Spei Satelles (SpeiSat) Spacecraft

SpeiSat physically keeps a nanobook with the Holy Father's book in his shell and a file containing the messages of hope to be spread during his journey.

SPEI-SATELLES is cubesat with communication purposes. It will send ASCII code corresponding to phrases in English, Spanish and Italian language. The phrases are no more than 3000 characters, 1000 for each language. The communication happens every at least 3 minutes. Commands can be sent to manage the onboard operation from ground.

SpeiSat hosts several components: two on-board computers, two communication systems in the UHF band (it is therefore equipped with two antennas), a battery for energy storage, small magnets for satellite stabilization after launch and a suite of thermal and inertial sensors to collect measurements in the space environment.

Spei Satelles is a space mission that aims to be a sign of hope for all humanity. Promoted by the Dicastery for Communication, the mission is coordinated by the Italian Space Agency (ASI), the public body that prepares and implements the Italian space policy in accordance with the Government guidelines.

The mission participants include the Polytechnic University of Turin, which designed and built the satellite, and the CNR which created the nanobook from which the entire mission originated. The logo is the work of the young people of the IUSVE of Venice while the pastoral/cultural coordination was assigned to the Digital Apostolate, Archdiocese of Turin.

Spei Satelles contains a nanobook, a 2x2x0.2 mm silicon slab on which the images, speeches and readings of the moment of prayer celebrated by Pope Francis on March 27, 2020 were imprinted by nanotechnologies, in the midst of the pandemic. Those words and those gestures have become an icon of hope, a seed of hope from which to start again.

During its stay in sun-synchronous orbit, Spei Satelles will transmit a radio signal that can be perceived with amateur instruments. The signal contains messages of hope from the magisterium of Pope Francis.

SpeiSat was entirely developed by a group of students in Politecnico di Torino, supervised by the researchers of the STAR group.

Rigorous simulations conducted using MATLAB and Simulink have substantiated the system's performance, demonstrating its ability to maintain the satellite's orientation within a few degrees of the desired position, even in the presence of external disturbances. Moreover, the telemetry data analysis has provided valuable insights into the satellite's dynamic behavior, with results closely aligning with the predicted outcomes from the simulations.

The observed patterns in angular velocity and magnetometer data have validated the accuracy of the predictive models, while occasional peaks in the data have highlighted transient disturbances and sensor noise.

Notably, the measurement of the angle 𝛽 between the satellite's body axis and the local magnetic field vector has revealed a cone-shaped motion, with deviations from perfect alignment attributed to sensor noise, residual electronic dipole effects, magnet mounting errors, and potential uncertainties in the hysteresis rod manufacturing process.

Despite the larger-than-expected deviation in the orbit-stabilized attitude from the simulation, as indicated by the on-board magnetometer, the ground operations after deployment were a success and communications with the satellite was carried out without major inconveniences regarding the attitude. This can be mainly attributed to the effective operation of the ACS, so it can be concluded that the system met the operational requirements.

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