Other • The figure below illustrates how the JAS supports intra-payload coincidence and triggering. There are two options: Serial Packets JAS nodes can transmit packetized signals via the communications architecture if latency requirements are not too stringent. Discrete Signals Discrete coincidence and trigger signals can be added to any node through the...
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Command and Host Processor Profile
Other • The Command and Host Processor (CH) profile defines a microprocessor-based solution suitable to construct nodes for mission data processing, spacecraft interfaces, and other applications requiring software execution on microprocessor platforms. Nodes based on the CH profile work alongside other nodes within the JAS architecture. The SMAC Profile and the Communication...
Command and Host Processor Profile
Profile • The Command and Host Processor (CH) profile defines a microprocessor-based solution suitable to construct nodes for mission data processing, spacecraft interfaces, and other applications requiring software execution on microprocessor platforms. The CH profile works alongside the RP Profile and PS Profile to implement nodes within the JAS architecture. The SMAC...
Communication Data Links
Specification • JAS nodes should communicate through one or more standard communications protocols. Serial communication protocols are the recommended approach but JAS does not preclude the use of parallel communication protocols. JAS also does not preclude the use of custom or legacy based communications.
Communication Profile
Profile • The Communication Profile defines standard interfaces for facilitating communication between RP, CH, and PS nodes within a JAS system. The Communication Profile focuses primarily on communication between payload applications. It leverages industry standards to support network-based communication using serial interfaces. A common set of communication protocols for space applications has...
Communication Specification
Specification • The Communication Specification provides details about network interfaces, communication services, and packet structures that were described in the Communication Profile. The figure below provides context of where the Communication Specification resides in the JAS standard. JAS Standard Hierarchy
Communications Profile
Other • The Communications Profile defines standard interfaces for facilitating communication between nodes within a JAS system. The Communications Profile focuses primarily on communication between payload applications. It leverages industry standards to support network-based communication using serial interfaces. Adherence to the Communications Profile and Communications Specification is the minimum required for a...
Companion Field Programmable Gate Array
Profile • A separate radiation-hardened companion FPGA is present on the CH node to implement timing functions, custom peripherals, and bridge to proprietary interfaces that may not be directly supported by the microprocessor. The FPGA typically attaches to the microprocessor through industry-standard bus interfaces, though the exact connection method will vary based...
Complete and Incomplete Hypercubes
Other • An overall good performer, hypercubes are very reliable and offer good performance. Complete hypercubes have fixed size of 2^d (i.e., 4, 8, 16, 32, 64, etc, nodes) but an extension to this structure (incomplete hypercubes) allows for arbitrary size. Hypercubes are constructed by beginning with two interconnected nodes (a 1-D...
Coordinate Definition
Specification • The JAS mechanical structure shall implement a coordinate system as a reference point for the design. The mounting of each component should be considered as the coordinate reference. The coordinate frame can originate on a pin-and-slot mounting. [Placeholder: Defining a coordinate frame helps to determine center of gravity, mass, envelopes...
Cube Connected Cycles
Other • Cube-connected cycles (CCC) are structures based on hypercubes (see Figure). Given a hypercube of dimension d, each hypercube node is replaced with a ring of size d. This causes the node degree of all nodes to be fixed at 3 regardless of network size! This structure excels when the port...
Custom Communications
Specification • Custom communications specifications by definition are not described by any single specification. The electrical parameters will be determined by the components involved in the design. For example, if the communications utilize gigabit (GTX) transceivers in an FPGA then the electrical requirements will be prescribed by the GTX specifications.
Data Transmit Queue
Specification • When packets from more than one channel are available for transmit, packets shall be transmitted in the order in which they are queued and in accordance with the transmit priority described above.
Data Types
Specification • The JAS standard does not require a specific length or encoding format for data types. Systems can define these based on what best suits their needs. Sizes, endianness, byte ordering, and bit ordering are typically driven based on the processing and memory architectures that are used. However, in order to...
Delayed Case
Specification • A delayed but recoverable scenario occurs when a receive TEP receives at least one CLOSE packet but the transmit TEP does not receive any ACK packets as shown in Figure 3. In this case the receive TEP will eventually transition to the CLOSED state via the timeout and the transmit...
Design Constraints
Specification • The following sections define some important design constraints that the program will levy on the system. The constraints will drive many of the choices in designing the mechanical system.
Design Thickness
Specification • For strength and buckling analyses, minimum material thickness shall be used. Minimum thickness is defined as the nominal thickness minus the lower tolerance and applies to metallic and nonmetallic structural elements. For modeling purposes and stiffness calculations, use nominal or expected values. For flexures the Maximum blade thickness shall be...
Design Ultimate Load
Specification • The JAS mechanical structure shall have sufficient strength to simultaneously withstand design ultimate loads, the corresponding temperature, pressure and accompanying environmental phenomena without failure.
Design Yield Load
Specification • The JAS mechanical structure shall withstand design yield loads, the corresponding temperature, pressure and associated environmental phenomena without permanent deformations, or permanent misalignments, of all components.
Device Access Service
Specification • The device access service, service type address 128, is used to request parameters from or command parameters to a specific device. The currently defined device access service parameters are shown in the following table. Service Type Service Subtype Subtype Description Cmd Tlm Service Parameters Data Types and Description 128 1...
Discrete Signaling
Profile • SMAC Discrete I/O and Data Bus Signaling The SMAC has capabilities to read and drive both discrete I/O values and data buses. The FPGA I/O dedicated for this purpose can be either configured as dedicated inputs and outputs or can be bi-directional with input or output behavior configured through the...
ECSS Packet Utilization Standard
Specification • The figures below show a PUS telecommand and telemetry packet and their utilization within the CCSDS space packet specification. The PUS specification uses the user-definable fields of the CCSDS space packet in order to create a PUS packet. The specification defines a secondary header that provides additional metadata such as...
Electrical Bonding
Specification • Each equipment design shall provide electrical continuity across mechanical interfaces in accordance with the design requirements of this specification. Electrical continuity will be achieved to the maximum practical extent by direct metal-to-metal contact across the entire interface surface. If the electrical resistance across mechanical interfaces is measured to be less...
Electrical Interconnects
Specification • JAS electrical design shall utilize commercial interconnect standards when applicable. The following sections are some examples of commercial interconnect standards that are recommended but not required.
Electrical Specification
Specification • The Electrical Specification provides details about power distribution, electrical interconnects, and communication data links that are used within a JAS-based system. The figure below provides context of where the Electrical Specification resides in the JAS standard. JAS Standard Hierarchy
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