S-band Telemetry Description DMC 211 October 2015

October 2015DMC 2112 Objectives The objectives of this course are to introduce the Trainee to the S-band Subsystem, its functions and capabilities, and details on how data is downlinked through S-band –Main focus is the contents and structure of the Essentials, Housekeeping 1 and Housekeeping 2 Telemetry Packets

October 2015DMC 2113 Outline Objectives S-band Overview S-band Transfer Description S-band Telemetry Packet Description S-band Pre-empted Packets Counter Dependent Parameters Packet Examples Summary References Acronyms

October 2015DMC 2114 S-band Overview S-band provides the command/monitor interface between the ISS and the United States Ground Segment (USGS) –This includes reception of Audio, commands, files and data uplinked to the ISS –Distribution of Audio, status, files, and data from the ISS S-band is controlled through the C&C MDM –All of the S-band hardware is attached to the C&C MDM Control Buses –There are two S-band strings for redundancy starting at 9A All Payload and Payload Support System commands are uplinked through S-band and all Payload Support System Status is downlinked via S-band

October 2015DMC 2115 S-band Interface Diagram * S-band String 2 is on the P6 Truss Segment through 11A before it is moved to the P1 Truss where it will then reside on CB CT-2 C&C MDM ACBSP-2XPNDR-2 U/L Commands, Files, Data D/L Command Responses, Files, Status Data CB CT-3* Audio ACBSP - Assembly Contingency Baseband Signal Processor ACRFG - Assembly Contingency Radio Frequency Group XPNDR - Transponder ACBSP-1XPNDR-1ACRFG-1 CB CT-1

October 2015DMC 2116 S-band Telemetry Contents S-band downlink contains command responses (for rejected commands), system status data, up to two crew audio channels, file and data dump data, and “Payload Safety data” –Audio data is formatted in Bitstream Virtual Channels –Digital data is formatted in CCSDS Packets Audio has a direct interface to the S-band Assembly Contingency Baseband Signal Processor (ACBSP) while all of the digital data is transferred through the C&C MDM for Downlink –The ACBSP performs the same function for S-band as the Ku Comm Unit performs for Ku-band (from the downlink perspective)

October 2015DMC 2117 S-band Downlink Transfers S-band telemetry will be used by the POIC to monitor the status of the Payload Support Systems the POIC is operating –All Payload Support System S-band status data used by the POIC will be contained in 3 separate Packets each of which uses the same APID but a different Format ID as specified in Word 7 of the S-band Telemetry Packet (reference CCSDS Training Course) The Essentials Packet contains most of the critical component status The Housekeeping 1 (HK 1) Packet contains status for Built in Test parameters and other non-critical status for some of the components and primary status for some of the components The Housekeeping 2 (HK 2) Packet contains status for Built in Test parameters and other non-critical status for some of the components

October 2015DMC 2118 Packet Construction Description The C&C MDM collects status from all of the System Devices (including the Payload MDM, APSs and PEHGs) and keeps the current status in its Current Value Table (CVT) –The data is placed within packets based on the “Profiles” built into the software during the Mission Build Facility (MBF) Command Control Software (CCS) Build Process Profiles define the contents of the Packet - the parameters contained within the Packets and their location –Program Unique Identifiers (PUI) are used to reference the parameters stored in the CVT which are to be placed in specific locations within the CCSDS Packets (Essentials, HK 1, and HK 2) PUIs are used by the software to keep track of where in memory data from the components are being stored and to build the Profiles –PUIs are not used onboard, only during the software build process

October 2015DMC 2119 Profile Description Profiles define (by PUI) the parameters and/or groups of parameters and their location within a Packet - MBF converts the “Word PUI” reference to a memory address MBF uses the Word PUI as a pointer to build the flight software profile - The Profile is nothing more than an array of memory addresses - Ground telemetry databases use the PUIs to process (or decomutate) the packet n CCSDS Headers Parameter 1 (16 bits) is represented by PUI X which is converted by MBF to Memory Address x01FB (for example), Parameter 2 (16 bits) is represented by PUI Y and has an offset into this packet of 16 bits and is stored in the CVT at memory address 0x1FC (for example)

October 2015DMC S-band Telemetry Packet Description Each Packet (Essentials, HK1 and HK2) is generated once every 100 msec (Processing Frame) The contents of the Packets contain 10 Hz, 1 Hz and 0.1 Hz data (a.k.a. Rate Groups) –10 Hz data is repeated in every Packet –1 Hz data is repeated in every 10th Packet –0.1 Hz data is repeated in every 100th Packet This means that for Essentials, HK 1 and HK 2 there are 100 Unique Packets which are repeated every 10 seconds This kind of Packet construction allows the maximum use of the limited S-band bandwidth (192 Kbps for downlink including overhead, 159 Kbps without overhead)

October 2015DMC S-band Telemetry Packet Description Examples of data contained in the Rate Groups –10 Hz data will contain the “Frame Count” (Processing Frame ID in the Secondary Header - Word 8) which uniquely identifies the Packet within the 100 Packet stream (range from 0-99) Time Stamp in the CCSDS Packet Secondary Header would be another example of 10 Hz data No 10 Hz data is contained within the Essentials Packet data field –1 Hz data includes critical parameters which require constant update for monitoring by the ground including Temperatures, Error Indicators and some component configuration status –0.1 Hz data may include component configuration status, Built in Test parameters, other status which does not change frequently

