[Starlink] Starlink for Tonga?

Fri Feb 18 07:48:08 EST 2022

This is such a cool summary of the current process...

Once I was wasting time in the Dartmouth engineering library (when I was supposed to be doing work). I found an older book about the laying of the first trans-Atlantic cable. They had terrible problems (their first effort failed), for example...

- It was a single strand insulated by gutta-percha (rubber-ish stuff I think). They tested for continuity by hourly (?) tests from a team on shore sending current one way for a minute, then the other way. They used a galvanometer to detect... Talk about low bits/second.
- When the cable broke, they used the same "back up and drag a grappling hook" technique to snag the cable and bring it up
- It weighed a ton - literally. If I remember correctly, each length from the sea floor to the surface weighed 6,000 pounds, so they had to hoist 12,000 pounds of cable to begin to find the broken end

Everything's the same... But a lot better :-)

Rich

> On Feb 18, 2022, at 5:27 AM, Ulrich Speidel <ulrich at cs.auckland.ac.nz> wrote:
> 
> I've heard nothing further about teleport establishment in Fiji, but that doesn't mean that nothing has happened.
> 
> Meanwhile, cable repair has progressed a good bit. The damage was far greater than originally envisaged. On the international cable, faults (complete cable ruptures and fibre damage) stretched over more than 80 km. The cable ran entirely SOUTH of the Hunga Tonga Hunga Ha'apai volcano (about 60 km away and shielded by a number of submarine mounts for at least parts of the damaged section). Yet the Reliance cable ship traced one disconnected cable piece end to about 5 km NORTH of its nominal route, found various sections had disappeared completely, and recovered sections of up to 9 km at a time from the seabed.
> 
> A bog standard cable break requires two holding drives (or drags), HD for short, to pick up each of the cable endpoints from the seafloor. It also requires either an ROV dive to check if the cable has completely separated at the fault position, or a cut if the cable is still held together by the steel. That cut can be done either by ROV as well, or if visibility doesn't permit ROV use, by a cutting drive (CD). Any HD or CD requires the cable ship to tow a seafloor grapnel / cutter device transversally across the cable, so they're easy to spot on position traces. The Reliance did no fewer than seven HD's in its eastern operations area near Tongatapu, where it worked first. Visibility there was good (so ROV could be used), but damage substantial. 
> 
> The ship then proceeded to the western end of the fault zone where reflectometer measurements from the Suva end had found a fault. Because of bad visibility, they did a CD followed by 2 HD's there, then noticed that there was fibre damage along the cable to Suva, so reeled that in and cut the damaged bit out.
> 
> They then proceeded to put a "mini-system" together. Let me explain: Enroute to Tonga, the Reliance stopped at Subcom's depot in Apia (Samoa) to load whatever cable they had in store there. This included spares not only for the Fiji-Tonga cable but also for various other cable systems in the wider region. Reliance left Apia with about 80 km of cable in total. The amount of cable that will need to be re-laid along the damaged international section is 90 km (you need to allow for a bit of cable lengthening due to slack being inserted when cable ends are being brought up from 2000 m (6000 ft) or so below). This means that the Reliance is re-using some of the cable recovered from the damaged section, and the whole "mini-system" will be one long stitch job. The damaged section also included a repeater worth US$230k, which they were trying to recover and which was still missing as of this morning - I've yet to hear from my contact as to whether they were successful on the last recovery attempt today (they've left the area after three drives and are heading West right now. The rest of the mini-system was going to be laid after the repeater recovery attempt (the overall success doesn't depend on the repeater being found, but the final repair bill does). I thus expect the cable repair to be completed in the next few days.
> 
> The domestic cable is another story altogether, unfortunately. This has a blind stretch of 77 km at present, as measured by optical reflectometer from Tongatapu and Ha'apai (there was meant to be a measurement from Vava'u yesterday but I haven't heard yet what this revealed, the cable from Tongatapu has two fibre pairs, one of which heads to each destination from a branching unit west of Ha'apai. That said, once the international cable has been fixed, the Reliance won't have enough cable left to complete the domestic job, even if some cable bits could be recovered there. The next available stock of suitable cable is in Europe, around 35-40 days one-way shipping away. They intend to bridge this time gap via satellite (and I'm sure would welcome a Starlink delegation with a teleport to connect to the international cable, too, especially now that the Australian Navy gave them Omicron along with their aid deliveries).
> 
> I've been in close contact with our volcanology / geophysics community here in NZ, who know the area well. The story of damage to the international cable is now shaping up to be a pretty complex one. What we know thus far is that it was neither the volcano's initial blast nor the subsequent tsunami that killed the cable - the outage began only well after the tsunami had hit. In all probability, it's been a combination of submarine landslides and turbidite waves from a variety of sources that hit hours and possibly many days after the eruption. Finding that a cable piece has moved 5 km TOWARDS the volcano points at an event south of the cable route, and the mix of seafloor visibilities encountered by the Reliance points at there having multiple events from multiple sources. There have been plenty of quakes upwards of M4 and even an M6.2 in the wider area that could have triggered slopes, especially with an extra layer of ash on them. Turbidite waves can travel up to 1000 km, aren't anywhere near as fast as a tsunami, and have long been known to have damaged cables in the past (see B.C. Heezen and M. Ewing, Turbidity currents and submarine slumps, and the 1929 Grand Banks Earthquake, American Journal of Science, v. 250, pp 849-873, December 1952. This quake killed 12 submarine cables over more than 18 hours).
> 
> Meanwhile, there's still limited satellite service in and out of Tonga, but I can confirm that e-mails (even with attachments) make it in and out OK.
> 
> 
> 
> On 18/02/2022 8:27 pm, Mike Puchol wrote:
>> Hi Daniel,
>> 
>> I added it after there was a confirmation on Twitter that SpaceX people were on the ground to set one up, and also, as two /27 blocks (IPv4) have been assigned to Fiji’s capital, under the Sydney POP, and they can be pinged.
>> 
>> Wether it’s at the teleport or not, unsure, but for simulation, an error of even a few km doesn’t really matter.
>> 
>> Best,
>> 
>> Mike
>> On Feb 18, 2022, 06:04 +0100, Daniel AJ Sokolov <daniel at falco.ca> <mailto:daniel at falco.ca>, wrote:
>>> On 2022-02-07 at 15:29, Mike Puchol wrote:
>>>> As far as placing a gateway in Fiji, it already has a teleport
>>>> facility, which will have power and fibre (unless that one has been
>>>> taken out too?). Checkhttps://goo.gl/maps/6BYXf4R17yys7zNe9 <checkhttps://goo.gl/maps/6BYXf4R17yys7zNe9>
>>> 
>>> Hey Mike, you put a "SUVA (Emergency)" ground station on starlink.sx.
>>> 
>>> Is that for simulation, or has Starlink actually installed a ground
>>> station in Fidschi by now? Would you have positive confirmation?
>>> 
>>> Thank you
>>> Daniel
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>> 
>> 
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> -- 
> ****************************************************************
> Dr. Ulrich Speidel
> 
> School of Computer Science
> 
> Room 303S.594 (City Campus)
> 
> The University of Auckland
> u.speidel at auckland.ac.nz <mailto:u.speidel at auckland.ac.nz> 
> http://www.cs.auckland.ac.nz/~ulrich/ <http://www.cs.auckland.ac.nz/~ulrich/>
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