Integrating Payload Data
Interfaces with LADEE Flight and
Ground Software
Douglas Forman
Millennium Engineering and Integration
Company (MEI)
LADEE FSW Payload I/F Developer
NASA-Ames Research Center
Moffett Field, CA
Craig Pires – LADEE C&DH Lead (NASA)
Matthew Dortenzio – LADEE Mission Ops Manager (NASA)
Michael Logan – LADEE FSW Dev / Ops Gnd Ctl (LMSI)
Mark Shirley – LADEE SE / Ops (NASA)
1
Overview
• LADEE Payloads
–Data Interfaces/Protocols
• LADEE Flight Software
– Payload Interface Architecture
• FSW Payload Integration Strategy
– Decisions and Rationale
• Lessons Learned (good and bad)
–Lessons Being Applied
2
Model-Based “Common-Bus” LADEE
• cFE/cFS Software Bus
– “Common Bus” H/W
– Loosely Coupled Apps
• Model Based Evolution
– Simulink/Autocode
• Closed Loop Simulation
• Auto-coded to various
fixed-fidelity Targets
• CCSDS Cmd/Tlm
– ITOS Ground S/W
3
LADEE Payloads
• UVS (Ultra-violet Spectrometer)
– Draper Labs
• NMS (Neutral mass Spectrometer)
– Goddard Spaceflight Center
• LDEX (Lunar Dust Environment
Experiment)
– LASP (University of Colorado at
Boulder)
• LLST (Lunar Laser Space
Terminal)
Control Electronics and High
Speed FSW Tlm
– MIT Lincoln Labs
• Star Tracker Camera
4
General Payload Data Interface Requirements
• Protocol (H/W and S/W)
– Clocking of bits / Data Rate
– Flow Control
– Message Framing / Synchronization
– Checksum
– RS422 Termination
• Payload Commanding/Telemetry
– Live from Ground and/or Stored
• Large Data Upload/Download
– Firmware Update, Image Download
• Periodic Messages to Payloads from S/C FSW
– Time Tag (PPS)
– Attitude, Ephemeris
• S/C FSW Payload Data Interface SOH and Fault Detection Tlm
• S/C FSW Collects Unexpected “Out-of-Band” (OOB) Data
5
UVS Data Interface H/W Architecture
RS422
230.4K bits/sec
Cmd Data
cPCI
LADEE CPU Rad750
Tlm Data
LADEE
Avionics Interface Board
(FPGA Programmable)
UVS
(Ultra-Violet Spectrometer)
6
UVS Data Interface
•
•
•
Custom Protocol based on interactive modem commands
– COTS Product with Flight Heritage (from Draper Labs)
– Default ascii mode (two letter commands: “AA”, “BB”)
• Ack/Nack for all commands
Integration Advantages
– Easy to debug interactively in ascii mode
– After initial set-up, spectral data produced periodically
– Standard RS-422 UART
Integration Challenges
– Early integration with ITOS (TLYF) complex
• Variable length tlm/cmd layered over fixed size packet definition
• Accomplished due to proximity of payload team
• ITOS STOL used for full regression tests before CDR
– S/C FSW Design slightly more complex
• Knowing how many bytes to expect from UVS and wrap in
APPID
7
NMS Data Interface H/W Architecture
RS422
2M bits/sec
cPCI
LADEE CPU Rad750
Cmd Data
Cmd Clock
Cmd Frame Valid
Ready for Cmd
Tlm Data
Tlm Clock
Tlm Frame Valid
Ready for Tlm
LADEE
Avionics Interface Board
(FPGA Programmable)
NMS
(Neutral Mass
Spectrometer)
COTS from Goddard
8
NMS Data Interface
• Instrument Transfer Frame H/W S/W Protocol
– Legacy (COTS) Instrument from Goddard
• Integration Advantages:
– Large data transfers supported (32 bit size field)
– Frame synchronization in hardware
– Flow control supported by hardware
• Integration Challenges:
– No early integration with ITOS
• ITOS complexity: Checksum and variable length