October 2015DMC S-band Telemetry Packet Description Structure of an S-band Telemetry Packet has 8 Words for the Header which contains fields that define the contents of the Packet –Version ID Field defines the Packet CCS S-band Telemetry Format (5SC, 6SC, etc.) which is usually specific to a stage or Flight –Format ID Field defines the contents of the data within the packet as an Essentials, Housekeeping (HK) 1, HK 2, Normal Data Dump, Extended Data Dump, RSA Pre-emptive Packet, etc –Frame ID is the actual Processing Frame Count Essentials, HK1 and HK2 Packets consist of 100 uniquely formatted packets specific to a CCS S-band Version repeating over a 10 second Time period (Major Frame) Frame ID directly corresponds to the Processing Frame Counter (range 0-99)

October 2015DMC S-band CCSDS Telemetry Packet Field ID Word # MSB LSB Primary Header 1 Version # (000) Type Sec Hdr Flg (1) Application Process ID (APID) Seq Flags Packet Sequence Count 2 Packet Length (# octets-1 following this field) 3 Secondary Header Time (MSBs of Coarse Time) 4 Time (LSBs of Coarse Time, LSB=1second) 5 Fine Time Check Word 6 Time ID ZOE TLM Packet Type Pckt ID (6 bits - Ess, HK1,HK2, Data Dump, etc) 7 Spare (0) Cmd/ Data Pkt (0) Version ID (4 bits Fligh Specifc) Frame ID (7 bits) 8 Spare (9 bits) Element ID

October 2015DMC Essentials Packet Description 8 Words Packet Headers 10 Hz Data 1 Hz Data 0.1 Hz Data 228 Words157 Words For this packet structure, the 1 Hz Data will be able to represent (228 Words * 10 Pckts/sec) 2280 unique words each second (the same parameters are telemetered each second) The 0.1 Hz rate group will be able to contain a maximum of (157 Words * 100 Pckts/10 sec) unique words over a 10 second time period (Major Frame)

October 2015DMC Packet Formats Based on the Downlink Technique Essentials, HK 1 and HK 2 each have unique profiles and are unique to the way the data is being downlinked –For example, the format of the Essentials Packet for Low Rate S-band is the same as that for High Rate S-band but different for downlinking via the Orbital Interface Unit (OIU) during docked operations of Visiting Vehicles (VV) –All of these downlink paths have different rates

October 2015DMC Certain Packets can be “Pre-empted” based on varying circumstances –For example the HK 1 Packet will be pre-empted (Delayed transmission) whenever MOD configures High Rate S-band for Extended Data Dump capability –Another example of a pre-empted packet would be HK 2 being pre-empted whenever a Ground based command is rejected by CCS resulting in CCS downlinking a Command Response Packet or Pre-emption by APM Telemetry packets –Essentials is the only one of the three S-band Packets used by the POIC which will not be pre-empted

October 2015DMC Counter Dependent Parameters All data in Essentials, HK 1 and HK 2 are “Counter Dependent” as defined in SSP 41154, Section –The Frame ID is the “counter” (correlates to the Processing Frame Counter) –Each of the 100 Essentials packets are distinguished from the other Essentials packets by the Frame ID as defined in Word 8 of the CCSDS Header (reference SSP 41154, Table ) The Packet containing a particular Processing Frame ID will contain unique data from the other 99 Processing Frames For example Frame ID 0 will always contain the exact same parameters but will only be downlinked once every 10 seconds (since there are 100 Processing frames) –This does not mean that the 1 Hz data being downlinked is not contained in another one of the processing frames (reference the 1 Hz data which will be repeated in Processing Frame 10, 20, 30, etc.) Frame ID consists of 7 bits to distinguish between each of the 100 Packets

October 2015DMC Essentials Packet Example Header E0E00 10 Hz1 Hz0.1 Hz Processing Frame ID 0 Header E1E01 1 Header E2E02 2 Header E3E03 3 Header E4E04 4 Header E5E05 5 Header E6E06 6 Header E7E07 7 Header E8E08 8 Header E9E09 9 Header E0E10 10 Header E1E11 11 Header E2E12 12

October 2015DMC Essentials Packet Example Header E8E88 10 Hz1 Hz0.1 Hz Processing Frame ID 88 Header E9E89 89 Header E0E90 90 Header E1E91 91 Header E2E92 92 Header E3E93 93 Header E4E94 94 Header E5E95 95 Header E6E96 96 Header E7E97 97 Header E8E98 98 Header E9E99 99 Header E0E00 00

October 2015DMC Upon completion of this course, the Trainee should have a basic understanding of the S-band Downlink transfers, the characteristics of the downlinked packets (Essentials, HK 1 and HK 2), pre-empting of the HK 1 and HK 2 packets, rate groups associated with each of the Packets, and definition of the term “Counter Dependent” –Counter Dependent means the contents of the Packet are defined by the Frame Counter which is contained in Word 8 of the CCSDS Packet Secondary Header

October 2015DMC References SSP contains a detailed description of the S-band telemetry packet formats and operations –This is the S-band Space to Ground ICD –The S-band High Rate Section for CCS (Section in Rev. B) is the most applicable section of the document to the POIC

October 2015DMC Acronyms ACBSPAssembly Contingency Baseband Signal Processor ACRFGAssembly Contingency Radio Frequency Group APIDApplication Processor Identifier APSAutomated Payload Switch C&CCommand and Control CCSCommand Control Software CCSDSConsultative Committee for Space Data Systems CVTCurrent Value Table D/LDownlink HKHousekeeping ISSInternational Space Station Ku Comm UnitKu band Communications Unit

October 2015DMC Acronyms LSBLeast Significant Bit MBFMission Build Facility MDMMultiplexer/Demultiplexer MSBMost Significant Bit OIUOrbital Interface Unit PEHGPayload Ethernet Hub Gateway POICPayload Operations Integration Center PUIProgram Unique Identifiers RSARussian Space Agency U/LUplink USGSUnited States Ground Segment VVVisiting Vehicle XPNDRTransponder