Specification • The JAS mechanical structure shall be designed to a prescribed Interface Control Drawing (ICD) as required by the application. Requirements called out in the ICD should include an answer to most of the design considerations in this specification.
Specification
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JAS Command Packet
Specification • JAS Command Packet All fields are shown in bits. The variable length application data field must be an integral number of bytes for the packet error control calculation. Spare bits may be used for padding purposes at the end to ensure the packets are an even number of bytes in...
JAS Efficient Exchange Protocol
Specification • The JAS Efficient Exchange Protocol (JEEP) uses the lower level SpaceWire data link layer to provide data delivery services to one or more higher level application processes. This document specifies the functional requirements for JEEP but does not specify the interfaces to the lower or higher level processes, which may...
JAS Packet Definition
Specification • The JAS Packet is built upon CCSDS and PUS packet standards. Some modifications were made to enforce a layered architecture in order to promote reuse of applications. The following sections will highlight these differences in more detail.
JAS Packet Service
Specification • Error: unable to migrate element with tag="" The CCSDS/SOIS subnetwork packet service standard can be referenced if a generic packet service is needed. The JAS Packet Service is an implementation of the CCSDS/SOIS packet service, specifically tailored for the JAS packet. The following diagram shows how the JAS Packet Service...
JAS Packets
Specification • Applications require a messaging format to allow them to communicate with each other. Legacy programs may already have a messaging format that they prefer to use. There is nothing that precludes any of the JAS communication protocols or data links from supporting these formats. The JAS Packet was developed for...
JAS Reliable Data Delivery Protocol
Specification • The JAS Reliable Data Delivery Protocol (JRDDP) uses the lower level SpaceWire data link layer to provide reliable packet delivery services to one or more higher level host application processes. This document specifies the functional requirements for JRDDP but does not specify the interfaces to the lower or higher level...
JAS Specific Services Definitions
Specification • The JAS specific services will be based on the PUS service concept. Most PUS services were created for communication between onboard applications and ground systems. JAS adds additional services to support more onboard payload functions. [Placeholder: Additional development is needed to define the JAS specific services to support onboard payload...
JAS Telemetry Packet
Specification • JAS Telemetry Packet All fields are shown in bits. The variable length application data field must be an integral number of bytes for the packet error control calculation. Spare bits may be used for padding purposes at the end to ensure the packets are an even number of bytes in...
JEEP Packet Format
Specification • All JEEP packets shall include a fixed length header, followed by a variable length payload. The figure below shows how the JEEP packet is embedded within the standard SpaceWire packet. Note that while a SpaceWire packet may have zero or more destination addresses before the JEEP header, the JEEP requires...
JRDDP Packet Format
Specification • All JRDDP packets shall include a variable length header, followed by a variable length payload, followed by a 2-byte CRC Trailer. The figure below shows how the JRDDP packet is embedded within the standard SpaceWire packet. Note that while a SpaceWire packet may have zero or more destination addresses before...
Junction Temperatures
Specification • The design shall show positive margin against thermal design so junction temperatures do not exceed maximum component values for worst case orbits at beginning (BOL) and end of life (EOL).
Life
Specification • The JAS mechanical structure shall be constructed of materials capable of performing for the necessary mission life time (for example, 3 years storage in an inert atmosphere and 10 years on orbit). This analysis will require extensive parts and materials screening and processing.
Loads
Specification • Loads shall be determined per the program Strength Qualification Plan.
Logical Connections
Specification • Upon initialization all TEPs shall be in the CLOSED state. OPEN/RESET Command When a transmit TEP transitions to the ENABLED state (as commanded by the host), it shall send an OPEN/RESET packet to its receive TEP and initiate an acknowledgement timer. CLOSE Command When a transmit TEP transitions to the...
MAGE Strength
Specification • The JAS mechanical structure shall consider tooling to hold it while installing and transporting components. Features for mounting the hardware that supports the system shall be included. A static 4 G load shall be used with positive margins per this document. Mechanical Aerospace Ground Equipment (MAGE)
Margins of Safety
Specification • Margin of Safety (MS) is defined as MS = 1/R - 1, where R is the ratio of the factored applied load (or stress) to the allowable load (or stress) and shall be greater than 0. Margin of Safety Calculation The specific failure theory used to determine the allowable load...
Mass Properties
Specification • The JAS mechanical structure shall attempt to optimize mass, center of gravity, and moments of inertia.
Material Properties and Allowables
Specification • The JAS mechanical structure design of the metallic parts shall use A Basis allowables from MIL-HDBK-5 or equivalent. The design of the composite parts shall use B Basis allowables generated using the methodology in MIL-HDBK-17 or equivalent.
Materials
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,...
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
Memory Access Service
Specification • Error: unable to migrate element with tag="" The following diagram shows how the JAS Memory Access Service fits into the overall communication stack. The Memory Access Service provides a standard interface to applications that allows them to remotely access memory on a JAS node across a communication link. This is...
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...
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