telemetry storage systems: a comparison of mission...

Telemetry Storage Systems:Telemetry Storage Systems:A Comparison of Mission ApproachesA Comparison of Mission Approaches

Robert Klar, Scott Miller and Paul WoodRobert Klar, Scott Miller and Paul WoodFSW FSW 20162016

(Not ITAR Restricted)(Not ITAR Restricted)

OverviewOverview

�� MagnetosphericMagnetospheric MultiscaleMultiscale (MMS)(MMS)–– Overview and Storage ApproachOverview and Storage Approach

�� Cyclone Global Navigation Satellite System (CYGNSS)Cyclone Global Navigation Satellite System (CYGNSS)–– Overview and Storage ApproachOverview and Storage Approach–– Overview and Storage ApproachOverview and Storage Approach

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MMS MissionMMS Mission

�� MagnetosphericMagnetospheric MultiscaleMultiscale(MMS)(MMS)

–– Constellation of 4 identically Constellation of 4 identically spacecraft in variably spaced spacecraft in variably spaced tetrahedron (7 km to several 100 km)tetrahedron (7 km to several 100 km)

•• Ground contacts must be Ground contacts must be multiplexed in time in order to multiplexed in time in order to retrieve data from all 4 spacecraft retrieve data from all 4 spacecraft retrieve data from all 4 spacecraft retrieve data from all 4 spacecraft each dayeach day

�� Objective: To discover the detailed physics Objective: To discover the detailed physics of the reconnection process including its of the reconnection process including its controlling factors, its spatial distribution, controlling factors, its spatial distribution, and its temporal behavior.and its temporal behavior.

https://mms.gsfc.nasa.gov

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�� Solving Solving MagnetosphericMagnetosphericAcceleration, Acceleration, Reconnection, and Reconnection, and Turbulence (SMART) Turbulence (SMART) Instrument SuiteInstrument Suite

–– Central Instrument Data Central Instrument Data

Fields CEB A

FPI IDPU A

CIRASA

Data/LVDSSpW

CIDP +28V

+28V

+28V

Data/LVDS

ActuatorsActuators

+28V

+28V

PSEESA

Actuator +28V

–– Central Instrument Data Central Instrument Data Processor (CIDP)Processor (CIDP)

•• SPARC ProcessorSPARC Processor•• Stores science data Stores science data

for the Instrument for the Instrument SuiteSuite

•• Instruments can Instruments can collect far more data collect far more data than can be sent via than can be sent via downlinkdownlink

CIDP A(1 of 2 blocks shown)

FEEPS 1

FEEPS 2

EIS

HPCA

Data/RS422

CIDP +28V

+28VData/LVDS

+28V

ASPOC 1

ASPOC 2

+28VData/LVDS

+28VData/LVDS

Data/RS422+28V

Data/RS422+28V

Inst. +28VA

CIRASB

PSEESB

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�� Highest resolution data is voluminousHighest resolution data is voluminous–– Collect best quality data for region of interestCollect best quality data for region of interest

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MMS Storage Approach MMS Storage Approach -- CFDPCFDP

�� CCSDS File Delivery ProtocolCCSDS File Delivery Protocol–– CFDP is a protocol for transferring files to and from a spacecraft CFDP is a protocol for transferring files to and from a spacecraft

memorymemory

•• Files can be transferred Files can be transferred reliablyreliably, where it is guaranteed that all data will be , where it is guaranteed that all data will be delivered without error, or unreliably, where a best effort delivery capability is delivered without error, or unreliably, where a best effort delivery capability is provided.provided.provided.provided.

•• Files can be transmitted through at various speeds through different link Files can be transmitted through at various speeds through different link types and through intermediate relay spacecraft.types and through intermediate relay spacecraft.

