Earth’s atmosphere passes visible light, but absorbs many (harmful) wavelengths. It acts as a security blanket, protecting us from dangerous radiation from the Sun.

HAB-2 carried four sensors to measure different types of Sun radiation. As the balloon flew higher, and the atmosphere got thinner, the sensors would register harmful effects of the Sun. The sensors were:

  1. Geiger counter to measure Gamma radiation
  2. SI1145 sensor to measure UV-Index
  3. ML8511 sensor to measure Ultraviolet A and Ultraviolet B bands
  4. GUVC-T21GH sensor to measure Ultraviolet C band
  5. MS5607 barometric pressure sensor to track altitude of the measurements

Sensor data was collected by Teensy micro-processor and saved into a CSV file on MicroSD card.

Prototype of the sensor board looked like this:

High Altitude Balloon - Sensor Board (prototype)

High Altitude Balloon – Sensor Board (prototype)

Schematics for the sensor board can be found here and source code can be downloaded from GitHub.

Every second, it saved the following readings into a file on SD card:

  1. Timestamp, in milliseconds since power-up
  2. From Si1145 sensor:
    • UV-Index, in 0.01 UV Index scale
    • Infrared light intensity
    • Visual light intensity
  3. From MS5607 sensor:
    • Temperature, in 0.01 degrees Celsius
    • Pressure, in Pascal
    • Altitude, in meters
  4. From ML8511 sensor:
    • UV A/B band intensity, in 0.01 mW/cm²
  5. From GUVC sensor:
    • UV-C intensity, in 0.01 mW/cm²
  6. From Geiger counter:
    • Count of Geiger tube pulses per second
    • Count of Geiger tube pulses per minute
    • Radiation, in uSv/hr
  7. Battery and 3.3V rail voltages
  8. In addition, it triggered DSLR camera (see next page)