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...
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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
Electromagnetic Compatibility
Specification • Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) are important design considerations which can be mitigated by the mechanical structure. EMI limits may be in place due to application-specific requirements, but more importantly, EMI can be detrimental to electronics because of the sensitive nature of many of the modern systems and...
Envelope
Specification • The assembled JAS mechanical structure shall attempt to fit the space available without violating any system-level keep out zones.
Environmental Exposure
Specification • Unless otherwise specified, the JAS mechanical structure shall meet these specifications during or after exposure to all environmental conditions specified in the Environmental specification. All of the intended application’s performance parameters must be considered to determine if the mechanical design can withstand the impacts of all environments.
Environmental Specification
Specification • The Environmental Specification provides details about environmental design considerations that should be considered for space applications of JAS. The figure below provides context of where the Environmental Specification resides in the JAS standard. JAS Standard Hierarchy
Environmental Test Flow
Specification • Programs using JAS should practice testing per industry standards wherever possible. The following tests and operational environments shall be applied to the components or structure in the following order. Events 1 through 5 shall be used for qualification acceptance testing. Events 1-6 shall be considered for fatigue calculations. 1) 24ea,...
Error Detection
Specification • Packet errors shall be detected by adding a CRC to each packet transmitted, checking it at the receiver, and discarding any erroneous packet.
Ethernet
Specification • Ethernet comprises a family of networking technologies with numerous media types and standards; 100Base-T (IEEE 802.3-2008:section 8) and 1000Base-T (IEEE 802.3-2008:section 40) the most popular in use today.
Exposure to Space Environment
Specification • This section is a system level consideration and is included for information purposes only. The view to space shall be considered for both thermal and radiation effects. Thermal-related issue: heat-dissipation Radiation-related: TID (lifetime), SEE, shielding and impact on mass
Factors of Safety
Specification • The JAS mechanical structure shall have strength margins of safety greater than zero when calculated from analytically derived structural loads. The factors of safety (FS), shown in the first table below, and test load factors, shown in the second table below, shall be applied to the limit loads. All laminated...
Fatigue
Specification • The JAS mechanical structure metallic elements shall be designed to withstand the effects of cyclic load condition caused by the design environment. The design environment includes all ground handling transportation, testing, launch and on orbit operational environments indicated in the Environmental Specification. MSFC-HDBK-505 Chapter 7 shall be implemented for fatigue...
File Access Service
Specification • The file access service, service type address 129 is used to read from or write to files within a file system. The currently defined file access service parameters are shown in the following table. Service Type Service Subtype Subtype Description Cmd Tlm Service Parameters Data Types and Description 129 1...
Form Factor
Specification • While no specific form factor standard is specified in JAS it is highly recommended that programs make use of a standards-based mechanical design such as VPX defined by VITA. Although VPX is preferred, other standards may be considered for use as well. The consideration of alternate standards should carefully consider...
Functional Description
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...
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.
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...
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...
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