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<p>Update just in from Tonga Cable is that the Reliance cable ship
will lay at least 55 km of fresh cable. They've spent the last 36
hours or so doing three traverses of the cable route around 30
nautical miles west of where the cable was broken at the Tongatapu
side.</p>
<p>This older post gives a bit of an idea of how the Reliance works:<br>
</p>
<p><a class="moz-txt-link-freetext" href="https://www.reddit.com/r/ThingsCutInHalfPorn/comments/4yttq7/reliance_undersea_cable_laying_repair_ship_te/">https://www.reddit.com/r/ThingsCutInHalfPorn/comments/4yttq7/reliance_undersea_cable_laying_repair_ship_te/</a><br>
</p>
<div class="moz-cite-prefix">On 8/02/2022 9:44 am, Ulrich Speidel
wrote:<br>
</div>
<blockquote type="cite" cite="mid:7d34164a-3ad7-ba9f-cd59-b550f4cf570b@cs.auckland.ac.nz">
<p><a class="moz-txt-link-freetext" href="https://matangitonga.to/2022/02/08/tonga-cable-broken" moz-do-not-send="true">https://matangitonga.to/2022/02/08/tonga-cable-broken</a><br>
</p>
<div class="moz-cite-prefix">On 8/02/2022 9:38 am, Ulrich Speidel
wrote:<br>
</div>
<blockquote type="cite" cite="mid:097bbcb6-987d-0461-fb2a-2c7c4a8c0c97@cs.auckland.ac.nz">
<p>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...</p>
<p>- Practical range from gateway ground station to user ground
station is more like 300-400 km. Fiji-Tongatapu is twice that
distance.<br>
- Countless images of gateways (and fencing around it) suggest
that satellite elevation from gateways needs to be a bit more
than 25deg.<br>
- Satellite density in the tropics is lowest for Starlink's
currently operational 53 degree inclination network.<br>
- 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.<br>
</p>
<p>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. <br>
</p>
<p>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. <br>
</p>
<div class="moz-cite-prefix">On 8/02/2022 8:06 am, Nathan Owens
wrote:<br>
</div>
<blockquote type="cite" cite="mid:CALjsLJtakscSULtwtunS+Evhu5yVBMnpuZZ2cMwR0JkjUNyE-g@mail.gmail.com">
<div dir="ltr">You can simulate it on <a href="http://starlink.sx" moz-do-not-send="true">starlink.sx</a>, maybe Mike will
chime in with what he found in doing that. <br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Mon, Feb 7, 2022 at
11:05 AM Christian von der Ropp <<a href="mailto:cvdr@vdr.net" moz-do-not-send="true" class="moz-txt-link-freetext">cvdr@vdr.net</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div>
<div>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.<br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>Am 07.02.2022 um 19:51 schrieb Nathan Owens:<br>
</div>
<blockquote type="cite">
<div dir="ltr">The current coverage radius of a
gateway/ground station with a 25 degree minimum
elevation is ~940km, so nothing in theory. <br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Mon, Feb 7,
2022 at 10:50 AM Daniel AJ Sokolov <<a href="mailto:daniel@sokolov.eu.org" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">daniel@sokolov.eu.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px
0px 0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Hello,<br>
<br>
I hope this is not offtopic: Starlink wants to
build a ground station on <br>
Fiji to supply Tonga with internet.<br>
<br>
The distance between Tonga and Fiji is about 750
km minimum. That's <br>
quite the distance.<br>
<br>
What does Starlink have to do to make this work?<br>
<br>
Cheers<br>
Daniel<br>
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<pre class="moz-signature" cols="72">--
****************************************************************
Dr. Ulrich Speidel
School of Computer Science
Room 303S.594 (City Campus)
Ph: (+64-9)-373-7599 ext. 85282
The University of Auckland
<a class="moz-txt-link-abbreviated moz-txt-link-freetext" href="mailto:ulrich@cs.auckland.ac.nz" moz-do-not-send="true">ulrich@cs.auckland.ac.nz</a>
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</pre>
</blockquote>
<pre class="moz-signature" cols="72">--
****************************************************************
Dr. Ulrich Speidel
School of Computer Science
Room 303S.594 (City Campus)
Ph: (+64-9)-373-7599 ext. 85282
The University of Auckland
<a class="moz-txt-link-abbreviated moz-txt-link-freetext" href="mailto:ulrich@cs.auckland.ac.nz" moz-do-not-send="true">ulrich@cs.auckland.ac.nz</a>
<a class="moz-txt-link-freetext" href="http://www.cs.auckland.ac.nz/~ulrich/" moz-do-not-send="true">http://www.cs.auckland.ac.nz/~ulrich/</a>
****************************************************************
</pre>
</blockquote>
<pre class="moz-signature" cols="72">--
****************************************************************
Dr. Ulrich Speidel
School of Computer Science
Room 303S.594 (City Campus)
Ph: (+64-9)-373-7599 ext. 85282
The University of Auckland
<a class="moz-txt-link-abbreviated" href="mailto:ulrich@cs.auckland.ac.nz">ulrich@cs.auckland.ac.nz</a>
<a class="moz-txt-link-freetext" href="http://www.cs.auckland.ac.nz/~ulrich/">http://www.cs.auckland.ac.nz/~ulrich/</a>
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