Results 1–25 of 144

Allocation of Service Types and Subtypes

Specification • The PUS provides a standard set of services that are targeted for communication between spacecraft and ground systems. Many of them may not be applicable to on-board communication between applications. However, nothing precludes their use in a JAS-based system. The PUS can be extended to add additional functionality to existing...

Communication Specification > JAS Packets > Packet Service Definitions > Allocation of Service Types and Subtypes

Backplane Connectors

Specification • JAS electrical design should utilize commercial connector standards when applicable. The VPX plug-in module to backplane connector is a Tyco Electronics MultiGig RT2 connector system which was chosen for its rugged mechanical performance and high-speed electrical performance, rated to 6.4 Gb/s and demonstrated to support data rates greater than 10...

Electrical Specification > Electrical Interconnects > VPX > Backplane Connectors

Backplane Topology

Specification • The backplane is a key element in achieving high-speed connections between the plug-in modules or nodes in the case of a JAS system. VPX compliant backplanes support a minimum signaling rate of at least 3.125 Gbps on any differential point-to-point connection. There are a small number of required signals on...

Electrical Specification > Electrical Interconnects > VPX > Backplane Topology

Buffer Fragmentation and Reassembly

Specification • In cases where a higher-level transmit application (or higher layer in a communications stack) must transmit a buffer of data that exceeds the JRDDP MTU size, the buffer must be fragmented into a series of JRDDP packets and then reassembled at the receive TEP before returning the buffer to the...

Communication Specification > SpaceWire > Protocols > JAS Reliable Data Delivery Protocol > Overall Functional Description > Buffer Fragmentation and Reassembly

CCSDS Telecommand and Telemetry Format Packet Standard

Specification • CCSDS Space Packet The CCSDS packet format consists of a packet primary header and packet data field. The header provides routing information for the packet and metadata that describes the packet. The data field is intended to be a user-defined field that can be customized for applications. Details of how...

Communication Specification > JAS Packets > CCSDS Telecommand and Telemetry Format Packet Standard

Channel Closing Process

Specification • The following sections present the interactions (in the form of UML Sequence Diagrams) between transmit and receive endpoints while closing a channel. Various error conditions are presented in order to show nominal, delayed, and worst case scenarios. The hexagonal icons represent the TEP states while the dashed green lines represent...

Communication Specification > SpaceWire > Protocols > JAS Reliable Data Delivery Protocol > Channel Operations > Channel Closing Process


Specification • Cleanliness is an important design consideration which can be mitigated by the mechanical structure and processes. Systems adjacent to an optical payload may have more strict cleanliness requirements than non-optical payload. The following sections describe the requirements which deal with Cleanliness considerations for the JAS mechanical structure.

Mechanical Specification > Design Constraints > Cleanliness

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.

Electrical Specification > Communication Data Links

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

Communication Specification

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...

Mechanical Specification > Mechanical Interface Design > Coordinate Definition

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.

Electrical Specification > Communication Data Links > Custom Communications

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...

Communication Specification > JAS Packets > JAS Packet Definition > Data Types

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.

Mechanical Specification > Design Constraints

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...

Mechanical Specification > Design Constraints > Structural Integrity > Design Thickness

Results 1–25 of 144