum. >>>> >>>> > satellite communication involves signals traveling vast distances >>>> through space. This creates significant delays. >>>> >>>> [SM] Sure distances might be larger, but propagation speed is around >>>> 100000Km/s faster... my main point is speed of light is a) dependent on the >>>> medium b) not the things that differentiates space from the earth's surface >>>> here, but mere geometry and larger distances on larger spheres... >>>> >>>> > 2. Clock Drift: Even highly precise atomic clocks, used in satellites, >>>> are susceptible to "drift" - gradually losing or gaining time. This drift, >>>> caused by factors like temperature variations, radiation exposure, and >>>> power fluctuations, can lead to inconsistencies in timekeeping across the >>>> network. >>>> > 3. Signal Degradation: As signals travel through space, they can >>>> degrade due to factors like atmospheric interference, ionospheric >>>> disturbances, and solar activity. This degradation can introduce noise and >>>> errors, impacting the accuracy of time synchronization messages. >>>> > 4. Limited Resources: Satellites have limited power and processing >>>> capabilities. Implementing complex synchronization protocols can be >>>> resource-intensive, requiring careful optimization to minimize their impact >>>> on other functionalities. >>>> > 5. Evolving Technologies: As satellite technologies and applications >>>> continue to evolve, new challenges related to synchronization might emerge. >>>> For example, the integration of constellations with thousands of satellites >>>> poses unique synchronization challenges due to the sheer scale and >>>> complexity of the network. >>>> > These challenges necessitate the development of robust and efficient >>>> time synchronization protocols for satellite networks and an integrated >>>> satellite and terrestrial networks >>>> > Are you aware of such time synchronization protocols? >>>> > I would think that using Satellite simulators is the most viable way >>>> to develop and test these protocols given that using satellites is not that >>>> easy. >>>> > Thanks >>>> > Hesham >>>> > >>>> > >>>> > >>>> > _______________________________________________ >>>> > Starlink mailing list >>>> > Starlink@lists.bufferbloat.net >>>> > https://lists.bufferbloat.net/listinfo/starlink >>>> >>>> -- >> Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail >> gesendet. >> -- Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail gesendet.