–– Class 1 Class 1 -- Unreliable transferUnreliable transfer

–– Class 2 Class 2 -- Reliable transferReliable transfer

–– Class 3 Class 3 -- Unreliable transfer Unreliable transfer via one or more waypoints in seriesvia one or more waypoints in series

–– Class 4 Class 4 -- Reliable transfer Reliable transfer via one or more waypoints in seriesvia one or more waypoints in series

•• File transfer can be initiated automatically by the onboard entity or manually File transfer can be initiated automatically by the onboard entity or manually by ground control.by ground control.

Since we do not relay through intermediate waypoints, only Class 1 and Class 2 service are implemented on the MMS CIDP

entity. In order to maximize the science data return, file transfer is initiated by the entity onboard.

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Why use CFDP?Why use CFDP?

�� Downlink is a precious resourceDownlink is a precious resource–– Ground contacts are limited Ground contacts are limited -- make the most of themmake the most of them–– Lost data can mean lost opportunities for scienceLost data can mean lost opportunities for science

�� Operations costs are a significant part of the mission Operations costs are a significant part of the mission budgetbudget

–– CFDP helps to automate routine data delivery operations to CFDP helps to automate routine data delivery operations to –– CFDP helps to automate routine data delivery operations to CFDP helps to automate routine data delivery operations to simplify operations, thereby providing some promise for reducing simplify operations, thereby providing some promise for reducing these coststhese costs

�� Standard protocol encourages interoperabilityStandard protocol encourages interoperability–– Benefit realized as CFDP is adopted on more missionsBenefit realized as CFDP is adopted on more missions

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�� CIDP Mass Memory is Virtual CIDP Mass Memory is Virtual FilestoreFilestore�� No File SystemNo File System

�� Partitioned into 4 MB fixedPartitioned into 4 MB fixed--size filessize files

�� Flash buffers managed in poolsFlash buffers managed in pools�� InIn--useuse

�� FreeFree

�� HeldHeld�� Available for downlinkAvailable for downlink

�� Downlink may occur while in region of Downlink may occur while in region of interestinterest

�� HighlightsHighlights

–– CCSDS Space Packet Protocol CCSDS Space Packet Protocol

is underlying protocolis underlying protocol

–– Class 2 (Reliable) with Class 2 (Reliable) with

Deferred NAKDeferred NAK

–– Class 1 (Unreliable) is backupClass 1 (Unreliable) is backup

CFDP Library

Communications System

Protocol Entity MIB(Config)

User Application

Virtual Filestore

�� Use NASA GSFC CFDP Use NASA GSFC CFDP

LibraryLibrary

�� Implements State Implements State

MachinesMachines

�� Interfaces to User Interfaces to User

Application, Virtual Application, Virtual

FilestoreFilestore and and

Communications SystemCommunications System

interestinterest

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RTEMS Real Time Operating System

Command

and Control

CSC

Instrument

Data

Processing

CSC

Data Data

Steering CSC

Trigger Trigger

Control CSU

Serial

Interfaces

Data Steering

Steering

ControlControl

& Status

Control &

Status Telecmds

DQ (other S/C)

Telemetry

CIDP

HK

Mass Memory

Controls

Mass

Memory

Telemetry

Telecmds

Telemetry


Multiplex

PDU/Packet Formatting

Frame Formatting

Spacecraft

Interface

CSC

Spacewire

OutOut

FIFO

DQ

& HK

Telemetry Telecommands

HKControlsPlayback/

Transfer

Control

CFDP

CSU

CFDP File Directive PDU

Packets

Real-time Telemetry

Packets

InIn

FIFO

Telecommand

Packets

AOS Transfer Frames

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File-data (one

chunk at a

time)

Meta-

data

Phase 1 Send Phase 1 Send

the file oncethe file once

Phase 2 Phase 2

HandoffHandoff

EOF*Retransmit

missing data

Phase 3 Phase 3

Fill gapsFill gaps

Ack-

Finished

Phase 4 Shut Phase 4 Shut

downdown(i.e., File System (i.e., File System

Deletes File)Deletes File)

Message sequence

CIDP


* Timers are used to ensure retransmission of the EOF, Nak, and Finished messages as

required. The Nak message reports all missing data (including Metadata).

