Joint Architecture Standard Overview Profile



Term Definition
Adaptability A system design property that refers to an architecture’s ability to be easily changed or adjusted to accommodate different system needs.
Address Translation allows addresses to be translated from abstract to physical

An operation during which a processor can simultaneously read a location and write it in the same bus operation. This prevents any other processor or I/O device from writing or reading memory until the operation is complete.

Atomic implies indivisibility and irreducibility, so an atomic operation must be performed entirely or not performed at all.

Availability The average fraction of time that a functioning payload is capable of performing its mission during any given week
Average Path Length The average distance between two nodes in the network over all pairs of distinct nodes.
Commercial de facto standard A commercially-invented standard, as opposed to open standards developed by (official) industry trade groups, academic organizations, engineering organizations or government organizations, which is so widely used that it has become an unofficial standard offering advantages similar to open standards, including well-defined functions and interfaces and availability of hardware, software and/or intellectual property from many sources
Configuration Element The smallest system components that are large enough to need their own requirements, specifications, test documents, and interface control documents (smallest hardware or software components that are the purview of system engineering)
Connectivity The capability for systems and subsystems to communicate (exchange information) with one another
Data processing Backend processing that further processes, analyzes, compares and sometimes fuses the data produced by signal processing stages to produce the final digitized information that will be transmitted to the ground
Datalink Convergence Protocols Communication protocols for addressing QoS requirements
Design Constraint Technical, operational, interface, environmental, programmatic or other requirements that restrict designers’ choices of design approaches or components
Diameter The longest path in the network between two nodes.
Element Short for configuration element
Extensibility Designed-in architectural structural features, “hooks” and mechanisms that will allow a system to be expanded and enhanced with new interfaces and capabilities to accommodate new needs and requirements without making major structural changes that would otherwise adversely affect existing peripheral elements
Fault detection Mechanism for detection of faults during normal operation
Fault tolerance Ongoing fault detection with automatic repair
Flexibility System design attribute which refers to the ability to adapt to unpredictable internal or external changes that could potentially affect its operational performance
Forward compatibility The ability of a system to accept input and provide output intended for later versions of itself
Graceful degradation The ability of a system to systematically degrade functionality and/or performance following a hard failure in a manner proportional to failure severity
Ground support equipment Equipment used for testing, handling or shipping of flight components while on the ground
Ground test equipment Any test equipment used to test all or any major component of the satellite on the ground, either pre- or post-integration; a subset of Ground Support Equipment
Hard fault A permanent system fault, such as a component failure, that either may not be recoverable or may be recoverable by switching in redundant hardware
Host platform The spacecraft or aircraft that carries the payload
Host system The full system consisting of flight and ground segments that includes the host platform as a major component
Information transfer rate The rate of information flow (in bits/second) over a communication channel, excluding overhead
Integrity provides an error detection capability
Interoperability The ability of diverse systems, subsystems or system elements to easily provide or receive services and/or actionable information to and from other systems, subsystems or system elements via standardized information formats
Joint Test Action Group Interface A standard test access port for testing and configuring components
Lane A point-to-point, full duplex, high-speed, serial connection comprised of two unidirectional serial communication channels.
Launch support equipment Equipment used for testing or providing support to a satellite while it is on the launch pad
Link A communication connection between nodes that may be an aggregation of lanes
Memory Access Protocols access memory devices that are located on remote nodes within a network
Messaging interface A serial or parallel data interface through which multiple bit messages are passed between system components
Messaging Protocols send arbitrary types of data (messages) between applications
Modularity The extent to which a complex system is constructed of a set of smaller modular components that can be designed, built and tested independently by separate design product teams
M-of-N redundancy Redundancy scheme that provides the necessary M components from the available N components (This implies the number of spare components is N-M.)
Network protocol Defines a “language” of rules and conventions for communication between network nodes, including data formatting, compression, error detection and correction (EDAC) coding and packaging as well as message acknowledgement and error handling procedures
Network topology The arrangement or mapping of network elements (links, nodes, etc.) showing the physical and/or logical interconnections between nodes

A node is an instantiation of an RP, CH, or PS profile

A self-contained, module-level architecture building block having functions including physical layer connectivity, power conversion, processing, memory and local configuration (a self-contained set of one or more hardware configuration elements that interface to a network)

Node Degree The degree of a node is equal to the number of links to which that node is connected.
Nondevelopmental items System elements developed on other programs that can be used in original or modified form in the proposed system
One-to-One redundancy Redundancy scheme that provides a dedicated replacement for a specific component in the system (sometimes referred to as A/B redundancy)
Open standard Vendor independent, publicly available, widely accepted standards defined and maintained by industry trade groups, academic or engineering organizations, government organizations or commercial entities, which offer transparent environments where designers can easily intermix hardware, software, networks, etc. of different vintages and from different manufacturers to meet a variety of needs
OSI model A layered, abstract description for communications and computer network protocol design
Payload Major satellite component that collects mission data
Payload elements Collection of configuration elements that comprise a payload
Physical layer The lowest layer of the 7 layer OSI model that typically defines the electrical interface (transceivers and communication media)
Platform Host satellite, spacecraft bus or aircraft
Prioritization allows data to be prioritized over the data link
Protocol Multiplexing allows multiple protocols to be simultaneously used on the network
Quality of Service Measure of network performance including but not limited to, transmission rates, error rates, etc.
Redundancy provides the capability to try alternative paths of communications if one fails
Reference design Fully functional initial design implementation to provide the engineer with a complete working representative example of all relevant design components
Resource Allocation provides dedicated bandwidth to applications
Retry provides the capability to automatically retransmit if there is an error
Router Synonymous with switch
Scalability A system property which indicates its ability to be readily expanded in order to accommodate additional work (Vertical scalability refers to the ability to add capability to a single node. Horizontal scalability refers to the ability to add additional nodes.)
Segmentation enforces a network Maximum Transmission Unit (MTU) size to promote fairness
Sequence Preservation guarantees the data is delivered in order
Signal processing Front-end (often high-bandwidth) processing that converts raw digitized sensor signals into the first level of “meaningful” data that may be further processed and compressed to produce digital information suitable for transmission to the ground via limited-bandwidth communication channels
Soft fault A system fault, such as a single-event upset, that is recoverable without switching in redundant hardware
Spacecraft bus Major satellite component that carries, protects, powers and provides services needed to operate one or more satellite payloads in space (referred to in the document as “the host platform or the platform”)
Store and forward communications A downlink communications architecture wherein mission and status/state-of-health (SOH) data are collected and stored onboard the satellite for transmission to the ground at a later time (used in systems that do not have full-time downlink communications)
Subsystem Aggregation of components that performs some distinguishable subset of system functions
Subsystem element Collection of configuration elements that implement a subsystem
Switch Synonymous with router
System An integrated composite of hardware, software, human and other physical elements that operate together to provide a capability to satisfy a set of specified functions
System component Generic term for any distinct part of a system (below the full-system level) that is defined by a set of requirements and a set of interface descriptions
System element Collection of configuration elements that implement a system
Triple modular redundancy A fault tolerant method in which three physically or logically redundant units perform the same process followed by a voting scheme that discards and thereby masks a minority (assumed faulty) result