Onboard Communication Systems for Low Cost Small Satellites

The development of a large number of Nano and Pico-satellite missions, with spacecrafts
of mass lower than 10 kg and 1 kg respectively, started in the beginning of
this century due to the availability of low-cost piggyback launch opportunities. Such
small satellites are usually built using commercially available electronic components
that are not qualified for the space environment. This approach reduces the total
cost of the satellite missions but at the expense of design effort which is needed not
to compromise the reliability of the designed spacecrafts. One of the foremost design
efforts in this regard is the design re-use method which extends the cost reduction to
the system level, and helps in simplifying the development cycle for a space mission.
The on-board communication subsystem consist of critical set of elements common
to every mission, and therefore is not exempt from such a design philosophy.
The on-board networks, on-board transceivers, and the protocols are all critical elements
for a spacecraft mission and, at the same time, some of the most specialized
and complex ones. Innovative data communication systems are therefore desirable
for the future space missions.
The size of the satellites keeps reducing as the time progresses, therefore the
harness mass and complexity inside the satellite becomes a prime challenge. An
innovative approach to smart harness is therefore necessary which reduces the wiring
harness for intra-satellite communication.
This thesis copes with several problems related to spacecraft subsystem development,
integration and testing and proposes some solutions that can help in both
keeping system development and production cost low while still achieving good performances.
Chapter 1 starts with the design goals of the work and introduction to the
Modular Architecture of Small Satellites (AraMiS) project. The biggest design goals
of space systems of current era are the cost, time and complexity issues. Modularity
and cost-sharing between multiple missions will appear as optimal solutions for
reducing development costs, while the use of commercial components (COTS) will
be presented as a way to simplify procurement and further lower system cost
In Chapter 2, the smart harness approach is proposed which reduces the traditional
harness complexities inside the small spacecrafts. The chapter focuses on the
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design of small spacecrafts which are completely modular and flexible. Modularity
at mechanical, electrical and testing level will be discussed in this chapter.
Chapter 3 addresses the complete life cycle of a subsystem module i.e. from
conception to the final design and testing. The module life cycle uses a variety of
Unified Modelling Language (UML) diagrams to fulfill different design stages.
Chapter 4 proposes different types of spacecraft configurations based on smart
harness approaches including physical module based, satellite on demand and reusable
design configurations.A design trade-off is also performed for these configurations.
Chapter 6 proposes the design technique of physical module based spacecraft
configuration which is based on physical plug and play connectors and logical slots
for the subsystem modules. A honeycomb based tile is discussed in this chapter
which is used for larger and more demanding spacecraft structures.
In Chapter 7, the requirement of data communication across different subsystems
of the spacecrafts are described. The use cases have been discussed and the
implementation rules have been defined in this Chapter.
Chapters 8,9 and 10 focus on module design for intra-satellite communication
purposes. The modules have been designed for wired as well as wireless data communication.
The wired solution is based on on-board data bus module for inter-tile
data communication. Wireless solutions included both optical and radio frequency
based solutions. The optical module has been designed for optical free space as well
as glass fiber based communication purposes. The comparison between theoretical
and practical results has been made. The radio frequency based module is based on
commercial module and simpliciTI protocol stack.
In Chapter 11, the functional testing of modules, tiles and whole satellites is
discussed. The testing scheme of functional test board is also highlighted in this
chapter.