StratoExplorer: payload for stratospheric balloon

mathias

Having experienced weightlessness on board a parabolic flight, as an (aero)space nerd, I am keeping one big dream for the future:

I would like to witness, with my own eyes, the curverture of the Earth as seen from space

Sadly, I am conscious of the fact that this goal cannot be reached without massive funding or support from outstanding individuals, such as Richard Branson or Elon Musk, that would offer me a ride.

Therefore, I am left with a poor man’s option – nonetheless challenging in nature – to launch a stratospheric balloon to the upper stratosphere at approx ~35km altitude and have my own eyes replaced by panoramic digital imagery. This goal can be reached with creative mechanical and digital engineering, some limited paperwork for air traffic control authorities (I am a pilot already – even excessive paperwork cannot scare me) and a budget roughly 2000 times lower than a ticket on Sir Richard’s Virgin Galactic.

For sure, I’ll get less bang for the buck, but I reckon it will be worth the effort !

This has actually been my entry project into IoT/µC-based digital electronics and of course I discovered that, in order to do this cleanly, I need to research and overcome some fundamental hurdles that led me to initially further other projects

Here are the main requirements and challenges met:

  1. reliable, low-power flight control unit
  2. continuous reception of 3D GPS position data and derivatives
  3. monitoring of inside/outside air temperature in a [-60C, 30C] temperature range
  4. long range (up to 40km) telemetry at reasonable data rates to transmit position and status
  5. panoramic color imagery with onboard storage of image data, possibly even limited downlink caps
  6. trajectory evaluation for landing site prediction
  7. asynchronous, periodic, fail-tolerant execution of onboard tasks

so far, these have been addressed as follows:

  1. while some people chose Raspberry-Pi as an easily maintainable unix platform for flight data management, a Pi’s power consumption and system overhead regarding interrupt handling and bare bones use of digital interfaces, led me to chose the Arduino-type advanced Teensy 3.6 32-Bit ARM Cortex-M4 180 MHz CPU as core for the flight hardware
  2. There is a range of light-weighted GPS devices available and I chose the ublox neo-6M GPS connected to Teensy via a serial interface. It is possible to adjust GPS mode during operations, switching from ground-based ranges of position and velocity to “space”-mode operations.
  3. Two Dallas DS18B20 digital temperature sensors fit to my range requirements and are attached to Teensy via single-wire serial interfaces with phantom power.
  4. Many people used to operate long range telemetry with 434Mhz frequency shift (FSK) modulated RTTY at rates of 50-300 baud and 10mW output. Apart from the transmitting unit being sensitive to temperature induced shifts of the carrier frequency, the receiving part is an adventurous undertaking, using SDR (software defined radio) and TTY decoding software – pretty much as radio amateurs decoding messages from the first generation of satellites. I got it working but it left a fragile impression on me which let me to switch to LoRa digital radio modules. Those are highly reliable, inexpensive, lightweight transceiver units that operate with multi-spectral modulation, sophisticated error-correction and multiple selectable bandwidth and packet length. Eventually I chose HopeRF 868Mhz SX1276 on both ends, an airborne ground plane 1/4 lambda antenna and a custom build (many thanks to Oleksandr from Ukraine !) Yagi antenna connected to the ground receiver. This is hassle free and solid hardware and initial tests inside a building and over a few hundred meters (with obstacles) were successful. A line-of-sight long range test, yet needs to be performed (most likely: Kalmit 49.321N 8.083E – Oberflockenbach/Weinheim 49.502N, 8.723E).
  5. Imagery will use two back-to-back mounted 2MP arducam OV2640 interfacing with Teensy on both Serial + SPI. I plan to rotate the camera assembly using a servo to rapidly step to 3-5 positions within the 180° hemisphere. Image acquisition requires approx 80-100ms per position with memory buffered storage to the Teensy’s SD card (8GB). Unlike other people, I am reluctant to launch expensive and heavy GoPro hardware and renounce to video recording. Moreover, with an amateur budget long range image or video transmission at acceptable bandwidth unfortunately is not feasible.
  6. GPS data is fed into a 120s buffer at 2s time intervals and a 3D linear regression solution is computed using a eigen-vector / matrix decomposition library that flawlessly runs on the Teensy. With the trajectory vector calculated, landing site is calculated from its intersection with the terrestrial plane and data is included in telemetry at payload decent (after helium balloon burst).
  7. One of the existing elements of programming activity is a custom library called myTaskScheduler. It allows to register independent services to be triggered at repetitive absolute (NTP- or GPS-time based) and relative time intervals. Support is provided to automatically process (average, sd, min, max) time series data collected by the registered services. Moreover, myTaskScheduler is able to perform health checks on services and if necessary respond to failures in a defined and reliable manner – without sending the global system into deadlock.

