Flight Software
Charlie Wildermann
Code 580.0
Mike Blau
Code 582
August 16-17, 2005
NASA’s Goddard Space Flight Center
19 - 1
FSW Requirement Flow-down
Mission Requirements
Document
Level 2
GN&C
Level 3
431-SPEC000063
FD
HiFi
C&DH
431-RQMT-000139
431-SPEC000062
431-SPEC000143
ACS
Analysis
ACS
Hardware
GN&C C&DH
GN&C
H/W ICD
GN&C
FSW Req
GN&C
Hardware
Level 4
FSW
Algorithms
NASA’s Goddard Space Flight Center
GN&C
FSW
431-RQMT-000168
C&DH
Hardware
C&DH
FSW Req
API
Instruments
431-ICD-000104…109
Instrument
Data ICDs
C&DH
H/W ICD
C&DH
FSW
19 - 2
Lunar Reconnaissance Orbiter (LRO)
FSW System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-58
Mission
Assurance
FSWR-1
The development of flight software for the LRO mission shall adhere to
the LRO Mission Assurance Requirements (MAR) document (TBD
number) and NPR-7150.2
Code 582 FSW development
processes will meet these
requirements
MRD-127
Software
Initialization
FSWR-5
The flight software shall provide a capability to effect a cold reset of the
flight software. The FSW shall initialize the C&DH hardware on cold
reset. This initialization shall include the RAD750 microprocessor, the
uplink and downlink hardware, the 1553 data bus, and the SpaceWire
data links. Errors detected on startup shall be handled as defined in the
LRO FDC ICD.
Mostly heritage FSW from SDO
and JWST
MRD-127
Software
Initialization
FSWR-85
Upon time-out of the watchdog timer, the flight software shall effect a cold
reset.
HW registers allow FSW to detect
reset type
MRD-127
Software
Initialization
FSWR-7
The flight software shall provide default values for proper initialization of
all key operating parameters following a power on or cold reset.
Default contents for all data tables
are stored in non-volatile memory
MRD-127
Software
Initialization
FSWR-9
The PROM based boot loader shall provide a capability to validate the
contents of the two EEPROM banks and run the code in the bank that
passes validation.
Redundant EEPROM banks are
used to mitigate soft-bit problems
MRD-122
Command Link
FSWR-12
The flight software shall support an uplink rate of 4 kbps
This rate is very easy with the
RAD750 processor
MRD-110 Data
Protocols
FSWR-11
The flight software command link shall utilize the CCSDS command path
service protocol; both COP-1 and bypass modes shall be supported
Heritage FSW from many
missions (SDO most recently)
MRD-110
Data Protocols
FSWR-32
The flight software shall format the housekeeping downlink telemetry as
recommended by the CCSDS AOS protocol
Heritage FSW from many
missions (SDO most recently)
NASA’s Goddard Space Flight Center
19 - 3
Lunar Reconnaissance Orbiter (LRO)
FSW System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-131
Absolute Time
Sequence
MRD-132
Relative Time
Sequence
FSWR-22
The flight software shall provide a stored command capability to receive,
store, and later execute sequences of commands
Heritage FSW from many
missions (SDO most recently)
MRD-50
Mission Phases
MRD-134 Diag
Telemetry
Support
FSWR-31
The flight software shall downlink sufficient housekeeping engineering
data to the ground to allow nominal spacecraft operation and
performance evaluation, as well as anomaly investigation and resolution
HK packet contents will be
documented early, then reviewed
by Ops and FSWM
MRD-123 Tm
Downlink
MRD-124 High
Rate Downlink
MRD-50
Mission Phases
FSWR-36
The flight software shall support downlink rates specified in the LRO
Mission Operations Concept Document (431-OPS-000042) section TBD.
S-band rates will be easy to
support. 100Mb Ka-band rate is
facilitated by SSR hardware DMA
MRD-118
Backup H/K
Storage
FSWR-50
The flight software shall store 2 hours of housekeeping data in local SBC
memory for later transmission to the ground station.
Data packets stored in files.
Code has Triana heritage
MRD-50
Mission Phases
FSWR-51
The flight software shall have the capability to record housekeeping
telemetry at a sampling rate of up to 32kb/sec
Recording rate for each HK
packet is table driven
MRD-110 Data
Protocols
FSWR-57
The flight software shall transmit stored data files to the ground using the
CFDP protocol (class 2 service).
