[aprssig] Pictures from recovery of Ham Radio Balloon today

[Ray McKnight]

<snip>
This balloon was launched from Huntsville Alabama, got into the jet stream 
at 117,000 ft and traveled 445 miles at 125 MPH almost to the ocean before 
finally bursting and parachuting down. It had an APRS package on board 
which functioned flawlessly all the way to the ground.
<snip>

Well, congratulations on a successful mission, but I take exception to there
being a "jet stream" at 117,000 ft!  The jet stream, actually there are
usually 3 "jets" in the northern hemisphere.  There are 3 jet streams in the
summertime, but the polar front jet and subtropical high jets can merge.  In
the winter, the polar jet retreats north, often to 50-60 degrees latitude,
and the tropical easterly jet usually located at 15N in the summer
disappears.  The tropical easterly jet is the "highest" of the 3, generally
located at around 100mb, or about 65,000 ft.  The other jets are usually no
higher than 200-250mb, or 40,000 ft.  

At the latitude of this flight, if it was flying at 117,000 and experiencing
that speed, it was most likely a result of the ozone layer.  The jet streams
are called that because since their discovery during WWII, high-altitude
aircraft have taken advantage of the strong west-to-east winds.  But the
only aircraft that fly at 117,000 ft are AFAIK possibly the SR-71 and some
NASA research birds.  There's not enough air at that altitude for normal
air-breathing turbines to support combustion.

There is, however, a 4th but largely ignored frontal zone jet called the
polar night jet, present only in the winter, located between 30-50 miles up,
above the ozone layer.