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Re: Laser Satellite Comms



-----Original Message-----
From: Dr Thomas A Clark (W3IWI) <clark@tomcat.gsfc.nasa.gov>
To: Bob Bruninga <bruninga@nadn.navy.mil>; amsat-bb@AMSAT.Org
<amsat-bb@AMSAT.Org>
Cc: Franklin Antonio <antonio@qualcomm.com>; sarex@AMSAT.Org
<sarex@AMSAT.Org>
Date: Tuesday, March 02, 1999 9:47 AM
Subject: Re: [amsat-bb] Laser Satellite Comms

[some stuff deleted]
>A comment was made about the lunar reflector. In point of fact, MANY
>satellites do carry retro-reflectors, including the new SUNSAT.
[more stuff deleted]
>The one "mirror ball" that would work better for communications was
>the Japanese Ajisai, launched with the first Fuji-Oscar satellite some
>years ago. Ajisai was big -- ~2 meters in diameter,  [rest of stuff
deleted]
------

Is anyone on this list old enough to remember a satellite called "Echo I"?
... Or "Echo II"?

It seems like what would *really be fun* is another "Echo" satellite.

I don't remember the dates of the Echo program, but it had to be back in
the early 1960s.   I was a kid at the time, and my dad used to "track" the
Echo satellites for a local amateur astronomy group.  Dad used to get little
teeny-tiny, itsy-bitsy  (8-1/2 x 11) computer printouts on onionskin paper
from
the Smithsonian Institution. These printouts were covered in tables of
numbers.
There was one page of numbers for each satellite, each week.

Dad would use a polar-coordinate grid, a slide rule, standard graph paper,
and
a whole lotta pencil lead, and would calculate azimuth, elevation, appear
times,
disappear times (earth-shadow entry), for Echo I and II, PAGEOS, and whole
host of other visible satellites.  All done manually, the good old fashioned
way.

Echo I and II were nothing more than *BIG* balloons.  I don't remember the
details,
but it seems like they were simply huge mylar (had mylar been invented yet?)
silvery balloons with a miniscule amount of gas (a CO-2 cartridge or less)
to keep them inflated in space.  They orbited for several years, and were
about
200-feet in diameter (or something like that, as I said I don't remember the
exact details).  They were *brilliant* ... first magnitude, or even
minus-one or
minus-two magnitude.  Their low orbits made them really zip across the sky.

It would seem that a big mylar balloon, with an auto-triggered CO-2
cartridge,
with a silvered surface (like those 98-cent emergency blankets at Wal-Mart)
would be a lot of fun to play with.  Talk about bouncing light signals!  Or
even
radio signals!  Microwave experimentation, anyone?  No need for a passband,
simply point your antenna and listen on anything your receiver will tune.
Or
set up a sked with someone on a quiet frequency... anywhere you are
authorized
to transmit.  I would think it would be fun to track transmitter
power-to-receiver
S-units across the spectrum.... how does wavelength relate to curvature
(balloon
radius), and what are the propagation charactertistics (bounce angles) at
the
various ham frequencies?

This passive technology seems like it would be a whoe lot more robust and
reliable than a complex telemetried satellite with transponders, batteries,
solar cells, radiation-hardened CPU's, attitude thrusters, phasers, -- am I
forgetting anything?    Not as much fun to build, perhaps, but a lot of fun
to
play with.   Perhaps lighter, too?  Easier to manifest (e.g., hitch a ride)?

Further, at minus-two magnitude, lots of ordinary people would
see it with their naked eyes, possibly stimulating interest in the hobby.
Another possible benefit:  since it is passive, the Keps would be good
for a longer time (compared to Mir and ISS which fire thrusters altering
their
orbits... seems like every single time I announce to my friends that I can
show
them the satellite, it's never there where my program tells me it will be!).

It would be interesting to measure the bounce angles of 144 vs 440 MHz
signals;  plot APRS data of the "heard" stations; look at the patterns;
etc.   Put the little sucker up high enough, in a polar orbit (or nearly
polar)
and you might get enough footprint coverage for a pile-up.  Put one even
higher and require specialty stations with high power and pre-amps to
work.  Put one lower and we might be able to use home stations
(unlikely HTs?) with omni antennas?  Shoot, with all the chatter on
2m, just aim a beam antenna at the little point of light and tune across
the band (any band!) and see what you hear!  :)

I'm sure that a balloon like this costs more than I would at first expect.
But cost is relative.  Would it cost more than Phase IIID?  More than
a picosat?  Less than a land-based 2m repeater and its cans?

I'm curious if anyone else thinks this might be a fun, low-budget way of
"working satellites"?   Just an idea, while we're taking about bouncing
signals off of orbiting hardware...  (or would a balloon be "soft" ware?)

----------------------------------------------------------------------------
--
David R. Fordham, CPA, CMA, Ph.D.
ARS KD9LA
James Madison University
School of Accounting
Mail Stop Code 0203
Harrisonburg, VA 22807

Phone:  540-568-3024
Fax:  540-568-3017
Email:  fordhadr@jmu.edu
Homepage:  http://cob.jmu.edu/fordhadr/


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