• Variable length tlm/cmd layered over fixed size packet definition
• Payload Team used existing GSE ; not funded/motivated for early ITOS
– Integration with FSW more complex
• Add/strip CCSDS Wrappers to/from telemetry/commands
• Checksum Computations for Time Sync Message
– Required custom H/W FPGA (lag between issues and fixes)
9
LDEX Payload I/F H/W Architecture
RS422
57.6K bits/sec
PPS
cPCI
Cmd Data
Tlm Data
LADEE CPU Rad750
LADEE
Avionics Interface Board
(FPGA Programmable)
LDEX
(Lunar Dust Environment
Experiment)
New Development from
University of Colorado at
Boulder LASP
10
LDEX Data Interface
• CCSDS Packet cmd/tlm I/F (same as S/C FSW)
– New development from LASP UC Boulder
– FPGA only ; no software on instrument
• Integration Advantages
– Allows Cmd/Tlm “bent-pipe” pass-through in S/C FSW
– Easy integration with FSW and ITOS
– Standard RS-422 UART H/W
• Integration Challenges
– No synchronization pattern in packet
• Used fixed fields in CCDS Primary Header
– Required custom H/W for PPS Signal
• Synchronized with periodic Time Msg
11
LLST Data Interface H/W Architecture
LVDH High Speed FSW Tlm
40M bits/ sec
Optical Module
Tlm Data
Tlm Clk
Tlm Frame Valid
LADEE CPU Rad750
Ready for Tlm
Internal
Data
Comm
Optical Link
Cmd Data
Tlm Data
RS422
115.2K bits/ sec
LADEE
Avionics Interface Board
(FPGA Programmable)
Lasercom
Control Electronics (CE)
12
LLST CE Data Interface
• CCSDS Packet cmd/tlm I/F (same as S/C FSW)
– New Development from Lincoln Labs MIT
• Integration Advantages
– Allows Cmd/Tlm “bent-pipe” pass-through in S/C FSW
– Early integration with ITOS and FSW
• No other GSE used – ITOS used before FSW EDU in place
• Easy Integration of FSW generated mesages
– Standard RS422 UART H/W
• Integration Challenges
– Packet size limited to 64K bytes (16 bit size field)
• CFDP implemented in payload FSW for large data upload
– No synchronization pattern in packet
• Used fixed fields in CCDS Primary Header
– Small buffer in UART ; S/W Flow Control Required
13
LLST High Speed Lasercom Data Interface
• Downlink of FSW tlm through Lasercom
– Multiplexed in with Lasercom test data
• 40MB/sec difficult to fill using FSW
• Implemented on FPGA
– Direct access to 1 GB Flash (File System)
• Dumped File System Partitions (5)
– Re-assembled and mounted on ground
• Pros:
– All payload and S/C SOH data available
– Minimal impact to S/C processing
14
LLST High Speed Lasercom Implementation
• FPGA transmits Memory Dump chunks
– Takes Flash Mass Storage Start, Stop Addresses as input
• Dumps all memory between Start and Stop Addresses
– CPU interrupted when full Transmission completes
• Lasercom Device Driver (on CPU)
– Only cPCI access is writing Start/Stop addresses
– Restarts transmission if looping flag set
• Ground Commands
– Set Start, Stop Addresses
– Set/Unset looping flags
• Workstation (linux) Post Processing
–
–
–
–
FPGA (H/W) headers processed and stripped
Binary data written to file
File mounted on workstation as a dos partition
All files and directories accessible
15
ST Camera Data Interface H/W Architecture
RS422
115..2K bits/sec
Cmd Data
cPCI
LADEE CPU Rad750
Tlm Data
LADEE
Avionics Interface Board
(FPGA Programmable)
Star Tracker Camera
16
Star Tracker Data Interface
• CCSDS Packet cmd/tlm I/F (defined in Vendor ICD)
