UHF band channel module design for micro and nano modular satellites

In Department of Electronics and Telecommunications (DET) of Polytechnic of Turin there are
projects involved in small satellites, CubeSat compatible but not limited to it. A project started
in 2007 called AraMiS, which stand for Modular Architecture for Satellites in italian, is born after
the first CubeSat compatible spacecraft developed in Turin, called PiCPoT. The main philosophy
in AraMiS is the modularity of the system in all its aspects.
This thesis work is focused on the engineering phase of the AraMiS telecommunication system
module, which will be applicable on every AraMiS spacecraft, including the CubeSat version,
named as AraMiS-C1. To accomplish this, it has been developed the whole set of system’s use
cases, the basic firmware design along with a new revision of the telecommunication hardware,
taking into account the already defined constraints and requirements of the AraMiS spacecraft
telecommunication system. The real challenge of this work is to bring into practice all the considerations
made for reliability purposes, and in part adapting them to obtain a final, modular and
reliable design.
In chapter 1 will be presented an introduction to the small satellite concept, letting the reader
understand more in depth the actual development of these small spacecrafts, and provides the basic
description of how a modular architecture like AraMiS can be the key to keep high dependability
on low costs, even on more complex systems which are not limited to CubeSat environment only.
Moreover, will be described briefly the ground telecommunication network which will going to be
used for low cost and university small satellites.
In chapter 2 is provided an UML introduction in order to understand better the notions adopted
in this work.
In chapter 3 is described the starting point of the system. Therefore are provided the specifications
to comply when developing the entire system. It is introduced the concept of the OSI Stack,
and as a consequence are provided the telecommunication protocols adopted to encapsulate the
frame, like the AX.25, and the protocols of the content of the frame, called AraMiS protocol.
In chapter 4 are shown the constraints which are needed to be taken into account when developing
a telecommunication module. Finally is implemented the whole set of the use cases of the system,
v
essential to implement the specifications to the module which will be designed.
In chapter 5 will be shown the final implementation of the system. It is devised an affordable
power handling and a new sensor unit sub-system. The OBC now have more control on the OBRF
hardware, to handle better the latch-up protection. More sensors are used in order to control
the different organization of the power supply sub-system. Therefore the sensors sub-system is
completely redesigned. All the hardware library is then reorganized updating the components and
creating reusable locks, to comply with the AraMiS philosophy.
In chapter 6 is going to be described the firmware designed starting from the previously described
use cases and the adopted hardware. The algorithms are devised starting from sequence diagrams
and finite state machines, mainly for being compliant with the AX.25 radio amateur protocol in
an affordable way. These algorithms are then implemented to correctly handle the RF streaming
and also described, when necessary, with sequence diagrams. All the on-board and the OBC
communications are also integrated with the AraMiS software modules already present in the
AraMiS library. Are also integrated the housekeeping functions and the transceiver drivers, and
are devised all the procedures to handle correctly the digital interface of the RF circuitry. The
software is written in C++.
In chapter 7 are analysed the possible physical constraints in order to achieve a reasonable
placement criteria of components on the PCB. Therefore, after a thermal rough worst case analysis
of the critical components, is shown the final PCB implementation.