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                                    Click photos to see larger versions

NSL-71 flew from Greensboro's Kiser Middle School on the morning of Thursday, May 16, 2019.  Throughout the school year, the Kiser's Meteorology Club met to work on this project.  Paul L. acted as consultant and participated in a couple club meetings via Skype.  This was the third year that this club conducted flights and the students were interested in the extreme environment of near-space -- temperature and radiation.

The club's 1m parachute, built in 2018, was reused; as was the small 808-clone camera and its plastic case -- See NSL-64.  This budget camera pointed down to give view of the payload and earth below.  The new 2019 payload box contained the following:
   -GMC-320+ Geiger Counter
   -808 #16 camera on a small outrigger with a larger battery inside the box
   -808 #16 camera just inside the box peeking outside, also fitted with a larger battery
   -A small live plant out on an outrigger arm in view of the two cameras
   -A sibling to that live plant, but safe and warm inside the box
   -Plant seeds inside the box; protected from the cold but not stronger types of radiation
   -Photos of the clubs members to be keepsakes of this mission
   -AP510 APRS tracker with internal temperature sensor
   -TTGO T-beam LoRa tracker with external temperature sensor
  The payload box being packed for flight

The entire payload, line, parachute etc massed 800g.  Around 0830EDT, a 600g cell was filled with H2 to give it about 1400g neck lift.
  The club's teachers wrestling the balloon, as seen from the downward-facing camera

 3...2...1... Launch!

 Moment of release from the downward-facing camera (note the payload's shadow)

  Note the two small outriggers sticking out of the payload at 45 degree angles

  The view downward of the school

This beautiful morning had a light, high-altitude haze.  The projected flight path headed down US-421 to Sanford, NC -- 2.5 hour flight and an easy 1 hour drive.  Some of the club members joined the chase in three chase cars, while others monitored progress back at the school.
The AP510 tracker kept the payload's position updated on 2m APRS.  It also provided temperature readings inside the payload.  Meanwhile, the LoRa tracker from NSL-69 sported a better battery and a temperature sensor for outside readings.  This 'backup' tracker used 100mW 434MHz LoRa to transmit its location down to a pair of receivers.  One receiver traveled in a chase car, while the other simply hung out a second-story window of Paul's home in Apex -- 100km away.
The three chase cars monitored https://tracker.habhub.org/ and also provided their positions to this live tracking map.

     Two camera views

The two 808 video cameras on the payload box recorded similar views.  One camera, exposed to the elements, stayed glued to a short outrigger arm.  It sat 30cm from another matching outrigger, which held the Kiser Tiger-naut (with space helmet of course) and the live plant sample.   The second camera lived mostly inside the payload and peeked out a window.  This camera sat only 15cm from the tiger.  Although a bit too close for a clear focus, it provided additional video of the plant in the event that the outside camera failed.

Video showed a gentle flight, with minimal spinning or swaying.  The payload passed through haze and a distinct layer of light clouds.

As the payload approached 29km altitude, its flight path crossed US-421.  The lead chase car waited directly below.  After some brief searching in the clouds, the balloon was spotted from the ground!
  The view down on US-421 95,000 feet below
 The balloon from the side of US-421 (sorry, poor cellphone photo)

The lead chase car crew got back into their car and continued towards Sanford.  If they had only waited another few minutes, they would have witnessed the balloon burst as the flight ascended over 30km.
      Various still images taken from the videos during burst

   The Fayetteville area from 101,560 feet

Above is a screenshot of the Habhub site a few minutes after burst.  The payload, already halfway down, begins to slow under parachute.  Note that the payload call-sign KD4BFP is listed twice on the left.  This represents the two trackers on-board; each with their own position, battery, and temperature telemetry.  Also visible on the map are the three chase cars heading toward the projected landing area further south in Sanford.

The three chase cars spread out in an attempt to intercept the falling payload.  One car pulled to the side of the highway in an attempt to see the orange parachute as it passed overhead.  They did not see it, but the downward facing camera saw them!

     Coming in for landing

The payload drifted down into a large gated community in southern Sanford.  The area appeared heavily wooded.  But the ballooning gods, pleased with the project, directed it to a small gap between the trees.

  Chase crew trying to gain access to the gated community

Once the payload touched-down, the tracking signals fell silent.  Considering the tall trees in the area, this meant that the payload either landed on low ground, or was somehow destroyed.  Did it land in a pond?

Eventually the chase cars, escorted by community security, made it to the general area of the last know position.  Thankfully, a tracker signal was heard and the payload was quickly located upside down on the ground.  Easy recovery.

    Club members recovering the payload as seen from the cars and the payload

Now it was time to get ice cream and review the videos !

Ascent rate details.                 While the outside went below -50C, the inside of the payload stayed warm. 

The students now have plenty of data to analyse.

  Flight visualization

The T-beam tracker worked very well.  The receiver back in Apex started picking up the signal while the balloon was 60km away!  After the flight, the tracker still had plenty of battery power to operate for several more hours.  The TMP36 temperature sensor bottomed-out at -50C, so we don't actually know just how cold it got as the payload descended through the frigid upper troposphere.