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| PUS Service | ||
| ## Space Packet Structure | ||
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| ### Packet Version Number | ||
| - Set to **0**, identifying it as a space packet (version 1 CCSDS packet). | ||
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| ### Packet Type Bit | ||
| - **0**: Telemetry packets. | ||
| - **1**: Telecommand packets. | ||
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| ### Secondary Header Flag | ||
| - Indicates the **presence or absence** of a secondary header: | ||
| - **Telemetry packets**: All include a secondary header, except spacecraft time packets. | ||
| - **Telecommand packets**: All include a secondary header, except CPDU command packets. | ||
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| ### Application Process ID (APID) | ||
| - **Uniquely identifies**: | ||
| - The source of telemetry packets. | ||
| - The destination of telecommand packets. | ||
| - Some values are reserved by CCSDS and unavailable for PUS services. | ||
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| ### Sequence Flags | ||
| - Unused by the protocol but set to **"11"** to indicate stand-alone packets. | ||
| - All packets in this Standard are **stand-alone packets**. | ||
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| ### Packet Sequence Count | ||
| - **Telemetry packets**: Incremented by 1 for each released packet and wraps at \(2^{14} - 1\). | ||
| - **Telecommand packets**: Use a sequence count or packet name to uniquely identify packets within a communication session. | ||
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| ### Packet Data Length Field | ||
| - Specifies the length of the **packet data field**: | ||
| - Value is **one less** than the number of octets in the data field. | ||
| - Total packet length = Packet data field length + 6 octets (primary header). | ||
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| ### Packet Data Field Structure | ||
| - **Telemetry Packets**: | ||
| - Secondary header. | ||
| - User data field. | ||
| - **Telecommand Packets**: | ||
| - Secondary header. | ||
| - User data field. | ||
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| - - - | ||
| ### Telemetry Packet Data Field | ||
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| #### Telemetry Packet Secondary Header | ||
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| 1. **Presence**: | ||
| - All telemetry packets, except spacecraft time packets, include a secondary header. | ||
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| 2. **Structure**: | ||
| - **Fields**: | ||
| - **Spacecraft Time**: Absolute, fixed-size. | ||
| - **PUS Version**: 4 bits, set to **2**. | ||
| - **Reference Number**: 4 bits, enumerated. | ||
| - **Message Type ID**: 8 bits, enumerated. | ||
| - **Service Type ID**: 8 bits, enumerated. | ||
| - **Message Subtype ID**: 8 bits, enumerated. | ||
| - **Message Counter**: 16 bits, unsigned integer. | ||
| - **Destination ID**: Application process user identifier. | ||
| - **Spare Field**: Optional, used to align header size to integral words. | ||
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| 3. **Time Reference**: | ||
| - **Status**: | ||
| - If capable, set to the status of the onboard time reference when tagging packets. | ||
| - If not capable, set to **0**. | ||
| - **Time Tag**: Stored in the time field of the header. | ||
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| 4. **Message Metadata**: | ||
| - **Type ID**: Set to the identifier of the report. | ||
| - **Counter**: | ||
| - If capable, set to the count of messages of this type. | ||
| - If not capable, set to **0**. | ||
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| 5. **Declaration Requirements**: | ||
| - Presence and bit-size of the spare field must be declared for each application process. | ||
| - Time field PFC (Packet Format Control) must align with the spacecraft's time service. | ||
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| #### Notes: | ||
| - The **PUS Version** indicates compliance with ECSS-E-ST-70-41C (version 2). | ||
| - The **Spare Field** adjusts header length and is application-specific. | ||
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| - - - | ||
| ### Telecommand Packet Data Field | ||
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| #### Telecommand Packet Secondary Header | ||
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| 1. **Presence**: | ||
| - All telecommand packets include a secondary header, except for CPDU command packets. | ||
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| 2. **Structure**: | ||
| - **Fields**: | ||
| - **Acknowledgement Flags**: 4 bits, controls reporting of request states: | ||
| - Bit 3: Successful acceptance by the destination application process. | ||
