As much as I like rocketry and cansats, the amount of telemetry data collected is limited, typically 5-15 minutes, as is the altitude (5,000 to 30,000 feet). In contrast, the data collected from balloon launch typically spans 2-3 hours and reaches an altitude of 35,000 feet. And a more slightly expensive high altitude balloon (HAB) can reach 60,000 feet and travel several times around the globe on a trip lasting several months. If you are interested in launching your own balloon, watch this webcast from Magnitude.io: https://drive.google.com/file/d/1xEjkH6-O_IB82LlpEFltDetJx49A9A94/view
ScienceHeads.org, a STEM groups out of Lake Forest, CA, US has successfully launched and recovered 6 high altitude balloons, the two most recent reaching altitudes of 100,000+ feet and landing in the southern California desert. These flights contain seed packages the students then plant and compare the seeds growth to the growth of control seeds. Information about the project can be found on their website at http://scienceheads.org/high-altitude-research-program-harp/ and http://scienceheads.org/hab6-high-altitude-balloon-launch/
Their most recent launch (HAB6) carried a flight recorder that I built, as well as several radios for tracking. I was member of the recovery team chasing the balloon over the desert to its landing 160 miles away. I’ve documented the flight and published the flight recorder data as well as instructions for downloading and exploring the data using CODAP at this location: https://fredricraab.wordpress.com/scienceheads-org-hab-6-balloon-flight/
You can learn almost as much from tracking weather balloons launched twice a day by the US and European weather services. Since July 2020, I’ve used Project Horus’s Radiosonde_auto_rx software running on a dedicated Raspberry Pi with a RTL-SDR to track weather balloons launched daily from the NOAA station in San Diego, CA, US and the US Army’s Yuma Proving Ground (Yuma, AZ, US). Tracks are posted in real-time to APRS.FI and HabHub. Radiosondes typically transmit in the 400-403Mhz range. More information about weather balloons and radiosondes can be found at: https://www.weather.gov/upperair/factsheet & https://en.wikipedia.org/wiki/Radiosonde