Flight #T2000-5 "APRS Demo"
Launch Date: June 24, 2000
June 24, 2000
Today we flew the Phoenix payload in its first tethered flight. The Amateur
Radio folks who help us chase were busy with Field Day (when radio hams
practise doing communications from the field with emergency equipment), and
wanted us to do a demo of an APRS system. Since the Phoenix payload already
had one installed and tested, we agreed to do a tethered flight to 100'
so they could receive the signal (this earns them extra Field Day points).
Like most of our tethered flights, this one did not go as planned. We
attempted to fill one of the 28 year old 600g balloons we inherited, but
it tore when we had about half the helium in it. We used the remaining
gas to fill two new 350g balloons, and attached them to the Phoenix gondola.
Unfortunately, the remaining gas was not quite sufficient to lift the
payload to 100' (more like 6 or 7 feet, depending on the wind). Even so, the
APRS signal was received, so the hams were happy.
I had modified the flight software to delete the audio tracking tone and
Morse ID (the APRS encoder transmits ID, so it's still legal), and had the
microcontroller only press the shutter buttons on the cameras and beep.
The cameras got jostled with the payload bumped on the ground, so only one
camera took photos and that one only a few. Given the dissapointing altitude
the payload achieved, this was not a big deal.
We also tried a new idea for retrieving the payload. Instead of having the
cutdown device drop the payload directly to the ground, an additional line
was added from the swivel to a ring that ran along the tether line. Thus,
when the cutdown triggered, the payload rapeled down the tether line to
the anchor point, slowed by the parachute. This system worked perfectly,
and will be considered for future tether work. It also has the advantage
that if the tether breaks, the payload still will execute a normal parachute
descent to the ground. The reason for having it slide down the tether is to
keep it from falling somewhere inconvienient (such as the flooded farm field
we were photographing during Persephone I.
Return to the UND HABP webpage.