| - Bit 2: Successful start of execution by the destination application process. | ||
| - Bit 1: Progress reporting of execution. | ||
| - Bit 0: Successful completion of execution. | ||
| - **PUS Version**: 4 bits, set to **2**. | ||
| - **Message Type ID**: 8 bits, enumerated. | ||
| - **Service Type ID**: 8 bits, enumerated. | ||
| - **Message Subtype ID**: 8 bits, enumerated. | ||
| - **Source ID**: 16 bits, identifies the source application process. | ||
| - **Spare Field**: Optional, aligns header size to integral words. | ||
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| 3. **Request Metadata**: | ||
| - **Message Type ID**: Set to the identifier of the request. | ||
| - **Source ID**: Set to the source identifier of the issuing application process. | ||
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| 4. **Declaration Requirements**: | ||
| - Presence and bit-size of the spare field must be declared for each application process. | ||
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| #### Notes: | ||
| - The **PUS Version** reflects compliance with ECSS-E-ST-70-41C (version 2). | ||
| - Acknowledgement flags provide flexibility in managing state reporting for telecommand requests. | ||
| - The **Spare Field** ensures compatibility with system-specific requirements. | ||
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| - - - | ||
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| ## Comprehensive Overview of the Packet Utilization Standard (PUS) | ||
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| ### Introduction | ||
| The **Packet Utilization Standard (PUS)**, part of the ECSS standards, defines a framework for using telemetry and telecommand packets to monitor and control spacecraft subsystems and payloads. Initially developed by ESA in the 1990s, PUS has become a widely adopted standard for spacecraft operations, reducing mission complexity and enhancing interoperability. | ||
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| ### Purpose | ||
| PUS establishes a unified structure for spacecraft communication, enabling: | ||
| - **Remote Monitoring**: Observing spacecraft status and health. | ||
| - **Command Execution**: Controlling onboard systems and payloads. | ||
| - **Operational Consistency**: Standardizing processes across missions. | ||
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| ### Key Features | ||
| - **Modular Services**: Provides predefined services for common spacecraft operations. | ||
| - **Tailorability**: Allows customization for mission-specific needs. | ||
| - **Interoperability**: Facilitates seamless interaction between ground stations and spacecraft. | ||
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| ### Standardized Services | ||
| PUS defines various services, each targeting a specific operational aspect. Below is a list of core services: | ||
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| | No. | Service Name | | ||
| |-----|----------------------------------------------| | ||
| | 1 | Telecommand Verification | | ||
| | 2 | Device Command Distribution | | ||
| | 3 | Housekeeping and Diagnostic Data Reporting | | ||
| | 4 | Parameter Statistics Reporting | | ||
| | 5 | Event Reporting | | ||
| | 6 | Memory Management | | ||
| | 8 | Function Management | | ||
| | 9 | Time Management | | ||
| | 11 | On-board Operations Scheduling | | ||
| | 12 | On-board Monitoring | | ||
| | 13 | Large Data Transfer | | ||
| | 14 | Packet Forwarding Control | | ||
| | 15 | On-board Storage and Retrieval | | ||
| | 17 | Test | | ||
| | 18 | On-board Operations Procedure | | ||
| | 19 | Event-Action | | ||
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| ### Benefits | ||
| 1. **Reduced Complexity**: By standardizing telemetry and telecommand operations, PUS simplifies spacecraft design and development. | ||
| 2. **Flexibility**: Missions can select and implement only the services they require. | ||
| 3. **Reliability**: Standardized procedures enhance robustness and minimize operational errors. | ||
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| ### Tailoring for Missions | ||
| Each mission can adapt PUS to its unique requirements by selecting relevant services, adjusting parameters, and defining custom extensions when necessary. The process involves: | ||
| - Assigning specific Application Process Identifiers (APIDs). | ||
| - Configuring service capabilities, such as memory management areas or telemetry event thresholds. | ||
| - Documenting these decisions in a Space-to-Ground Interface Control Document (ICD). | ||
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| ### Applications | ||
| PUS is a cornerstone of ESA missions, including Rosetta, Envisat, and Integral. It is also suitable for missions with diverse architectures, from centralized systems to distributed networks onboard spacecraft. | ||
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