Development of a University Femtosatellite

Recently, the attention in designing small satellites has rapidly grown by European universities,
Politecnico di Torino has adopted several standards and put its effort in developing its own satellite.
AraMis (Architettura Modulare per Satelliti) is the evolution of previous project PiCPot and
consists in the development of nano and pico satellites orbiting in LEO (Low Earth Orbit) for
university purposes.
In particular AraMis aims to build a modular satellite configurable in different shapes in which
each module is independent from the other ones and capable of working in stand-alone mode. The
communication among the elements, known as tiles, takes place through proper buses.
Each module has a specific role and can work alone or together with other modules to improve the
performance of the system. The project is considered as low-cost since it uses COTS components
and exploit the re-usability of different units so reducing design costs.
Object of this thesis is to exploit AraMis standard to develop a femtosatellite (a satellite having a
weight lower than 100g) having features of a typical satellite with in addition some peculiarities.
The idea is to develop a constellation of femtosatellites able to communicate each other, exchange
generic messages, measure the distances inside the constellation and modify the distance according
to the user needs. To start with, we consider a constellation made of two satellites placed opposite
one to the other.
The system has a modular structure, following the AraMis philosophy, and it is made of a
magnetometer, a magnetic actuator, a solenoid and a telecommunication module as main units. It
Abstract
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has a disk shape, where on a surface there is the RF electronics, on the other one there are solar cells
for supply system, finally the solenoid is placed around the disk.
The magnetometer and magnetic actuator are taken from AraMis project and adapted to the
particular case while the telecommunication module is entirely designed and developed customized
for the application. The communication module (named 1B35_Intersatellite_Communication in the
thesis) is realized so it can be re-utilized for future works involving a communication between two
identical nodes (placed on different satellites or on the same satellite).
The system is based on CC2510 system on chip provided by Texas Instrument and simpliciTi
protocol for telecommunication. The main reasons are:
· low cost;
· low power consumption;
· custom protocol (simpliciTi), provided by Texas Instrument easy to use;
· RSSI technique integrated;
· possibility to use 2.4GHz as working frequency;
One of the system purposes is to measure the distance between two satellites, this is achieved
through RF techniques (RSSI) and magnetic techniques (generation and measurement of magnetic
field). Another important issue is to let satellites get closer or separated, the motion is obtained
through attractive and repulsive magnetic force, generated by the actuator and electromagnet (also
used in measurement operations).
In this thesis, we are introducing for the first time a femtosatellite in the AraMis project, so no
particular initial constraints are given. During the thesis several configurations have been
considered and analyzed to find the better solution for the case study. The general structure of the
system is completely described and documented by using UML language, for a particular unit (the
telecommunication unit) we proceed instead with the hardware and software realization.
As results, we have set up the general structure of the femtosatellite, analyzed several issues and
implemented a good basis for future development. One possible application could be using the
femtosatellites to transport small objects in space environment.
Finally, another important result is the realization of the telecommunication unit, fully implemented
in hardware and software but not tested.