Specification • The receiver shall send a positive acknowledgment (ACK) packet for each DATA packet received without error.
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...
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...
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...
Buckling and Crippling
Specification • Evaluation of buckling strength shall consider the combined action of primary and secondary stresses and their effects on general instability, local or panel instability, crippling, and creep.
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...
Buffer Segmentation 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 JEEP MTU size, the buffer must be segmented into a series of JEEP packets and then reassembled at the receive TEP before returning the buffer to the...
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...
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...
Specification • Each transport channel shall operate independently from other transport channels.
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.
Coating Surface Resistivity
Specification • The thickness of all chemical film treatments need to be controlled to provide low surface resistivity. Surface resistivity shall be less than 1 x 109 ohm/ square.