Ack-EOF Nak* Finished*

COMM

SpW TC for

every Frame

Sent

GROUND

Spw TC for

every Frame

Sent

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�� Application InterfaceApplication Interface–– Calls to CFDP LibraryCalls to CFDP Library

•• Set Configuration (i.e. MIB) Set Configuration (i.e. MIB) DynamicallyDynamically

•• Give Request to LibraryGive Request to Library•• Give PDU to LibraryGive PDU to Library•• Control delivery rate for Control delivery rate for

PDUsPDUsFunction invoked to send

�� Virtual Virtual FilestoreFilestore InterfaceInterface–– Callbacks from libraryCallbacks from library

•• File I/O primitivesFile I/O primitivesfopen(), fseek(), fread(), fwrite(), feof(), fclose()

•• Other Other PosixPosix primitivesprimitivesrename(), remove(), tmpnam()


Function invoked to send next data PDU

•• Register callbacks for Register callbacks for IndicationIndication

–– Callbacks from LibraryCallbacks from Library•• CFDP IndicationsCFDP Indications

�� Communication System Communication System InterfaceInterface

–– Callbacks from LibraryCallbacks from Library•• Open PDU channelOpen PDU channel•• Channel Ready?Channel Ready?•• Send PDU on channelSend PDU on channel

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�� Virtual Virtual FilestoreFilestore InterfaceInterface–– Callbacks from libraryCallbacks from library

•• File I/O primitivesFile I/O primitivesfopen() - transfer file to Output Buffer and optionally perform compression

Set start offset to 0

Return corresponding buffer index

fread()

�� Communication System InterfaceCommunication System Interface–– Callbacks from LibraryCallbacks from Library

•• Open PDU channelOpen PDU channelInitiate HW handshaking

•• Channel Ready?Channel Ready?HW ready if SpW link is up

•• Send PDU on channelSend PDU on channelSend File Directive PDUs to Data Formatter to include in VC stream

Ignore File Data PDUs – these


fread()

If first call after fopen() or fseek(), then initiate HW playback

Simply advance read count

fseek()

Set HW start offset for retries

fwrite()

Not allowed

Ignore File Data PDUs – these are being generated by the

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�� Use Virtual FilenamesUse Virtual Filenames–– Mass Memory Buffer Index + TimestampMass Memory Buffer Index + Timestamp

�� Hardware forms File Data PDUsHardware forms File Data PDUs�� Software forms and responds to File Directive PDUsSoftware forms and responds to File Directive PDUs�� Hardware/Software SynchronizationHardware/Software Synchronization

–– Hardware provides for configuration of start and end offsets in Hardware provides for configuration of start and end offsets in


–– Hardware provides for configuration of start and end offsets in Hardware provides for configuration of start and end offsets in Mass Memory BufferMass Memory Buffer

•• Aligned on segment boundaries (i.e. ~ 1 KB)Aligned on segment boundaries (i.e. ~ 1 KB)–– Once playback is initiated, HW transfers File Data PDUs until Once playback is initiated, HW transfers File Data PDUs until

completedcompleted•• Interrupt wakes up SW task when a number of segments Interrupt wakes up SW task when a number of segments

have been transferredhave been transferred•• SW task calls CFDP Library rate control function in a loop to SW task calls CFDP Library rate control function in a loop to

match up file read pointer with those segments sent by HWmatch up file read pointer with those segments sent by HW

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CYGNSS MissionCYGNSS Mission

�� Cyclone Global NavigationCyclone Global Navigation Satellite Satellite System (CYGNSS)System (CYGNSS)

�� Constellation of 8 lowConstellation of 8 low--earth earth orbiting microsatellites that orbiting microsatellites that receive both direct and receive both direct and reflected signals from the reflected signals from the Global Positioning System Global Positioning System (GPS) satellites(GPS) satellites

�� Direct signals pinpoint Direct signals pinpoint

Objective:Objective:

Study the relationship between ocean surface properties, moist atmospheric Study the relationship between ocean surface properties, moist atmospheric

thermodynamics, radiation and convective dynamics, to determine how a tropical thermodynamics, radiation and convective dynamics, to determine how a tropical

cyclone forms and strengthens.cyclone forms and strengthens.

