https://matangitonga.to/2022/02/08/tonga-cable-broken On 8/02/2022 9:38 am, Ulrich Speidel wrote: > > I've been watching (and commenting on) this ever since one of our MPs > tweeted Elon Musk with a plea for help for Tonga (and as the PhD > supervisor of Tonga's first PhD student in Computer Science and > someone who has had Pacific connectivity at the core of his work, I've > got a fairly good understanding of what "Tonga offline" means in > practice). That said... > > - Practical range from gateway ground station to user ground station > is more like 300-400 km. Fiji-Tongatapu is twice that distance. > - Countless images of gateways (and fencing around it) suggest that > satellite elevation from gateways needs to be a bit more than 25deg. > - Satellite density in the tropics is lowest for Starlink's currently > operational 53 degree inclination network. > - It's my understanding that dishys don't actually track using their > motors, which they use only to position themselves initially in the > direction of the highest satellite density (=wherever your closest > 53rd parallel is, basically). That's a strategy that doesn't really > work in the tropics because you can't see the sky above the 53rd > parallel. So here, your dishys would need to know to point > west-north-west. > > While it's encouraging to see Starlink send folk to Fiji to scout > things out (there are plenty of Fijian outlying islands where Starlink > service would be welcome, too, at least by the locals, not necessarily > by the regulators), I don't hold my breath on them making serious > inroads when it comes to alleviating the current connectivity crisis. > > The cable ship (CS SubCom Reliance) tasked with repair of the cable is > on site and, judging by its AIS track, has located the end of the > cable coming from Tongatapu. It appears to have shifted a significant > distance south (around 1-2 km), possibly as a result of a turbidite > flow (underwater landslide) from a seamount in the area that was > triggered by the eruption at Hunga further north (my going theory > anyway - there's a seamount right where it needs to be for that sort > of damage and there's no other event that explains the timing of the > cable outage). Either way, if the area is suitable for re-laying the > cable, Tonga should be back online within the next week. Otherwise add > a week or two. > > On 8/02/2022 8:06 am, Nathan Owens wrote: >> You can simulate it on starlink.sx >> , >> maybe Mike will chime in with what he found in doing that. >> >> On Mon, Feb 7, 2022 at 11:05 AM Christian von der Ropp >> wrote: >> >> But in practice the satellites won't be sitting and waiting at >> the edge of this 940km radius. They are moving in and out the >> radius and the question is if satellite density is high enough so >> that once the serving satellite loses its gateway link there's >> another satellite in the 940km radius which also covers Tonga. >> And then this new satellite cannot be within certain elevation >> angles (~60-80° at 0° azimuth) where the geostationary arc >> crosses Fijian skies and the gateway antennas have to seize >> emission. My gut feeling is that availability in Tonga would be >> <90% simply because it's too far out at the edge of a Fijian >> gateway's range where there will be frequent service interruptions. >> >> >> Am 07.02.2022 um 19:51 schrieb Nathan Owens: >>> The current coverage radius of a gateway/ground station with a >>> 25 degree minimum elevation is ~940km, so nothing in theory. >>> >>> On Mon, Feb 7, 2022 at 10:50 AM Daniel AJ Sokolov >>> wrote: >>> >>> Hello, >>> >>> I hope this is not offtopic: Starlink wants to build a >>> ground station on >>> Fiji to supply Tonga with internet. >>> >>> The distance between Tonga and Fiji is about 750 km minimum. >>> That's >>> quite the distance. >>> >>> What does Starlink have to do to make this work? >>> >>> Cheers >>> Daniel >>> _______________________________________________ >>> Starlink mailing list >>> Starlink@lists.bufferbloat.net >>> https://lists.bufferbloat.net/listinfo/starlink >>> >>> >>> >>> _______________________________________________ >>> Starlink mailing list >>> Starlink@lists.bufferbloat.net >>> https://lists.bufferbloat.net/listinfo/starlink >> >> _______________________________________________ >> Starlink mailing list >> Starlink@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/starlink >> >> >> >> _______________________________________________ >> Starlink mailing list >> Starlink@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/starlink >> > -- > **************************************************************** > Dr. Ulrich Speidel > > School of Computer Science > > Room 303S.594 (City Campus) > Ph: (+64-9)-373-7599 ext. 85282 > > The University of Auckland > ulrich@cs.auckland.ac.nz > http://www.cs.auckland.ac.nz/~ulrich/ > **************************************************************** > > > -- **************************************************************** Dr. Ulrich Speidel School of Computer Science Room 303S.594 (City Campus) Ph: (+64-9)-373-7599 ext. 85282 The University of Auckland ulrich@cs.auckland.ac.nz http://www.cs.auckland.ac.nz/~ulrich/ ****************************************************************