{"id":1767,"date":"2015-03-27T14:01:20","date_gmt":"2015-03-27T14:01:20","guid":{"rendered":"http:\/\/www.daveakerman.com\/?p=1767"},"modified":"2015-03-27T15:38:28","modified_gmt":"2015-03-27T15:38:28","slug":"partial-eclipse-from-afar","status":"publish","type":"post","link":"http:\/\/www.daveakerman.com\/?p=1767","title":{"rendered":"Partial Eclipse From Afar"},"content":{"rendered":"

Back in December I was approached by the BBC about launching a high altitude weather balloon flight during the forthcoming solar eclipse which was total over the Faroe Islands but approx 85-90% over much of the UK.<\/p>\n

After some discussion we planned the flight to be from Leicester Racecourse where the BBC were holding a event for the public, with mainly school groups in the morning and open to everyone in the evening. \u00a0So no trip to the Faroes for me!<\/p>\n

The aim for the launch was to get photographs of the eclipse from above the clouds (there are always clouds during a UK eclipse!). \u00a0To see the moon’s shadow would mean launching much further north, especially as the forecast winds meant that we had to limit the maximum altitude to about 30km. \u00a0We did though hope to get some filtered shots of the sun, to reveal the shape of the moon crossing.<\/p>\n

\"path720\"<\/p>\n

For most\u00a0balloon flights, it’s easy enough to delay the flight if the wind predictions compromise the flight or if the launch winds are too strong to launch in. \u00a0This time though we had one chance and one chance only! \u00a0Even delaying for an hour would mean that there’s little point in launching. \u00a0Flight predictions start coming in about 6 days before launch, though they usually do not start to get accurate until about 3 days prior. \u00a0It’s always tempting to check those initial, unreliable forecasts and sure enough I did so. \u00a0They looked OK, however as later predictions came in, the forecasts got worse, with the flight path going over London (bad) to land in Kent (a small target at that distance). \u00a0Worse, if the balloon burst early (which happens) the flight would land worryingly close to Gatwick.<\/p>\n

I ran a few different scenarios, using larger or smaller balloons, each with more or less gas, and found no good flight paths at all. \u00a0A short flight would miss London but land in the rather built up area west of the M25 (and too close to Heathrow). \u00a0It became obvious that, if we were to launch from Leicester, the only safe flight would be a very slow ascent, to go south from\u00a0Leicester, missing London, then turn east over the English Channel to make landfall near Dieppe! \u00a0We seriously considered doing just that, with a chase team setting off early to be in France ready for the landing, but logistically this was always going to be a pain (especially getting the video files back to Leicester in time). \u00a0We also looked at possibly launching from somewhere else.<\/p>\n

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Showing Tim just how crap a cheap Chinese aerial really is (answer: very)<\/em><\/p>\n

Fortunately though, predictions continued to move the flight westward. \u00a0About 2 days prior to launch we could see the possibility of doing a “normal” flight to about 30km, landing not that far south of Leicester. \u00a0The only remaining worry was overshooting the landing spot and getting close to Luton Airport, so to avoid this we aimed for a point SW of Milton Keynes and used a Totex balloon (chosen for their reliability in bursting when they are supposed to!). \u00a0So, finally and to everyone’s considerable relief, we had a nice safe flight plan that would work. \u00a0As a bonus, the forecast ground winds were very low, so it looked like we would have an easy launch.<\/p>\n

\"IMG_0104\"<\/a><\/p>\n

As this was a photographic flight, the payload was designed to allow for multiple cameras – both video cameras and Pi cameras connected to A+ boards and the PITS+ tracker board. \u00a0We used 4 Replay XD Prime X<\/a>\u00a0cameras, each pointing in a different direction:<\/p>\n