A Low-Cost Sounding Balloon Experiment

Watching the meteorological balloons customarily launched from our city, we wondered how we could develop an experiment to allow our students to effectively gather data about the low atmosphere and at the same time ke6ep our limited financial budget. When you hear about atmospheric balloons, you usually think about balloons with large envelopes of nylon or mylar with payloads between 1 or 10 kg. They ascend to very high altitudes, have a data radio transmitter, and are not recoverable. This setup would be too expensive for us. In order to keep the cost low, the payload containing the data recorded had to be recovered, and therefore, the balloon must not go tens of kilometers away. We ruled out tethered balloons, which would not have recovery problems but can hardly go beyond 100 m high because of the weight of the tether and of lateral winds. Based on some estimates of ascension speed for small balloons and probable horizontal wind intensities, we decided that in order to easily recover the payload we had to limit its ascension to about 2 km high. At this altitude, the payload would have to be released from the balloon by means of a timer.