Specification • The JEEP provides efficient, best-effort delivery of packets. In-order delivery is only guaranteed if there are no transmission errors over the SpaceWire link, e.g., bit errors or dropped packets, and there are no routing options which could cause a segmented packet to be transmitted or received out of order. JEEP...
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Fundamental Frequency
Specification • The first mode of the JAS mechanical structure shall be greater than 500 Hz when mounted to a rigid surface.
Gasketing
Specification • The JAS mechanical structure shall use EMI gasketing to reduce EMI emissions as appropriate for the intended application.
Generalized Star
Other • The generalized star topology is a topology that attempts to wire the network together in such a way that each node is the center of a small star (see Figure). Given a dimension d, these networks will have d! nodes and each node will have a fixed degree of d-1....
Gigabit Interfaces
Profile • Gigabit interfaces are those that run at line speeds of one gigabit per second and above (>1 Gbps). These interfaces are often tasked with the primary purpose of pushing large amounts of mission data to other nodes for processing. Some examples of these interfaces include: Serial RapidIO SpaceFibre Gigabit Ethernet...
Gigabit Interfaces
Profile • Gigabit interfaces are those that run at line speeds of one gigabit per second and above (>1 Gbps). These interfaces are often tasked with the primary purpose of pushing large amounts of mission data to other nodes for processing. Some examples of these interfaces include: Serial RapidIO SpaceFibre Gigabit Ethernet...
Gigabit Interfaces
Profile • Gigabit interfaces are those that run at line speeds of one gigabit per second and above (>1 Gbps). These interfaces are often tasked with the primary purpose of pushing large amounts of mission data to other nodes for processing. Some examples of these interfaces include: Serial RapidIO SpaceFibre Gigabit Ethernet...
Glossary
Other • 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 Atomic An operation during which a processor can simultaneously read a location and write it...
Gravity Release Impact
Specification • The JAS mechanical structure shall remain within given displacements as applied by determining gravity release impacts on the mechanical structure.
Grounding
Specification • Grounding provisions are required for the mechanical design to eliminate the potential for ESD charging on floating metal. Any component members with surface areas greater than 20 cm2 shall have a grounding provision. Bolted fittings are acceptable as grounding provisions if the joint meets the electrical resistance requirement for bonding....
Header
Specification • JRDDP Packet Format Destination Address The first byte of the header shall contain the Destination SpaceWire Logical Address (SLA) field that is associated with the destination TEP to which the packet is being sent. Protocol ID The second byte of the header shall contain the SpaceWire Protocol ID field and...
High Speed Data Switch
Profile • Processing intensive systems may require many RP nodes to reduce large amounts of sensor data to an information set that can be downloaded to ground through bandwidth-limited downlinks. In many of these situations, processing will be distributed across many RP nodes connected through gigabit interfaces. A high-speed data switch could...
Host Vehicle Interface
Profile • The primary function of this instantiation is to enable connection between the CH node and host vehicle by providing appropriate connectors and bridging differing electrical signaling standards. A mezzanine connector, active transceivers, level shifters, and connectors for cabling to the host vehicle are common examples of components that would be...
Host Vehicle Interface and Configuration Manager
Profile • The primary role of the CH node in this application is to connect payloads to the host vehicle and to serve as the system controller for payload operations. These functions are implemented through software services running on the radiation-hardened microprocessor. Host Vehicle Interface and Configuration Manager Instantiation A radiation-hardened FPGA...
Humidity
Specification • The JAS housing shall meet all performance specifications during exposure to relative humidity varying from 0% to 60%.
Humidity Impact
Specification • The JAS mechanical structure shall maintain the electronics/PCBs within given displacements as applied by determining humidity impacts on the mechanical structure. If composite structures are used, the humidity should remain between a saturated composite at nominal 60% RH test area and a dry composite at 0% RH humidity vacuum environment...
Hybrid Fat Trees
Other • A hybrid fat-tree is an extension to the fat-tree topology. Hybrid fat-trees perform well when minimizing average path length and network diameter. One advantage to this design is typically about half of the nodes in this design will have a fixed degree of 2. However, other nodes have large degree,...
Interconnect Technologies
Profile • This profile describes the interconnect technologies supported by JAS. Each interconnect will be comprised of three layers based on the RapidIO standard: the Logical Layer; the Transport Layer; and the Physical Layer. The figure below shows a mapping of the interconnect layers to the OSI layers. The Application Layer is...
Interface Control
Specification • The JAS mechanical structure shall be designed to a prescribed Interface Control Drawing (ICD) as required by the application. Requirements called out in the ICD should include an answer to most of the design considerations in this specification.
JAS CCSDS SOIS
Profile • The JAS communication architecture is based on the Consultative Committee for Space Data Systems (CCSDS) Spacecraft Onboard Interface Services (SOIS) reference communication architecture. SOIS describes a layered architecture that allows applications to be abstracted from the specific communication data links. The SOIS architecture describes four layers: the Application Layer, the...
JAS Command Packet
Specification • JAS Command Packet All fields are shown in bits. The variable length application data field must be an integral number of bytes for the packet error control calculation. Spare bits may be used for padding purposes at the end to ensure the packets are an even number of bytes in...
JAS Efficient Exchange Protocol
Profile • The JAS Efficient Exchange Protocol (JEEP) is a best-effort packet transmission protocol that can be used to send messages between applications over a SpaceWire data link. JEEP is similar to the JRDDP protocol in that provides a segmentation capability to promote fairness between all applications needing to communicate on the...
JAS Efficient Exchange Protocol
Specification • The JAS Efficient Exchange Protocol (JEEP) uses the lower level SpaceWire data link layer to provide data delivery services to one or more higher level application processes. This document specifies the functional requirements for JEEP but does not specify the interfaces to the lower or higher level processes, which may...
JAS Essential Elements
Other • The following essential elements are the minimum required to develop a JAS-compliant system. Communication Interface (physical, preferably serial) Protocols to communicate over the physical interface Network-connected nodes that implement the communication interface and protocols Network routing and addressing scheme(s) All of these items are tailorable based on recommendations in the...
JAS Packet Definition
Specification • The JAS Packet is built upon CCSDS and PUS packet standards. Some modifications were made to enforce a layered architecture in order to promote reuse of applications. The following sections will highlight these differences in more detail.
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