The NASA Glenn Research Center, through a contract with General Dynamics C4 Systems, Spectrum Astro Space Systems, has developed a radiation-tolerant, single-board, four-port 10/100-Mbps Ethernet router as an enabling technology for future spacecraft architectures. Under a previous contract, General Dynamics C4 Systems (previously Spectrum Astro, Inc.), developed other space network hardware, including a 10/100 Mbps-Ethernet network interface controller (NIC) and a four-port 100-Mbps Ethernet hub. These space network hardware devices utilize Open Systems Interconnection (OSI) standards for space-based communications applications. The OSI standard is a well-recognized layered reference model that specifies how data should be sent node to node in a communications network. For some time, the terrestrial industry has recognized the benefits and flexibility of targeting hardware developments around OSI standards, in particular the commonly used Transmission Control Protocol/Internet Protocol (TCP/IP). The Internet would not be what it is today without OSI. The space community can leverage these standards and technologies, developed for ground networks, to reduce flight mission schedule, cost, system complexity, mass, and power requirements. In the future, even lower costs and streamlined options could result from using modular, commercial-off-the-shelf hardware in test and flight hardware.
A space router is an enabling or bridge technology for implementing IP addressing over a communications system in space. Space communications architectures differ considerably from ground networks in that many entities typically share a ground network. In ground applications, data packet collisions and congestion are more of a problem, and the hardware and software techniques used to mitigate these are more important. Space communications links are usually controlled by a single entity, such as a ground station linking to a single spacecraft asset, or cross communications links between spacecraft. Links in space usually do not fail because of data packet collisions or congestion but because of poor signal quality created by insufficient transmit power or available bandwidth from the ground link or cross link. Glenn has been working on developing versions of TCP that are tuned specifically for the parameters that are significant on space links.
Four aggregate key areas of router design were analyzed through trade-off studies: (1) architectures, (2) protocols, (3) data processing, and (4)control and network management. On the basis of the results of these studies, a radiation-tolerant 6U factor (six rack units, or 10.5 in. high), compact Peripheral Component Interconnect (cPCI) space network router (see the photograph) was developed at General Dynamics C4 Systems through a contract managed at Glenn. The board was designed to flight specifications including thermal and mechanical standards, according to flight manufacturing procedures.
Space network router board.
The space network router can support various architecture configurations suitable for a spacecraft with a typical downlink connection. For data processing, the router used a field-programmable gate array (FPGA) design with an embedded 32-bit reduced instruction set computer (RISC) processor. The router has four 10/100-Mbps Ethernet ports and expansion capability for additional Ethernet, serial (HDLC/RS-422), SpaceWire, FireWire, or Universal Serial Bus (USB) ports. The routing protocol implemented was Routing Information Protocol (RIP); however, for future considerations and scalability, the Open Shortest Path First (OSPF) protocol was recommended. The space router was implemented with a console port with an RS-422 standard interface that could interface to other spacecraft serial interfaces for control and configuration while in flight.
In conclusion, the space router is an enabling or bridge technology that will be useful in a variety of space communications applications including point-to-point links, onboard instrument and asset control, IP-compliant operation, and spacecraft command and data handling. It represents one piece of the architecture required to enable a principal investigator on a terrestrial Internet site to seamlessly interact with spacecraft assets in near real time.
Find out more about the research of Glenn’s Communications Division: http://ctd.grc.nasa.gov
Glenn contact:
Robert E. Jones, 216-433-3457, Robert.E.Jones@nasa.gov
Authors:
Robert E. Jones, James Joseph, and Jennifer Lazbin
Headquarters program office:
Earth Science Technology Office
Programs/projects:
Advanced Information Systems Technology, Constellation
Last updated: September 7, 2007
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