– COTS implementation of Packet Utilization Standard (PUS)
• Integration Advantages
– Allows Cmd/Tlm “bent-pipe” pass-through in S/C FSW
• Facilitated un-documented features
– (For example: Image Download)
– Image File Chunking built in to COTS cmd/tlm I/F
– Could have facilitated early integration with ITOS and FSW
• No ST ETU available for FSW testing (coded to ICD)
– Standard RS-422 UART H/W
• Integration Challenges
– ITOS Integration with PUS is tricky
• One APPID ; msg type in PUS header ; variable len pkts
– No synchronization pattern in packet
• Used fixed fields in Primary and PUS Headers
17
High Level “Loosely-Coupled” FSW Architecture
OFSW
Command
& Mode
Processor
Actuator
Manager
State
Estimator
Safe Mode
Controller
Attitude
Control
System
Thermal
Control
System
Power
Control
System
Battery
Charge
System
Memory
Scrub
Hardware
I/O
Software Bus
Scheduler
Stored
Commands
Health &
Safety
Memory
Manager
File
Manager
Memory
Dwell
CCSDS File
Delivery
Checksum
Housekeeping
Data
Storage
Telemetry
Output
Command
Ingest
System Support, O/S Services and Device Drivers
Telemetry
Gnd Cmds
KEY
Sensor Data
FSW Internal
FSW External
Limit
Checker
Simulink
Task
cFS
Task
Hand
Written
Task
18
Context of Payload I/O Apps
Command
& Mode
Processor
Attitude
Control
System
State
Estimator
Power
Control
System
Software Bus
Stored
Commands
Data
Storage
EPSIO
HWIO:
Payload I/O APPS
LDEXIO, UVSIO, NMSIO,
LLCDIO, HLLCDIO,
Star Tracker IO (STIO)
Telemetry
Output
Command
Ingest
Device Drivers
NOTE: Data Flow is shown between cFE Apps using
shaded dotted lines
for clarity.
The messages actually go through the Software Bus.
Power
Switch
19
Payload Initialization Message Flow
Command
& Mode
Processor
1a
State
Estimator
Attitude
Control
System
Power
Control
System
Software Bus
1
Stored
Commands
Data
Storage
EPSIO
HWIO:
Payload I/O APPS
LDEXIO, UVSIO, NMSIO,
LLCDIO, HLLCDIO, STIO
Telemetry
Output
Command
Ingest
Device Drivers
Initialization Sequence
1 – Achieve Attitude Mode to satisfy Payload Pointing Requirements
2 – Power on Payload Device
3 – Send Initialization Commands to Payload
Power
Switch
20
Payload Initialization Message Flow
Command
& Mode
Processor
State
Estimator
Attitude
Control
System
Power
Control
System
2a
Software Bus
2
Stored
Commands
Data
Storage
EPSIO
HWIO:
Payload I/O APPS
LDEXIO, UVSIO, NMSIO,
LLCDIO, HLLCDIO, STIO
Telemetry
Output
Command
Ingest
Device Drivers
Initialization Sequence
1 – Achieve Attitude Mode to satisfy Payload Pointing Requirements
2 – Power on Payload Device
3 – Send Initialization Commands to Payload
Power
Switch
21
Payload Initialization Message Flow
Command
& Mode
Processor
State
Estimator
Attitude
Control
System
Power
Control
System
Software Bus
Stored
Commands
Data
Storage
EPSIO
HWIO:
Payload I/O APPS
LDEXIO, UVSIO, NMSIO,
LLCDIO, HLLCDIO, STIO
Telemetry
Output
Command
Ingest
3b
Device Drivers
Initialization Sequence
1 – Achieve Attitude Mode to satisfy Payload Pointing Requirements
2 – Power on Payload Device
3 – Send Initialization Commands to Payload
Power
Switch
22
Live Payload Cmd/Tlm Message Flow
Command
& Mode
Processor
Attitude
Control
System
State
Estimator
Power
Control
System
Software Bus
1
Stored
Commands
Data
Storage
Other
Hardware
I/O
HWIO:
Payload I/O APPS
