High data rate space transmissions through visible lightcommunication.
 

On Jun 28, 5:31*pm, Robert Clark wrote:
On Jun 28, 1:41 pm, Richard Clark wrote:

On Sun, 28 Jun 2009 17:14:14 +1000, "Peter Webb"

wrote:
Furthermore, the radiation from a reflected area is isotropic - goes in all
directions - and hence very little is directed towards the earth.

Actually, it is lambertian in its distribution, and it would have a
major lobe that was directed in rather typical fashion (at the same,
but negative angle to the norm to the surface). *However, as is the
intent of your response, very much less will find its way to the
intended target.

73's
Richard Clark, KB7QHC

*This describes the reflection from the Iridium antennas as specular
where most of the reflected light is concentrated in a single
direction:

SeeSat-L Apr-98: Method for predicting flare.http://satobs.org/seesat/Apr-1998/0175.html

*About specular reflection:

Specular reflection.http://en.wikipedia.org/wiki/Specular_reflection

*We could get even higher concentration of the image by using
parabolic mirror reflectors.

* *Bob Clark

Yes, and it was all doable as of more than a decade ago. However, at
the rate we're going, perhaps another century is required.

~ BG

High data rate space transmissions through visible light communication.
 

Robert Clark wrote:
I had been thinking about methods of high data rate transmission in
regards to getting *video* transmissions from Mars orbiter missions. I
was irritated by the spotty coverage of the Mars surface at the best
resolutions so I wanted to send real-time *continuous* imaging back to
Earth receiving stations at the highest imaging resolutions. This
would require very high transmission rates, much higher than what is
currently used.
The idea would be to use light transmissions but only of the on-off
variety. You would use a large surface, many meters across, capable of


Bob,
You might not want to cross-post to 5 groups.

1) what spotty coverage? I doubt any gaps are due to the lack of data
bandwidth from Mars to Earth, except when MRO goes behind Mars, or
similar line of sight interruptions. There's a non-zero cost to running
DSN antennas, too. In any case, getting sufficient bandwidth in a pipe
to earth isn't a matter of technology, it's a matter of money.
2) Optical comm with very high bandwidths is a subject of research and
development at NASA (at JPL) and the USAF (at Lincoln Labs). Lots of
interesting ideas for receivers on the Earth, etc. Doesn't take a huge
telescope or high powers at either end. They use, IIRC, a form of pulse
position modulation.


There was a special issue of IEEE Proceedings October 2007 (Special
issue on Technical Advances in Deep-Space Communications and Tracking)
that discusses a lot of this stuff. (including optical) Read it and
learn, rather than just looking at press releases and formulating ideas
from that.

High data rate space transmissions through visible lightcommunication.
 

On Jun 29, 11:42*am, Jim Lux wrote:
...

* There was a special issue of IEEE Proceedings October 2007 *(Special
issue on Technical Advances in Deep-Space Communications and Tracking)
that discusses a lot of this stuff. (including optical) Read it and
learn, rather than just looking at press releases and formulating ideas
from that.

And also picking the brains of people on these forums.

Bob Clark ;-)

Detecting the HDTV for the Google Lunar X Prize, applications tothe SETI search.
 

On Jun 16, 9:43*pm, Jim Lux wrote:
...

Look up LOFAR or the SKA (Square Kilometer Array) for a fairly well
funded scheme.

LOFAR.
http://en.wikipedia.org/wiki/LOFAR

LOFAR like my proposal is to use many separate dipoles to detect long
wavelength radio waves. However, it is to have only 10,000 dipoles
whereas mine at the end will have ca. 1 billion dipoles.

The progenitors of the LOFAR project have argued in papers that it
could be used for the SETI search. However, this article by well known
SETI search scientist Seth Shostak argues LOFAR will be too weak to
detect Earth type radio transmissions at a distance of say 55 light-
years by a factor of 1 million:

Listening for ET’s Television.
November 9, 2006
by Seth Shostak, Senior Astronomer
http://www.seti.org/Page.aspx?pid=917

Then since my proposal will be about 100,000 times more sensitive
than LOFAR, it could detect Earth-like radio transmissions to about
1/3 the distance of 55 lightyears, or to about 18 lightyears way.
There are several star systems in that range. The Shostak article
notes you could get several hundred times better sensitivity by
listening to certain stars over months or years. Then my proposal
could detect such transmissions out to even 55 lightyears and further.


Bob Clark

Detecting the HDTV for the Google Lunar X Prize, applications to the SETI search.
 

On Tue, 30 Jun 2009 11:37:29 -0700 (PDT), Robert Clark
wrote:

The Shostak article
notes you could get several hundred times better sensitivity by
listening to certain stars over months or years.

And if you lost your keys at night, you might find them faster looking
under street lights.

Yet another troll.

73's
Richard Clark, KB7QHC