ESA Document - Emits - ESA

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HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 201 of 422
Used for interconnection of IP-cores into FPGAs or ASICS. The use of reprogrammable FPGAs
in future, if supported by good specification of interfaces will allow in-flight hardware
reconfiguration and upgrade.
3.3.6.1.6.2 Board level and backplane level bus (as VME, PCI or PCI express [RD36],
Spacewire)
Will allow the use (widespread now in commercial computers) of modular electronic boards.
Once the transition between parallel busses to high-speed serial busses will be complete modulelevel
cross-strapping will also become easier.
3.3.6.1.6.3 Very low speed bus (e.g. I2C or 1-wire)
The use of these common solutions will allow considerable mass saving on simple sensors and
transducers. A very low speed bus (10 kbit/s-500 kbit/s) may then be interesting to implement a
low-power sensor bus. For example, the OneWire standard [RD31] supports 16 kbit/s and 142
kbit/s communication. It relies on a single pair of wires for both power supply and
communication.
3.3.6.1.6.4 Low-speed Bus
Low-speed busses are the ones commonly known as command and control busses. MIL-STD-
1553B has been the most successful one, even despite the standard lack of implementation of
any networking capability. CAN has recently gained the attention of space community after
having became a de-facto standard for automotive industry.
3.3.6.1.6.5 High-speed Bus
Spacewire is the ideal candidate for a point-to-point data connection requiring 100 s of MBps,
but the development of an Ethernet-style on-board bus is still a task to be performed. Those
kinds of busses, like MIL-1773, shall have the possibility to be physical media independent, and
to be put both on optical fibres or copper wirings.
3.3.6.1.6.6 Very high speed bus
Following the increase of data rates on on-board data busses in the 2020s a multi-Gigabit optical
on-board connection shall be also available. Note that concurrent operation of shared computing
power means heavy network load, and solutions like that will be probably necessary.
3.3.6.1.6.7 Wireless communication
Wireless communication will be the preferred mean to connect dynamically payloads or PDAs to
the integrated avionics system. The standards already available (like IEEE 802.11a/b/g,
Bluetooth and IEEE 802.15.4) would be enough for the needs of HMM systems.
3.3.6.1.7 Request for enhanced capabilities
A scenario imagining an integrated modular avionics for a HMM can already be quite realistic.
Integrated modular avionics, with several small intelligent units concurrently running distributed
software acting as a control entity of the craft, is the only way to cope with the reliability
requests (together with mass power and cost savings) of such a mission and will provide a new