�� Direct signals pinpoint Direct signals pinpoint satellite positions, while the satellite positions, while the reflected signals respond to reflected signals respond to the ocean surface roughness, the ocean surface roughness, which can be used to derive which can be used to derive wind speedwind speed

http://clasp-research.engin.umich.edu/missions/cygnss

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CYGNSS MissionCYGNSS Mission

http://clasp-research.engin.umich.edu/missions/cygnss

The 8 CYGNSS microsatellites are at an inclination of 35 degrees and are each capable of

measuring 4 simultaneous reflections, resulting in 32 wind measurements per second

across the globe. Ground tracks for 90 minutes (left) and a full day (right) of wind samples

are shown above.

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CYGNSS Storage Trade StudyCYGNSS Storage Trade Study

Considerations CFDP Custom Packet Replay

Cost to Design No Impact Minimal Negative Impact

�� To CFDP or not to CFDP?To CFDP or not to CFDP?

�� In contrast to MMS which had long contacts (1 hour / day), CYGNSS has much In contrast to MMS which had long contacts (1 hour / day), CYGNSS has much shorter contacts (10 minutes / two days).shorter contacts (10 minutes / two days).

�� USN does not have bandwidth to relay playback data in realUSN does not have bandwidth to relay playback data in real--timetime

�� NoNo substantial benefit to using CFDP in this casesubstantial benefit to using CFDP in this case

Cost to Design No Impact Minimal Negative Impact

Cost to Implement in FSW Moderate Negative Impact Moderate Negative Impact

Cost to Implement in EGSE Moderate Negative Impact Minimal Negative Impact

Ground System and

Operations Software

Major Negative Impact Minimal Negative Impact

FSW Size Moderate Negative Impact Minimal Negative Impact

FSW Processor Load Moderate Negative Impact Minimal Negative Impact

Downlink Rate Moderate Negative Impact No Impact

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CYGNSS Storage ApproachCYGNSS Storage Approach

�� Hybrid Hardware/Software ImplementationHybrid Hardware/Software Implementation–– Use CCSDS Space Packet Protocol without CFDPUse CCSDS Space Packet Protocol without CFDP

–– Simple Sequential Simple Sequential Input/OutputInput/Output

�� HardwareHardware

�� Does playback heavy liftingDoes playback heavy lifting

�� Maximizes downlink*Maximizes downlink*

�� Read back CCSDS Space Read back CCSDS Space

�� SoftwareSoftware

�� Does recording heavyDoes recording heavy--liftinglifting

�� Command ERASE of Flash Command ERASE of Flash blocksblocks�� Read back CCSDS Space Read back CCSDS Space

PacketsPackets

�� Formats packets into frames Formats packets into frames and ultimately CADUsand ultimately CADUs

�� One block at a timeOne block at a time�� Interrupt software when Interrupt software when

block playback completeblock playback complete

�� Write complete pages of Write complete pages of FlashFlash

�� Flash blocks only contain Flash blocks only contain complete packets to complete packets to facilitate hardware facilitate hardware playbackplayback

�� TracksTracks bad blocksbad blocks

�� Chains together consecutiveChains together consecutiveblocksblocks for playbacksfor playbacks

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* - A hardware implementation of the CFDP protocol would be much more complex.


