Specification • The JAS mechanical structure shall be constructed of materials capable of performing at the specified orbit for a minimum of ten years after being stored in an inert gas environment and after exposure to clean air during testing, launch, and ascension. The use of the following materials is prohibited: Zinc,...
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Mechanical
Profile • The recommended PS implementation is on a 6U VPX board, as defined in the VITA 46 standard and the Mechanical Specification. VPX is preferred for a number of reasons, a few of which include: 3U and 6U board formats to accommodate varying sizes High-density connectors and flexible pinout Availability of...
Mechanical
Profile • The recommended RP implementation is on a 6U VPX board, as defined in the VITA 46 standard and the Mechanical Specification. VPX is preferred for a number of reasons, a few of which include: 3U and 6U board formats to accommodate varying sizes High-density connectors and flexible pinout Availability of...
Mechanical Interface Design
Specification • The JAS mechanical structure as described in this Mechanical specification will support applications intended for a space environment and will provide stable mechanical structure for the electronics during launch and while operating in a high vacuum.
Mechanical Specification
Specification • The Mechanical Specification provides details about mechanical interface design, environmental impacts, and design constraints that should be considered for implementing mechanical structures in a JAS-based system. The figure below provides context of where the Mechanical Specification resides in the JAS standard. JAS Standard Hierarchy
Megabit Interfaces
Profile • There are several megabit interfaces that may be utilized on the RP node. Some examples of these include: SpaceWire RS-422, RS-232 MIL-STD-1553 CAN bus SpaceWire is the preferred solution for systems requiring data rates below 200 Mbps. SpaceWire links can scale from 2 to 200 Mbps at full duplex and...
Megabit-class Interfaces
Profile • There are several megabit-class interfaces that may be utilized on the PS node. Some examples of these include: SpaceWire RS-422, RS-232 MIL-STD-1553 CAN bus SpaceWire is the preferred solution for systems requiring data rates below 200 Mbps. SpaceWire links can scale from 2 to 200 Mbps and are well suited...
Memory Technologies
Profile • RP Node Memory Technologies External memory is often included on RP node instantiations to support the FPGA’s processing. Among other uses, memory provides storage for sensor data and working space to implement processing algorithms. Any combination of memory technologies, including Synchronous Dynamic Random Access Memory (SDRAM), Static Random Access Memory...
Mezzanine Connector
Specification • A very useful option for plug-in modules is the ANSI/VITA 57 standard FPGA Mezzanine Card or FMC. This standard specifies an industry standard form factor utilizing a low profile, high-speed, high-pin count connector. The FMC connector can support very high bandwidths. The FMC approach solves the problem of how to...
Molecular Contamination
Specification • For all components that will be in the vicinity of an optical payload and anywhere that contamination at the molecular level is an issue, all parts and materials must comply with ASTM E 595 for less than 1% Total Mass Loss (TML) and 0.1% CVCM. Thermal bake-out of all components...
Molecular Thermovac Testing
Specification • Thermovac temperature testing is required to determine dissipation at full power modes. A test plan needs to be developed and coordinated with the System Engineer.
Mounting Distortion Impact
Specification • The JAS mechanical structure shall maintain the electronics/PCBs listed below within given positions with distortions less than expected for the intended application.
Network Interfaces
Profile • All JAS nodes communicate through a standard set of interfaces that adhere to standard protocols. Refer to the Electrical Specification for physical layer technical information and Communication Specification for details on standard data protocols. This section describes megabit-class interfaces, with line speeds below one gigabit per second ( The protocols...
Network Interfaces
Profile • All JAS nodes communicate through a standard set of interfaces that adhere to standard protocols. Refer to the Electrical Specification for physical layer technical information and Communication Specification for details on standard data protocols. This section describes two classes of network interfaces, megabit interfaces with line speeds below one gigabit...
Network Topologies
Other • The selection of network topology is a critical component when developing multi-node or multi-point system architectures. A good choice of topology will require less power, have less complexity, higher reliability, and will orchestrate network traffic smoothly and quickly between nodes. Conversely, a poor choice of topology will introduce complex and...
Obscuration
Specification • All JAS mechanical structure components shall be placed to prevent obscuration of the system view of space if the JAS electronics box will be used to radiate. Structural elements shall be kept an appropriate distance away from the JAS electronics housings.
Operating Temperatures
Specification • Operational temperatures are provided in thermal study for the nominal orbit. Excursions from predicted operational temperatures shall be increased by 11C (bilateral) when these temperatures are utilized in all fatigue analysis. For the purposes of fatigue the temperature excursion within an orbital season may be considered. For the purposes of...
Operational Vibrations
Specification • The JAS housing shall meet all of the displacement budgets, while subjected to the operational environment produced by the acceleration in file, TBD. These shall be used as base inputs.
Orientation
Specification • The JAS housing shall meet mechanical alignment performance specifications in any direction.
Packaging for Thermal Dissipation
Specification • The preliminary JAS mounting details are defined by the baseplate details in ICD drawing xxxxxx. The JAS electronics box is meant to mount through the blue baseplate shown in the figure below. The figure shows a nominal 3x3 stack in an exploded view. JAS Mounting Exploded View Conducted Self-radiated panels...
Packet Addressing and Routing
Specification • Packets will be identified and routed in the system using the SAPID, DAPID, ST, and SST. Applications shall provide these fields to the JAS Packet Service to create the stream of packets that will be sent across the communication channel. Communication channels and addresses, such as a SpaceWire address, can...
Packet Error Control
Specification • Even though JAS network protocols offer a guaranteed delivery option, there still exists the possibility of an error being introduced into a packet while it is being created or transferred from memory to the communication channel. To provide an additional layer of error detection all JAS packets shall contain a...
Packet Sequencing
Specification • The use of the packet sequencing fields within the JAS packet is different from the definition in the CCSDS and PUS standards. The original intention of the packet sequence counter was to provide two functions. First, it was used in combination with the sequence flags to reassemble data sets that...
Packet Service Definitions
Specification • [Placeholder: services reserved for and specific to JAS; this is a lead in to describe the services. Contact SNL if immediate support is needed with this topic. Content will be developed for JT 2.0.]
Particulate Contamination
Specification • Internal Cavities will be wiped clean with isopropyl alcohol and allowed to air dry for 30 minutes prior to close out; the structure will be covered during the drying process. The surfaces will be visibly clean. Visibly clean is defined as no contamination visible when viewed from 6-18 inches away...
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