A group of six students from the Alpajés High School in Aranjuez (Spain), during their last course year, were worried about the environmental situation of the rivers Tajo and Jarama which cross our village. As futures technologist, they decided to monitorize them from a distance of one km of altitude in the troposphere with the help of a small space probe.
Our town, Aranjuez, is fortunate to have two rivers, but these are quite neglected, and it does not hurt to worry about them. That is why they have decided to send a message of awareness through our space probe with current images of the situation of our rivers, accompanied by scientific data of the current atmospheric situation.

By using a temperature and humidity sensor (DHT22) connected to an Arduino microcontroller, and with the help of a radio Lora transmitting device (Dragino shield), they will receive the data by telemetry to a earth station where a computer could store and represent it graphically. In addition, the microcontroller sends this data in format by serial connection to a Raspberry Pi Zero board, so it can be stored on a memory card in order to collect the data, just in case the radio signal fails during the probe’s journey into space. Moreover, the Zero board has attached a small camera which is programmed to take pictures from the space of the riverbeds each five seconds and they will be revised after finishing the experiment.

The space probe is made by means of a custom 3D printing small cylinder in which the different devices they use are placed, and transported to the troposphere by an helium globe, to be able to successfully carry out our mission. Regarding the antenna of the earth station, they have used a cardboard base and metal rods for the directors and the dipole. To calculate the distance between directors, and thus take the correct frequency of the information (868 Mhz), they use a measurement program for Yagi antennas. With the measurements obtained, we cut the rods and build the antenna structure, and finally put the wire to connect it at the Lora shield of the earth station.

Some minutes after the launch, the small cylinder should land and must be located by using a GPS device. As for the parachute, we have decided on a regular octagonal shape according to the area and perimeter of said polygon with a circular hole in the middle being 1/3 of the octagon. The landing success will depend of the braking caused by the parachute itself. Some formulas have been carried out with different areas and sizes of the central hole seeing which was the most effective.

The group of students make this activity possible by meeting every Tuesday since January after their classes to continue their research, and share the progress made outside the classroom by creating an Instragram account (#deltariver) in which they document every week the progress of the project. For these meetings, they have been provided by the teaching staff with a technology workshop with the necessary materials, tools and devices.

In my opinon, as teacher supervisor of the experiment, and despite the future difficulty of the challenge during the launch and landing of the probe, the activity can be qualified as a success whereas my pupils have had a great opportunity to put into practice their theoretical knowledge related with physics, maths, engineering and coding.

By Leopoldo Mosquera (Scientix Ambassador from Spain)