[Laser] Balloon and LEDs

[stjohn at ocsnet.net]

I too have noticed the wild rotation of the package.  A few years ago we
were just south of Flagstaff at the QRP party there in August, and a
balloon they launched went round and round, dizzyingly.

I wondered then about a swivel attachment [perhaps a magnetic bearing]
to the balloon, to negate the rotation, and a horizontal axis gyrodisk,
revved up to speed before launch, and maintained in spin by a small
impulse pack aboard the package.

More clearly, the swivel would be two north or south magnetic fields,
with the payload floating on the magnetic almost frictionless field.
The gyrodisk would be light material, with the axis horizontal, and the
disk vertical in one of the 360 degree headings.  The disk would be
accelerated to a fast rpm, and then a small electical pump would keep it
up near to the original speed.  Over the three hours, the rotation could
deteriorate.  The camera would then be moved by remote control vis a vis
the stable platform.  Kind of like a steadicam in the movies.

LEDs right now are available throughout the spectrum.  Might Green be
better that others, as that is the frequency where our eyes are most
sensitive?  Worth debate.

Best to you, James.

Tom Upton AD6N


This is a project that is not quite a laser project, at least not yet.

There is a local group that sends up balloon packages for fun and
education.
They have sent payloads for radio tracking, telemetry beacons, APRS
tracking,
Amateur TV, and cut down control uplink.

I spoke to one of the group about a light communication related
package.  He
said that they had tried a strobe light that was unsuccessful in that it
did
not improve the ability to see the balloon with the naked eye.  The
group is
always looking for another experiment to send up so they have another
reason to
have a launch event.  So he encouraged me to come up with a "package
design",
and suggested that it start with a simple beacon to demonstrate light
band
down link and perhaps optical tracking.  They have a microcontroler
board that
could provide a data stream to it.

I invite suggestions from you for this first beacon project, or for
future
missions.  I was thinking of a hemisphere of bright LEDs flashing at
audio
frequency.  I could use some suggestions on this.  I thought of
modulating the
light beacon with an audio "carrier" modulated with MCW alternating with
BPSK
signals to compare the two modes.  MCW because it could be decoded
electronically
and by eyeball as a flashing light.  PSK31 or PSK64 might be superior
for
electronic decoding.  I still need to select an audio frequency -- any
recommendations from you?    I am thinking of sendin call sign and a
time code that could
be corelated to the APRS altitude and location tracking that will be the

primary payload (and used to recover the package).

A typical simple mission profile would be a launch before 10 AM near
Hutchinson, Kansas, a two hour climb to about 100,000 feet for balloon
burst, then a 1
hour to return to the ground by parachute.  Ground track would be 30 to
200
miles depending on winds aloft, eastward or southeastward.  The horizon
at peak
altitude should be about 300 miles away.
The balloons tend to spin and swing the payload ( ATV pictures often
show the
horizon instead of the Earth below, or full rotations in a few seconds.)
so a
wide field of view is needed.  It will also be in constant motion,
vertically
and horizontally.

Future experiements that I have though about are: a night launch for
improved
optical tracking, passive retro-reflector,  voice signal instead of
digital
data (AM or 40 kHz subcarrier FM),  radio uplink with the light beacon
repeating (uplink could be data or voice), a light uplink (requires a
wide field of
view detector array) with a radio repeating downlink, distance
measurement (with
light beam as uplink, downlink, or both), a servo alt-az system to point
a
"narrow" field of view sensor or emmiter.

I am still working on how many LEDs and what pattern would give a
useable
transmission pattern, or the duty cycle on the light emitter.  Also if
anyone can
suggest a method of dampening the balloon payload oscillations that does
not
weigh much, it would help.

James
N5GUI