CFDP code has been tested in
FSW tech lab.
NASA’s Goddard Space Flight Center
19 - 4
Lunar Reconnaissance Orbiter (LRO)
FSW System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-36 High Data
Rate
FSWR-64
The flight software shall communicate with the SSR over the
Spacewire Bus as specified in the SSR User's Guide (doc name and
number TBD)
I/F is similar to the NFS standard.
SSR is treated like a network file
server.
MRD-37 Data
Storage
FSWR-63
The flight software shall copy local housekeeping data files to the SSR.
Local storage is only for
emergencies. SSR can hold
many days worth of HK data.
MRD-37 Data
Storage
FSWR-65
The flight software shall store science data in files on the SSR,
formatted as specified in the instrument data ICDs.
File formats are unique to each
inst. Facilitates data analysis at
SOCs
MRD-35 Data
Storage
FSWR-68
The flight software shall use the 1553 bus to communicate with the
relevant Observatory subsystems as specified in the LRO Electrical
ICD (number TBD).
Heritage FSW from many
missions (SDO most recently)
MRD-114 Mission
Time Requirement
MRD-43 Time
Maintenance
FSWR-72
The flight software shall maintain an onboard spacecraft time driven
from the hardware mission elapsed timer (MET).
Heritage FSW from many
missions (SDO most recently)
MRD-42 Time
Knowledge
MRD-43 Time
Maintenance
FSWR-73
The flight software shall support the ability to synchronize the
spacecraft time clock to ground-based UTC.
FSW maintains an adjustable S/C
time correction factor (SCTF)
NASA’s Goddard Space Flight Center
19 - 5
Lunar Reconnaissance Orbiter (LRO)
FSW System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-20 Spacecraft
Safing
MRD-133
Telemetry
Monitoring
FSWR-79
The flight software shall possess sufficient onboard autonomy to allow
basic fault detection and correction.
Telemetry monitoring/response is
a standard FSW feature
MRD-128
Reprogrammability
FSWR-95
The flight software shall provide the capability to load code and data
from the ground to RAM
Allows checkout of FSW changes
before making them permanent
MRD-128
Reprogrammability
FSWR-96
The flight software shall provide the capability to load code and data
from the ground to non-volatile memory.
Allows FSW changes to be made
permanent after checkout
MRD-20
MRD-133
FSWR-113
The GN&C flight software shall monitor the health of each sensor and
actuator and provide status telemetry that can be monitored by the
C&DH flight software.
Manage GN&C Suite of
Electronics
MRD-41
FSWR-115
The GN&C flight software shall accept and validate spacecraft
ephemeris tables.
Validating critical ephemeris
uplinks is standard FSW practice.
MRD-41
FSWR-116
The GN&C flight software shall interpolate between spacecraft
ephemeris tables entries to compute the ephemeris for a specific time
Recent missions have used
propagators, however we have
access to a heritage interpolator.
NASA’s Goddard Space Flight Center
19 - 6
Lunar Reconnaissance Orbiter (LRO)
FSW System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-41
FSWR-117
The GN&C flight software shall accept and validate Lunar ephemeris
tables
Validating critical ephemeris
uplinks is standard FSW practice.
MRD-41
FSWR-118
The GN&C flight software shall interpolate between Lunar ephemeris
tables entries to compute the ephemeris for a specific time.
Recent missions have used
analytic models, however the
heritage s/c interpolator can be
used for lunar ephemeris.
MRD-49
FSWR-120
The GN&C flight software shall compute ground station position vectors
in J2000 GCI coordinates.
Similar to the problem of
computing a TDRSS vector.
MRD-49
FSWR-122
The GN&C flight software shall maintain an estimate of the 3 axis attitude
of the observatory with respect to the J2000 GCI coordinates.
Heritage FSW from many
missions (SDO most recently)
MRD-49
MRD-84
FSWR-126
The GN&C flight software shall support use of an uplinked target
quaternion table.
Heritage FSW from MAP.
MRD-14
MRD-49
MRD-84
FSWR-127
The GN&C flight software shall compute a Lunar Nadir Positive-X
Velocity (LNPXV) target quaternion.
Similar to the Earth-pointing
missions.
NASA’s Goddard Space Flight Center
19 - 7
Lunar Reconnaissance Orbiter (LRO)
FSW System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-10
MRD-97
FSWR-130
The GN&C flight software shall compute the total angular momentum in
the body reference frame.