next steps (in a long way still to go …)

  • integrate LoRa and imagery control software with myTaskScheduler
  • wrap myTaskScheduler into a conditional “flight plan” logic to determine activities on launch, ascent, decent, landing.
  • develop software for the hand-held receiver (recovery) unit (LoRa + ESP8266), telemetry aggregation and data display on a dashboard powered by Grafana
  • consolidation of flight hardware on a custom-made PCB (the current wired setup not being reliable enough for field testing)

12th European Space Conference 2020

mathias

New Decade, Global ambitions: Growth, Climate, Security & Defense

Egmont Palace, Brussels. 21-22. Jan 2020.

Those were some cold and foggy winter days in Brussels. I had been successful to get one of the conference tickets as a freelance aerospace party – actually the overwhelming number of participants were executives from the aerospace industry, EU and ESA officials, government bodies from EU countries and journalists.

I felt like little fish – that’s what I was indeed – swimming happily in the sea between the big aerospace tankers. A few month ago, I had resolved to attend this conference in response to my growing interest in the developments of Space 2.0. I wanted to learn from a close distance about the spirit which makes Europe move in this new field – in friendship, but also autonomous from it’s big brothers: US & Russia.

To make it short, those two days by far exceeded my expectations and I returned home very much inspired from this pan-European experience. Within the first minutes of the conference I noticed that the EU had a particular significance to me: My ability to pick up conversations in number of languages other than English – be it German, French or Spanish – helped a great deal to absorb information and interact with the people around me.

I would considering myself a Tech Nerd and of course I was thrilled from the statements of the big industry players with regard to ongoing or upcoming earth exploration missions, the perspective of a lunar or planetary missions or just “physics brought to service“, i.e. orbital platforms for secure quantum-cryptography servicing the EU. The need for environmental monitoring supporting the analysis of ecological damage or the requirement for secured communication are fundamental political questions that reach far beyond the naked interest in technological competition and economic profit.

At the very end of those two days, I very much enjoyed the speech delivered by EU commissioner Thierry Breton (who had to rush back to Brussels from his encounter with US president Trump, just a few hours ago at the Davos WEF). In fact, Breton, who has a long curriculum with technology companies, convincingly presented the European spirit, while cheerfully switching language between French, a few words of German and English.

Pyongyang (DPRK) Intl. Marathon

mathias
Kim Il Sung square, Pyongyang DPRK

Science and technology are a propellant for building a thriving country, and the happiness of the people and the future of the country hinge on their development.

Kim JONG UN

It was in spring 2018 when Donald Trump and Kim Jong Un discovered their mutual friendship and engaged in a surprising – but, as we know, not so long lasting – friendship. It seemed as if the ice was melting on the Korean peninsula ! Just one year after having been invited to a medical/IT conference in Seoul, I was about to draw plans to set foot in the North, Pyongang, capital of the People Democratic Republic of Korea.

Setting foot in North Korea, how about doing this in a sportive way ? For instance, by repeating footsteps just about ten thousand times scaling the half-marathon distance (21.0975km) in the streets of the capital of one of the planets’s most isolated countries. I was able to get a seat on a tour organized by a Chinese agency offering ordinary westerners (with the exception of people holding a US passport) the opportunity to travel to North Korea and participate in the Pyongyang International (Half)Marathon.

Eventually, after a vaction stay with my son in Dubai, I was heading East alone to spend one night in Shanghai before boarding on 06 April 2018 flight JS158, one of Air-Koryo’s Antonow An-148 aircraft. What a change: Dubai – Shanghai – Pyongyang !

Alltogether, I spent 3 exciting days in the city. I traveled to the DMZ to catch a view across the border to see the South Korean flag waiving on the other side of the fence, delimited by the famous lineup of small blue wooden baracks hosting the UN troups. On the morning of the last day, the actual running was a very mixed experience: extremely hard since I had to drag myself along the track due to an upset stomach and shivers (I tried to spare myself any thoughts of requiring medical treatment inside the country), on the other side: The surreal aspect of smiling, cheerful North-Koreans supporting my lost capitalist soul on the race track, having ample room on the empty streets of the capital decorated by big, colorful posters proclaiming the potent destruction of their ennemies.

after a long journey, once I arrived back in Frankfurt, I found a note stuck under the windshield wipers of my car: “You made it !” (merci Sylviane !)