What Sensors Do
Sensors fulfill an interesting role in the world of science and engineering. When a sensor is designed and built it does not simply communicate the temperature, pressure, or any piece of information in some kind of raw form. Instead, sensors are connected to instruments that understand signals as voltages and then this voltage is turned into useful and meaningful information (0s and 1s), usually through an analog-to-digital converter. This means that what sensors do in our world is convert real-world measurements of the type of signal that the sensor is sensitive to, and it provides a voltage response that is used to measure the environment that the sensor is subjected to.
What to Do with Sensors
There are many resources to pull from for inspiration on designing your own sensor suite if you are not sure where to begin. One thing to consider is that your mission is made possible (and inspired) by radiosondes, which are launched twice per day from around the world (there are 92 launch sites just in North America) into the stratosphere to feed atmospheric conditions into weather models. One main difference between your mission and a radiosonde (at least I hope so) is that radiosondes are not recovered after their flight. To make up for this, radiosondes transmit their data down to a ground station continuously, which you can also do but it is a significant body of extra work that is not required for a successful balloon mission.
Scientific Lineage: Radiosondes
Radiosondes contribute to numerical models of the atmosphere by recording these measurements:
Geographical position (Latitude/Longitude)
Wind (both wind speed and wind direction)
Cosmic ray readings at high altitude
There can also be great interest and value in recording engineering information (system health or “housekeeping” data) for your homebuilt payload like battery voltage, battery temperature, and motion with an Inertial Measurement Unit (IMU; usually at least 3 axes of acceleration and of rotation, while sometimes there is magnetometer data as well). Other science data can come from designed payloads that, for example, expose seeds to cosmic rays and the near-vacuum of the stratosphere, measure the distribution of scattered light across the electromagnetic spectrum, monitor sound propagation through different levels of the atmosphere, determine the rate of data corruption in a storage device, or show what your favorite toy looks like when taking remote-control selfies from space. If you don’t have too many ideas already, you can find many other,,,,,, examples of experiments that have been conducted from high altitude balloons if you do a search online. If your thirst for experiments is still not quenched then you can take a look at the 100,000+ sensors at Digi-Key. Otherwise, for most sensor needs you will be well-served by SparkFun.
More to Explore
Has there ever been an anemometer, pitot tube, or static (pressure) port on an amateur high altitude balloon mission? Is this an area of fresh investigation? For a very detailed look at more sensor and experiment topics you can see Chapter 8 of the high altitude ballooning guide by L. Paul Verhage.