Test and Integration of an On Board Computer for nanosatellites

Today the industrial and academic interest in space and space-related
activities is rapidly growing. A cost-effective access to space would open
a wide range of new opportunities and markets, especially for SMEs (Small
Medium Enterprise) and Universities, which otherwise cannot access space
due to high cost. Lower costs would allow to test in field (in space)
theories and ideas which would otherwise be unaffordable to do.
Unfortunately, the cost-effective access to space, which is also envisaged
by ESA, is still many years ahead. There is still a lack of devices,
circuits, systems suited to develop satellites, ground stations and related
services at costs compatible with the budget of academic institutions and
SMEs. As soon as the development time and cost of small satellites will
fall below a certain threshold (e.g. 100,000 to 500,000 euros), appropriate
business models will likely develop to ensure a cost effective and
pervasive access to space, and related infrastructures and services.
The most effective way to reduce the cost of a nano or micro-satellite
mission is to reduce as much as possible design and non-recurrent
fabrication costs, which usually account for more than 90% of the overall
budget. Reducing them can be achieved by sharing the design among a large
number of missions.
The first step in this direction was the development of a small low cost
nano satellite, which started in the year 2004: the name of this project
was PiCPoT (Piccolo Cubo del Politecnico di
Torino) designed by some departments of Polytechnic University of Turin,
in particular the Electronics and the Aerospace departments.
The main goal of the project was to evaluate the feasibility of using COTS
(Commercial-Off-The-Shelf) components in a space project in order to
greatly reduce costs; COTS components are indeed easily available and low
cost, but not much reliable for space applications.
The internal subsystems modularity was also a key goal to allow a further
cost reduction for future missions.
Starting from the PiCPoT experience, in 2006 a new project called AraMiS
which is the Italian acronym for Modular Architecture for Satellites was
developed..
In this diagram is shown ARAMIS Project, in its subparts:
1. OUTER Tiles : tiles regularly placed on the outer surface of the
satellite, with a double function: mechanical and functional;
2. INNER Tiles : tiles internal to satellite, mission dependent.
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Class – ARAMIS Project
Design reuse is an efficient way to reduce design and non-recurrent
fabrication costs.
AraMiS is a family of satellites with modular architecture, based on a
small number of flexible and powerful modules which can be reused as much
as possible in different missions. Using the same module more times
obviously allows to share design, qualification and testing costs and to
reduce the time-to-launch. These modules are called “Tiles”.
The first step in the AraMiS project was to identify the most common and
critical subsystems, that are:
1. mechanical subsystem;
2. power management subsystem;
3. telecommunication subsystem;
4. on-board processing subsystem;
5. payload support;
6. ground segment.
The basic idea was to design an architecture made of one or more modular
intelligent tiles. Most of them placed on the outer surface of the
satellite for a double function: mechanical and functional. The inner part
of the satellite is mostly left empty (except for the on board processor
and payload support tile), to be filled by the user-defined payload, which
is the only part to be designed and manufactured ad-hoc for each mission.
Each tile has been designed, manufactured and tested in relatively large
quantities.
An increased design effort has been done, to compensate for the lower
reliability of COTS devices, therefore achieving a reasonable system
reliability at a reduced cost.
Class – OUTER Tiles
Outer tiles are tiles placed on the external surface of satellite, and can
be of two types: Power Management Tile and Telecommunication Tile.
Class – INNER Tiles
Inner tiles can be of many types depending on the mission. One of the
developed tile is the Payload support.
Class – Power Management Tile
Power management, composed mostly of a solar panel, a rechargeable battery
to store energy, a battery charger, a microcontroller-based Housekeeping
module to keep track of voltages, currents and temperatures inside the tile
and an active magnetic and/or inertial asset control for AOCS
An appropriate number of such tiles (depending on power requirements of the
mission) are placed around a cubic or prismatic shape (or displaced after
satellite release) and represent a pre-designed and pre-assembled modular
power management subsystem.
Class – Telecommunication Tile
Telecommunication, composed mostly of a microcontroller-based programmable
transceiver, a 437MHz or 2.4GHz modem, a power amplifier (for transmission)
and low-noise amplifiers (for reception), an antenna system. At least one
such tile is placed as one of the faces of the satellite, preferably
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pointing to ground, and takes care of reliable data and command exchange
to/from ground.
In this tile is also placed the On-board processor: takes care for all data
handling for Housekeeping, and interfaces to the user-defined payload. CPU
power and memory are available for the user, so that simple payloads may
use it instead of having their own processor.
Class – Payload support
Mechanical and interfaces for Payload.