LDEXIO, UVSIO, NMSIO,
LLCDIO, HLLCDIO, STIO
1a
2
3a
Telemetry
Output
Command
Ingest
2a
Device Drivers
Live Cmd/Tlm Message Flow
1 – Build and Transmit Periodic (time/att) msg to payload
2 – Receive Ground Commands and pass to Payload
3 – Receive Payload Data and pass to Ground
3
23
Stored Payload Cmd/Tlm Message Flow
OFSW
Command
& Mode
Processor
Attitude
Control
System
State
Estimator
Power
Control
System
1
Software Bus
Stored
Commands
2
Other
Hardware
I/O
HWIO:
Payload I/O APPS
Data
Storage
3a
LDEXIO, UVSIO, NMSIO,
LLCDIO, HLLCDIO,
STIO
1a
Telemetry
Output
Command
Ingest
2a
Device Drivers
Stored Cmd/Tlm Message Flow
1 – Build and Transmit Periodic (time/att) msg to payload
2 – Receive Stored Commands and pass to Payload
3 – Receive Payload Data and pass to Data Storage
3
24
Downlink of Stored Payload Data
CCSDS FILE DELIVERY PROTOCOL (CFDP)
http://public.ccsds.org/publications/archive/727x0b4.pdf
CCSDS File
Delivery
(CFDP)
Software Bus
Re-transmit
Chunk
Requests
File
Chunks
LADEE Science Team
Telemetry
Output
Command
Ingest
System Support, O/S Services and Device Drivers
Telemetry
Gnd Cmds
SVN Server
Payload Data Files
25
LADEE Payload Integration Strategy
• Program Decisions
– No Payload (or ST) ETU/EDUs for FSW Testing
• Cost/Schedule Savings
– Travelling Road Show (Suitcase Simulator)
• FSW EDU travels to Payload Sites
• ST ETU available to FSW for only 3 days
– Payload Simulator (with H/W I/F) for FSW Testing
• Delivery/Fidelity inadequate for FSW development
• S/C FSW Decisions
– Minimal S/C FSW Processing of Payload Data
• “Bent-Pipe” pass through as much as possible
– Iterative FSW Development Coupled with TRS testing
• Payload Decisions
– H/W, S/W Interface Protocols
– Early Integration with ITOS Gnd S/W (or not)
26
LADEE Travelling Road Show (TRS)
• Ensure H/W I/F
compatibility before I&T
• Early EDU Integration at
Payload Sites
– Draft ICDs ; Working
Prototypes
– Iterative Maturation
– Logged Data Analyzed
• Left EDU/SDU at MIT
– Remote S/W Updates
No I&T or flight issues
27
Lessons Learned
• Bent-pipe pass-through of payload cmd/tlm advantageous
– Early “Test Like You Fly” Ground System Integration
– Simplifies S/C FSW logic
– Gives power (rope) to Payload Teams
– COTS/Legacy may not preclude modification
• Travelling Road Show was Effective
– No Payload H/W interface issues found in I&T
• Iterative Payload FSW ICD/Integration was Effective
– Minimal Payload-related FSW defects during I&T
• TRS Test Acceptance Criteria needed more scrutiny
– FSW device driver issue identified during S/C I&T
– Issue present, but not detected in TRS EDU testing
• More time (>3 days) with the Star Tracker ETU needed
– FSW Risks realized during S/C I&T and Flight
28
Lessons Being Applied
• Biosentinel – Deep Space Cubesat
– Re-using LADEE architecture (cFE/cFS, ITOS)
– 3 payloads: 2 new developments, one legacy provided by
JSC
• Ames responsible for all payload integration and testing
• Early-ish acquisition GNC H/W Engineering Units planned
– Includes Star Tracker
• Requiring CCSDS packets on new developments
• Existing JSC Linear Energy Transfer Payload
– Will add/strip CCSDS headers to/from tlm/cmd
• Planning to use ITOS interface before FSW/EDU ready
– Similar to LLCD CE strategy
– Test Like you Fly ASAP
29