Re: Barack Obama Pits Space Explorers Against School Children

On 3 Dec, 15:48, Fred J. McCall <fmcc...@xxxxxxxxxxxxx> wrote:
Fred J. McCall <fmcc...@xxxxxxxxxxxxx> wrote:

:Ian Parker <ianpark...@xxxxxxxxx> wrote:

:
::On 3 Dec, 14:37, Fred J. McCall <fmcc...@xxxxxxxxxxxxx> wrote:
::> Ian Parker <ianpark...@xxxxxxxxx> wrote:
::>
::> :
::> :Space has got to be packaged in terms of what directly relates to life
::> :on Earth. The dinosaurs were wiped out by an Asteroid strike. We have
::> :the technology to divert asteroids, we need to spend a relatively
::> :small (in terms of the amounts of money that are spent by governments)
::> :to ensure that this does not happen. We don't want out children going
::> :the way of T Rex.
::> :
::>
::> The man in the street doesn't regard that as a credible threat and
::> wouldn't spend a nickel on it until the asteroid is actually coming.
::>
::
::I don't know. Depends on the amount of money involved and the risk. If
::you are talking $500 million this is small in the scheme of things. If
::more - probably not. When you talk about $500m not being that great a
::sum, it IS a big sum if the net benefit is perceived to be zero.
::
:
:Which is what I just said, above. The man in the street perceives the
:net benefit of any such scheme as zero until the asteroid is actually
:on the way.
:
::
::>
::> :
::> :OPEC has far to much power. Perhaps eventually space solar power has a
::> :role to play. We need NOW to work on small scale demonstrations. SSP
::> :has got one important by product. If you can produce a spot 1km in
::> :size that will have enormous implications for WiFi particularly in
::> :remote areas.
::> :
::>
::> Ridiculous! Again, Ian appears ignorant of the fact that there is
::> ALREADY satellite internet.
::>
::
::Indeed yes, however there is a matter of scaling. A satellites, so far
::can deal only with a very limited number of conversations. The bulk of
::comunications is carried on fiber optic cables. Satellites only
::provide a premium service for mobile communications. Fiber optic
::capabilities are going up.
::
:
:And SPS isn't going to change that.
:
::
::Also satellites need large attennae.
::
:
:Most people don't consider a 1" dish 'large'.
:

Uh, make that 1' (actually, probably about 18"). Bloody keyboard has
a mind of its own.

:
::
::With a much larger receiver in
::space you can
::
::a) Have a WiFi transmittor/receiver.
::b) Have a lot of people connected.
::
:
:You really don't know much of anything about anything, do you?
:
:1) An SPS transmitter is not a receiver.
:
:2) You're moving the relay from LEO to GEO, so more power is required
:to talk up to it (or a much larger antenna on the ground
:transmitting).
:
:3) The physical size of the receiver has NOTHING to do with how many
:people can be connected (and I'm not aware that even current services
:are turning people away for capacity reasons).
:
:4) WiFi is *NOT* going to work at those ranges. Hell, WiFi is good
:for a couple hundred feet. Up the transmission power so that it can
:be seen from orbit and you don't need the satellite anymore (because
:everyone on the ground will be lost in the cacophony anyway).
:
::
::>
::> :
::> :It will also render "Great Firewalls obsolete. You may
::> :or may not be able to see the Great Wall from LEO. You are able to see
::> :neither the Great Wall nor the Great Firewall from GEO.
::> :
::>
::
::Hey if we go on like this there will be no hard justification for
::space at all.
::
:
:Which brings us back to the original problem.
:
:I find it amusing, though, that Ian Parker's take on things is "knock
:down my loony schemes and there's no reason for space at all".

Look it is not JUST the size of the attenna although that is a lactor.
It is also to do with the total bandwidth. Suppose I stand somewhere
and draw a 500m radius circle center me. Now at GEO the receiver has
enough resolution to distinguish me from someone outside my circle. In
fact the receiver will take an FFT of the signal it is receiving. This
means that people in my circle will have a full satellite bandwidth
(10GHz say). If the satellite has lower resolution you will have 10GHz
on a 100km or even 1000km radius. I think I should have made that
clear.

A demonstrator will have this 500m circle.


- Ian Parker
.

Relevant Pages

  • Re: Source(s) of GPS error
    ... Differential correction sources include user provided reference stations, community base stations, governmental beacon transmissions, FM sub-carrier transmissions and geosynchronous satellite transmissions. ... UEE includes receiver noise, multipath, antenna ... Troposphere--Errors in the corrections of pseudorange caused by tropospheric effects ... These errors were closely correlated with the satellite clock, ...
    (sci.geo.satellite-nav)
  • food from space
    ... Each satellite has a rail gun and fires 2 meals per second - to people ... all over the Earth aided by low cost GPS guidance systems and ceramic ... delivered within 30 minutes or less anywhere on Earth. ... the asteroid belt earlier.. ...
    (sci.space.policy)
  • Re: NEW GPS with the best sensitivity of antenna!!!
    ... > I have head that under tree cover after rain GPS doesn't work. ... the geometry of the satellites being used with respect to receiver ... diffraction, ans scattering of the satellite signal by trees, utility ... Satellite clock--Errors in the transmitted clock, ...
    (sci.geo.satellite-nav)
  • Re: Evidences for the ether
    ... |> | How does a GPS receiver determine it's position? ... | A GPS satellite emits its time together with data that make ... | A receiver receives this signal. ... and the time of the satellite clocks when the signals were sent. ...
    (sci.physics.relativity)
  • Re: Evidences for the ether
    ... |> v is zero when the satellite is directly overhead (smallest sphere, ... |> to penetrate at lower speed), so any height error is down to the clock being ... |> GPS receivers regularly get altitude errors. ... |> That is really how GPS works, and they'll be happy to sell you a receiver, ...
    (sci.physics.relativity)
Loading