Heritage FSW from many
missions.
MRD-8
MRD-90
MRD-91
FSWR-131
The GN&C flight software shall provide a CSS Sun Pointing attitude
control mode.
Heritage mode from many
missions. FSW implements
algorithms supplied by GN&C
MRD-9
MRD-49
FSWR-134
The GN&C flight software shall provide a science attitude control mode.
Heritage mode from many
missions. FSW implements
algorithms supplied by GN&C
MRD-10
MRD-88
MRD-97
FSWR-137
The GN&C flight software shall provide a Delta-H control mode.
Heritage mode from many
missions. FSW implements
algorithms supplied by GN&C
MRD-10
MRD-87
FSWR-140
The GN&C flight software shall provide a Delta-V attitude control mode.
Heritage mode from many
missions. FSW implements
algorithms supplied by GN&C
MRD-20
MRD-133
FSWR-143
The GN&C flight software shall monitor the performance of each control
mode and provide status telemetry that can be monitored by the C&DH
flight software.
Heritage GN&C and C&DH FSW
relationship.
MRD-10
MRD-87
FSWR-147
The GN&C flight software shall send propulsion commands at the control
law execution rate.
Typically send actuator
commands at the controller rate.
NASA’s Goddard Space Flight Center
19 - 8
Lunar Reconnaissance Orbiter (LRO)
FSW System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-15
MRD-84
FSWR-149
The GN&C flight software shall read SA orientation data at 1 Hz (TBD)
and compute a solar array normal to sun angle.
Standard requirement when a
spacecraft has articulating arrays.
MRD-15
MRD-84
FSWR-150
The GN&C flight software shall command the SA gimbals at 1Hz (TBD) to
orient the SA normal to the sunline.
A 1Hz rate can easily be
accommodated by a RAD750
processor.
MRD-16
MRD-84
FSWR-153
The GN&C flight software shall read HGA orientation data at 5 Hz (TBD)
and compute an HGA-pointing direction vector in the spacecraft body
frame.
Standard requirement when a
spacecraft has a gimbaled HGA.
Note mechanical complexities
when tracking can present
challenges.
MRD-16
MRD-84
FSWR-154
The GN&C flight software shall command the HGA gimbals at 5Hz (TBD)
to point the HGA towards a ground station.
5Hz can be accommodated. Note
the rate could be much higher
depending on the “intelligence”
HGA controller
NASA’s Goddard Space Flight Center
19 - 9
LRO Flight Software Architecture
Spacecraft
Data
Recorder
Checksum
EDAC
Memory
Scrubber
Memory
Manager
Memory
Dwell
Self
Test
GN&C
Applications
(5)
Instrument
Manager
Software
HK Data
Storage
Scheduler
Stored
Commanding
File
Manager
Local
Storage
Health &
Safety
Manager
New C&DH Task
CFDP File
Transfer
Inter-task Message Router (SW Bus)
1553 Bus
Support
Telemetry
Output
Command
Ingest
Software
Bus
Time
Services
Executive
Services
Event
Services
Table
Services
Heritage C&DH Task
Cmd (UDP COP-1)
New GN&C Task
Summit Chip
cFE Task
NASA’s Goddard Space Flight Center
S-Band COMM
(up/down)
Transponder
Real-time Telemetry (UDP)
Backup path for files (CFDP)
19 - 10
LRO FSW Verification
• Pre-release verification
– Peer reviews of SW design
– Code walkthroughs
– Unit tests
• Post-release verification in FSW lab
– Build Tests
– Requirements verification matrix of L4&L5 rqmts
• Verification of final build
– System Tests
• Verify L3 requirements and selected L4s
• Run on “FlatSat”
• IV&V
– WVa group validates process and run code analysis
– Code 300 SQA participates throughout SW development
NASA’s Goddard Space Flight Center
19 - 11
LRO FSW Summary
• LRO FSW architecture defined
– VxWorks, cFE forms the SW core
– Heritage FSW subsystems selected from Triana and SDO
• FSW development process defined
– Developed and documented by code 582 for CMMI
compliance
– LRO-specific process documents are in work
• FSW development labs being prepared
– Lab designs baselined
– Most components in house or on order
• FSW team members identified and ready to work
• FSW is ready to proceed with preliminary design
NASA’s Goddard Space Flight Center
19 - 12