UK High Altitude Society

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PicoAtlas IX


  • Atlas RFM22b Board
    • ATmega328
    • RFM22b
    • 4Mhz crystal
    • 1.8v stepup
    • uBlox Max6 1.8v GPS
  • 1x 92cm Foil Balloon


  • RTTY 434.342Mhz
  • 50baud, 425shift, ASCII-8, no parity, 2 stop
  • String: $$$$PICO,99,21:12:01,514980017,-527928,9,7,6,1,3*014E
    • $$$$Callsign,count,HH:MM:SS,Latitude,Longitude,Altitude,Sats,Navmode,Powersaving,Lock*Checksum
  • Reboots the radio every 20 strings
  • GPS powersaving won't start unless lock has been achieved for more then 5 strings

Predicted Flight Path

Flight Report


  • Launch time: 02/03/15 15:03:05
  • Final data point : 04/03/15 00:57:07
  • Total flight time
    • 122040 seconds
    • 2034 minutes
    • 33.9 hours
    • 1.41 days
  • Max altitude: 4960m
  • Lowest altitude: 12m
  • First night time float: 3600m
  • First day time float: 4750m


Flight Report

Launch was very easy, winds were approximately 3mph, balloon was filled indoors, measuring the ascent rate to get the correct volume of helium. We then took it out side and released it. Initially it climbed up to 400m and then started to descend back down to 200m altitude. It continued to bounce between 100 and 300m not able to ascend further and drifted south. We were able to follow it visually from the launch site for 20mins and then Steve followed it in the car. After an hour it suddenly started ascending again. Most likely this was due to an temperature inversion layer as the free lift was so little it wasn't able to break through this layer.

Once ascending it rose up at approximately 0.8m/s and settled down to float for the night, in the morning it started rising again and found a higher float altitude during sunlight hours. Finally descent occurred at night where it gradually dropped and did not have enough lift to compensate for the cool temperatures. Last data was at 1000m altitude over Wales and most likely landing near to that point, nothing was heard in the morning but any station.

Tracking was excellent for this flight, helped by the local flight path. Frequency stability was good due to polystyrene directly over the radio module which allowed people to leave their radios and dl-fldigi tuning for the whole flight.


  • Excellent flight
  • Demonstrated that you can do a truly long duration flight
  • 2 float periods - night and day float during which it appears the balloon was super-pressured.
  • Final descent was due to cooling without sunlight and the loss of helium over the flight meaning it didn't have enough helium to support the payload
  • Interesting post launch flight where it appears to have been caught in an inversion layer.
  • Payload worked really well, with rock solid transmission through out.

Future Ideas

  • Would need repeating
    • Aim for 0.5 -0.7m/s ascent rate to get a low night time float altitude which gives you a bit of flexibility for your higher daytime float
    • Need perfect launch conditions - avoid inversion layers and clouds
  • Launch in the morning - investigate whether it can survive an sunset early on in its flight profile as it still has enough gas
  • Simple ballast system to rescue if it does start to descend
  • Fix the uplink to the RFM22b as this would allow some fun with the slow floaters.
  • Fly the APRS transmitter if flight path has it going across Europe.
  • How far could you fly in 33 hours…
projects/picoatlas/picoatlasix.txt · Last modified: 2013/03/08 07:15 by jcoxon

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