Congratulations to CEFAST from Brazil for winning an Honorable Mention for Best Educational Initiative this year! The text from their submitted report is pasted below:
CEFAST Aerospace is a group of Brazilian students from Federal Center of Technological Education of Minas Gerais - CEFET-MG Campus Belo Horizonte, composed of high school and college students.
The team's initial goals can be divided into two: a) to take part in national and international competitions that focus on the aerospace sector, in order to learn about aeronautics, space engineering, and team cooperation; b) to promote events on other campi of CEFET-MG, sharing knowledge, presenting the project and motivating other students to start their own research.
That said, the Global Space Balloon Challenge was a great opportunity to expand the team comprehension in electronics, mechanics, power management, administration and programming.
The first action taken was organizing a few workshops on astronomy and aeronautics, that took place in the cities of Belo Horizonte and Araxá. After attending such events, students from Araxá felt inspired to create their own team.
Another workshop and the final parachute tests occurred in the CEFET-MG Campus Contagem, and the launch at “Horizonte Perdido” near CEFET-MG campus Araxá, in partnership with the city team (PET CEFET-MG/Araxá).
To restrict the project and increase the challenge, the launched payload was a picosatellite named MGL II, a little bigger than the Cubesat 1U - CubeSat Design Specification model, aiming at fiting the electronic components.
The MGL II CubeSat was launched at the “Horizonte Perdido”, located in Araxá, MG - Brazil, by a Kaymont 350g atmospheric balloon (model HAB-350).
The main electronic components used at the launch were: a Raspberry PiTM 3, along with the Pi CameraTM 3; and an Arduino Nano, along with a GPRS module (GSM SIM800L) and a GPS module (GPS-NEO-6M). A Personal Spot Trace Tracker was also present, and it was important to guarantee the recovery of the CubeSat, sending the latitude, longitude and altitude from the cube with a new report every five minutes.
For the implementation of the satellite localization system, a redundancy strategy was used. The first item, the Arduino module, was used to send text messages to a specific mobile phone device, through a cellular chip. This module sent the GPS coordinates obtained along the course of the CubeSat. Independently, the SPOT module communicates via satellite through a system offered by the company.
However, due to the limitations of the transceivers, loss of communication with the satellite at high altitudes were expected, since the cellular GSM signal used by the GPRS loses power with the altitude, and the SPOT signal was unstable even during the laboratory tests.
In order to reduce signal interference and keep module dimensions small, it was developed two Printed Circuit Boards (PCBs) for the localization and sensing system, avoiding the use of wires and making them less prone to noise and misconnection.
In order to take pictures and record videos, the team modified the camera Python script, managed by the “picamera” library. The algorithm developed set the camera to record for 10 minutes, saving it in two 5-minutes files. After that, the camera was also set to take 10 photos for the next minute. This way, the image recording would be safer, guaranteeing at least 5 minutes of footage, in case of unexpected file corruption.
For joining the Arduino statistics, a program was developed gathering the data obtained by the GPS and GPRS modules using the Arduino IDE with the specific libraries of each electronic component.
To power up the picosatellite system, three 3.7V batteries were used based on the power demand to support the Arduino and Raspberry kits. For that, substantiated calculations were made and, based on that, two batteries were connected in series to increase the total tension provided to the Arduino as it works with a 5V~12V DC tension. The other battery was used as an energy source to the Raspberry PiTM 3 and the Pi CameraTM 3.
This department is responsible for the project and construction of a structure that can fit all the electronic components, batteries and camera, be resistant enough to endure the launch, the flight and the landing, and also be as light as possible.
After some research, the chosen manufacturing process was 3D printing with ABS filament, selected due its low weight and high resistance. The application of this building method was useful to test the team skills and start learning about the technology. For the thermal protection of the internal components, a Styrofoam cover was fixed to the 3D printing, with a special styrofoam-spec glue.
A parachute system was designed based on the weight of the payload and the launch specifications, expecting a 5 m/s descent rate. An assembly of two parachutes was used to match this specification.
The launch, as expected, resulted in a 20,9 km ascension, during 215 minutes, and it was successfully recovered 50,12 km away from the site (considering a straight line between the launch and recover - as seen on figure 4). The full CubeSat assembly was tied on the top of a tree, in a farm.
Through the recovery of the MGL II picosatellite, it was able to collect 59 videos and 302 photos during the flight of the CubeSat. In this way, it was able to analyze and verify the results of the Pi Camera.
The functionality of the camera was a great concern of the team, since several difficulties could appear during the trajectory, mainly because it was a fragile module when analyzing its physical building, and also because of the fragile connection between the camera and the main board, that could disconnect due to turbulence. In this sense, when analyzing the captured results, it’s possible to see that the programming behaved as expected, presenting good video capture (still and motion) without corrupted files, and no physical disconnection between the camera and the controller board. In addition, the camera lens has proved itself capable of withstanding the adverse environment with no problem, such as risk of fogging due to moisture and cold temperatures (for instance, thermal insulation), and even the danger of breaking down (as a consequence of good mechanical assembly).
During the mission, there were communication failures due to high altitude, as foreseen by the team during the development of the project. Communication systems stopped working when the CubeSat reached an altitude above 7 km. However, the contact was restored when the Cubesat returned to a lower altitude, making it possible to retrieve it, which provided precious learning for the coming team launches.
The mechanical structure could not be tested in its maximum, bearing in mind where and how it fell, but the thermal protection was proved effective and the components were working well after the landing. Also, the parachute system results were acceptable, since the average speed of descent was around 7m/s, by calculations made using the time and distance of the fall.
The electronic components will be better implemented for future missions, and also, new modules will be studied for future use, in this way, opening paths to many other types of aerospace missions.
The programing learned by the team will be very useful to new projects that will use microcontrollers and small single-board computers and it’s success in the mission motivated all the team members to improve even more in this field.
The Styrofoam protection has given the result wanted, but it was heavier than foreseen, very large and difficult to remove after the landing.
The knowledge acquired is going to be used in the 2nd CubeDesign, a brazilian competition, where the team is going to apply new ideas for an improved CubeSat, and its first CanSat.
The HAB launches are a nice way to test ideas, components, materials, structures and building methods. The team plans to launch biological payloads from CEFET-MG in the next year, to increase the intercampi relationship.