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.
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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.
Multiplexed Logical Channels
Specification • The protocol shall support multiple simultaneous logical connections over a single SpaceWire link.
Nominal Case
Specification • In the nominal case the close packet is immediately acknowledged by the receive TEP and the transmit TEP transitions to the CLOSED state. The receive TEP transitions to the CLOSED state after the expiration of its timer. The purpose of the receive TEP’s delay in the CLOSING state is to...
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.
Overall Functional Description
Specification • This protocol describes the mechanism for reliable transfer of data packets over a SpaceWire connection and adds the following capabilities to a SpaceWire link: Multiplexed Logical Connections Reliable Delivery Missing packet detection Out of sequence packet reordering Buffer fragmentation and reassembly
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 Sequence Numbers
Specification • An 8-bit sequence number shall be assigned to each packet transmitted.
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...
Payload
Specification • JRDDP Packet Format Secondary Header (Optional) The presence of the optional secondary header is indicated by the Secondary Header Flag in the Packet Control field. If a secondary header is present, its contents and format are implementation dependent and shall be documented in a program specific document. The secondary header...
PCI Express
Specification • PCI Express, or PCIe, is another multi-lane high speed serial interconnect technology. Each lane is a full-duplex data stream comprised of two differential signaling pairs, one for transmitting and one for receiving.
Platform Management Service
Specification • The platform management service, service type address 130 is used to configure, manage, and monitor network specific resources. The currently defined platform management service parameters are shown in the following table. Service Type Service Subtype Subtype Description Cmd Tlm Service Parameters Data Types and Description 130 11 Network Topology Upload...
Potential Flight Capability
Specification • Each component of the JAS mechanical structure should consider Flight capability as this will force consideration of design, flight, and test environments described in this specification. The JAS mechanical structure should be designed for the specific application intended.
Power Distribution Architecture
Specification • JAS will accept at least one primary input power source supplied to the system. The primary input power will connect directly to the Power Supply or PS node in a JAS arrangement. The PS node converts the primary input voltage to a lower voltage which is then sent to all...
Pressure
Specification • The JAS structure shall meet all performance specifications during and after exposure to pressures varying from atmospheric to the space environment of 10-14 Torr. All thermal-vacuum ground based testing shall be conducted at pressures less than 10-6 Torr.
Pressure Change
Specification • The structure shall be designed to survive the change of pressure specified in the figure below. The launch and ascent pressure environment will lie between Pc(Max) and Pc(MIN). Pressure Change Within the envelope defined in figure above, the local rates of change will remain between the values shown in the...
Primary Power Conversion
Specification • JAS will provide the capability to convert primary power to secondary power.
Primary Power Conversion Efficiency
Specification • The converter should be optimized for efficiency to reduce power consumption and avoid unnecessary heat generation through power dissipation. The exact design of the primary converter will depend upon the required efficiency and the exact nature of the input power.
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