[AR] Re: cubesat data rates question
- From: Henry Spencer <henry@xxxxxxxxxxxxxxx>
- To: "arocket@xxxxxxxxxxxxx" <arocket@xxxxxxxxxxxxx>
- Date: Wed, 27 Nov 2013 23:57:49 -0500 (EST)
On Wed, 27 Nov 2013, JOHN HALPENNY wrote:
> Have any of these satellites tried to pass data on to a phone network in
> order to get results down without waiting for a pass? Or is it:
> - technically difficult?
> - expensive?
> - just not worth the trouble?
I assume you're thinking of Iridium and Globalstar... people certainly
have *thought* about it, a lot, for 20+ years now. But those systems are
optimized for voice and don't have terribly high data rates, and they're
not designed to be used by fast-moving, high-Doppler, very-high-altitude
(by ground standards) terminals. (The altitude matters because
continuous coverage at ground level doesn't necessarily translate to
continuous coverage at satellite altitudes, even low satellite altitudes.)
I expect it's possible, given enough effort, but as far as I know,
nobody's actually flown anything of the sort.
Ground cell systems have some of the same problems, plus the satellite is
too far away to get a good signal into them, and if it could, it could be
heard simultaneously by far too many cells. Again, the systems really
aren't designed for this, and it would be challenging to use them.
If you can afford a big chunk of mass and power, you can talk to the
Inmarsat GSO birds. (Spacehab's "Enterprise" proposal for a commercial
ISS module was going to do that, to bypass NASA's clogged communications
infrastructure.) But if your budget for communications is half a
kilogram and one or two watts, that's not going to work.
Henry Spencer
henry@xxxxxxxxxxxxxxx
(hspencer@xxxxxxxxxxxxx)
(regexpguy@xxxxxxxxx)
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