• Author: Speretta Stefano PhD
  • Description:

    With the name space mission”, developers usually reference to arti cial satellites orbiting
    around the Earth or around other celestial bodies. Satellites are complex machines made
    by several sub-systems which integrate state-of-the-art electronic, optical and mechani-
    cal devices. Beside the harsh space environment, the satellite should also stand launch
    accelerations an vibrations which usually last for only few minutes but can cause severe
    damages to it, if proper solutions have not been employed. Satellite development and
    launch are quite expensive, as compared to every-day electronic systems, because the en-
    vironment poses strong constraints on it and because no servicing can be performed to
    repair damaged systems. Only few organizations world-wide could a ord these high costs
    which were mainly due to fact that satellites were always seen as an ad-hoc system, devel-
    oped and produced in just few items for a speci c mission. Costs were extremely high (in
    the range of multi hundred millions or billion dollars) and only military and governative
    organizations could a ord it. In the last years, this concept changed dramatically, such
    that many companies or even universities started developing their own satellites: cost
    reduction strategies allowed to shift mission cost down to less than one million for small
    missions and this triggered a widespread interest in space systems, also from the didactic
    point of view.
    Many organizations around the world started researching about cost e ective solutions
    for space systems and this thesis is going in the same direction. Many approaches can be
    followed to save money in the development, production, testing and operational phases
    of the project. In literature many approaches are suggested, but the most well-known
    one is the CubeSat: a cube-shaped 10 cm wide satellite weighting maximum 1 kg. This
    is a basic unit, which can be composed to create bigger structures: unfortunately this
    standard is limited to a mechanical modularity in the design. Taking modularity to a high
    level, involving the whole satellite could help in further reduce system costs and increase
    performances: this is the idea that lies behind the AraMiS architecture, which will be
    presented in this work.
    This thesis will cope with several problems related to space systems development, and
    show some solutions that can help in both keeping system development and production
    cost low while still achieving good performances. In Chapter 2 the space environment in
    which satellites will have to operate will be presented, showing how to numerically evaluate
    satellite environmental constraints, with focus on low Earth orbit (LEO). Chapter 3 deals
    with particle interactions with matter and will be in particular about radiation e ects
    on electronic components. Particle transport in matter will be addressed to evaluate the
    shielding e ects that a thin layer can have on particle
    uxes, to better understand the
    radiation environment inside the satellite. A novel technique will be presented to compute
    protons transport in matter which speeds-up computation by many orders of magnitude.
    Space systems development costs will be addresses in Chapter 4: a cost model de-
    veloped by NASA will be presented, and based on it, cost reduction solutions will be
    presented. Modularity and cost-sharing between multiple missions will appear as opti-
    mal 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 5, an overview of many low-cost design techniques will be presented,
    with a focus on those employed in the development of AraMiS.
    In Chapter 6, the AraMiS architecture will be analyzed, focusing on the di erent mod-
    ules this architecture is composed by and on the advantages that this novel architecture has
    to achieve high performances and fault tolerance with a low development and production
    cost. Chapter 7 deeper analyzes three AraMiS sub-systems, which were developed during
    these three years: a latch-up protection system used to protect commercial components
    from latch-up e ects, a wireless data communication bus, developed for reducing harness
    mass and routing problems in a small satellite, a power management sub-system and a
    power distribution bus, used to route power to all the satellite sub-systems and to supply
    them. These sub-systems are the satellite backbone and their modularity and scalability
    gives great
    exibility to the AraMiS architecture.
    Chapter 8 addresses instead some of the tests that were performed at di erent levels on
    the system, to qualify it for space operations. Radiation tolerance tests were also preformed
    on some of the components that are used in the satellite to ensure their endurance.

  • Year: 2010
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