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[sevenlayermuddle]

This is second attempt to start this topic, the first one disapeared.   Apologies if it reappears.

But is anybody else following Inmarsat's endeavours?

Inmarsat managed to get another satellite up this week, on the end of a Proton rocket.   It had been delayed a few months, after an unrelated Proton blew up earlier in the year, as have  many other Protons.

But this new satellite completes their 'Global Xpress' system, which will provide Global high speed broadband.   And unlike what 'BT' may think of as 'global', they really mean it... anywhere on or above the surface of the earth, including passenger flights and cruise ships.   Only exceptions, I understand, are North and South poles. 

http://www.bbc.co.uk/news/science-environment-34075611

I'm sure the service won't be cheap, but still impressive.

[AArdvark]

Thanks

I caught the bbc news article.

It was *very* important that the rocket worked this time 
Inmarsat need to be able to complete with other company's working in the Ka-band, as mentioned in the article.

I read about what Inmarsat was doing 6 'ish months ago after a random link got me there.
Very interesting

[sevenlayermuddle]

I have been told, but not sure if it's true, that the Protons are more or less just old Russian ICBM missiles from the Cold War.   That might explain why a high failure rate is acceptable.

I believe Inmarsat will also launch a further satellite, to be used if any of the three existing satellites should fail.  And I don't think they're trusting that one to a Proton, using a U.S. launch service instead.

[AArdvark]

Correct it was from a family that started as a ICBM
https://en.wikipedia.org/wiki/Proton_%28rocket_family%29
https://en.wikipedia.org/wiki/Proton-M

See also
Ars Technica Article about How NASA recreated/re-engineered the F1 Moon Rocket.
Really good article that I am sure either mentions the Proton or it is in the comments which are also very good from Rocket Engineers & others.
http://arstechnica.com/science/2013/04/how-nasa-brought-the-monstrous-f-1-moon-rocket-back-to-life/

I have a scatter gun interest in everything so read all kinds, often by accident. 

[Weaver]

It's bad that it doesn't work in the polar regions. Ships up there really need help sometimes and of the can't contact anyone that's dangerous.

I read with interest RevK's (www.revk.uk) experiences with the old Inmarsat network using a pager-like device on a cruise ship in the Caribbean, which was so slow it was hardly good enough for email, but you could tweet with it, and it kept him in touch with his blog. It was pretty expensive.

A higher speed system would be great if it's affordable.

[sevenlayermuddle]

Not sure where I saw the limitations at North and South poles.

But if true, I would imagine the same would apply to any geostationary satellite service.   The satellites have to be over the equator so from the actual poles, no matter which direction you face, they would be obscured by the horizon.

If that is the limitation, it would be interesting to know how big the dead zone might be?  Any O level maths student with a pencil, paper and pocket calculator, and given diameter of planet and height of satellite, ought to be able to work out the dead zone.  But these days, that no longer implies that I personally could work it out.   

[Weaver]

Iirc, the geostationary satellites are so far out that it just comes (almost) down to cos( latitude ).  But obviously there will be a small completely dead zone near the poles. A better expression would be something like
    cos^-1( earth_radius / geostationary_orbit_radius)
If my creaking brain still works.

You could have a constellation of satellites in a non-equatorial orbit, even a polar orbit.

Someone was I believe talking about doing a solution specifically for the high Arctic for the safety of ships, maybe it's the constellation type of design, I've no idea.

[Weaver]

As I recall that was one of the questions I was asked in order to get into university: work out how far out a geostationary satellite is. The other one was, “when I let go of this pencil, where does the momentum come from?”

Fortunately I wasn't phased.

[sevenlayermuddle]

Is this a good time to say "Come on now it isn't rocket science". 

[Weaver]

I do hope someone sorts it out some day because if I were in trouble in the Arctic or on a boat I would really like some comms so I could get help. The increasing importance of the Northern Sea Route is increasing the case for High Arctic good comms. That's the Siberian North Coast route from Scandinavia round to the Bering Strait and Japan.

[AArdvark]

Not sure where I saw the limitations at North and South poles.

It is plainly shown on the Inmarsat site when showing the coverage for their phones etc
Does not go into the why but 'caveats away' the variability of coverage towards the extreme ends of the satellite footprint.

Global Xpress does not change this as far as I can see (No coverage maps found yet ! )

[loonylion]

there are comms available at the north and south poles, they're just served by a different platform.

[AArdvark]

there are comms available at the north and south poles, they're just served by a different platform.

I have seen the portable Sat dish type comms (use by TV companies for live remote news reports sometimes) but cannot find anything like that from Inmarsat.
I thought they would have done it but maybe it is what their competitors do.

[loonylion]

not sure if BGAN (satellite broadband) is available at the poles, but satphones certainly are. And that's the type of comms you'd want if you were in distress at said locations.

[AArdvark]

That is what I have seen.
A sat phone with the ability to plug into a 'Briefcase' with a portable free standing Sat Dish plugged in. (Size of a large parabolic microphone dish)
You can plug Camera feeds and Microphone feeds into the 'Briefcase'.