ENG_STORED_DIAGSCI_STORED_NOM SCI_STORED_RAWFlash Block W

Flash Block X + 1 Flash Block Y + 1 Flash Block Z + 1

Contains a single ENG_FILL

packet that is used to flush

the VCDU buffer out of the

hardware at the conclusion

of any TLM playback

First Flash Block

�� CCSDS Space Packets stored in partitions that consist of sequential blocks of Flash CCSDS Space Packets stored in partitions that consist of sequential blocks of Flash memorymemory

ENG_STORED_NOM

Nominal Engineering

Played Back through

FPGA on VC2

ENG_STORED_DIAG

Diagnostic Engineering

Played Back through

FPGA on VC2

SCI_STORED_NOM

Nominal Science (DDMs)

Played Back through

FPGA on VC3

SCI_STORED_RAW

Raw IF Science

Played Back through

FPGA on VC3

Flash Block W

Flash Block X Flash Block Y Flash Block Z Last Flash Block

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Next Block

To Be

Recorded

uint32_t

Block just

before

Next Block to

be Played

Back

uint32_t

Block Area

Start Index

uint32_t

Block Area

Length

uint32_t

Next Record

Page

uint32_t

Number of

Bytes Buffered

uint32_t

Overwrite

Status

uint32_t

Ticking Byte

Counter

uint32_t

Engineering

Stored

Nominal

[Block

Index]

[Block Index] [Block Index] [Block Index] [Page Number] [Number of

Bytes]

[Overwrites

Allowed]

[Byte Counter]

CYGNSS Storage ApproachCYGNSS Storage Approach�� Data Structures Data Structures -- Flash Allocation Table (FAT)Flash Allocation Table (FAT)

�� Track playback and record pointers for circular buffersTrack playback and record pointers for circular buffers

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Engineering

Stored

Diagnostic

[Block

Index]


Bytes]

[Overwrites

Allowed]

[Byte Counter]

Science Stored

DDM

[Block

Index]


Bytes]

[Overwrites

Allowed]

[Byte Counter]

Science Stored

RAW

[Block

Index]


Bytes]

[Overwrites

Allowed]

[Byte Counter]


Block N+1

Block N+2

Block N+3

Block N+4 s = size of

telemetry type

record_blk

EMPTY!

record_blk points to the block that is to be written next.

playback_blk+1 points to the block that is to be played back next.

If playback_blk+1 = record_blk, then the type is EMPTY (nothing to playback).

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Block N+4

Block N+5

Block N+s-2

Block N+s-1

…

telemetry type

partition in

blocks

playback_blk

Block N+1

Block N+2

Block N+3

Block N+4 s = size of

telemetry type

record_blk points to the block that is to be written next.

playback_blk+1 points to the block that is to be played back next.

If record_blk = playback_blk, then the type is FULL (nothing to record).

FULL!


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Block N+4

Block N+5

Block N+s-2

Block N+s-1

…

telemetry type

partition in

blocks

playback_blk

record_blk

Erase Counts

uint32_t

Block Status

uint32_t

Block #1 [Erase Count 1] [NOT-BAD / BAD]




Size =

128 kB

MRAM

CYGNSS Storage ApproachCYGNSS Storage Approach�� Data Structures Data Structures -- Flash Block Table (FBT)Flash Block Table (FBT)

�� Track number of ERASE cycles and bad blocksTrack number of ERASE cycles and bad blocks

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….continued….

MRAM

SummarySummary

�� MagnetosphericMagnetospheric MultiscaleMultiscale (MMS)(MMS)–– Used CFDP as a frontUsed CFDP as a front--end for a primitive file systemend for a primitive file system

–– Reliable file transfer provided in the protocolReliable file transfer provided in the protocol

–– Worked well for daily contacts of about 1 hourWorked well for daily contacts of about 1 hour

�� Cyclone Global Navigation Satellite System (CYGNSS)Cyclone Global Navigation Satellite System (CYGNSS)–– Used a simple sequential record/playback approachUsed a simple sequential record/playback approach

–– Reliable file transfer not provided by the protocol but loss is Reliable file transfer not provided by the protocol but loss is tolerabletolerable

–– Expect to work well for short contacts where playback data is Expect to work well for short contacts where playback data is buffered by USN and not relayed in realbuffered by USN and not relayed in real--time to mission operationstime to mission operations

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Questions?Questions?

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