Lasers to carry 622 Mbps Earth-Moon link If all goes to plan, the next few weeks will bring a revolution in communication with spacecraft, with two space-based laser communications demonstrations due to take to the skies. The European Space Agency's Alphasat – also the largest telecommunications satellite built in Europe – is due to launch on July 25. While the …
Hell, lasers (but more commonly microwaves) are already used in some site-to-site communications for bog-standard network already.
The problem is more about the vast distance and the delay than actually how to get the data to the ground. It's a good start on a solar-system-wide communications network, though.
And there was I thinking the big difference was doing it between two objects in totally different orbits which I imagine is a tadge more complicated compared to doing it between two objects bolted in a fixed position to the same land mass (or failing that two continental plates moving at a relative mm/year to each other).
Not really - NASA pretty much has that sorted.
Even a cheap amateur "go-to" telescope can keep the ISS in view from Earth at all times enough for that kind of thing. Stick a satellite dish on such a device instead of a telescope and it's done. Hell, it even accounts for Earth's rotation, obstacles in the way, etc. Hell, my cell-phone can do it with it's magnetic and accelerometer sensors good enough to make a "push-to" app as an android app.
The problem is not keeping it in sight (so much as keeping it in orbit at all), or talking to it when you know where it is. The problem really is that the data network is MUCH MUCH more latent than we are used to, and very noisy, and that involves vast amounts of buffering and protocol redesign to make it work.
Actually putting something in orbit around the Moon / Mars is infinitely more difficult in comparison to all that. However, once it's there we can track so much space junk and can still communicate with Voyager etc. (70's technology, notice) that actually finding and sending data isn't a problem. It's how to make it work nicely as more than just a single-mission fixed data stream and more like NASA's dream of a deep-space network. And that involves throwing TCP out of the window.
"What happens when it's cloudy ?"
2 possible approaches or some combination of these 2:
a. Use somewhere at high altitude in the Atacama desert for the downlink, or somewhere else where it's cloudy very infrequently, degrade to conventional slower downlink when conditions require it . High altitude desert locations are likely best suited.
b. Have more than 1 downlink station on the ground, and routing between satellites to whichever ones have non-cloudy downlinks accessible.
wow!
broadband from space - broadband links to the moon! whatever next?
my family get their BT phone link via microwave dish link (20miles) then a further 2 miles of 'saggy' copper cable to their property.
disruptions are frequent - storms. low flying aircraft and best of all, can't report a fault as the nearest phone box (yes still exists) is linked to same microwave link!
cellphones work on top of the hills (1000ft asl) - sometimes.
they even get freeview telly in the winter but broken signals in the summer - you guessed it leaves and sheep/cattle in the signal path........
they've asked for broadband - no chance say BT engineers
farmers nearby ask for broadband - no chance say BT engineers
it was suggested an optical laser link might work - BT said no - guess they worried it could have been pointed it at BT HQ!
amazing what technology can do with money behind it - back to baked bean cans & string then!
If you really are at the end of a bit of wet string which BT don't find economical to service then the fact that you have a phone box might be an advantage to you, you need to complain to Ofcom that the phone box has poor availability because BT has an obligation to provide a good service to them. I was also told that phone boxes also have a dual function in that they have switching priority in case of a national emergency (just in-case Tom Cruise needs to call the English President at the last minute to save the world).
http://www.ofcom.org.uk/static/archive/oftel/publications/consumer/2003/pcbdd0304.htm
But also two words: community broadband, if you have a community which is poorly served you could club together and get satellite broadband from the likes of Avanti. A lot more expensive than BT, but if you club together you would at least get a wider range of services. Perhaps you could even use VoIP between the locals and save some money. You would need some emergency provision though and I don't know what the licensing is like for operating a small scale telco. But there are plenty of rural broadband initiatives who would be willing to offer help, 'social enterprise' I think the BBC called it on a recent report.
Sometimes it is better to stop bitching about what other people aren't doing for you and do it yourself.
Yes the Ping time will be huge, but you always have that in space communications. I wonder about tracking the earth base from the moon. Earth-Moon should be simple enough but who sets up and checks alignment from the Moon side.
Do we have contact with extraterrestrial network engineers?
I suspect that they would use a low bandwidth RF link for monitoring & control, something with less directionality but lower gain. That way the two units could share location information for initial synchronisation then just let it run. I don't know how much risk there is of dust from the limited atmosphere on the moon, but that would be one of my biggest concerns given the mechanical components inherent in laser communications.
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